10.59987/ads/2011.3-4.31-39
Introduction. The aim of this systematic review is to estimate accuracy and reproducibility of craniometric measurements and reliability of landmarks identified with computed tomography (CT) techniques in 3D cephalometric analysis.
Methods. Computerized and manual searches were conducted up to 2011 for studies that addressed these objectives. The selection criteria were: (1) the use of human specimen; (2) the comparison between 2D and 3D cephalometric analysis; (3) the assessment of accuracy, reproducibility of measurements and reliability of landmark identification with CT images compared with two-dimensional conventional radiographs. The Cochrane Handbook for Systematic Reviews of Interventions was used as the guideline for this article.
Results. Twenty-seven articles met the inclusion criteria. Most of them demonstrated high measurements accuracy and reproducibility, and landmarks reliability, but their cephalometric analysis methodology varied widely.
Conclusion. These differencies among the studies in making measurements don’t permit a direct comparison between them. The future developments in the knowledge of these techniques should provide a standardized method to conduct the 3D CT cephalometricanalysis.
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3D cephalometric analysis obtained from computed tomography. Review of the literature
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                                                                                                            Literature review



    3D cephalometric analysis obtained from
    computed tomography. Review of the literature




                                                                                                                li
                                                                                                             na
    Giulia Rossini, DDS, Ph.D student                             anatomical structures being imaged. The 2-D cephalometric
    Costanza Cavallini, MD                                        radiography allows bidimensional evaluation of craniofa-
    Michele Cassetta, DDS, Ph.D                                   cial morphology and growth, but ignore the mediolateral




                                                                                                          io
    Ersilia Barbato, DDS, MS                                      axis. Frontal cephalometric radiographs are useful for fa-
                                                                  cial asymmetry assessment but neglect the postero-an-
                                                                  terior dimension.




                                                                                   az
    "Sapienza" University of Rome, Rome, Italy                    These problems may be overcome using computed to-
    Department of Oral and Maxillofacial Sciences                 mography (CT) imaging techniques that produce three-di-
                                                                  mensional images of cranial bone, jaws and the sur-
                                                                  rounding tissues, allowing to focus the anatomic structures
    Corresponding author:                                         more accurately than 2D conventional radiography. Different




                                                                                 rn
    Dott. Giulia Rossini                                          techniques has been developed in order to obtain three-
    Via Flaminia 808c - 00191 Rome, Italy                         dimensional landmarks and to generate 3-D cephalograms,
    E-mail: giulia.rossini@uniroma1.it                            after combining and integrating the data of both 2-D
                                                                  cephalograms (lateral and postero-anterior).




                                                                      te
                                                                  The advantages of three-dimensional medical computed
                                                                  tomography (CT) imaging are already well established in
    Summary                                                       different dental specialities: management of trauma to the
                                                              In  maxillofacial skeleton, surgical facial reconstruction, or-
    Introduction. The aim of this systematic review is to         thognathic surgery, dental implants, complicated extrac-
    estimate accuracy and reproducibility of craniometric         tions and endodontic treatments (1-3). Nevertheless, its
    measurements and reliability of landmarks identified          use has been limited in orthodontics due to high-radiation
    with computed tomography (CT) techniques in 3D ce-            dose, cost, lack of availability, poor resolution and difficulty
                                                   ni
    phalometric analysis.                                         in interpretation. These issues may be addressed by re-
    Methods. Computerized and manual searches were                cent cone beam innovations in CT technology, and could
    conducted up to 2011 for studies that addressed the-          substantially alter the way that patients who have poten-
                                            io

    se objectives. The selection criteria were: (1) the use       tially complex orthodontic problems are managed.
    of human specimen; (2) the comparison between 2D              Afterwards, the advantages brought by Cone Beam Com-
    and 3D cephalometric analysis; (3) the assessment of          puted Tomography (CBCT) technology, as lower radiation
    accuracy, reproducibility of measurements and relia-
                                   iz



                                                                  dose, clearer images, more precision and reliability dur-
    bility of landmark identification with CT images com-         ing the visulizing of landmarks compared with conventional
    pared with two-dimensional conventional radiographs.          CT, bring to ask if 3D cephalometry obtained with CBCT
    The Cochrane Handbook for Systematic Reviews of In-           technology can fully replace the traditional cephalometry.
                  Ed




    terventions was used as the guideline for this article.       Moreover, because many of the patients had conventional
    Results. Twenty-seven articles met the inclusion cri-         cephalometric records in the past as part of their docu-
    teria. Most of them demonstrated high measure-                mentation, it is important to know whether cephalometric
    ments accuracy and reproducibility, and landmarks re-         radiographs obtained from CBCT scans are comparable
    liability, but their cephalometric analysis methodolo-        to conventional cephalometric records when evaluating a
    gy varied widely.                                             longitudinal series that contains both types of radi-
 IC




    Conclusion. These differencies among the studies in           ographs. If the two types of radiographs are not compa-
    making measurements don’t permit a direct compa-              rable, then the cephalometric data obtained from CBCT
    rison between them. The future developments in the            scans cannot be used to evaluate growth and treatment
    knowledge of these techniques should provide a stan-          outcomes longitudinally4.
C




    dardized method to conduct the 3D CT cephalometric            The aims of this review are to assess the quality of three-
    analysis.                                                     dimensional cephalometic analysis obtained from com-
                                                                  puted tomography and to determine if there is general con-
    Key words: three-dimensional cephalometry, compu-             sensus in the literature concerning the reliability, accura-
©




    ted tomography, accuracy, reliability, reproducibility.       cy and reproducibility of cephalometric landmarks and
                                                                  measurements obtained from CT 3D images.

    Introduction
                                                                  Methods
    Conventional cephalometric analysis presents the same
    limits of the radiograph on which it is performed: the two-   Criteria for considering studies for this review
    dimensional character and geometric distortion of the         The follow criteria were used to select the studies for this

    Annali di Stomatologia 2011; II (3-4): 31-39                                                                               31
    G. Rossini et al.


    review: general measures to find studies on three-di-             Orthodontic and Dentofacial Orthopedics; 7 were from the
    mensional cephalometric analysis, specific selection cri-         Angle Orthodontist; 2 from the International Journal of Oral
    teria to improve the quality of the study and exclusion cri-      Maxillofacial Surgery, and 3 from the Oral Surgery, Oral
    teria.                                                            Medicine, Oral Pathology, Oral Radiology and Endodon-
    General selection criteria included: (1) studies that iden-       tology; the last articles were selected from the Journal of
    tified landmarks in the maxillofacial area on CT images;          Craniomaxillofacial Surgery, Dentomaxillofacial Radiolo-




                                                                                                                    li
    (2) studies that explained how to conduct 3D cephalometric        gy, Journal of Orofacial Orthopedics, Journal of Oral and
    analysis; (3) only human radiographic studies.                    Maxillofacial Surgery, European Journal of Orthodontics,




                                                                                                                 na
    Specific selection criteria included studies that (1) evalu-      Biomedical Imaging and Interventional Journal.
    ated accuracy and reliability of cephalometric measure-           Fourteen studies used orthodontic subjects and thirteen
    ments conducted on three-dimensional CT images; (2) eval-         human dry skulls.
    uated the reproducibility of cephalometric landmarks on           A summary of the results from the 27 articles is present-




                                                                                                              io
    3D CT images; (3) determined whether cephalometric                ed in Table 1.
    measurements performed on CT cephalograms are com-
    parable with measurements on conventional cephalograms;           Measurement accuracy and landmark reliability
    (4) used both human dry skulls and orthodontic patients.          Lagravère and Major5 examined the intra-examiner relia-




                                                                                      az
    Exclusion criteria: (1) measurements of internal cranial          bility of a new proposed skeletal landmark, ELSA, locat-
    structures and temporomandibular joint (TMJ) were ex-             ed equidistant to centers of foramina spinosum. Ten ado-
    cluded because the focus was on skeletal landmarks that           lescent patients were scanned using a NewTom QR-DVT
    are of interest to clinical orthodontist; (2) areas outside the   9000 CBCT scanner (Aperio Services, Verona, Italy). Im-




                                                                                    rn
    maxillofacial boundaries; (3) facial trauma or tumor in the       ages were analyzed with AMIRA software (Mercury Com-
    maxillofacial area were also excluded because they                puter System, Berlin, Germany). Axial, sagittal, coronal,
    would distort the normal anatomy of the region.                   and 3D reconstructions were used in locating the landmark.
    No sex and age restriction was applied.                           The intra-examiner reliability has a kappa value of 0.998.




                                                                          te
                                                                      The authors concluded that this novel landmark is an ad-
    Methods of this review                                            equate landmark for use as a reference in 3D cephalometric
    The following electronic data bases were searched                 analysis with 3D volumetric images. Moshiri et al.6 com-
    through September 2011: Google Scholar beta, PubMed               pared the accuracy of linear measurements made on con-
    and Science Direct. The following keywords were used:
                                                                  In  ventional lateral cephalograms (LCs) captured on pho-
    three-dimensional cephalometry; computed tomography;              tostimulate phosphor cephalograms (PSP) with 3 meth-
    accuracy cephalometric measurements; reliability three-           ods for simulating lateral cephalograms with CBCT. The
    dimensional cephalometry; reproducibility.                        linear distances between anatomical landmarks on den-
    To determine whether the keywords had covered all arti-
                                                    ni
                                                                      tate dry human skulls were measured by observers using
    cles on 3D cephalometry, the following journals were man-         digital calipers for S-N, Ba-N, M-N, ANS-N, ANS-PNS, Pog-
    ually screened: The American Journal of Orthodontics and          Go, Go-M, Po-Or, and Go-Co. The skulls were imaged with
    Dentofacial Orthopedics, The Angle Orthodontist, The Eu-          CBCT with a single 360° rotation, producing 306 basis im-
                                          io


    ropean Journal of Orthodontics.                                   ages and achieving 0.4 mm isotrophic voxel resolution on
    In addition, references from each identified article were         volumetric reconstruction for making ray-sum recon-
    manually screened for articles that were missed by elec-          structed cephalograms. Two other cephalogram ap-
                                 iz



    tronic search engines. Finally, all manual and electronic         proaches were used with the CBCT system: a single trans-
    searches were solicited for review articles.                      mission image generated as a scout image designed to
    All abstract that dealt CT three-dimensional cephalomet-          check patient positioning before CBCT, and a single-frame
                 Ed




    ric analysis were read, and the full texts of all relevant ar-    lateral basis image. Conventional digital lateral cephalo-
    ticles were collected and reviewed. Ambiguous articles were       grams (LCs) were acquired with the photostimulable
    also read to avoid inappropriate exclusion. All procedures        phosphor system. Images were imported into a cephalo-
    were performed indipendently by two authors (GR, CC),             metric analysis program (Dolphin Imaging Cephalometric
    and differencies were resolved by rereading and discus-           and Tracing Software, Chatsworth, Calif) to compute the
    sion until consensus was reached.                                 included linear measurements. Analyses were repeated
                                                                      3 times and statistically compared with measured anatom-
 IC




                                                                      ic truth with ANOVA (P ≤.05). The intraclass correlation co-
    Results                                                           efficient was determined as an index of intra- and inter-
                                                                      examiner reliability. The intraclass correlation coefficient
    A total of 480 abstracts without overlap were found by the        (ICC) for the LCs was significantly less than for the meas-
C




    search methods. Only 43 abstracts met the inclusion cri-          ured anatomic truth and for all CBCT-derived images. CBCT
    teria or were retrieved because the abstract did not pro-         images either produced with individual frames or recon-
    vide enough information to justify exclusion. Fourteen ar-        structed from the volumetric data set were accurate for all
    ticles were excluded according to the selection and ex-           measurements except Pog-Go and Go-M. CBCT scout im-
©




    clusion criteria. Two more were excluded after reading and        ages had the second highest accuracy for all measure-
    discussing, because one tested the accuracy of an algo-           ments except Pog-Go, Go-M, and Go-Co. Conventional LCs
    rithm that corrects measurements made on conventional             had the least accuracy, and were accurate only for Po-Or
    lateral head film to corresponding dimensions observed            and ANS-N. In conclusion CBCT-derived 2-dimensional
    in a CBCT scan, and the other one scanned an acrylic head         LCs proved to be more accurate than LCs for most linear
    phantom to determine the reproducibility of maxillofacial         measurements calculated in the sagittal plane. No ad-
    anatomic landmarks. Therefore 27 studies remained.                vantage was found over single-frame basis images in us-
    Nine articles were selected from the American Journal of          ing ray-sum generated cephalograms from the CBCT vol-

    32                                                                                    Annali di Stomatologia 2011; II (3-4): 31-39
    3D Cephalometric Analysis Obtained from Computed Tomography. Review of The Literature


    Table 1 - Search results.




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                                                         In
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                  Ed
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                                                                                              (continues)

    Annali di Stomatologia 2011; II (3-4): 31-39                                                     33
    G. Rossini et al.


    Table 1 - Search results.                                                                                            (continued)




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                                                                                    az
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                                                                        te
                                                                In
                                                   ni
                                         io
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    umetric data set. Olszewski et al.7 tested the accuracy of      between the ACRO 3D software and the 3D measuring in-
    the measurements done on 3D CT surface renderings               strument. Periago et al.8 performed 20 orthodontic linear
    (ACRO 3D) in relation to those directly taken on 26 dry skull   measurements between anatomical landmarks on 23 hu-
    with the help of a 3D measuring instrument. There were          man skulls, using a digital caliper. The skulls were imaged
    no significant differences in the accuracy of measurements      with CBCT using the i-CAT system, and the CBCT data

    34                                                                                 Annali di Stomatologia 2011; II (3-4): 31-39
    3D Cephalometric Analysis Obtained from Computed Tomography. Review of The Literature


    were exported from the XoranCat software in DICOM mul-           ternal meatus left 0.84 (CI, 0.61, 0.94), auditory external
    ti-file and imported into Dolphin 3D (version 2.3) on the        meatus right 0.90 (CI, 0.73, 0.96), orbit left 0.83 (CI, 0.52,
    same computer. While many linear measurements between            0.93), and orbit right 0.80 (CI, 0.49, 0.92) landmarks. Fora-
    cephalometric landmarks on 3D volumetric surface ren-            men Spinosum (FS), Center Coordinate Point (ELSA), Au-
    derings obtained using Dolphin 3D software generated from        ditory External Meatus (AEM), and Dorsum Foramen Mag-
    CBCT datasets may be statistically different from anatom-        num (DFM) demonstrated adequate reliability and could




                                                                                                                   li
    ic dimensions, most can be considered to be sufficiently         be used for determining a standardized reference system.
    clinically accurate for craniofacial analyses. Lopes et al.9     The same Author12 afterwards confirmed his previous re-




                                                                                                                na
    studied the accuracy of 6 angular measurements based             sults: the intra-observer reliability was good for all meas-
    upon 9 conventional craniometric anatomical landmarks            urements. The correlation coefficient between the first and
    on 28 dried skulls, that were scanned with a 64-row mul-         second measurements ranged between 0.69 and 0.98, with
    tislice CT. These angular measurements were identified in-       an average of 0.91. The standard error for the conventional




                                                                                                             io
    dependently in 3D CT images by 2 radiologists, twice each.       cephalometric radiographs was significantly smaller for nine
    Subsequently, physical measurement were made by a third          measurements out of 12, as compared with the standard
    examiner. The results demonstrated no statistically sig-         error of the measurements on the 3D models. Berco et al.13
    nificant difference between inter- and intra-examiner            determined the accuracy and reliability of 3D cranio-facial




                                                                                      az
    analysis. The mean difference between the physical and           measurements obtained from CBCT scans of a dry human
    3D-based angular measurements was -1.18% and -                   skull, obtained with 2 skull orientations. Seventeen land-
    0,89%, respectively, for both examiners, demonstrating high      marks were identified on the skull, and twenty-nine inter-
    accuracy. Maxillofacial analysis of angular measurements         landmark linear measurements were made directly on the




                                                                                    rn
    using 3D CT volume rendering by 64-row multislice CT is          skull and compared with the same measurements made
    established and can be used for orthodontic and dento-           on the CBCT scans. All measurements were made by 2
    facial orthopedic applications. Cevidanes et al.10 have used     operators on 4 separate occasions. The method errors were
    presurgery CBCT scans of 12 patients (6 class II and 6           0.19, 0.21, and 0.19 mm in the x-, y- and z-axes, re-




                                                                         te
    class III) randomly selected from a pool of 159 patients to      spectively. Repeated measures analysis of variance
    determine the reliability of obtained two-dimensional            (ANOVA) showed no significant intra- or inter-examiner dif-
    cephalometric measurements using two virtual head ori-           ferences. The mean measurement error was –0.01 mm
    entations from cone-beam computed tomography (CBCT)              (SD, 0.129 mm). Five measurement errors were found to
    models: visual natural head position (simulated NHP) and
                                                                 In  be statistically significantly different. The Authors concluded
    3D intracranial reference planes (3D IRP). The CBCT              that CBCT allows for clinically accurate and reliable 3D lin-
    scans were obtained by NewTom 3G (QR-NIM s.r.l.,                 ear measurements of the craniofacial complex and that skull
    Verona, Italy) and the volume data were exported in DI-          orientation during CBCT scanning does not affect the ac-
    COM format into Dolphin Imaging software (version 10.5,          curacy or the reliability of these measurements. Hassan
                                                    ni

    Dolphin Imaging & Management Systems, Chatsworth,                et al.14 assessed the accuracy of linear measurements on
    Calif). Three observer created and digitized four CBCT-gen-      3D surface-rendered images of 8 dry human skulls gen-
    erated lateral cephalograms per patient, two using simu-         erated from CBCT datasets and compared them with those
                                            io


    lated NHP and two using 3D IRP at intervals of at least 3        made on 2D tomographic slices and on 2D lateral and PA
    days. ICC (intraclass correlation coefficients) indicated good   cephalometric projections. Moreover, the Authors evalu-
    reliability both within each head orientation and between        ated the influence of head position of the patient in the
                                   iz



    orientations. Of the 50 measurements, the reliability co-        scanner on measurement accuracy as Berco done13. Ten
    efficients were ≥ 0.9 for 45 measurements obtained with          linear distances were defined for cephalometric meas-
    3D IRP orientation and 36 measurements with simulated            urements. The physical and radiographic measurements
                  Ed




    NHP. The difference in mean values of the two orientations       were repeated twice by three independent observers and
    exceeded 2 mm or 2° for 14 (28%) of the measurements.            were compared using repeated measures analysis of vari-
    Lagravère et al.11 evaluated intra- and inter-examiner re-       ance (P = 0.05). The radiographic measurements were also
    liability of 3D CBCT-generated landmarks in patients who         compared between the ideal and the rotated scan posi-
    needed maxillary expansion. CBCT scans were taken us-            tions. The radiographic measurements of the 3D images
    ing the NewTom 3G (Aperio Services, Verona, Italy) at 110        were closer to the physical measurements than the 2D
    kV, 6.19 mAs, and 8 mm aluminum filtration. CBCT images          slices and 2D projection images. No statistically significant
 IC




    were converted to DICOM format and rendered into a vol-          difference was found between the ideal and the rotated
    umetric images with AMIRA software (AMIRA, Mercury               scan measurements for the 3D images and the 2D to-
    Computer Systems Inc, Berlin, Germany). Sagittal, axial,         mographic slices. A statistically significant difference (P <
    and coronal volumetric slices, as well 3D reconstruction         0.001) was observed between the ideal and rotated scan
C




    of the image, were used to determine landmark positions.         positions for the 2D projection images. The findings indi-
    In this system, the XY-plane moves from top to bottom, the       cate that measurements based on 3D CBCT surface im-
    XZ-plane moves from front to back, and the YZ-plane              ages are accurate and that small variations in the patient’s
    moves from left to right. The predetermined coordinate sys-      head position do not influence measurement accuracy. Van
©




    tem and origin (0, 0, 0) established by AMIRA for each im-       Vlijmen et al.4 compared the conventional cephalometric
    age were used and were the same for every examiner. Then         measurements with those obtained with the CBCT
    examiners located landmarks on the images. Intra-examiner        cephalometric radiographs taken from 40 dry human skulls.
    reliability for x, y, and z coordinates for all landmarks was    Intra-examiner reliability for both the conventional cephalo-
    greater than 0.97 with 95% confidence interval (CI, 0.96,        mentric radiographs and CBCT-constructed cephalomet-
    0.99). Inter-examiner reliability for x, y, and z coordinates    ric radiographs was good for all measurements. The cor-
    for all landmarks was greater than 0.92 (CI, 0.87, 0.96),        relation coefficient between the first and the second
    with the exception of the x-components of the auditory ex-       measurements ranged between 0.91 and 0.99, with an av-

    Annali di Stomatologia 2011; II (3-4): 31-39                                                                                 35
    G. Rossini et al.


    erage of 0.97. The standard error for CBCT-constructed              were scanned with a Philips MX 8000 IDT Multi-slice CT
    cephalometric radiographs was significantly smaller for 8           System (V 2.5; Philips Medical Systems, The Netherlands)
    measurements, compared with the standard error of the               with a high-resolution bone algorithm, 512 X 512 matrix,
    conventional cephalometric radiographs. Brown et al.15 com-         120 kV, and 100 mA. Axial scans were obtained with a 1-
    pared the in vitro reliability and accuracy of linear meas-         mm slice thickness and parallel to the Frankfurt horizon-
    urements between cephalometric landmarks on CBCT 3D                 tal plane. The 3D model of the axial images was recon-




                                                                                                                      li
    volumetric images with varying basis projection images to           structed using Mimics v12.01 (Materialise) software, and
    direct measurements on human skulls. The Authors directly           3D cephalometric analyses were performed. Standard lat-




                                                                                                                   na
    measured 16 linear dimensions between 24 anatomic sites             eral and frontal cephalograms of the dry skulls, on which
    marked on 19 human skulls, which were imaged with CBCT              clay markers were replaced with metallic balls and pins,
    (i-CAT). No difference in mean absolute error between the           were taken by Odontorama PC (85kV, 10 mA; Trophy Ra-
    scan settings was found for almost all measurements. The            diologie, Croissy-Beauborg, France). All metric meas-




                                                                                                                io
    average skull absolute error between marked reference               urements were made between the outermost points of balls
    points was less than the distances between unmarked ref-            and pins during manual and 3D virtual model measure-
    erence sites. CBCT resulted in lower measurements for               ments. All measurements on 2D radiograms were made
    nine dimensions (mean difference range: 3.1 mm ± 0.12               between the center points of pins and balls. In all cephalo-




                                                                                        az
    mm to 0.56 mm ± 0.07 mm) and a greater measurement                  metric analyses, 18 landmarks and 29 measurements (17
    for one dimension (mean difference 3.3 mm ± 0.12 mm).               lateral and 12 frontal) were used. Measurements were eval-
    No differences were detected between CBCT scan se-                  uated in three groups, as follows: group I (computer-as-
    quences. Moreira et al.16 demonstrated the accuracy of 15           sisted 3D cephalometric measurements), group II (phys-




                                                                                      rn
    maxillofacial linear and 6 angular measurements obtained            ical cephalometric measurements) and group III (con-
    by CBCT (i-CAT - Imaging Sciences International, Hatfield,          ventional 2D cephalometric measurements). All meas-
    PA) images marked on 15 intact human skulls. No statis-             urements were statistically insignificant between the
    tically significant differences were found of the compari-          computer-assisted 3D and manual measurements. On the




                                                                            te
    son between the physical and CBCT-based linear and an-              other hand, the differences between the conventional 2D
    gular measurements for both examiners (P = .968 and .915,           and the manual measurements were statistically signifi-
    P = .844 and .700, respectively). de Oliveira et al.17 eval-        cant. The greatest amount of magnification was found at
    uated intra- and inter-examiner reliability in 3D landmark          the Nasion-Menton distance (14.6%), which was located
    identification using CBCT images. Twelve presurgery
                                                                    In  at the farthest distance from the central x-ray beam in the
    CBCTs were randomly selected from 159 orthognathic sur-             lateral cephalogram (P < .01). For the same reason, the
    gery patients. Three observers independently repeated 3             greatest enlargement (16.2%) was observed in the distance
    times the identification of 30 landmarks in the sagittal, coro-     between the zygomaticomaxillary sutures on the con-
    nal, and axial slices. The ICC was >0.9 for 86% of in-              ventional frontal cephalogram (P < .01). The computer-
                                                      ni

    traobserver assessments and 66% of interobserver as-                aided 3D cephalometric measurements were found to be
    sessments. Only 1% of intraobserver and 3% of interob-              more accurate than the conventional cephalometric meas-
    server coefficients were <0.45. The systematic difference           urements. Medelnik et al.20 evaluated the accuracy of dif-
                                            io


    among observers was greater in X and Z than in Y di-                ferent cone-beam CTs (CBCTs/DVTs) and a multislice spi-
    mensions, but the maximum mean difference was quite                 ral CT (MSCT) scanner. A human fresh-frozen cadaver
    small. Overall the intra- and inter-observer reliability was        head was scanned with four CBCTs (Accuitomo 3D, 3D
                                  iz



    excellent. Nalçaci et al.18 assessd the reliability of 3D an-       eXam, Pax Reve 3D, Pax Zenith 3D) and one MSCT (SO-
    gular cephalometric approaches and the reproducibility of           MATOM Sensation 64) scanner. The three- dimensional
    landmark identification by comparing this method with au-           (3D) reconstruction of the volume data sets and location
                  Ed




    thenticated traditional 2D cephalometry. Eighteen cephalo-          of the anthropometric landmarks (n=11), together with lin-
    metric landmarks and 14 cephalometric angular meas-                 ear (n=5) and angular (n=1) measurements were carried
    urements were used. Two different orthodontists performed           out by three examiners using the program VoXim® 6.1. The
    both 2D and 3D cephalometric analyses. To assess in-                measurements were taken twice at a 14-day interval. De-
    traobserver reproducibility two sets of recordings made by          scriptive analyses were made and the standard deviations
    each observer in each modality were used. The intraob-              were used to compare differences in the accuracy of land-
    server reproducibility for the first and the second observ-         mark identification. The descriptive statistics showed dis-
 IC




    er ranged from 0.35° to 0.57° and from 0.42° to 0.65°, re-          tinct differences in the reference points in the three axes
    spectively. Furthermore, no significant differences were ob-        of the coordinate system. Because of anatomical and mor-
    served between the measurements of the two observers                phological factors, the pogonion and gnathion reference
    (P > 0.05). A comparison of 2D and 3D cephalometric                 points displayed higher standard deviations when set on
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    measurements showed significant differences in U1-NA                the transverse plane (SDCBCT Pog: 0.66–1.57 mm;
    and U1-SN parameters (P < 0.05). However, the param-                SDMSCT Pog: 0.14–1.09 mm; SDCBCT Gn: 1.05–1.77
    eters SNA, SNB, ANB, SND, NA-Pog, AB-NPog, Ns-Ba,                   mm; SDMSCT Gn: 0.20–0.85 mm), thus showing less ac-
    IMPA, FMIA, SN Ans-Pns, L1-APog and L1- NB did not                  curacy. However, standard deviations on the sagittal and
©




    show any significant differences (P > 0.05). The Authors            vertical planes were smaller. Genion, anterior nasal spine
    also concluded that the 3D angular cephalometric analy-             and infradentale had very low standard deviations on all
    sis is a fairly reliable method, like the traditional 2D cephalo-   three planes. The distance Mfl-Mfr and angle Krl-Krr-Ge
    metric analysis. Olmez et al.19 used different sections of          revealed significantly smaller standard deviations in the
    13 dry skulls to determine the accuracy and the differences         MSCT (SDCBCT Krl-Krr-Ge: 0.51–0.75 mm; SDMSCT Krl-
    between manual and cephalometric measurements, us-                  Krr-Ge: 0.22 mm). Frazão Gribel et al.21 assessed the ac-
    ing computer-assisted three-dimensional (3D) analysis and           curacy and reliability of craniometric measurements made
    conventional two-dimensional (2D) techniques. The skulls            on CBCT scans and lateral cephalograms of twenty-five

    36                                                                                      Annali di Stomatologia 2011; II (3-4): 31-39
    3D Cephalometric Analysis Obtained from Computed Tomography. Review of The Literature


    human skulls. CT scans were made using the iCAT Next             servers × 2 identifications ×9 measured distances × 2 meth-
    Generation (Imaging Sciences International, Hatfield,            ods = 1872 measurements. The intra-observer intraclass
    Pa) CBCT unit. A standardized protocol of the iCAT for the       coefficient of correlation for the 2D X-rays methods lay be-
    extended (17 X 23 cm) field of view (FOV) with 0.3 mm slice      tween 0.6040 and 0.9053. The inter-observer intraclass co-
    thickness, 26.9 seconds acquisition time was used. The           efficient of correlation for the 2D X-ray method lay between
    raw images were exported using the iCAT native software          0.1330 and 0.8409. The inter-observer intraclass coefficient




                                                                                                                  li
    (iCAT Vision) into DICOM 3 multifiles. The DICOM images          of correlation for the 3D CT method lay between 0.9362
    were loaded into SimPlant Ortho 2.0 (Materialise Dental,         and 0.9965. The Authors concluded that inter- and intra-




                                                                                                               na
    Lueven, Belgium) software. A custom analysis was created         observer reproducibility proved to be significantly superi-
    using the dedicated ‘‘3D Cephalometric’’ software module.        or (p < 0.0001) following the 3D CT method, compared with
    The custom 3D analysis (COMPASS 3D) was saved to be              the Delaire’s two-dimensional cephalometric analysis. The
    used with all CT scans. The same skulls subsequently were        same Author in 201024 measured the reproducibility of os-




                                                                                                            io
    used to obtain lateral cephalograms. The x-ray unit was cal-     seous landmark identification from two recently described
    ibrated optimally at 60 kV, 66 mA, and 0.16 seconds. Lin-        three-dimensional (3D) cephalometric analyses: 3D-
    ear and angular measurements were performed on both              ACRO and 3D-Swennen analyses. A total of 1144 meas-
    3D and 2D cephalograms. At the end linear distances were         urements were performed to estimate intra-observer re-




                                                                                      az
    directly measured using a digital caliper on the skulls. The     producibility for both of the 3D cephalometric analyses. A
    Authors concluded that no statistically significant difference   total of 2288 measurements were performed to estimate
    was noted between CBCT measurements and direct cran-             inter-observer reproducibility for both of the 3D cephalo-
    iometric measurements (mean difference, 0.1 mm). All             metric analyses. This study shows that the 3D-ACRO analy-




                                                                                    rn
    cephalometric measurements were significantly different          sis is significantly more reproducible than the 3D-Swen-
    statistically from direct craniometric measurements (mean        nen analysis (p1⁄40.0027). Cattaneo et al.25 in order to eval-
    difference, 5 mm). Significant variations among meas-            uate the landmarks reproducibility analyzed a conventional
    urements were noted. Some measurements were larger               lateral cephalogram and 2 sets of CBCT-synthesized




                                                                         te
    on the lateral cephalogram and some were smaller, but a          cephalograms, maximun intensity projection (MIP) and Ray-
    pattern could be observed: midsagittal measurements were         Cast from 34 patients. The absolute differences in degree
    enlarged uniformly, and Co-Gn was changed only slight-           between 3 observers were calculated for every angle, and
    ly; Co-A was always smaller. However CBCT craniomet-             independently for each of the 3 imaging tecniques. The Stu-
    ric measurements computed by a dedicated ‘‘3D Cephalo-
                                                                 In  dent-Newman-Keuls post-hoc test showed: significant sta-
    metric module’’ are extremely accurate. Damstra et al.22 de-     tistical differences between the 3 observers for 3 angular
    termined the reliability and the measurement error (by           measurements on the conventional cephalograms (Ili-ML,
    means of the smallest detectable error) of 17 commonly           P = 0.026; NL-Ols, P = 0.045; Oli-ML, P = 0.038). No an-
    used cephalometric measurements made on 3-dimensional            gular measurements were statistically different for the MIP
                                                    ni

    (3D) cone-beam computed tomography images. Twenty-               technique; 1 angular measurement had a statistically dif-
    five CBCT scans were randomly selected, and 3D images            ference for the RayCast technique (N-S-Ba, P = 0.042).
    were rendered, segmented, and traced with the SimPlant           However, in all cases, the differences were much small-
                                            io


    Ortho Pro software (version 2.1, Materialise Dental, Leu-        er than the accepted 1 standard deviation (SD) for the re-
    ven, Belgium). This was repeated twice by 2 observers dur-       spective angle according to the Björk analysis. The cal-
    ing 2 sessions at least 1 week apart. Measurement error          culated measurements did not differ between the 3 image
                                   iz



    was determined by means of the smallest detectable dif-          technique. The Ray-Cast technique proved to be more re-
    ference. Differences were analyzed with Wilcoxon signed          producible than the MIP. Van Vlijmen et al.4 assessed the
    rank tests. Intraobserver and interobserver reliability val-     reproducibility of the landmarks identifing 15 landmarks on
                  Ed




    ues were calculated by means of intraclass correlation co-       both types of cephalometric radiographs on all images 5
    efficients (ICC) based on absolute agreement. The Authors        times with a 1-week interval. The Authors found that the
    concluded that there were great variations of measurement        reproducibility of measurements in the CBCT-constructed
    errors between the angular (range, 0.88°-6.29°) and lin-         cephalometric radiographs was higher, compared with the
    ear (range, 1.33-3.56 mm) variables. The greatest meas-          reproducibility of measurements in conventional cephalo-
    uring error was associated with the dental measurements          metric radiographs. There was a statistically significant dif-
    U1-FHPL, L1-MdPL. and L1-FHPL (range, 3.80°-6.29°).              ference (P<.05) between this two methods of radiographs
 IC




    ANB angle was the only variable with a measuring error           for the following measurements: SNB, Ar-A, Ar-Pog,
    of 1° or less for both observers. The intraobserver agree-       NSL/NL, NL/ML, ILs/NL, Lii/ML, interincisal angle, and Ii
    ment of all measurements was very good (ICC, 0.86-0.99).         to A-Pog. For most of these measurements the actual mean
    Except for SN-FHPL (ICC, 0.76), interobserver agreement          average difference ranged from – 1.54° to 1.45°, similar
C




    was very good (ICC, >0.88).                                      to, or smaller than, the standard error for the repeated
                                                                     measurements. Only the difference between CBCT meas-
    Reproducibility of measurements                                  urements and conventional measurements for the absolute
    Park et al.23 assessed the reproducibility of the landmarks      distance Ar-A and Ar-Pog was greater than their standard
©




    and a subject was chosen at random; 19 landmarks were            error, but still less than 1 mm. In 2010 the same Author26
    identified 5 times in 1 session by an operator 2 weeks af-       identified 17 landmarks on the cephalometric radiographs
    ter the first session. A paired t-test between the 2 sessions    and on the 3D models. All images and 3D models were
    was carried out by using SAS version 8.2. The Author con-        traced five times with a time-interval of 1 week and the
    cluded that all landmarks were reproducible, with a no sig-      mean value of repeated measurements was used for fur-
    nificant intra-examiner error between the 2 sessions (P          ther statistical analysis. Distances and angles were cal-
    >.0.1). Olszewski et al.7 evaluated the reproducibility of the   culated. Reproducibility of the measurements on the con-
    3D CT cephalometric method using 26 dry skulls ×2 ob-            ventional cephalometric radiographs was higher, compared

    Annali di Stomatologia 2011; II (3-4): 31-39                                                                                37
    G. Rossini et al.


    with the reproducibility of the measurements on the 3D           possibility of comparing the right and the left side of the
    models. A statistically significant difference between the       skull, and the anatomic structures were not superimposed
    conventional cephalometric radiographs and the 3D mod-           which improved the visibility of the reference landmarks.
    els was found for the following measurements: ANB, SNB,          The Authors found more advantages of the CT technique:
    NL/ML, NSL/BOP, NSL/ML, NSL/NL, Is to A-Pog. The av-             the real possibility to perform three-dimensional meas-
    erage difference ranged from –3.118° to 0.828°. For most         urements on the lines and the angles and to visualized si-




                                                                                                                    li
    measurements this difference was considerably smaller            multaneously soft tissues including the fat, muscle and the
    than the standard deviation of the variable measured. For        air way. Cattaneo et al.25, after comparing cephalometric




                                                                                                                 na
    SN/ML the difference (3.118) was 89% of standard devi-           measurements performed on conventional cephalograms
    ation, for the SN/NL difference (1.748) this was 66%. For        with those on CBCT-synthesized images, found that
    all other measurements it was less than 40%. In the study        CBCT-synthesized cephalograms could successfully re-
    conducted by Lagravère et al.11 the principal investigator       place conventional headfilms.




                                                                                                              io
    located the landmarks in the XY, XZ and YZ planes five           Several studies have confirmed the three-dimensional geo-
    times on different days, and four other investigators located    metric accuracy of CBCT technique8,9,19. Most Authors stat-
    the landmarks once for each image. Spherical markers of          ed that CBCT gave accurate two- and three-dimensional
    0.5 mm diameter were placed, indicating the position of          measurements regardless of skull orientation, and that




                                                                                      az
    the landmark. Intra- and inter-examiner reliability values       CBCT was reliable for taking linear measurements of the
    were determined using ICCs. Intra- and inter-examiner re-        maxillo-facial skeleton4,6,10,12,14,17,21,22,25-28. Most of them
    liability for x, y, and z coordinates for all landmarks were     have used human dry skulls in order to increase meas-
    acceptable, all being greater than 0.80. Most of the mean        urements accuracy and landmarks reliability. This reduced




                                                                                    rn
    measurement differences obtained from trials within the          the chance of errors in landmark identification because it
    principal investigator in all three axes were less than 1.5      made an accurate identification of bony landmarks more
    mm. Inter-examiner mean measurement differences gen-             likely since there was no overprojection of soft tissues. Iden-
    erally were larger than the intra-examiner differences. Lud-     tification of landmarks were very important in comparative




                                                                         te
    low et al.27 compared the precision of landmark identification   studies. Although the landmarks could be determined on
    on CBCT images and conventional lateral cephalograms.            computer software, clay and metallic markers were placed
    The Authors radiographed twenty presurgical orthodontic          on dry skulls to use the exact same points in all meas-
    patients with conventional lateral cephalograms (Ceph) and       urements. Clay markers were preferred to the metallic
    CBCT techniques, and then five observers plotted 24 land-
                                                                 In  markers to prevent artifacts during the CT imaging.
    marks using computer displays of multi-planer recon-             Berco et al.13 and Bholsothi et al.29 concluded that linear
    struction (MPR) CBCT and Ceph views during separate              measurements on 3D shaded surface renderings from
    sessions. The Authors concluded that the MPR displays            CBCT datasets using commercial cephalometric analysis
    of CBCT volume images provide generally more precise
                                                    ni
                                                                     software had variable accuracy: most midline-to-midline
    identification of traditional cephalometric landmarks. More      linear measurements and some midline-to-midline angu-
    precise location of condylion, gonion, and orbitale over-        lar measurements were not different, while other types of
    comes the problem of superimposition of these bilateral          measurements were significantly different. Moreira et al.16
                                          io


    landmarks seen in Ceph.                                          did not find statistically significant differences between the
    Medelnik et al.20, as reported before in this review, beyond     physical and CBCT-based linear and angular measure-
    the accuracy landmarks evaluation, assessed the repro-           ments.
                                 iz



    ducibility of anatomical landmarks of different cone-beam        Van Vlijmen et al.26 showed that for most measurements
    CTs (CBCTs/DVTs) and a multislice spiral CT (MSCT)               there was no clinically relevant difference between angu-
    scanner, on a human fresh-frozen cadaver head, from the          lar and linear measurements performed on conventional
                 Ed




    standard deviations on the three planes. The Authors coc-        cephalometric radiographs, compared with cephalomet-
    nluded that MSCT yielded smaller (sometimes significantly)       ric measurements on 3D models of skulls. They demon-
    standard deviations than CBCT in maxillary distance (Spa-        strated also that the measurement error for 3D measure-
    Spp), mandibular height (Id-Gn), bimental width (Mfl-Mfr),       ments was larger than that for conventional 2D meas-
    and coronoid-genio angle (Krl-Krr-Ge), and that the re-          urements. This could be explained by the fact that adding
    producibility of landmark identification in all the volume im-   the third dimension an additional source of inaccuracy is
    ages was good.                                                   introduced.
 IC




                                                                     Some other Authors4,7,11,20,23,24,26,28 found that the repro-
                                                                     ducibility of their own measurements in the CBCT-con-
    Discussion                                                       structed cephalometric radiographs was higher, compared
                                                                     with the reproducibility of measurements in conventional
C




    The multislice CT and Cone beam computed tomography              cephalometric radiographs.
    overcomes most of the limitations of intra-oral radiography.
    The increased diagnostic data should result in more ac-
    curate diagnosis and monitoring and therefore improved           Conclusion
©




    decision making for the management of orthodontic prob-
    lems. When indicated, three-dimensional CBCT scans may           This review of the literature allows to reach the following
    supplement conventional two-dimensional radiographic             conclusions:
    techniques and can be used in conjunction with routine           • in literature there is a limited number of studies re-
    craniofacial bidimensional evaluation. Olszewski et al.7 af-         garding the accuracy of measurements and reliabili-
    firmed that although diagnoses based on both two- and                ty of landmarks identification with computed tomog-
    three-dimensional analyses were adequate, the three-di-              raphy (CT) technique in the maxillofacial area;
    mensional analysis gave more informations such as the            • the few studies present in the literature described dif-

    38                                                                                    Annali di Stomatologia 2011; II (3-4): 31-39
    3D Cephalometric Analysis Obtained from Computed Tomography. Review of The Literature


        ferent landmarks identification and measurements,                        14. Hassan B, van der Stelt P, Sanderink G. Accuracy of three-di-
        which impede a direct comparison between them;                               mensional measurements obtained from cone beam computed to-
    •   a standardized and widely approved 3D cephalomet-                            mography surface-rendered images for cephalometric analysis: in-
        ric analysis is still not described;                                         fluence of patient scanning position. European Journal of Ortho-
                                                                                     dontics 31 (2009) 129-134. doi:10.1093/ejo/cjn088. Advance Ac-
    •   the high accuracy and reproducibility of measurements
                                                                                     cess publication 23 December 2008.
        and reliability of cephalometric landmarks on CT im-




                                                                                                                                     li
                                                                                 15. Brown AA, Scarfe WC, Scheetz JP, Silveira AM, Farman AG. Lin-
        ages permit to perform a successfully and safely                             ear accuracy of cone beam CT derived 3D images. Angle Orthod.
        cephalometric analysis;




                                                                                                                                  na
                                                                                     2009;79:150-7.
    •   to obtain consistent and reproducible data from three-                   16. Moreira CR, DDS, MS, Sales MAO, Lopes PML, Cavalcanti MGP,
        dimensional landmark identification on CT images it                          DDS, Pessoa J. Assessment of linear and angular measurements
        would be mandatory to follow a protocol for operator                         on three-dimensional cone-beam computed tomographic images.
        training and calibration.                                                    Oral Surg Oral Med Oral Pathol Oral Radiol Endod 2009;108:430-
                                                                                     436.




                                                                                                                               io
                                                                                 17. de Oliveira AEF, Cevidanes LHS, Phillips C, Motta A, Burke B, Tyn-
                                                                                     dall D. Observer reliability of three-dimensional cephalometric land-
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C




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©




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    Annali di Stomatologia 2011; II (3-4): 31-39                                                                                                      39
