Radiation exposure during midfacial imaging using 4- and 16-slice computed tomography, cone beam computed tomography systems and conventional radiography

OBJECTIVES: Radiation doses were determined to balance risks against usefulness of the different modalities available for the imaging of the facial skeleton. METHODS: An Alderson Rando Phantom, armed with lithium fluoride thermoluminescent dosemeters (TLDs) was exposed using a set of four conventional radiographs (orbital view, modified Waters view, orthopantomography, skull posterior--anterior 0 degrees ), two different cone beam computed tomography (CBCT) (NewTom 9000 and Siremobil Iso-C3D), and multislice computed tomography (CT) modalities (Somatom VolumeZoom and Somatom Sensation 16). TLDs from 14 well defined anatomical sites lying within the primary beam as well as the TLD corresponding to the thyroid gland were evaluated. RESULTS: Multislice CT showed the highest exposure values. Exposure levels of the CBCT systems lay between CT and conventional radiography. Dose measurement for the 16-slice CT revealed nearly the same radiation exposure as the 4-slice system when adapted examination protocols were used. CONCLUSIONS: Selection of the most appropriate imaging modality should be performed in view of the delivered doses, required image quality and information and the clinical circumstances.     

3D-imaging of the facial skeleton with an isocentric mobile C-arm system (Siremobil Iso-C3D)

OBJECTIVES: The purpose of this study was to compare three-dimensional (3D) imaging of the facial skeleton using an isocentric mobile C-arm system vs CT. METHODS: A dried human skull was scanned using a Siremobil Iso-C3D and a multi-detector CT (SOMATOM Volume Zoom; Siemens Medical Solutions, Erlangen, Germany) to compare reconstructed data sets. For each group of scans a standard protocol and a high resolution protocol were used. Image quality was analysed using six anatomical and six virtual structures in the primary reconstructed axial images of both data sets of the Siremobil Iso-C3D compared with CT. A receiver operating characteristic (ROC) study was performed with six examiners. RESULTS: The original categorical response data revealed no significant differences in sensitivity and specificity (P < 0.05). However, image quality of the reconstructed images of the Siremobil Iso-C3D was inferior to the CT images, with metal artefacts having a more prominent negative effect. CONCLUSIONS: The Siremobil Iso-C3D produces 3D images of the facial skeleton suitable for imaging osseous structures. No significant differences were found in sensitivity or specificity between the two methods. Metal objects degrade the image from the Iso-C method to a greater extent than those from CT.     

Comparison of 2D OPG image versus orthopantomogram from 3D CBCT from the forensic point of view

Forensic dental identification has employed traditionally 2D digital radiological imaging techniques. More recently, 3D cone beam computer tomography (CBCT) data, widely applied in clinical dentistry, have been gradually used. The purpose of this study was to compare the precision and quality of 2D digital orthopantomogram (OPG) and 2D OPG images generated from cone beam computed tomography (CBCT). The study sample consisted of 50 patients with archived conventional 2D OPG and 3D CBCT images. Patients signed an informed consent form to take part in our study. Measurements of the mandible, teeth and dental restorations were taken by two observers on calibrated 2D OPG and 3D CBCT-to-OPG images using measurement functionalities of DOPLHIN software. Acquired dimensions were compared side by side and images of fillings were superimposed. For better visual comparison and more efficient image registration, the methods of spline interpolation were used. The pairs of absolute measurements obtained from conventional OPG and CBCT-to-OPG-converted images were highly correlated (p < 0.05). However, larger, and horizontally measured distances were revealed to be more affected than shorter vertically taken measurements. In relative terms, CBCT-generated width/length indices of the canines and the first molars ranged from 84% to 99.8% of those acquired from traditional OPGs. In addition, corresponding points on the teeth and fillings were compared side by side and in superimposition. The average coincidence of images was 6.1%. The results revealed that for selected metric variables 2D OPGs and 3D CBCT-generated OPGs were complementary and could be used for forensic comparisons.     

Radiofrequency ablation under 3D intraoperative Iso-C C-arm navigation for the treatment of osteoid osteomas

Objective:

To evaluate the efficacy of intraoperative three-dimensional (3D) Iso-C C-arm-navigated percutaneous radiofrequency ablation (RFA) of osteoid osteomas.

Methods:

35 patients (20 males and 15 females) with osteoid osteomas underwent treatment with intraoperative 3D Iso-C C-arm navigation-guided RFA. The tumour was first biopsied for pathological examination, the core needle was removed and the RFA needle was inserted into the nidus. Post-operative X-rays and CT scans were performed to evaluate the degree of ablation and to assess for recurrence at 3-month follow-up. Patients also completed a visual analogue scale (VAS) both pre-operatively and 3 days post-operatively to subjectively assess pain.

Results:

Pathological diagnosis confirmed osteoid osteoma in 19 cases. The other 16 cases were not pathologically diagnosed owing to inadequate biopsy specimens. In all cases, localized pain was immediately relieved following RFA. Patients reported significantly decreased pain, with mean pre-operative VAS scores of 3.4 reducing to 0.80 at 3 days post-operatively and further to 0.06 at 3-month follow-up (p < 0.05). The mean follow-up time was 15.5 months (range: 3–38 months).

Conclusion:

3D Iso-C C-arm navigation-guided RFA is a safe and effective option for the treatment of osteoid osteomas and may be considered in place of intraoperative CT-guided and open resection.

Advances in knowledge:

C-arm image-guided percutaneous RFA mitigates the need for pre-operative CT as well as intraoperative scintigraphy, provides real-time imaging of the anatomy, facilitates accurate resection of the tumour and enables immediate confirmation of excision.     

Diagnostic performance of multi-slice computed tomography using 2D and 3D images in the assessment of Le Fort fractures

Objective

The aim of this study was to assess the role of multislice computed tomography (MSCT) using 2D and 3D images in evaluation of different types of Le Fort fractures.

3D iGuide穿刺技术在DynaCT引导射频消融治疗大肝癌中的应用

目的：评价3D iGuide穿刺技术在DynaCT引导射频消融（RFA）治疗大肝癌中的可行性及安全性。 方法：选取2016年9-12月在解放军总医院介入放射科住院治疗的孤立性大肝癌患者19例,行DynaCT扫描并选择3D iGuide技术引导射频针穿刺后实施RFA术,评价术后的技术成功率、术中及术后并发症、治疗效果。 结果：19例患者全部操作成功,技术成功率为100%,术中及术后并发症以疼痛为主,并未出现严重并发症;术后1个月影像学复查评估治疗效果,完全缓解（CR）17例、部分缓解（PR）2例。 结论：3D iGuide穿刺技术在DynaCT引导射频消融治疗大肝癌中安全、有效且操作简便,具有极强的可行性,为RFA治疗肝癌提供新的引导方法。     

3D segmentation of dental crown for volumetric age estimation with CBCT imaging

International Journal of Legal Medicine - In adult dental age estimation, segmentation of dental volumetric information from different tooth parts using cone-beam computed tomography (CBCT) has...     

Planning and intraoperative visualization of liver catheterizations: new CTA protocol and 2D-3D registration method

RATIONALE AND OBJECTIVES: Two-dimensional and three-dimensional (2D-3D) registration for angiographic liver interventions is an unsolved problem mainly because of two reasons. First, a suitable protocol for computed tomography angiography (CTA) to contrast liver arteries is not used in clinical practice. Second, in spite of a valuable body of research results in the neuroradiology community, an adequate registration algorithm that addresses the difficult task of 2D-3D alignment of abdominal vessel structures has not been developed yet. MATERIALS AND METHODS: We address the first issue by introducing an angiographic computed tomography (CT) scanning phase. The scan visualizes arteries similar to the vasculature captured with an intraoperative C-arm acquiring digitally subtracted angiograms. Furthermore, we propose a registration algorithm using the new CT phase that aligns arterial structures in two steps: 1) Initialization of one corresponding feature using diameter information and 2) optimization on three rotational and one translational parameters to register vessel structures that are represented as centerline graphs. We form a space of good features by iteratively creating new graphs from projected centerline images and by restricting the correspondence search only on branching points (the vertices) of the vessel tree. RESULTS: We show convergence and robustness of the proposed algorithm on synthetic data, as well as head phantom and four consistent patient data sets. We compare our results with those of a recently proposed method. Moreover, we evaluate different visualization techniques and show that a transfer of planning information to intraoperative data is a benefit for interventional workflow. CONCLUSIONS: Introducing a new CTA protocol and a two-step 2D-3D registration algorithm, the proposed method creates a strong link between radiologists and interventionalists by bringing preoperative patient and planning information to interventional workflow.     

Comparative study of jaws with multislice computed tomography and cone-beam computed tomography

Purpose

The aim of this study was to compare the dosimetric and diagnostic performance of multislice computed tomography (MSCT) and cone-beam computed tomography (CBCT) in the study of the dental arches.

Materials and methods

Effective dose and dose to the main organs of the head and neck were evaluated by means of thermoluminescent dosimeters (TLDs) placed in an Alderson Rando anthropomorphic phantom and using a standard CBCT protocol and an optimised MSCT protocol. Five patients with occlusal plane ranging from 54 cm to 59 cm who needed close follow-up (range 1–3 months) underwent both examinations. Image quality obtained with CBCT and MSCT was evaluated.

Results

Effective dose and dose to the main organs of the head and neck were higher for MSCT than for CBCT. Image quality of CBCT was judged to be equivalent to that of MSCT for visualising teeth and bone but inferior for visualising soft tissues. Beam-hardening artefacts due to dental-care material and implants were weaker at CBCT than at MSCT.

Conclusions

When panoramic radiography is not sufficient in the study of the teeth and jaw bones, CBCT can provide identical information to MSCT, with a considerable dose reduction. MSCT is, however, indicated when evaluation of soft tissue is required.     

3D CT cinematic rendering of mycotic aneurysms

Mycotic aneurysms are uncommon but emergent conditions in which infection of a vessel leads to a contained rupture. Progression to frank rupture, thrombosis, distal embolization, and death can occur. The widespread availability of computed tomography (CT) and its ability to obtain high-resolution, contrast-enhanced, volumetric images rapidly has made it the modality of choice for evaluating mycotic aneurysms. Three-dimensional CT visualizations can provide important information to surgeons and interventionalists prior to attempting repair of these lesions. In this case series, we demonstrate the appearance of mycotic aneurysms with the novel 3D CT visualization methodology known as cinematic rendering (CR). CR makes use of a more complex lighting model than has previously been utilized with other 3D CT techniques, allowing for enhanced surface detail and realistic shadowing effects. These features of CR may have utility in evaluating mycotic aneurysms and in pre-procedural/pre-operative planning, although a prospective study definitively evaluating this has not yet been performed.     

Dosimetry of the cone beam computed tomography Veraviewepocs 3D compared with the 3D Accuitomo in different fields of view

OBJECTIVES: This study compares tissue-absorbed and effective doses of the cone beam CT (CBCT) units, the Veraviewepocs 3D and the 3D Accuitomo, in different protocols. METHODS: The absorbed organ doses were measured using an anthropomorphic phantom loaded with thermoluminescent dosemeters (TLDs) in 16 sensitive organ sites. Both CBCT units were deployed with different fields of view (FOVs): 3D Accuitomo using two protocols (anterior 4 x 4 cm scan and anterior 6 x 6 cm scan) and Veraviewepocs 3D using three protocols (anterior 4 x 4 cm scan, anterior 8 x 4 cm scan and panoramic + anterior 4 x 4 cm). Equivalent and effective doses were then calculated, the latter based on the International Commission on Radiological Protection's (ICRP) 2005 recommendations. RESULTS: The lowest effective dose was observed for the 3D Accuitomo 4 x 4 cm (20.02 microSv), the highest for the 3D Accuitomo 6 x 6 cm (43.27 microSv). The effective dose recorded for Veraviewepocs 3D was 39.92 microSv for the 8 x 4 cm scan, 30.92 microSv for the 4 x 4 cm scan and 29.78 microSv for the panoramic + 4 x 4 cm scan protocol. CONCLUSIONS: The radiation doses delivered by both machines were in comparable ranges when using 4 x 4 cm FOV. A smaller FOV should be used for dental images, whereas a larger FOV should be restricted to cases in which a wider view is required.     

Soft tissue thickness in Brazilian adults of different skeletal classes and facial types: A cone beam CT – Study

The aim in this study was to evaluate the influence of skeletal class, facial type, and sex on soft tissue thickness (STT) of the craniofacial midline in a Brazilian subpopulation. Thus, 121 cone beam computed tomography (CBCT) scans (54 males and 67 females, age 21 to 40 yrs) composed the study sample. Patients were classified according to skeletal class (class I, II, and III) and facial type (brachycephalic, mesocephalic, and dolichocephalic), and STT was measured (mm) in 10 landmarks in the craniofacial midline for each CBCT scan. Multivariate analysis of covariance evaluated facial STT with regard to multiple independent variables (sex, age – covariate, facial type, and skeletal class). TEM and rTEM assessed the intra-examiner agreement. STT was significantly greater in males than in females for all regions measured (p < 0.05), except for the pogonion-pogonion’ landmark (p>0.05). In general, class III individuals had significantly thicker soft tissue in the maxilla – subspinale-subnasale’, prosthion-labrale superius’, and incision-stomion’ regions, while class II subjects had thicker soft tissue in the infradentale-labrale inferius’ mandibular landmark (p < 0.05). Regarding facial type, dolichocephalic individuals showed significantly thicker soft tissue in the supramentale-supramentale’ mandibular landmark, whereas brachycephalic subjects had thicker soft tissue in maxillary regions – prosthion-labrale superius’ and incision-stomion’ (p < 0.05). rTEM values were below 5% for most landmarks, and all TEM values were below 1 mm. Skeletal class and facial type influence STT, showing a soft tissue compensation, with deeper soft tissue in areas with lower skeletal development, and/or where bone is positioned more posteriorly.     

Impacted teeth in the maxilla: usefulness of 3D Dental-CT for preoperative evaluation

OBJECTIVE: To compare the shapes of roots of impacted teeth shown in three-dimensional computed tomographic images (3D Dental-computed tomography (CT) images) and plain radiographs and to determine whether 3D Dental-CT images are useful for examination before performing an operation for extraction of a maxillary impacted tooth. METHODS AND PATIENTS: Images obtained from patients who had impacted teeth in the maxilla, including impacted mesial supernumerary teeth in 13 patients, impacted incisors in two patients, impacted canines in 11 patients, impacted premolars in four patients and impacted molars in three patients, were used in this study. In all patients, plain radiographs and 3D Dental-CT images were retrospectively reviewed by an oral radiologist for evidence of root dilaceration before operations to extract the impacted teeth were performed. The findings in the images were compared with intraoperative findings in all cases. RESULTS: The mean specificity and sensitivity of plain radiographs were 95 and 8%, respectively, while those of 3D Dental-CT images were 100 and 77%, respectively. There was a statistically significant (P<0.01) difference between the depiction capabilities of plain radiographs and 3D Dental-CT images with regard to dilacerations of roots of impacted teeth. DISCUSSION AND CONCLUSION: CT may enable radiologists to make a quick and accurate diagnosis of tooth impaction. 3D Dental-CT images are useful for determining the root shape of an impacted tooth in the maxilla.     

Segmentation process significantly influences the accuracy of 3D surface models derived from cone beam computed tomography

Aims

To assess the accuracy of surface models derived from 3D cone beam computed tomography (CBCT) with two different segmentation protocols.

Materials and methods

Seven fresh-frozen cadaver heads were used. There was no conflict of interests in this study. CBCT scans were made of the heads and 3D surface models were created of the mandible using two different segmentation protocols. The one series of 3D models was segmented by a commercial software company, while the other series was done by an experienced 3D clinician. The heads were then macerated following a standard process. A high resolution laser surface scanner was used to make a 3D model of the macerated mandibles, which acted as the reference 3D model or “gold standard”. The 3D models generated from the two rendering protocols were compared with the “gold standard” using a point-based rigid registration algorithm to superimpose the three 3D models. The linear difference at 25 anatomic and cephalometric landmarks between the laser surface scan and the 3D models generate from the two rendering protocols was measured repeatedly in two sessions with one week interval.

Results

The agreement between the repeated measurement was excellent (ICC = 0.923–1.000). The mean deviation from the gold standard by the 3D models generated from the CS group was 0.330 mm ± 0.427, while the mean deviation from the Clinician's rendering was 0.763 mm ± 0.392. The surface models segmented by both CS and DS protocols tend to be larger than those of the reference models. In the DS group, the biggest mean differences with the LSS models were found at the points ConLatR (CI: 0.83–1.23), ConMedR (CI: −3.16 to 2.25), CoLatL (CI: −0.68 to 2.23), Spine (CI: 1.19–2.28), ConAntL (CI: 0.84–1.69), ConSupR (CI: −1.12 to 1.47) and RetMolR (CI: 0.84–1.80).

Conclusion

The Commercially segmented models resembled the reality more closely than the Doctor's segmented models. If 3D models are needed for surgical drilling guides or surgical planning which requires high precision, the additional cost of the commercial segmentation services seem to be justified to produce a more accurate surface models.     

Effective dose estimates for cone beam computed tomography in interventional radiology

Objectives

To compare radiation doses in cone beam computed tomography (CBCT) with those of multi-detector computed tomography (MDCT) using manufacturers’ standard protocols.

Methods

Dose-levels in head and abdominal imaging were evaluated using a dosimetric phantom. Effective dose estimates were performed by placing thermoluminescent dosimeters in the phantom. Selected protocols for two CBCT systems and comparable protocols for one MDCT system were evaluated. Organ doses were measured and effective doses derived by applying the International Commission on Radiological Protection 2007 tissue weighting factors.

Results

Effective doses estimated for the head protocol were 4.4 and 5.4 mSv for the two CBCT systems respectively and 4.3 mSv for MDCT. Eye doses for one CBCT system and MDCT were comparable (173.6 and 148.4 mGy respectively) but significantly higher compared with the second CBCT (44.6 mGy). Two abdominal protocols were evaluated for each system; the effective doses estimated were 15.0 and 18.6 mSv, 25.4 and 37.0 mSv, and 9.8 and 13.5 mSv, respectively, for each of the CBCT and MDCT systems.

Conclusions

The study demonstrated comparable dose-levels for CBCT and MDCT systems in head studies, but higher dose levels for CBCT in abdominal studies. There was a significant difference in eye doses observed between the CBCT systems.

Key Points

? Cone beam computed tomography (CBCT) is increasingly utilised in interventional radiology. ? Effective doses for selected CBCT and MDCT protocols were estimated and compared. ? Dose levels in CBCT and MDCT were comparable for head studies. ? Dose levels were higher in CBCT for abdominal studies.     

3D volume rendering using multislice CT for dental implants

OBJECTIVES: To determine the precision and accuracy of three-dimensional (3D) volume rendering spiral multislice computed tomography (CT)-based linear measurements of the mental foramen for dental implants, in vitro, and their precision, in vivo. METHODS: Five cadaver heads were imaged by multislice spiral CT (Toshiba Aquilion) with 0.5 mm thick axial slices (0.5 mm/0.5 s of table feed) at 0.5 mm interval reconstructions. The image data sets were transferred to a networked computer workstation. Using computer graphics the data were analysed with a 3D volume rendering technique using Vitrea software. Two oral and maxillofacial radiologists, independently, made electronic linear measurements from the superior border of the mental foramen to the crest of the alveolar process. The soft tissues were removed and physical measurements made using a 3 Space (Polhemus, Colchester, VT, USA) electromagnetic digitizer with a personal computer running Windows 98. The same linear measurements of 15 patients using the same imaging methodology were performed and the precision was analysed. RESULTS: The findings showed no statistically significant inter- or intra-observer differences in vitro and in vivo, or between imaging and physical measurements in vitro (P>0.05). CONCLUSIONS: 3D multislice spiral CT imaging allows highly accurate measurements for dental implant placement in proximity to the mental foramen. Computer graphics software, using volume rendering is suitable for implant planning.     

Cone-beam computed tomography: a new low dose, high resolution imaging technique of the wrist, presentation of three cases with technique

Cone-beam computed tomography (CBCT) is a relatively new technique. It generates a 3D image by emitting a pulsed cone-shaped X-ray beam. CBCT has become a very useful and widely used technique for dentomaxillofacial imaging over the last decade. It provides clear, high resolution multiplanar reconstruction images. Previously, the images could only be generated while the patient was sitting with his/her head fixed in position. With the presented new generation CBCT (NewTom 5G, QR, Verona, Italy), a more free positioning of the patient, either lying or sitting, is possible. In this way, skeletal imaging of various body parts becomes possible. In this article we present three clinical cases of CBCT imaging of the wrist, describe the background of the technique, and discuss the advantages and disadvantages of CBCT imaging.     

Human identification through frontal sinus 3D superimposition: Pilot study with Cone Beam Computer Tomography

As a unique anatomical feature of the human body, the frontal sinus morphology has been used for identification of unknown bodies with many techniques, mostly using 2D postero-anterior X-rays. With the increase of the use of Cone-Beam Computer Tomography (CBCT), the availability of this exam as ante-mortem records should be considered. The purpose of this study is to establish a new technique for frontal sinus identification through direct superimposition of 3D volumetric models obtained from CBCT exam, by testing two distinct situations. First, a reproducibility test, where two observers independently rendered models of frontal sinus from a sample 20 CBCT exams and identified them on each other's list. In the second situation, one observer tested the protocol and established on different exams of three individual. Using the open source DICOM viewer InVesallius^® for rendering, Mesh Lab^®, for positioning the models and CloudCompare for volumetric comparison, both observers matched cases with 100% accuracy and the level of coincidence in a identification situation. The uniqueness of the frontal sinus topography is remarkable and through the described technique, can be used in forensic as an identification method whenever both the sinus structure and antemortem computer tomography is available.     

Estimation of exposure dose from CBCT for prostate IMRT and approach to reduce local exposure dose

Intensity modulated radiation therapy (IMRT) requires a precise set-up for which 3D matching using cone beam computed tomography (CBCT) is useful. Because images are acquired before every irradiation, investigating the exposure dose is essential. Such studies have been reported, but fewer reports have attempted to compare the dose with those in other modalities, as we did in this study. The exposure doses for imaging using 3 devices, including on board imager(OBI) CBCT, were measured using a tough water phantom, a self-made phantom, and a radiophotoluminescence glass dosimeter. The highest measured value was observed on OBI CBCT: the exposure dose was 4.3 times higher at some measurement sites than that from CT. Because this phenomenon is derived from the projection angle, a localized increase in the exposure dose may be prevented by changing the projection angle on each acquisition. Because the exposure dose for OBI CBCT was the highest and acquisition is performed before every irradiation, procedural modification is necessary, such as minimizing acquisition and the use of ultrasonography to confirm urine retention.