Normal pancreatic volume assessment using abdominal computed tomography volumetry.

ABSTRACT: To determine the normal range of pancreatic volume (PV) in Chinese adults using computed tomography (CT) volumetry. To assess the relationships of PV with patient demographics and clinical parameters. To analyze the degree of correlation between PV values determined by manual segmentation and those calculated by formulas.A total of 240 adults (120 women, 120 men) between the ages of 18 and 79 years were reviewed. There were 6 groups of patients, with 40 patients in each decade regarding age. PV was segmented manually on computed tomography images slice by slice for each patient, and 2 formulas were used to calculate PV∗ and PV#.The mean PV was 77.44 ±â€Š19.11 cm3 (range from 28.55-138.15 cm3). PV was significantly correlated with height (r = 0.427, P < .001), weight (r = 0.525, P < .001), body mass index (r = 0.377, P < .001), the width of the first lumbar vertebral body (r = 0.166, P = .01), the transverse abdominal diameter (r = 0.455, P < .001), and the sagittal abdominal diameter (r = 0.456, P < .001). There was a negative correlation between PV and age (r = -0.209, P = .001). The correlation coefficients between PV and PV∗ and PV# were 0.676 and 0.376, respectively, with both P < .001.PV associated with patient demographics and clinical parameters. A more accurate and simpler formula should be used in the future to calculate and monitor changes in PV.

Clinically applicable artificial intelligence system for dental diagnosis with CBCT.

In this study, a novel AI system based on deep learning methods was evaluated to determine its real-time performance of CBCT imaging diagnosis of anatomical landmarks, pathologies, clinical effectiveness, and safety when used by dentists in a clinical setting. The system consists of 5 modules: ROI-localization-module (segmentation of teeth and jaws), tooth-localization and numeration-module, periodontitis-module, caries-localization-module, and periapical-lesion-localization-module. These modules use CNN based on state-of-the-art architectures. In total, 1346 CBCT scans were used to train the modules. After annotation and model development, the AI system was tested for diagnostic capabilities of the Diagnocat AI system. 24 dentists participated in the clinical evaluation of the system. 30 CBCT scans were examined by two groups of dentists, where one group was aided by Diagnocat and the other was unaided. The results for the overall sensitivity and specificity for aided and unaided groups were calculated as an aggregate of all conditions. The sensitivity values for aided and unaided groups were 0.8537 and 0.7672 while specificity was 0.9672 and 0.9616 respectively. There was a statistically significant difference between the groups (p = 0.032). This study showed that the proposed AI system significantly improved the diagnostic capabilities of dentists.

Vessel territory mapping after cerebral revascularization surgery using selective angiographic flat detector perfusion imaging.

The technical feasibility and diagnostic potential of angiographic flat-detector perfusion imaging technique, combining digital subtraction angiography with a flat-detector computed tomography steady-state perfusion imaging, was explored in patients treated with direct or indirect revascularization surgery. This short communication is about an imaging modality with great potential for evaluation, comparison and grading of vascular perfusion territory areas and anatomical location selectively perfused by direct and indirect cerebral bypasses.

Influence of mandibular positioning on the accuracy and reliability of linear measurements on cone beam CT using different voxels and two software programs / Influência do posicionamento mandibular na acurácia e confiabilidade de medidas lineares em tomografia computadorizada de feixe cônico utilizando diferentes voxels e dois softwares

Objetivo: este estudo avaliou a acurácia e confiabilidadedas medidas lineares em exames detomografia computadorizada de feixe cônico(TCFC), em dois softwares, utilizando diferentesvoxels e variando o posicionamento da mandíbula.Material e Métodos: 10 imagens de TCFC demandíbulas humanas com 25 pontos foram obtidas,usando diferentes protocolos de aquisição(0.250, 0.300, 0.400-mm voxels) e orientações damandíbula (centralizada, rotacionada 10° lateralmentepara direita e esquerda, inclinada 10° para cima e para baixo); 14 medidas foram realizadasnas reconstruções multiplanares nos softwares XoranCate OsiriX. Os achados foram comparadoscom as medidas físicas através de um paquímetrodigital. O teste ANOVA e o coeficiente de correlaçãoforam utilizados com p < 0,05. Resultados:não houve diferença estatisticamente significantequando as medidas foram comparadas em aquisiçõescom diferentes tamanhos de voxels emambos os softwares. A posição da mandíbula nãoinfluenciou nas medidas. Nenhuma diferença foiencontrada quando os valores foram comparadosentre os softwares e o paquímetro digital. Conclusão:as medidas lineares em ambos os softwaresforam confiáveis e acurados comparados a mensuraçãofísica em todos os protocolos. A acuráciae a confiabilidade das mensurações não influenciaramde acordo com as variações de posicionamentoda mandíbula.(AU)

Objective: this study evaluated the accuracy and reliability of linear measurements on cone beam CT (CBCT) scans in two software programs, using different voxels and varying mandible positioning. Material and methods: CBCT images of 10 human mandibles with 25 markers were obtained using different acquisition protocols (0.250, 0.300, 0.400-mm voxels) and mandible orientations (centered, rotated 10° laterally to right and left, tilted 10 up and down); fourteen measurements were carried out on the multiplanar reconstructions in XoranCat and OsiriX Lite software programs. The findings were compared to physical measurements using a digital caliper. ANOVA and correlation coefficient tests were used, at α = 0.05. Results: there was no statistically significant difference when the measurements were compared in acquisitions with different voxel sizes analysed in both software programs. Mandibular positioning changes did not influence the measurements. No differences were found when the values were compared between the software programs and the digital caliper. Conclusion: linear measurements in both programs were reliable and accurate compared with physical measurements when using all acquisition protocols. The accuracy and reliability of the measurements were not influenced by variations in the mandible positioning.(AU)

Prediction of microvascular invasion of hepatocellular carcinoma: value of volumetric iodine quantification using preoperative dual-energy computed tomography.

BACKGROUND: To investigate the potential value of volumetric iodine quantification using preoperative dual-energy computed tomography (DECT) for predicting microvascular invasion (MVI) of hepatocellular carcinoma (HCC). METHODS: This retrospective study included patients with single HCC treated through surgical resection who underwent preoperative DECT. Quantitative DECT features, including normalized iodine concentration (NIC) to the aorta and mixed-energy CT attenuation value in the arterial phase, were three-dimensionally measured for peritumoral and intratumoral regions: (i) layer-by-layer analysis for peritumoral layers (outer layers 1 and 2; numbered in close order from the tumor boundary) and intratumoral layers (inner layers 1 and 2) with 2-mm layer thickness and (ii) volume of interest (VOI)-based analysis with different volume coverage (tumor itself; VOIO1, tumor plus outer layer 1; VOIO2, tumor plus outer layers 1 and 2; VOII1, tumor minus inner layer 1; VOII2, tumor minus inner layers 1 and 2). In addition, qualitative CT features, including peritumoral enhancement and tumor margin, were assessed. Qualitative and quantitative CT features were compared between HCC patients with and without MVI. Diagnostic performance of DECT parameters of layers and VOIs was assessed using receiver operating characteristic curve analysis. RESULTS: A total of 36 patients (24 men, mean age 59.9 ± 8.5 years) with MVI (n = 14) and without MVI (n = 22) were included. HCCs with MVI showed significantly higher NICs of outer layer 1, outer layer 2, VOIO1, and VOIO2 than those without MVI (P = 0.01, 0.04, 0.02, 0.02, respectively). Among the NICs of layers and VOIs, the highest area under the curve was obtained in outer layer 1 (0.747). Qualitative features, including peritumoral enhancement and tumor margin, and the mean CT attenuation of each layer and each VOI were not significantly different between HCCs with and without MVI (both P >  0.05). CONCLUSIONS: Volumetric iodine quantification of peritumoral and intratumoral regions in arterial phase using DECT may help predict the MVI of HCC.

Vestibular Alveolar bone height measurement: Accuracy and Correlation between direct and indirect techniques.

Cone Beam Computed Tomography (CBCT) has modified the perspective of dentistry images, providing manipulable threedimensional images with a 1:1 patient:image ratio. Treatments and diagnosis are modified or corroborated by CBCT; however, its accuracy in thin structures such as cortical bone has been subjected to critical review. The aim of this study is to correlate the measurement of vestibular alveolar bone height using direct measurements and measurements performed with cone-beam tomographic images with standard (SD) voxel resolution. Thirty incisor and premolar teeth of patients undergoing open curettage were measured with a high-precision caliper and with Cone Beam Computed Tomography (CBCT) at an SD resolution of 0.16 mm voxels in a 3D Orthophos XG Sirona scanner. Intra-observer evaluation was performed using the intraclass correlation coefficient (ICC). Direct measurements and CBCT measurements were correlated using Pearson correlation (PCC). The mean difference between indirect and direct measurements was 3.15 mm. Paired t test and Pearson Correlation coefficient determined that all measurements differed statistically from each other with p<0.05. With the CT scanner and protocol used in this study, CBCT images do not enable accurate evaluation of vestibular alveolar bone height.

La tomografía de haz cónico (CBCT) ha modificado la perspectiva de la imagenología en odontología que brinda una imagen tridimensional manipulable con una relación 1:1, paciente: imagen. Los tratamientos y diagnósticos se ven modificados o corroborados por el CBCT; sin embargo, la exactitud que presenta en estructuras delgadas como las corticales óseas ha sido sometida a críticas. El objetivo fue correlacionar la medición de la altura del hueso alveolar vestibular mediante mediciones directas y las realizadas con imágenes tomográficas de haz cónico con resolución de vóxel estándar (SD). Treinta dientes incisivos y premolares de pacientes sometidos a un curetaje abierto se midieron con un calibrador de alta precisión y una tomografía computarizada de haz cónico (CBCT) a una resolución SD de 0,16 mm de vóxeles en un escáner 3D Orthophos XG Sirona. La evaluación intraobservador se realizó utilizando el coeficiente de correlación intraclase (ICC), y las mediciones directas y las mediciones CBCT se correlacionaron utilizando la correlación de Pearson (PCC). La diferencia media entre las mediciones indirectas y directas fue de 3,15 mm. La prueba t pareada y el Coeficiente de Correlación de Pearson determinaron que todas las mediciones fueron estadísticamente diferentes entre sí con una p <0.05. Con el escáner de TC y el protocolo utilizado en este estudio, las imágenes CBCT no permiten una evaluación precisa de la altura del hueso alveolar vestibular.

Vestibular Alveolar bone height measurement: Accuracy and Correlation between direct and indirect techniques / Medición de la altura del hueso alveolar vestibular: precisión y correlación entre técnicas directa e indirecta

ABSTRACT Cone Beam Computed Tomography (CBCT) has modified the perspective of dentistry images, providing manipulable threedimensional images with a 1:1 patient:image ratio. Treatments and diagnosis are modified or corroborated by CBCT; however, its accuracy in thin structures such as cortical bone has been subjected to critical review. The aim of this study is to correlate the measurement of vestibular alveolar bone height using direct measurements and measurements performed with conebeam tomographic images with standard (SD) voxel resolution. Thirty incisor and premolar teeth of patients undergoing open curettage were measured with a highprecision caliper and with Cone Beam Computed Tomography (CBCT) at an SD resolution of 0.16 mm voxels in a 3D Orthophos XG Sirona scanner. Intraobserver evaluation was performed using the intraclass correlation coefficient (ICC). Direct measurements and CBCT measurements were correlated using Pearson correlation (PCC). The mean difference between indirect and direct measurements was 3.15 mm. Paired t test and Pearson Correlation coefficient determined that all measurements differed statistically from each other with p<0.05. With the CT scanner and protocol used in this study, CBCT images do not enable accurate evaluation of vestibular alveolar bone height.

RESUMEN La tomografía de haz cónico (CBCT) ha modificado la perspectiva de la imagenología en odontología que brinda una imagen tridimensional manipulable con una relación 1:1, paciente: imagen. Los tratamientos y diagnósticos se ven modificados o corroborados por el CBCT; sin embargo, la exactitud que presenta en estructuras delgadas como las corticales óseas ha sido sometida a críticas. El objetivo fue correlacionar la medición de la altura del hueso alveolar vestibular mediante mediciones directas y las realizadas con imágenes tomográficas de haz cónico con resolución de vóxel estándar (SD). Treinta dientes incisivos y premolares de pacientes sometidos a un curetaje abierto se midieron con un calibrador de alta precisión y una tomografía computarizada de haz cónico (CBCT) a una resolución SD de 0,16 mm de vóxeles en un escáner 3D Orthophos XG Sirona. La evaluación intraobservador se realizó utilizando el coeficiente de correlación intraclase (ICC), y las mediciones directas y las mediciones CBCT se correlacionaron utilizando la correlación de Pearson (PCC). La diferencia media entre las mediciones indirectas y directas fue de 3,15 mm. La prueba t pareada y el Coeficiente de Correlación de Pearson determinaron que todas las mediciones fueron estadísticamente diferentes entre sí con una p <0.05. Con el escáner de TC y el protocolo utilizado en este estudio, las imágenes CBCT no permiten una evaluación precisa de la altura del hueso alveolar vestibular.

Cone-Beam Computed Tomography vs. Multi-Slice Computed Tomography in paleoimaging: where we stand.

Paleopathology and anthropology are fields of research which have benefited from the use of diagnostic imaging since its introduction in the clinical setting. The deriving discipline, that is, paleoimaging, has effectively employed several diagnostic techniques. However, while Multi-Slice Computed Tomography (MSCT) has found its role in paleoimaging, Cone-Beam Computed Tomography (CBCT), despite its several advantages with regard to MSCT, is still struggling to find a clear position in this field. The aim of our study is to evaluate the possible advantages CBCT could bring to paleoimaging. We describe the characteristics and role of CBCT in clinical applications, in forensic and legal medicine, and in paleopathology. We report the study of an ancient mandible by means of CBCT and MSCT, in order to compare the quality of the images in terms of spatial resolution. CBCT allows to obtain good quality images of mineralized tissues. Moreover, the possibility of imaging metallic manufacts makes the technique suitable for the study not only of bony remains, but also of museum and archaeological artifacts. Our study highlights the strengths of CBCT as a valid imaging technique for the study of ancient bone remains and manufacts. A revision of the current uses of CBCT is provided and gives insights into the possible role it can cover in bioarchaeological studies. Further evaluation is needed in terms of possible applications of this technique to paleopathology. We strongly encourage the use of CBCT in paleoimaging, and suggest a broader application of the technique to the study of archaeological samples.

Implementation of a modified quality assurance protocol for CBCT machines within UT health San Antonio School of Dentistry.

OBJECTIVES: To implement the quality control assurance protocol (including the re-establishment of baseline data from 2016) to monitor the stability of image quality of CBCT machines located within the UT Health San Antonio School of Dentistry. METHODS AND MATERIALS: Five CBCT machines ProMax 3D Mid® (Planmeca Oy, Helsinki, Finland), 3D Accuitomo XYZ Slice View Tomograph® (Model MCT-1, Type EX-1F8; Fushimi-ku, Kyoto: J. Morita Mfg. Corp), Veraviewepocs 3D (Model R100; Fushimi-ku, Kyoto: J. Morita Mfg. Corp), PreXion3D Excelsior® (PreXion, San Mateo, CA), and i-CAT FLX Series® (Imaging Sciences International, Hatfield, PA) were tested for Artifact, Contrast-to-Noise Ratio, Noise, Spatial Resolution, and Contrast Resolution using a custom insert configuration in the SEDENTEXCT IQ phantom. RESULTS: Four-scan benchmark mean values for Artifact, Contrast-to-Noise, Noise, Spatial Resolution, and Contrast Resolution were determined for the five machines tested with associated alert and action level thresholds calculated. CONCLUSION: This newly developed QA protocol established image quality baseline values. Recommended tests, frequency, and actions levels have been updated and control charts established for future trend analysis to enable proper implementation of a QA protocol monitoring CBCT machines at UT health San Antonio.

Comparing third molar root development staging in panoramic radiography, extracted teeth, and cone beam computed tomography.

This study aimed at performing and comparing third molar development staging in extracted teeth (EX), panoramic radiography (PAN), and cone beam computed tomography (CBCT). Extracted third molars (n = 158, 95 maxillary, 63 mandibular) from 102 patients (36 males, 66 females) having at least one preoperative PAN and one CBCT were studied. Third molar development staging was performed in PAN, EX, and CBCT using Gleiser et al. (1955) technique modified by Köhler et al (1994). A polytomous logistic regression model was used to compare the staging performed in EX and CBCT with the gold standard staging in PAN. The pair-wise stage comparisons between third molar modalities revealed 63.3% equal staging. In all other comparisons, a maximum difference of one stage was detected. No statistically significant differences between the three staging modalities were detected (p = 0.26). The comparison between EX and PAN staging revealed higher similarity (p = 0.98 in stages 5-10) than the comparison between CBCT and PAN staging (p = 0.81 in stages 5, 7, and 9, and p = 0.80 in stages 6, 8, and 10). The studied third molar staging technique originally designed in PAN can be applied for third molar staging EX and in CBCT.

Volumetric segmentation of glioblastoma progression compared to bidimensional products and clinical radiological reports.

BACKGROUND: Detection of progression is clinically important for the management of glioblastoma. We sought to assess the accuracy of clinical radiological reporting and measured bidimensional products to identify radiological glioblastoma progression. The two were compared to volumetric segmentation. METHODS: In this retrospective study, we included 106 patients with histopathologically verified glioblastomas and two separate MRI scans obtained before surgery. Bidimensional products based on measurements on the axial slice with the largest tumor area were calculated, and growth estimations from the clinical radiological reports were retrieved. The two growth estimations were compared to manual volumetric segmentations. Inter-observer agreement using the bidimensional product was assessed using Kappa-statistics and by calculating the difference between two neuroradiologist in percentage change of the bidimensional product for each tumor. RESULTS: Clinical radiological reports and bidimensional products showed fairly equal accuracy when compared to volumetric segmentation with an accuracy of 67% and 66-68%, respectively. There was a difference in median volume increase of 6.9 mL (2.4 vs 9.3 mL, p < 0.001) between tumors evaluated as stable and progressed based on the clinical radiological reports. This difference was 8.1 mL (2.0 vs 10.1 ml, p < 0.001) when using the bidimensional products. The bidimensional product reached a moderate inter-observer agreement with a Kappa value of 0.689. For 32% of the tumors, the two neuroradiologists calculated a difference of more than 25% using bidimensional products. CONCLUSIONS: Clinical radiological reporting and the bidimensional product exhibit similar accuracy. The bidimensional product has moderate inter-observer agreement and is prone to underestimating tumor progression, as an average glioblastoma had to grow 10 mL in order to be classified as progressed. These findings underline the assumption that one should try to move towards volumetric assessment of glioblastoma growth in the future.

Impact of use of optical surface imaging on initial patient setup for stereotactic body radiotherapy treatments.

PURPOSE: To evaluate the effectiveness of surface image guidance (SG) for pre-imaging setup of stereotactic body radiotherapy (SBRT) patients, and to investigate the impact of SG reference surface selection on this process. METHODS AND MATERIALS: 284 SBRT fractions (SG-SBRT = 113, non-SG-SBRT = 171) were retrospectively evaluated. Differences between initial (pre-imaging) and treatment couch positions were extracted from the record-and-verify system and compared for the two groups. Rotational setup discrepancies were also computed. The utility of orthogonal kVs in reducing CBCT shifts in the SG-SBRT/non-SG-SBRT groups was also calculated. Additionally, the number of CBCTs acquired for setup was recorded and the average for each cohort was compared. These data served to evaluate the effectiveness of surface imaging in pre-imaging patient positioning and its potential impact on the necessity of including orthogonal kVs for setup. Since reference surface selection can affect SG setup, daily surface reproducibility was estimated by comparing camera-acquired surface references (VRT surface) at each fraction to the external surface of the planning CT (DICOM surface) and to the VRT surface from the previous fraction. RESULTS: The reduction in all initial-to-treatment translation/rotation differences when using SG-SBRT was statistically significant (Rank-Sum test, α = 0.05). Orthogonal kV imaging kept CBCT shifts below reimaging thresholds in 19%/51% of fractions for SG-SBRT/non-SG-SBRT cohorts. Differences in average number of CBCTs acquired were not statistically significant. The reference surface study found no statistically significant differences between the use of DICOM or VRT surfaces. CONCLUSIONS: SG-SBRT improved pre-imaging treatment setup compared to in-room laser localization alone. It decreased the necessity of orthogonal kV imaging prior to CBCT but did not affect the average number of CBCTs acquired for setup. The selection of reference surface did not have a significant impact on initial patient positioning.

Fiducial markers visibility and artefacts in prostate cancer radiotherapy multi-modality imaging.

BACKGROUND: In this study, a novel pelvic phantom was developed and used to assess the visibility and presence of artefacts from different types of commercial fiducial markers (FMs) on multi-modality imaging relevant to prostate cancer. METHODS AND MATERIALS: The phantom was designed with 3D printed hollow cubes in the centre. These cubes were filled with gel to mimic the prostate gland and two parallel PVC rods were used to mimic bones in the pelvic region. Each cube was filled with gelatine and three unique FMs were positioned with a clinically-relevant spatial distribution. The FMs investigated were; Gold Marker (GM) CIVCO, GM RiverPoint, GM Gold Anchor (GA) line and ball shape, and polymer marker (PM) from CIVCO. The phantom was scanned using several imaging modalities typically used to image prostate cancer patients; MRI, CT, CBCT, planar kV-pair, ExacTrac, 6MV, 2.5MV and integrated EPID imaging. The visibility of the markers and any observed artefacts in the phantom were compared to in-vivo scans of prostate cancer patients with FMs. RESULTS: All GMs were visible in volumetric scans, however, they also had the most visible artefacts on CT and CBCT scans, with the magnitude of artefacts increasing with FM size. PM FMs had the least visible artefacts in volumetric scans but they were not visible on portal images and had poor visibility on lateral kV images. The smallest diameter GMs (GA) were the most difficult GMs to identify on lateral kV images. CONCLUSION: The choice between different FMs is also dependent on the adopted IGRT strategy. PM was found to be superior to investigated gold markers in the most commonly used modalities in the management of prostate cancer; CT, CBCT and MRI imaging.

Intrafraction 4D-cone beam CT acquired during volumetric arc radiotherapy delivery: kV parameter optimization and 4D motion accuracy for lung stereotactic body radiotherapy (SBRT) patients.

PURPOSE: Elekta XVI 5.0 allows for four-dimensional cone beam computed tomography (4D CBCT) image acquisition during treatment delivery to monitor intrafraction motion. These images can have poorer image quality due to undersampling of kV projections and treatment beam MV scatter effects. We determine if a universal intrafraction preset can be used for stereotactic body radiotherapy (SBRT) lung patients and validate the accuracy of target motion characterized by XVI intrafraction 4D CBCT. METHODS: The most critical parameter within the intrafraction preset is the nominal AcquisitionInterval, which controls kV imaging acquisition frequency. An optimal value was determined by maximizing the kV frame number acquired up to 1000 frames, typical of pretreatment 4D CBCT. CIRS motion phantom intrafraction phase images for 16 SBRT beams were obtained. Mean target position, time-weighted standard deviation, and amplitude for these images as well as target motion for three SBRT lung patients were compared to respective pretreatment 4D CBCTs. Evaluation of intrafraction 4D CBCT reconstruction revealed inclusion of MV only images acquired to remove MV scatter effects. A workaround to remove these images was developed. RESULTS: AcquisitionInterval of 0.1°/frame was optimal. The number of kV frames acquired was 567-1116 and showed strong linear correlation with beam monitor unit (MUs). Phantom target motion accuracy was excellent with average differences in target position, standard deviation and amplitude range of ≤0.5 mm. Target tracking for SBRT patients also showed good agreement. Evaluation of phase sorting wave forms showed that inclusion of MV only images significantly impacts intrafraction image reconstruction for patients and use of workaround is necessary. CONCLUSIONS: A universal intrafraction imaging preset can be used safely for SBRT lung patients. The number of kV projections with MV delivery parameters varies; however images with fewer kV projections still provided accurate target position information. Impact of the reconstruction workaround was significant and is mandated for all 4D CBCT intrafraction imaging performed at our institution.

Image quality improvement for medium and large field of view Elekta XVI scans.

Cone-beam computed tomography (CBCT) has become the standard imaging technique for many sites treated with Radiotherapy. The Elekta X-ray Volumetric Imaging (XVI) system allows for the acquisition of CBCTs with three different diameters; small (27 cm), medium (41 cm) and large (50 cm) (Elekta in XVI Corrective Maintenance Manual R5.0, Elekta, Stockholm, 2013). Images are used to ensure accurate patient positioning as well as checking for changes in the patient contour or internal geometry, and image quality must be high enough to achieve these goals. This paper describes two simple adjustments which can lead to improved image quality for medium and large field of view (MFOV and LFOV) scans. The first involves measuring a default distance in the XVI software (kV Source to Detector Distance) to improve spatial resolution and geometric scaling of both MFOV and LFOV scans. The second involves correcting a uniformity issue seen at our centre with LFOV scans, allowing us to use this FOV for assessing patient contour changes on large patients. The implementation and effects of both adjustments are explored in this paper, and workflows are proposed for optimising both parameters.

Investigation of a Novel Decision Support Metric for Head and Neck Adaptive Radiation Therapy Using a Real-Time In Vivo Portal Dosimetry System.

In adaptive radiation therapy of head and neck cancer, any significant anatomical changes observed are used to adapt the treatment plan to maintain target coverage without elevating the risk of xerostomia. However, the additional resources required for adaptive radiation therapy pose a challenge for broad-based implementation. It is hypothesized that a change in transit fluence is associated with volumetric change in the vicinity of the target and therefore can be used as a decision support metric for adaptive radiation therapy. This was evaluated by comparing the fluence with volumetric changes in 12 patients. Transit fluence was measured by an in vivo portal dosimetry system. Weekly cone beam computed tomography was used to determine volume change in the rectangular region of interest from condyloid process to C6. The integrated transit fluence through the region of interest on the day of the cone beam computed tomography scan was calculated with the first treatment as the baseline. The correlation between fluence change and volume change was determined. A logistic regression model was also used to associate the 5% region of interest volume reduction replanning trigger point and the fluence change. The model was assessed by a chi-square test. The area under the receiver-operating characteristic curve was also determined. A total of 46 pairs of measurements were obtained. The correlation between fluence and volumetric changes was found to be -0.776 (P value <.001). The negative correlation is attributed to the increase in the photon fluence transport resulting from the volume reduction. The chi-square of the logistic regression was found to be 17.4 (P value <.001). The area under the receiver-operating characteristic curve was found to be 0.88. Results indicate the change in transit fluence, which can be measured without consuming clinical resources or requiring additional time in the treatment room, can be used as a decision support metric for adaptive therapy.

3D cone-beam CT of the ankle using a novel twin robotic X-ray system: Assessment of image quality and radiation dose.

PURPOSE: To evaluate image quality (IQ) and radiation dose in cone-beam computed tomography (CBCT) of the ankle using a novel twin robotic X-ray system. METHOD: We examined 16 cadaveric ankles with standard-dose (FD) and low-dose (LD) protocols using the new system's CBCT mode. For comparison, we performed multi-slice CT imaging (MSCT) with a clinical protocol. Three radiologists assessed IQ, noise and artifacts in bone and soft tissue on a five-point Likert scale (1= poor IQ; strong noise or artifacts; 5= excellent IQ; minimal noise or artifacts). Volume CT dose indices (CTDIvol) were calculated for radiation dose comparison between CBCT and MSCT. RESULTS: Overall IQ was described as very good or excellent by reader 1/2/3 in 62.5/87.5/56.3% of LD, 87.5/87.5/81.3% of FD and 100/87.5/87.5% of MSCT studies. Readers agreed that IQ was better in MSCT than LD (R1/R2/R3; p ≤ 0.008), two also found advantages of MSCT over FD (R1/R3; p ≤ 0.034). Soft tissue noise and artifacts were stronger in FD (all p ≤ 0.002) and LD (all p ≤ 0.001). In bone, artifacts and noise were also more severe in LD (all p < 0.001) and FD (all p ≤ 0.003). CTDIvol for clinical MSCT scans without dose modulation (15.0 ± 0.0 mGy) were higher than for FD (5.3 ± 1.0 mGy) and LD studies (2.9 ± 0.6 mGy; both p < 0.001). CONCLUSIONS: Despite MSCT providing better overall IQ than the twin robotic X-ray system's CBCT mode, both cone-beam protocols offer very good IQ in most studies and are suitable for clinical ankle imaging. Standard-dose and especially low-dose CBCT studies deliver up to five times less radiation dose than MSCT imaging.

Cone-beam computed tomography airway measurements: Can we trust them?

INTRODUCTION: Pharyngeal airway space (PAS) assessment has been used in the past for a better understanding of orthodontic and surgical outcomes; however, this analysis could be unreliable. Our objective was to evaluate possible changes in the PAS reading in the same patient from their consecutive cone-beam computed tomography (CBCT) scans. METHODS: We evaluated a total of 27 patients' CBCT scans obtained at 2 time points with the use of a standardized acquisition protocol. The mean age at T0 was 31 years (range 17-62 years) and the follow-up records (T1) were taken after 4-6 months. Dolphin Imaging software was used to measure the volumes of the nasopharynx, oropharynx, and hypopharynx. We also evaluated the craniocervical position with the use of a lateral cephalogram. RESULTS: The variables exhibited high intraclass correlation coefficients (ICCs) when measuring the same CBCT scan twice (T0 and T0). However, The ICC between the measurements performed on the first and second CBCT scans (T0 and T1) showed that the only variable with high reproducibility between the 2 scans was cranial base, with an ICC >0.97. Average differences of 682.1 mm3, 2255.3 mm3, and 517.4 mm3 were found for the nasopharynx, oropharynx, and hypopharynx, respectively. Regarding the cephalometric angles, average differences between T0 and T1 scans were 0.6°, 2.7°, and 0.4° for OPT.CVT, OPT.SN, and cranial base, respectively. CONCLUSIONS: Different CBCT exams with equal scanning and patient positioning protocols can result in different 3D PAS readings. A more careful interpretation of CBCT volumetric data to achieve adequate conclusions of the clinical outcomes is necessary.

The growing concern of radiation dose in paediatric dental and maxillofacial CBCT: an easy guide for daily practice.

OBJECTIVES: To provide an indication-based and scanner-specific radiation dose and risk guide for paediatric patients undergoing dental and maxillofacial cone beam computed tomography (CBCT) examinations. METHODS: Five commercially available scanners were simulated in EGSnrc Monte Carlo (MC) code. Dedicated, in-house built, head and neck voxel models, each consisting of 22 segmented organs, were used in the study. Organ doses and life attributable risk (LAR) for cancer incidence were assessed for males and females, aged 5 to 14 years old, for every clinically available protocol: central upper and lower incisors, upper and lower premolars, upper and lower jaws, cleft palate, temporal bone, sinus, dentomaxillofacial complex, and face and skull imaging. Dose results were normalised to the x-ray tube load (mAs) and logarithmic curves were fit to organ dose and risk versus age data. RESULTS: Females demonstrated higher LAR values in all cases. A well-established dose decreasing pattern with increasing age-at-exposure was observed. Central upper incisor protocols were those with the lowest risk, contrary to skull protocols which provided the highest LAR values. Salivary glands and oral mucosa were the highest irradiated organs in all cases, followed by extrathoracic tissue (ET) in protocols where the entire nasal cavity was inside the primary field. The dose to thyroid was considerably high for younger patients. CONCLUSIONS: This work provides an extensive dose assessment guide for 5 dental CBCTs, enabling detailed dose assessment for every paediatric patient. KEY POINTS: • Radiation dose concerns due to the growing use of paediatric dental and maxillofacial CBCT underline the need for justification that should in part be based on radiation exposure in radiology. • Patient-specific dose calculations based on Monte Carlo simulations and head-neck paediatric voxel models overcome the limitations of conventional thermoluminescent dosimeter (TLD) dosimetry and provide proper guidance for justification of CBCT exposures. • Monte Carlo simulations with head-neck models reveal an organ dose and radiation risk decreasing pattern with increasing age at exposure, and with decreasing size of the scanning volume of interest (field of view).

Coronary CT angiography radiation dose trends: A 10-year analysis to develop institutional diagnostic reference levels.

PURPOSE: To develop institutional diagnostic reference levels (IDRL) for coronary CT angiography (CCTA) according to patient size by analyzing radiation dose changes over the past 10 years. MATERIALS AND METHODS: This IRB approved retrospective investigation analyzed radiation dose data from CCTA between 2007 and 2016 at our institution. Annual trends in radiation dose were described for each scanner type and scanning mode. Radiation levels were analyzed for normorhythmic patients, patients with prior coronary artery bypass grafting (CABG), arrhythmia, and according to patient size and tube voltage. Median, and quartile values for volume CT dose index (CTDIvol), dose-length product (DLP), and size-specific dose estimate (SSDE) were calculated. Wilcoxon rank-sum test and Kruskal Wallis test were performed to assess the significance of quantitative data. RESULTS: 35,375 examinations from 33,317 patients (median age, 58 [50-66] years; male patients, 21,087 [58.7%]) were analyzed. CTDIvol, DLP, and SSDE significantly decreased by 9.0%, 30.8%, and 40.1% (all P < 0.05) for all examinations, respectively. All radiation dose metrics progressively decreased across scanning modes (especially retrospectively ECG-gated spiral and prospectively ECG-triggered high-pitch spiral acquisition mode), but did not significantly change across scanners in the last 6 years. CTDIvol and DLP increased with patient size when water-equivalent diameters were >19 cm for normorhythmic and CABG patients. In arrhythmic patients, CTDIvol increased progressively with water-equivalent diameters across all groups. CONCLUSION: CCTA radiation dose has progressively decreased in the past decade except in patients with prior CABG and arrhythmia. Size-specific IDRLs may optimize radiation utilization in these patients going forward.