Somatom Definition AS Research Articles

Evaluation of computed tomography anode voltage in clinical application: the influence of profiled filters

Monitoring of operational parameters of X-ray diagnostic equipment, including computer tomographs, is mandatory during acceptance and periodic tests in medical organizations. The importance of control of anode voltage of X-ray radiator is described (as one of the main technical parameters in diagnostic tests of patients, which can influence the quality of visualization and safe operation of the equipment). Anode voltage is evaluated by non-invasive methods using universal dosimeters in the user mode of equipment operation. The influence of profiled filters of Somatom Definition AS, SOMATOM go.All (Siemens, Germany) scanners on the accuracy of anode voltage measurement was investigated. The tests were conducted in clinic conditions without partial removal of the gantry (a structural element of the tomograph, inside which the system “X-ray emitter – detector” is located) and connection to the high-voltage circuit of the device. The distance between the sensitive elements of the measuring device and the displacement of the center of the sensing area relative to the position of the central axis of the X-ray beam of computed tomography scanner were taken into account. Normalized curves of kerma values, anode voltage values and their approximating analytical functions were obtained using a Piranha R&F/M 657 universal dosimeter (RTI Electronics AB, Sweden) at its displacement relative to the laser centralizer of computed tomography scanner. Based on the scheme for noninvasive estimation of anode voltage value, a formula of the relative deviation of the measured value of the anode voltage associated with the presence of a profiled filter at the output of the X-ray emitter of the tomograph and the displacement of the center point of the sensitive area of the measuring device relative to the central axis of the X-ray beam of the tomograph is obtained. The validity of the data based on the formula is confirmed experimentally. The results of the study will be helpful to technical specialists who maintain or control the X-ray computed tomography operating parameters.

Rainbow trout (Oncorhynchus mykiss, Walbaum 1792) adenocarcinoma investigation with various diagnostic imaging techniques.

Diagnostic imaging techniques provide a new aspect of the ante-mortem and post-mortem diagnostics in fish medicine. Ultrasonography, computed tomography (CT) and magnetic resonance imaging (MRI) can provide more information about the internal organs and pathognomic lesions. The authors used diagnostic imaging techniques to evaluate and describe the neoplastic malformation in a 3-year-old female rainbow trout (Oncorhynchus mykiss). The fish was examined with Siemens Somatom Definition AS + CT scanner and Siemens Biograph mMR scanner. The animal was lethargic and showed anorectic signs and muscular dystrophy. During the post-mortem investigation, histopathology and immunohistochemistry were also performed allowing us to identify the neoplasms. The results showed a large soft tissue mass in the first mid-intestine segment, which proved to be an adenocarcinoma. This subsequently led to digestion problems and absorption disorders. Immunohistochemically, neoplastic cells of carcinoma revealed E-cadherin and pancytokeratin positivity. This is the first study to report the use of MRI and CT for studying gastrointestinal adenocarcinoma in rainbow trout.

Comparison between manual-calculated and IndoseCT-calculated SSDE based on Deff and Dw methods on truncated CT images

IntroductionSize-specific dose estimation (SSDE) is suggested for accurate measurement of CT dose. Various methods have been developed for SSDE calculation by both manual and automated methods. However, truncation artefact may affect the specific size determination and SSDE calculation. In this article, we evaluate how truncation affects measurements of SSDE and compare the manual SSDE measurement based on individual sizes (effective diameter, Deff and water equivalent diameter, DW) with the automated calculation using IndoseCT software on truncated CT images. MethodsA phantom study was conducted using Siemens SOMATOM Definition AS + CT scanner with two CTDI phantoms of different sizes, 22 cm and 32 cm. Phantom images were acquired by varying the phantom positioning to simulate truncation percentages (TP) of 5%, 10%, 15%, and 20%. The SSDE values were manually calculated based on the Deff and Dw methods (AAPM, 2014). SSDE was also calculated automatically using IndoseCT software (Version 20 b) and compared with manual calculation. The percentage error due to different TP was calculated in comparison to the non-truncated image (TP 0%). The errors due to truncation on SSDE calculation was also compared between both manual and automated methods. Statistical analysis was carried out to determine the statistical differences and correlation. ResultsThe findings show that Deff for non-truncated image yields better results with lower percentage errors (mean PEmanual = 0.75% and mean PEautomated = 0.14%) as compared to Dw (mean PEmanual = 6.11% and mean PEautomated = 5.81%). There is a positive strong correlation between percentage error and truncation percentage. There are strong positive correlations between TP and percentage error, PE (r = 0.96 and r = 0.94) in determination of SSDEDeff and SSDEDw, respectively. Deff approach resulted higher percentage error as compared to Dw. ConclusionTruncation is strongly correlated with SSDE calculation, and therefore correction for truncation artefact is crucial to minimise error in SSDE measurement. The automated calculation of SSDE can be confidently replaced the manual method in both Deff and Dw approaches to ensure rapid and accurate SSDE measurement.

Influence of Contrast Media Temperature and Concentration on Patient Comfort and Safety in Computed Tomography: CATCHY II Trial.

Previous research on the necessity to reduce the viscosity of contrast media (CM) by either prewarming CM before injection during computed tomography (CT) or by using less concentrated CM has yielded conflicting results. In addition, there is limited evidence on patient comfort. The aim of the study was to examine if prewarming CM, with varying CM concentrations, is superior to CM at room temperature, with respect to patient comfort and safety in CT. All elective patients scheduled for contrast-enhanced CT scans at Maastricht University Medical Center+ between October 27, 2021 and October 31, 2022 were eligible for inclusion when a questionnaire evaluating patient comfort was completed. This 1-year period was divided into 4 intervals (4 groups): group 1 (370 mg I/mL, 37°C), group 2 (370 mg I/mL, room temperature), group 3 (300 mg I/mL, 37°C), and group 4 (300 mg I/mL, room temperature). All CT scans were performed using state of the art equipment (Siemens Healthineers; SOMATOM Force and SOMATOM Definition AS, Forchheim, Germany). Contrast media injections were performed using a dual-head power injector (Stellant; Bayer Healthcare, Berlin, Germany) and individualized to body weight and/or tube voltage, depending on the CM protocols. After the CT scan, patients completed a questionnaire covering the primary outcomes comfort, pain, and adverse events such as feelings of heat, nausea, vomiting, itchiness, urticaria, difficulty breathing, dizziness, goosebumps, or an odd taste. Technicians were asked to report any adverse events, including extravasation and allergic-like reactions. The secondary outcome involved attenuation (in Hounsfield unit, HU), which was evaluated by assessing the HU of the coronary arteries for vascular CT, and liver enhancement in portal venous CT. The Kruskal-Wallis test was used for continuous scale outcomes and χ 2 tests for examining adverse events. Results showed no significant differences examining comfort score ( P = 0.054), pain sensation ( P = 0.469), extravasation ( P = 0.542), or allergic-like reaction ( P = 0.253). Significant differences among the 4 groups were found with respect to heat sensation and dizziness ( P = 0.005 and P = 0.047, respectively), showing small effect sizes. All other adverse effects showed no significant results. No significant differences were observed in coronary attenuation among the 4 groups in coronary CT angiography ( P = 0.113). When analyzing attenuation in portal venous CT scans, significant differences were found among the 4 groups ( P = 0.008). Administrating prewarmed CM is nonsuperior compared with CM at room temperature in relation to patient comfort and safety, regardless of CM concentration. These findings suggest that prewarming CM before usage is unnecessary, which will improve the efficiency of daily clinical workflow and brings environmentally friendly benefits.

Flat panel CT versus multidetector CT in skull base imaging: are there differences in image quality?

BackgroundPurpose of this study was to compare image quality of the skull base in standard 20s protocol flat panel computed tomography (FPCT) with the new time and dose improved 10s protocol as well as with 128 slice multidetector computed tomography (MDCT).Methods10 whole skull preparations were scanned with either 128 slice MDCT(SOMATOM Definition AS+, Siemens, Erlangen) or FPCT (AXIOM-Artis, Siemens, Erlangen) using 10s or 20s protocol.ResultsFPCT provides significantly better image quality and improved delimitation of clinically relevant structures in the anterior, temporal and posterior skull base compared to 128 slice MDCT. The 20s FPCT protocol yielded best delimitability of evaluated skull base structures. However, the shorter, dose saving 10s FPCT protocol was still significantly superior to 128 slice MDCT regarding delimitability of skull base structures and additionally showed no significant inferiority compared with the 20s FPCT protocol.ConclusionsThe 10s FPCT protocol yields a significantly better image quality at a comparable radiation dose exposure in imaging skull base structures compared to MDCT.Trial registration371/2017BO2.

Dose development in sinonasal imaging over the last decade – a retrospective patient study

BackgroundComputed tomography (CT) has become the primary imaging modality for visualization of the paranasal sinuses. In this retrospective, single center patient study the radiation dose development in the past 12 years in CT imaging of the paranasal sinuses was assessed.MethodsThe computed tomography dose index (CTDIVol) and dose length product (DLP) of a total of 1246 patients (average age: 41 ± 18 years, 361 females, 885 males) were evaluated, who received imaging of the paranasal sinuses either for chronic sinusitis diagnostic, preoperatively or posttraumatically. Scans were performed on three different CT scanners (Somatom Definition AS, Somatom Definition AS+, Somatom Force, all from Siemens Healthineers) and on one CBCT (Morita) ranging from 2010 to 2022. Reconstruction techniques were filtered back projection and three generations of iterative reconstruction (IRIS, SAFIRE, ADMIRE, all from Siemens Healthineers). Group comparisons were performed using either parametrical (ANOVA) or non-parametrical tests (Kruskal-Wallis Test), where applicable.ResultsOver the past 12 years, there was a 73%, 54%, and 66% CTDIVol reduction and a significant (p < 0.001) 72%, 33%, and 67% DLP reduction in assessing the paranasal sinuses for chronic sinusitis, preoperatively and posttraumatically, respectively.ConclusionTechnological developments in CT imaging, both hardware and software based, have led to a significant reduction in dose exposure in recent years. Particularly in imaging of the paranasal sinuses, the reduction of radiation exposure is of great interest due to the often young patient age and radiation-sensitive organs in the area of radiation exposure.

Assessment of Utility of Computed Tomography Pulmonary Angiography in Pulmonary Embolism

Background: Among all the available diagnostic tools, computed tomography (CT) is the preferred diagnostic tool for clinically suspected pulmonary embolism (PE) cases. Further, with the development of multi–detector row CT (MDCT) technology, previous limitations of CT have been overcome effectively. For patients with clinical suspicion of PE, MDCT pulmonary angiography has become the first line of modality for the diagnosis. Aims and Objectives: To evaluate various common observations of CT pulmonary angiography (CTPA) in suspected cases of PE that could accurately determine the choice of management. Materials and Methods: Fifty patients with clinically suspected PE referred to the department of Radiodiagnosis for CTPA from various departments were studied in the cross-sectional study. CT images were obtained with a SIEMENS 64-slice multi-detector CT scanner (somatom definition AS). Images were reconstructed into 3D, axial, coronal, sagittal maximum intensity projection sections, and volume rendering techniques. The axial as well as reformatted coronal and sagittal images were evaluated. Results: The incidence of PE was 52%. The incidence of PE was highest in patients older than 60 years (30.8%) and males (30.3%; p=0.662). The most common symptoms evoking a suspicion of pulmonary embolism were dyspnea (69.2%), followed by chest pain (15.4%), cough (11.5%), and hemoptysis (3.8%). Out of 26 patients who had PE, 61.5% had right ventricular enlargement. DVT (23.1%) was the most common past history. The majority of the patients had thrombus in the right main pulmonary artery (21.1 %), followed by the left main pulmonary artery (19.3 %). Conclusion: In clinically suspected cases of PE, MDCT pulmonary angiography was a useful diagnostic tool. CTPA is the modality of choice for its rapid, minimally invasive, and well-tolerated nature.

Morphometric Study of Lumbar Spinal Canal Dimensions in Bosnia and Herzegovina Population.

The lumbar spinal canal consists of 5 interconnected lumbar vertebrae through which the final part of the spinal cord passes and the lumbar and sacral spinal nerves that form the cauda equina. The lumbar canal stenosis can directly affect neurological symptoms and pain in the lumbar region and lower extremities. Due to the frequency of such symptoms, lumbar stenosis has been the subject of research around the world. The objective of this study was to measure, analyze and compare the mediosagital and interpeduncular diameters of the lumbar spinal canal in the population of Bosnia and Herzegovina to other populations around the world. We conducted a retrospective descriptive study on patients (n=200) who underwent Multi-slice computer tomography (MSCT) performed on a 40-slice CT scanner (Siemens Somatom Definition AS) for lumbar pain between January 1, 2013 and December 31, 2014. Age, gender, midsagittal (MSG) and interpeduncular (IP) diameters of the lumbar spine were recorded for each patient. Results of our study show that the largest MSG diameter is at L1 level for both sexes, with an average length of 19,06mm, and the smallest at L3 level, with an average length of 16,66mm. Our study shows that the MSG diameter is significantly larger in females than males on all levels from L1 to L5. In both sexes, MSG diameter shows the form of an hourglass with narrowing at L3 level. IPD is largest at L5 level for both sexes, with an average length of 31,94mm, and the smallest average length at L1 level, at 24,78mm. IPD diameter is significantly larger in males than females on all levels from L1 to L5. IPD shows a tendency of growth from L1 to L5 in both sexes. There were significant differences in the dimensions of the lumbar spine canal between female and male patients. We found significant difference in MSG and IP diameters measurements between Bosnian and Herzegovinian population compared to other populations. The dimensions of the lumbar canal provide a baseline of normative data for the evaluation of patients presenting with lower back pain and lumbar canal stenosis in study population.

Combination of vertebral bone quality scores from different magnetic resonance imaging sequences improves prognostic value for the estimation of osteoporosis

Background ContextRecent findings revealed a correlation between vertebral bone quality based on T1-weighted (VBQT1) magnetic resonance imaging (MRI) and volumetric bone mass density (vBMD) measured using quantitative computerized tomography. The coherence of VBQ for other MRI sequences, such as T2 or short tau inversion recovery (STIR), has not been examined. The combination of different VBQs has not been studied. PurposeThe aims of the study were to confirm the correlation between VBQT1 and vBMD and to examine VBQs from other MRI sequences and their combination with vBMD. Study Design/SettingThis was a retrospective cross-sectional study. Patient SampleThe sample consisted of patients older than 18 years, who received treatment at a level-one university spine center of the German Spine Society for degenerative or traumatic reasons in 2017–2021. Outcome MeasuresThe outcome measures were the correlation of VBQs from different MRI sequences with vBMD and the association of VBQs with osteopenia/osteoporosis. MethodsPatients’ VBQ was calculated based on the signal intensities of the vertebral bodies L1–4 in T1-, T2-, and STIR-weighted MRI. The VBQ was standardized according to the signal intensity of the cerebrospinal fluid. The vBMD was determined using data from a calibrated scanner (SOMATOM Definition AS+) and processed with CliniQCT (Mindways Software, Inc., USA). Groups were divided according to vBMD into the following groups: (I) osteoporosis/osteopenia (< 120 mg/m3) and (II) healthy (≥120 mg/m3). An analysis of the correlation between various VBQs and vBMD as well as receiver operating characteristic (ROC) and binary regression analyses were performed for the prediction of osteoporosis/osteopenia. ResultsWe included 136 patients (women: 56.6%) in the study (69.7 ± 15.0 years). According to vBMD, 108 patients (79.4%) had osteoporosis/osteopenia. Women were affected significantly more often than men (p = .045) and had significantly higher VBQT1 and VBQT2 values than men (VBQT1: p = .048; VBQT2: p = .013). VBQT1 and VBQT2 values were significantly higher in patients with osteoporosis/osteopenia than in healthy persons (VBQT1: p<.001; VBQT2: p = .025). VBQT1 and VBQT2 were significantly negatively correlated with vBMD with a moderate effect size (p<.001), while VBQSTIR was not significantly correlated with vBMD, although it showed a positive coherence. The combination of different VBQs in terms of VBQT1 × VBQT2 / VBQSTIR distinctly increased the effect size of the negative correlation with vBMD compared to VBQ alone. A cutoff value for VBQT1 × VBQT2 / VBQSTIR of 2.9179 achieved a sensitivity of 80.0%, a specificity of 75.0%, and an area under the curve (AUC) of 0.775 for the determination of osteoporosis. The mathematical model derived from the binary logistic regression showed an excellent AUC of 0.846. ConclusionsThis study confirms a significant correlation between VBQT1 and vBMD. The combination of VBQs from different MRI sequences enhances the prognostic value of VBQ for the determination of osteoporosis. While safe clinical application of VBQ for the determination of osteoporosis requires further validation, VBQ might offer opportunistic estimation for further diagnostics.

Truncation Effects on Effective Diameter Measurement for Size-specific Dose Estimation in Computed Tomography (CT) Imaging

The determination of size specific dose estimation (SSDE) has been proposed for accurate CT dose assessment. The SSDE introduction has prompted numerous manufacturers and researchers to develop various methodologies that have progressed from manual to automated methods in SSDE determination. Few studies reported on truncation effects with respect to specific size and SSDE determination and CT manufacturers are yet to incorporate truncation correction in their system [1,2].&#x0D; This study aimed to evaluate the effects of truncation artifacts on the measurement of effective diameter (Deff) and SSDE in CT imaging. A phantom study was performed using CTDI phantom of different diameters, 22 and 32 cm with Siemens SOMATOM Definition AS+ CT scanner. Phantom images of different truncation percentage (TP) of 5%, 10%, 15%, and 20% were simulated and acquired. The Deff and SSDE were determined based on the displayed CTDIvol, and the AAPM correction factor table was used to calculate the SSDE accurately [3]. The percentage error for each TP in comparison with non-truncated image (TP 0%) was computed.&#x0D; Results showed the percentage error (PE) for both Deff and SSDE increased as the TP increased. The PE was determined by comparing the Deff and SSDE of each TP with non-truncated (TP 0%) image. Table 1 shows the values of PE of truncated images of different TP (5%, 10%, 15%, and 20%) for both Deff and SSDE in phantom sizes of 22 and 32 cm. However, it can be observed that PE values for SSDE of 5% and 10% truncation were similar for both phantom sizes. This is because the correction factors for 5% and 10% were similar and had resulted in similar calculated SSDE. The highest recorded PE was observed in 20% truncation that determined the largest difference in Deff and SSDE with non-truncated image.&#x0D; This study demonstrates that there is a linear relationship between truncation percentage with measured Deff and SSDE computation. It can be concluded that the percentage error in Deff measurement and calculated SSDE will increase as TP increased. Therefore, the effects of truncation artefacts should be carefully considered in SSDE calculation for accurate estimation especially in development of automated calculation.

CТ densitometry as an additional method in the diagnosis of pulmonary hypertension: a prospective study

INTRODUCTION: This article presents the results of application of CT densitometry in the computed tomography (CT) of the chest to diagnose various forms of pulmonary hypertension.OBJECTIVES: To determine the diagnostic value of CT densitometry using comparative analysis of lung tissue density in patients with various forms of pulmonary hypertension.MATERIALS AND METHODS: The study included 528 patients diagnosed with pulmonary hypertension by means of right heart catheterization (RHC) of the National Research Cardiac Surgery Center, Republic of Kazakhstan. All patients were divided into 4 groups according to the classification of pulmonary hypertension of the World Health Organization (ESC/ERS Guidelines) from 2015. The first group included 254 patients with pulmonary hypertension pulmonary hypertension due to left heart disease (PHLHD). The second group included 210 patients with pulmonary arterial hypertension (PAH). The third group included 49 patients with chronic thromboembolic pulmonary hypertension (CTEPH). The fourth group — 15 patients with pulmonary hypertension due to respiratory disease (PHDRD). The mean age of the patients was 52.15±16.75 years. Contrast-enhanced chest CT imaging performed with a 64-slice multislice computed tomography system (Somatom Definition AS, Siemens) with post-processing to assess the lung tissue densitometric parameters, analyse the diameters of the pulmonary trunk and its main branches. The CT examination was carried in accordance with an «Embolism» protocol with intravenous administration of a contrast agent according to indications. Statistics: analysis was conducted using the Statistica 10 software. To quantitatively compare the two groups nonparametric Mann-Whitney test and the Kruskal-Wallace test were applied. Mean value and standard deviation in the format of «M±S» were used for quantitative parameters. Correlation analysis was carried out using Spearman’s nonparametric rank correlation.RESULTS: In patients with severe pulmonary hypertension a tendency for fibrotic changes was most clearly observed in cases of pulmonary hypertension due to left heart disease (–809.92±26.52), and emphysematous changes in the pulmonary arterial hypertension group (–843.27±43.88).CONCLUSION: CT lung densitometry should be performed in all patients with suspected pulmonary hypertension as an additional method of examination.

Anthropomorphic phantom organ dose assessment using optically stimulated luminescence dosimeters unified in multi-detector computed tomography

This organ dose profile investigation is based on a technology that allows for the acquisition of densely sampled dose data, obtained using modified nanoDot™ OSLDs and a typical anthropomorphic Alderson Radiation Therapy phantom (ARTM 1092 model). The CT scan parameters were based on adult chest-abdomen and head region CT procedures, which were performed using a Siemens Somatom Definition AS+ at Hospital Sultanah Aminah in Johor. In studying the scanned region, the tube voltage and exposure duration values were considerably altered, with modulation approaches significantly altering the dosage distribution. In the head-neck procedure, the average absorbed dose per slice for the brain and thyroid was 3.469–33.645 mGy and 3.372–34.528 mGy, respectively. The distribution of chest-abdomen region organ dose mapping explains that the lungs received the highest organ dose, receiving a dose of 20.795 mGy from protocol P4, a setting of 140 kV tube voltage in the CT chest-abdomen protocol. The organ dosage levels in this investigation varied from 2.277 to 20.794 mGy, depending on tube voltage, tube current, and exposure period, as well as the organ composition, location, and surrounding anatomic structures. The average absorbed dosage in the lungs per slice varied from 3.439 to 20.794 mGy. The most significant coefficient of variation (CoV) for dosage samples of the lungs inside separate slices was 13%. The radiation dose patterns are consistent with similar tests and modalities, with variations dependent on tube voltage, exposure period, tube current, slice collimation, and pitch factor. The LED and CAL measured data (Mean ± SD) were determined to be an average of 4657 ± 563 and 1677 ± 31 counts, respectively. The supplied data is evidence of the microStar reader's superior performance.

Analysis of Anatomical Variations of the Main Arteries Branching from the Abdominal Aorta by Multidetector Computed Tomography

Introduction: Embryological development of the aorta being a complex process can lead to a variety of congenital variants. It may result in complications during abdominal laparoscopic and radiological interventions. Prior knowledge can identify the anatomy, which may require special attention at the time of surgery/interventions. Diagnostic imaging with multidetector computed tomography (MDCT) allows accurate and noninvasive preoperative evaluation. To identify and to evaluate the anatomical variation of major arteries branching from the abdominal aorta using MDCT. Material and Methods: Five hundred patients of different age groups referred to the Department of Radiodiagnosis, Dayanand Medical College and Hospital, Ludhiana, for MDCT abdomen were included in the study. It was performed on 128-slice MDCT Siemens Somatom Definition AS scan machine. Results: The results showed that anatomical variation occurs in a high percentage of patients. In the celiac axis, it occurred in 34.6% of cases, out of which the most common variant was a replaced right hepatic artery (3.7%). Celiacomesenteric trunk was observed in 0.2% of patient. Single renal artery was observed (43.2%) while accessory renal artery in 41.6% and early branching in 15.2%. Discussion and Conclusion: Prior knowledge of variations of these vessels can prevent iatrogenic injuries.

Technical Note: Clinical modeling and validation of breast tissue expander metallic ports in a commercial treatment planning system for proton therapy.

To validate breast tissue expander metallic port (MP) models in a commercial treatment planning system (TPS) in proton pencil beam scanning (PBS) treatments for breast cancer patients with breast tissue expanders. Three types of MPs taken out of a Mentor CPX4, a Natrelle 133, and a PMT Integra breast tissue expanders and a 650 cc saline filled Mentor CPX4 expander were placed on top of acrylic slabs, and scanned using a Siemens Somatom Definition AS Open RT CT scanner. Structure templates for each of the MPs were designed within Eclipse TPS. The CT numbers for the metallic parts were overridden to reflect measured or calculated relative proton stopping powers (RPSPs). Mock targets were contoured in acrylic to represent postmastectomy chest-wall radiation therapy (PMRT) targets. Plans with different beam incident angles were optimized using the Eclipse TPS to deliver uniform prescription dose to the target using Hitachi Probeat-V PBS beams. Eclipse calculated doses and an in-house Monte Carlo (MC) code calculated doses were compared to the measured Gafchromic EBT3 film doses in acrylic. TPS/MC and film dose comparison results showed that (1) 3%/2mm/10% threshold Gamma pass rates were better than 90.8% in the acrylic target region for all plans; (2) comparing TPS and film doses for the individual beam plans in the MP dose shadow areas, the area with dose difference above 5% ([ΔA] 5%) ranged from 1.1 to 5.0 cm2 , and the maximum dose difference ([ΔD] 0.01 cm2 ) ranged from 12.5% to 25.0%; (3) comparing MC and film doses for the individual beam plans in the MP dose shadow areas, the (ΔA) 5% varied from 1.1 to 2.9 cm2 and (ΔD) 0.01 cm2 varied from 8.5% to 24.2%; (4) for a plan composed of three individual beams treating through the Mentor CPX4 expander, the TPS (ΔA) 5% was less than 0.13 cm2 , and the (ΔD) 0.01 cm2 was less than 6% in the MP dose shadow areas. It is feasible to treat patients with tissue expanders using multiple PBS beams using a structure template with CT number overridden to represent the measured/calculated RPSP for MPs for PBS treatment planning. MC dose was more accurate than analytical dose in the areas with high dose gradient caused by the density heterogeneity of the breast tissue expander MPs.

The Effective Dose Analysis of Head CT-Scan on Adult Patients

This study was aimed to determine the difference of the effective dose from the clinical and theoretical on the head CT-Scan examination of adult patients and compare the data with the permitted dose limit from BAPETEN. The data collected at Haji Hospital Surabaya using MSCT Siemens Somatom Definition AS 64 Slice on five adult patients, aged between 28-67 years old. The step before the scanning process were adjusting the voltage (kV) and current values (mA) on the CT-Scan. The scanning duration for each patient was 4s and resulted in head images with CTDIvol and DLP values displayed on the monitor screen. The effective dose limit value for the head CT scan was 2.8 mSv, according to BAPETEN. The study results showed that the effective dose on head CT Scan examination was below the safe dose limit value, while the different fractions between the clinical and theoretical of Patient A, B, C, D, and E was 4.11%; 5.46%; 6.19%; 6.52%; and 5.42%, respectively.

Impact of iterative reconstruction algorithms on the applicability of Fourier-based detectability index for x-ray CT imaging.

The increasing application of iterative reconstruction algorithms in clinical computed tomography to improve image quality and reduce radiation dose, elicits strong interest, and needs model observers to optimize CT scanning protocols objectively and efficiently. The current paradigm for evaluating imaging system performance relies on Fourier methods, which presuppose a linear, wide-sense stationary system. Long-range correlations introduced by iterative reconstruction algorithms may narrow the applicability of Fourier techniques. Differences in the implementation of reconstruction algorithms between manufacturers add further complexity. The present work set out to quantify the errors entailed by the use of Fourier methods, which can lead to design decisions that do not correlate with detectability. To address this question, we evaluated the noise properties and the detectability index of the ideal linear observer using the spatial approach and the Fourier-based approach. For this purpose, a homogeneous phantom was imaged on two scanners: the Revolution CT (GE Healthcare) and the Somatom Definition AS+ (Siemens Healthcare) at different exposure levels. Images were reconstructed using different strength levels of IR algorithms available on the systems considered: Adaptative Statistical Iterative Reconstruction (ASIR-V) and Sinogram Affirmed Iterative Reconstruction (SAFIRE). Our findings highlight that the spatial domain estimate of the detectability index is higher than the Fourier domain estimate. This trend is found to be dependent on the specific regularization used by IR algorithms as well as the signal to be detected. The eigenanalysis of the noise covariance matrix and of its circulant approximation yields explanation about the evoked trends. In particular, this analysis suggests that the predictive power of the Fourier-based ideal linear observer depends on the ability of each basis analyzed to be relevant to the signal to be detected. The applicability of Fourier techniques is dependent on the specific regularization used by IR algorithms. These results argue for verifying the assumptions made when using Fourier methods since Fourier-task-based detectability index does not always correlate with signal detectability.

Paediatric radiation dose and cancer risk associated with body effective diameter during CT thorax examination

Paediatric patients are considered vulnerable to radiation exposure and have a greater risk of developing radiation-induced cancers due to active growth cells. Radiation dose from a CT examination is the highest among other imaging modalities and can become harmful if unoptimised. Thus, the aim of this study is to evaluate the influence of paediatric size on SSDE value and to estimate cancer risk occurrence in specific organs of paediatric patients receiving CT chest examination. Data such as volume-weighted CT dose index (CTDIvol), dose length product (DLP) and patient's demography were retrospectively collected from a 64-slice CT scanner (Siemens Somatom Definition AS+) at University Malaya Medical Centre. A total of 120 patients were categorised into four age groups: G1 (0 – < 1 years), G2 (1 – < 5 years), G3 (5 – < 10 years), and G4 (10 – < 15 years). SSDE value was estimate in accordance with the American Association of Physicists, 2011 in Medicine (AAPM) report 204. The effective dose (E) and SSDENCICT obtained from National Cancer Institute Dosimetry System (NCICT) were then compared to the conventional SSDE value. The highest value of CTDIvol, DLP and E were found in group G4 with 4.9 ± 2.5, 185.0 ± 140.8, and 4.2 ± 2.0, respectively. Moreover, there is only slightly different of SSDE value between the G1 and G2 groups with a factor of 0.91. No significant difference (p > 0.05) was observed between the SSDEAAPM and SSDENCICT across all age groups. The cancer risk estimated shows thyroid organs receives the highest probability of cancer incidence in both the genders, which was calculated to be 2.1 for males and 3.9 for females per 100,000 procedures, respectively. Nevertheless, adequate justification of paediatric CT scans and dose optimisation are required to reduce unnecessary exposure and radiation-induced risks.

CT imaging character of different brain regions in different ages of Diannan small-ear pigs.

To collect and establish normal data of the brain regions of Diannan small-ear (DSE pigs, basically throughout measuring and comparing computed tomography values of the barin. 12 ordinary DSE pigs were divided into juvenile, adult, old groups based on the physiological ages (n=4) A SOMATOM Definition AS 64-row 128-slice 4D spiral CT scanner (SOMATOM Definition AS, Germany) was used to collect CT images of DSE pigs, record and analyze the scanning data. Compared with the juvenile group, the CT values of the right frontal lobe, right parietal lobe, right temporal lobe, left temporal lobe, and right occipital lobe were significantly higher in the elderly group. Compared with the adult group, the CT values of the right frontal lobe, left frontal lobe, right parietal lobe, right temporal lobe, left temporal lobe, and right occipital lobe of the elderly group were significantly higher. The results of the study can be used to evaluate the changes in CT values of various brain regions in piglets of different ages and future pig head injury models or other studies that require CT-based analysis.

Effect of Phantom Size and Tube Voltage on the Size-Conversion Factor for Patient Dose Estimation in Computed Tomography Examinations

Introduction: This study aimed to establish the conversion factors to normalize the output dose of volumetric computed tomography dose index (CTDIvol) to the patient dose (i.e. size-specific dose estimate (SSDE)) for various phantom diameters and tube voltages. Material and Methods: In-house cylindrical acrylic phantoms with physical diameters ranging from 8 to 40 cm were developed in this study. Each phantom had a hole in the center and four holes in the peripheral areas. The phantoms were scanned by a Siemens Somatom Definition AS CT Scanner using different tube voltages (i.e. 80, 100, 120, and 140 kVps) and with 200 mAs and 10 mm slice thickness. In addition, the doses in every hole and phantom were measured using a Raysafe X2 CT Sensor. The weighted SSDE (SSDEw) values were calculated using the five holes in every measurement. The size-conversion factors for the body and the head CTDI phantoms were established by dividing the SSDEw for various sizes with the SSDEw at the water-equivalent diameter of 33.90 cm and 16.95 cm, respectively. Results: The results revealed that the size-conversion factor exponentially decreased with an increase in the phantom size. It was also found that the size-conversion factor was affected by the tube voltages. Furthermore, the different size-conversion factor between 80 and 140 kVp was more than 15% in very thin and obese patients. Conclusion: Higher accuracy of the size-specific dose estimation can be achieved considering the impact of the tube voltages beside the size of the patient.

Combination of dual-energy computed tomography and iterative metal artefact reduction to increase general quality of imaging for radiotherapy patients with high dense materials. Phantom study.

To evaluate the use of pseudo-monoenergetic reconstructions (PMR) from dual-energy computed tomography, combined with the iterative metal artefact reduction (iMAR) method. Pseudo-monoenergetic CT images were obtained using the dual-energy mode on the Siemens Somatom Definition AS scanner. A range of PMR combinations (70-130keV) were used with and without iMAR. A Virtual Water™ phantom was used for quantitative assessment of error in the presence of high density materials: titanium, alloys 330 and 600. The absolute values of CT number differences (AD) and normalised standard deviations (NSD) were calculated for different phantom positions. Image quality was assessed using an anthropomorphic pelvic phantom with an embedded hip prosthesis. Image quality was scored blindly by five observers. AD and NSD values revealed differences in CT number errors between tested sets. AD and NSD were reduced in the vicinity of metal for images with iMAR (p<0.001 for AD/NSD). For ROIs away from metal, with and without iMAR, 70keV PMR and pCT AD values were lower than for the other reconstructions (p=0.039). Similarly, iMAR NSD values measured away from metal were lower for 130keV and 70keV PMR (p=0.002). Image quality scores were higher for 70keV and 130keV PMR with iMAR (p=0.034). The use of 70keV PMR with iMAR allows for significant metal artefact reduction and low CT number errors observed in the vicinity of dense materials. It is therefore an attractive alternative to high keV imaging when imaging patients with metallic implants, especially in the context of radiotherapy planning.