Average Computed Tomography Research Articles

Regional Ultrahigh-Resolution Rescan in a Clinical Whole-Body CT Scanner Using a Contact Detector Insert.

Ultrahigh-resolution, low-dose rescans in a region of interest following a general screening computed tomography (CT) scan is motivated by the need to reduce invasive tissue biopsy procedures in cancer screening. We describe a new method to meet the conflicting demands of ultrahigh resolution, high-speed and ultralow-dose, and the first proof-of-concept experiment. With improving detector resolution, the limiting factor for the system resolution of whole-body CT scanners shifts to the penumbra of the source focal spot. The penumbra unsharpness is minimized by inserting flat-panel detector(s) that are in direct contact with the body. In the hybrid system, the detector insert and the CT detector acquire data simultaneously, whereby the standard CT images give the position and orientation of the detector insert(s) as needed for tomosynthesis reconstruction. Imaging tests were performed with a compact photon-counting detector insert on resolution targets of both high- and low-contrast as well as a mouse specimen, all inside a body phantom. Detector insert tomosynthesis provided twice the resolution of the CT scanner alone at the same dose concentration. The short 2-cm beam collimation of the tomosynthesis rescan gave an effective dose equivalent to 6% of an average CT scan in the chest or abdomen.

Diagnostic value of multislice spiral computed tomography (CT) combined with CT angiography for intra-abdominal undescended testis secondary seminomas

ObjectiveTo discuss the diagnostic value of multislice spiral tomography (CT) combined with CT angiography (CTA) technology in intra-abdominal undescended testis secondary seminoma cases.MethodsWe retrospectively analyzed the CT and CTA imaging features of CT and CTA findings of nine patients with an intra-abdominal undescended testis secondary seminoma.ResultsThe tumors in all nine patients were mainly solid, and the average CT value was 38.4 ± 3.4 HU. Low-density areas of various sizes were visible in the tumors, and calcifications were detected in two patients. The tumors in eight patients had a complete capsule, which pressed on the surrounding structures. In one patient, the tumor had an incomplete capsule, which invaded the surrounding structures. Some of the solid tumors showed progressive and slight enhancement on the CT-enhanced scans. The values in the arterial phase, venous phase, and delayed phase were 46.3 ± 5.1 (40–55 HU), 57.3 ± 7.3HU (48–68 HU), and 65.1 ± 7.2HU (56–77 HU), respectively, with an average increase rate of 27.0 ± 7.2 HU. No enhancement was found in low-density areas on the CTA scans, and the supply arteries of the tumors in the nine patients all originated from the abdominal aortic wall 2–3 cm below the renal ostia. These arteries became thickened and tortuous when near the tumors, and there were no branching vessels. In eight patients, the supply arteries of the tumors originated from the posterior tumor and ended inside the tumor, and they originated from anterior of the tumor in one patient. Testicular venous drainage was detected in three patients, and lymph node metastasis in the abdominal aorta detected in two cases.ConclusionAn intra-abdominal undescended testis secondary seminoma exhibits a characteristic appearance on CT. CTA shows a three-dimensional testicular vascular pedicle sign of a seminoma. A combination of CT and CTA can improve the diagnostic accuracy of an intra-abdominal undescended testis secondary seminoma.

Role of Computed Tomography Volumetry in Preoperative Donor Renal Function Evaluation of Living Related Kidney Transplantation

IntroductionRenal scintigraphy is used to evaluate split renal function. A computed tomography (CT) examination is also carried out for donor safety and appropriate transplantation surgery, and the renal volume (CT volumetry) can be obtained at that time. In this study, we evaluated donor kidney function by inulin clearance (Cin) before and after donor nephrectomy in living donor renal transplantation, and the predictive role of CT volumetry was compared with diethylenetriamine pentaacetic acid (DTPA). MethodFrom November 2005 to April 2018, 34 cases of living donor transplantation conducted at Fukuoka University Hospital were retrospectively studied. The donated kidney weight was measured in 25 cases, and postoperative Cin was measured in 19 cases. ResultsThe average donor age was 51.7 years old (from 35 to 71). Preoperative Cin and postoperative Cin of donors were 86.3 mL/min/1.73 m2 (from 59.5 to 138.3) and 52.3 (from 40.5 to 76.6), respectively. The average CT volumetry of donated kidneys was 153.9 mL (from 107.8 to 219.3). Correlations of weight and DTPA and CT volumetry of donated kidneys were r = 0.033 (P = .8770) and r = 0.763 (P < .0001), respectively. Correlations of glomerular filtration rate of DTPA and CT volumetry and Cin of postoperative donor residual kidneys were r = 0.66 (P = .002) and r = 0.555 (P = .014). ConclusionThere was a significant correlation between CT volumetry and the weight of the removed kidneys, and a correlation between Cin after donor nephrectomy and CT volumetry of the remaining kidneys, but it did not exceed the predictive role of DTPA. However, it was suggested that it is worthy to use as a preoperative examination for split renal function equivalent to DTPA.

Model Image-Based Metal Artifact Reduction for Computed Tomography.

Metal implants often produce severe artifacts in the reconstructed computed tomography (CT) images, causing information and image detail loss and making the CT images diagnostically unusable. In order to eliminate the metal artifacts and enhance the diagnostic value of the reconstructed CT images, a post-processing metal artifact reduction algorithm, based on a tissue-class model segmented by thresholding and k-means clustering with spatial information, is proposed. The image inpainting technique is incorporated into the algorithm to improve the segmentation accuracy for CT images severely corrupted by metal artifacts. A study of a water phantom and of two sets of clinical CT images was performed to test the algorithm performance. The proposed method effectively eliminates typical metal artifacts, restores the average CT numbers of different tissues to the proper levels, and preserves the edge and contrast information, thus allowing the accurate reconstruction of the tissue attenuation map. The quality of the artifact-corrected CT images allows them to be subsequently used in other clinical applications, such as three-dimensional rendering, dose estimation for radiotherapy, attenuation correction for PET and SPECT, etc. The algorithm does not rely on the use of the raw sinogram and so is not limited by the proprietary format restrictions.

Analysis of the Treatment Efficacy of Percutaneous Catheter Drainage Under CT Guidance for Severe Acute Necrotizing Pancreatitis

Background: Percutaneous catheter drainage (PCD) therapy is an important treatment for severe acute pancreatitis. Objectives: The purpose of this retrospective study was to analyze the relevant risk factors of computed tomography (CT) guided PCD during the treatment of infected pancreatic necrosis (IPN) in severe acute pancreatitis. Patients and Methods: This is a retrospective study. From January 2013 to November 2016, 162 patients suffering from severe acute pancreatitis with IPN were assessed using CT-guided PCD. Abdominal CT scan was performed for the patients. The interventional therapist chose the location and puncture according to the image. Depending on the efficacy and process of the treatment, these patients were divided into a PCD success treatment group and a PCD combined with surgery group. Factors affecting the success of PCD treatment were analyzed by logistic regression analysis. Results: Among the 162 cases, 71 cases (43.82%) were in the PCD success group and 91 cases (56.17%) were in the PCD combined with surgery group. Through the course of treatment, CT values of piercing zone, acute physiology and chronic health evaluation II (APACHEII) scores and modified CT severity index (MCTSI) scores showed statistically significant correlation with the therapeutic effect of PCD under CT guidance. A further multivariate analysis found that the CT value of puncture area is the best predictor for efficacy and when the CT value got higher the PCD efficacy would become lower. We performed further analysis of the factors associated with the average CT value in the puncture area which was higher than 20 Hounsfield unit (HU), and found that the length of time from patient admission to drainage, APACHEII scores, MCTSI scores and C reactive protein (CRP) levels were risk factors for PCD treatment efficacy. Conclusion: CT values of piercing zone is the major risk factor affecting the curative effect of CT guidance PCD. For patients with higher CT values in the puncture area, the longer time from patient admission to drainage, the higher APACHEII scores and MCTSI scores. Higher levels of C reactive protein seem to lower the curative effect.

The accuracy of non-contrast chest computed tomographic Scan in the detection of pulmonary thromboembolism

Background Pulmonary embolism (PE) is a critical chest disease resulting in high mortality rates if undetected. This study aimed to evaluate the role of noncontrast multislice computed tomography in the detection of PE. Patients and methods One hundred patients requested for computed tomography (CT) pulmonary angiography and underwent noncontrast and contrast-enhanced CT images of the chest, which were reviewed separately. The average CT attenuation differences between the high-attenuation clots and pulmonary arteries were computed. Findings in the noncontrast images were correlated with the contrast-enhanced images. Results Twenty-six of 100 patients were positive for PE in computed tomography angiography; the mean age (±SD) was 56.73 (±9.11) years, and 17 (65.4%) were female individuals. The hyperdense lumen sign has an overall sensitivity of 50% and specificity of 98.6%. As for the other 13 patients, 10 of them had more than one indirect sign. The peripheral wedge-shaped opacity was the most common indirect sign that revealed high specificity (91%) and was statistically significant. Conclusion Noncontrast chest CT scan has a good role in the evaluation of PE through detection of the hyperdense lumen sign, which is a good indicator of acute pulmonary thromboembolism, particularly in cases involving the central pulmonary arteries or peripheral wedge-shaped opacity, as a useful indirect sign.

Delivered Dose Distribution Visualized Directly With Onboard kV-CBCT: Proof of Principle

To demonstrate proof of principle of visualizing delivered 3-dimensional (3D) dose distribution using kilovoltage (kv) cone beam computed tomography (CBCT) mounted onboard a linear accelerator. We apply this technique as a unique end-to-end verification of multifocal radiosurgery where the coincidence of radiation and imaging systems is quantified comprehensively at all targets. Dosimeters (9.5-cm diameter N-isopropylacrylamide) were prepared according to standard procedures at one facility and shipped to a second (remote) facility for irradiation. A 4-arc volumetric modulated arc therapy (VMAT) multifocal radiosurgery plan was prepared to deliver 20Gy with 6-MV photons to 6 targets (1-cm diameter). A dosimeter was aligned via CBCT and irradiated, followed by 3 CBCT scans acquired immediately, with total time between pre-CBCT and final CBCT <30minutes. Image processing included background subtraction and low-pass filters. A dose-volume structure was created per target with the same volume as the planned prescription dose volume, and their spatial agreement was quantified using volume centroid and the Jaccard index. For comparison, 5 diagnostic computed tomography (CT) scans were also acquired after >24hours with the same spatial analysis applied; comparison with planned doses after absolute dose calibration also was conducted. Regions of high dose were clearly visualized in the average CBCT with a contrast-to-noise ratio of 1.7±0.7, which increased to 5.8±0.5 after image processing, and 11.9±3.7 for average diagnostic CT. Centroids of prescription isodose volumes agreed with the root mean square difference of 1.1mm (range, 0.8-1.7mm) for CBCT and 0.7mm (0.4-0.8mm) for diagnostic CT. The dose was proportional to density above 10 to 12Gy with a 3D gamma pass rate of 94.0% and 99.5% using 5% for 1-mm and 3% for 2-mm criteria, respectively (threshold=15Gy, using global dose criteria). This work demonstrates for the first time the potential to visualize in 3D delivered dose using onboard kV-CBCT (0.5×0.5×1mm3 voxel size) immediately after irradiation with a sufficient contrast-to-noise ratio to measure radiation and imaging system coincidence to within 2mm.

Giant cell tumour of the bone treated with denosumab: How has the blood supply and oncological prognosis of the tumour changed?

BackgroundDenosumab is gradually applied to refractory or unresectable giant cell tumour of the bone. Whether denosumab can effectively reduce the blood supply of tumour and bring benefit is worthy of study. The aim of the study is to evaluate the related changes after treatment: blood supply, surgical plan downstaging, surgical difficulty and oncological prognosis. MethodsA self-case–control study was performed from June 2014 to November 2016, and 18 patients were enrolled. Patients received subcutaneous denosumab 120 mg every 4 weeks preoperatively, with additional doses administered on Days 8 and 15 during the first month of therapy. The initial treatment duration was 12 weeks. After 12 weeks treatment, enhanced CT examination was performed for evaluating whether surgical treatment was practicable. The patients received preoperative denosumab treatment for 5 (median 3, range 3–12) months in average. The microvessel density of tumour samples was calculated for evaluating tumour blood supply. The computed tomography (CT) enhancement rate was compared before and after treatment. The related changes of parameters were recorded as the following: clinical benefits, serious side effects, enhancement rate of CT, surgical plans, intraoperative blood loss, operative time, surgical difficulty, histological changes and local recurrence. The patients were followed up every 3 months postoperatively. ResultsThe average CT enhancement rate of lesions was 2.08 and 1.40 before and after treatment (p = 0.000), respectively. The unenhanced CT value was significantly increased after treatment (p = 0.038). The CT enhancement rate changed more significantly in pelvic or sacral lesions than that in limb lesions (p = 0.024). Sixteen cases underwent final surgery, and surgical plan was downstaged. The histological examination showed tumour cells were significantly reduced or even disappeared after treatment. The microvessel density decreased significantly after treatment. The mean postoperative follow-up was 18.8 (10–31) months, and five patients had local recurrence. The high local recurrence rate (4/6) in sacral tumours may be related to the increased difficulty of curettage. ConclusionDenosumab treatment can reduce the blood supply of giant cell tumour. The sacral or pelvic lesions changed more significantly than limb lesions. The surgical plan downstaging can also be achieved. The clear margin after denosumab treatment facilitated tumour resection but, increased difficult in curettage surgery, and high recurrence rate of sacral tumour is being concerned. The Translational Impact of this ArticleDenosumab is a new type of humanized monoclonal antibody which showed some effect in the treatment giant cell tumor of bone. Pre-operative treatment with denosamub can reduce intra-operative blood loss and down-stage surgical plan in suitable cases.

Interplay Effect of Target Motion and Pencil-Beam Scanning in Proton Therapy for Pediatric Patients.

Purpose:To investigate the effect of interplay between spot-scanning proton beams and respiration-induced tumor motion on internal target volume coverage for pediatric patients.Materials and Methods:Photon treatments for 10 children with representative tumor motions (1–13 mm superior-inferior) were replanned to simulate single-field uniform dose–optimized proton therapy. Static plans were designed by using average computed tomography (CT) data sets created from 4D CT data to obtain nominal dose distributions. The motion interplay effect was simulated by assigning each spot in the static plan delivery sequence to 1 of 10 respiratory-phase CTs, using the actual patient breathing trace and specifications of a synchrotron-based proton system. Dose distributions for individual phases were deformed onto the space of the average CT and summed to produce the accumulated dose distribution, whose dose-volume histogram was compared with the one from the static plan.Results:Tumor motion had minimal impact on the internal target volume hot spot (D2), which deviated by <3% from the nominal values of the static plans. The cold spot (D98) was also minimally affected, except in 2 patients with diaphragmatic tumor motion exceeding 10 mm. The impact on tumor coverage was more pronounced with respect to the V99 rather than the V95. Decreases of 10% to 49% in the V99 occurred in multiple patients for whom the beam paths traversed the lung-diaphragm interface and were, therefore, more sensitive to respiration-induced changes in the water equivalent path length. Fractionation alone apparently did not mitigate the interplay effect beyond 6 fractions.Conclusion:The interplay effect is not a concern when delivering scanning proton beams to younger pediatric patients with tumors located in the retroperitoneal space and tumor motion of <5 mm. Children and adolescents with diaphragmatic tumor motion exceeding 10 mm require special attention, because significant declines in target coverage and dose homogeneity were seen in simulated treatments of such patients.

Four-dimensional Plan Optimization for the Treatment of Lung Tumors Using Pencil-beam Scanning Proton Radiotherapy.

Purpose This study aimed to evaluate the effectiveness of four-dimensional (4D) robust optimization for proton pencil-beam scanning (PBS) treatment of lung tumors.Patients and methods In seven patients with lung cancer, proton beam therapy was planned using 4D robust optimization over 4D computed tomography (CT) data sets. The gross target volume (GTV) was contoured based on individual breathing phases, and a 5-mm expansion was used to generate the clinical target volume (CTV) for each phase. The 4D optimization was conducted directly on the 4D CT data set. The robust optimization settings included a CT Hounsfield unit (HU) uncertainty of 4% and a setup uncertainty of 5 mm to obtain the CTV. Additional target dose objectives such as those for the internal target volume (ITV) as well as the organ-at-risk (OAR) dose requirements were placed on the average CT. For comparison, three-dimensional (3D) robust optimization was also performed on the average CT. An additional verification 4D CT was performed to verify plan robustness against inter-fractional variations.Results Target coverages were generally higher for 4D optimized plans. The difference was most pronounced for ITV V70Gy when evaluating individual breathing phases. The 4D optimized plans were shown to be able to maintain the ITV coverage at full prescription, while 3D optimized plans could not. More importantly, this difference in ITV V70Gy between the 4D and 3D optimized plans was also consistently observed when evaluating the verification 4D CT, indicating that the 4D optimized plans were more robust against inter-fractional variations. Less difference was seen between the 4D and 3D optimized plans in the lungs criteria: V5Gy and V20Gy.Conclusion The proton PBS treatment plans optimized directly on the 4D CT were shown to be more robust when compared to those optimized on a regular 3D CT. Robust 4D optimization can improve the target coverage for the proton PBS lung treatments.

OA194] Calculation of the patient size for abdominal radiography in terms of water equivalent diameter

Purpose Estimate the patient size, in terms of water equivalent diameter (WED), for conventional abdominal anterior-posterior (AP) radiography by using parameters available in the DICOM-header. Methods The hypothesis of the present project was that the ratio of the incident air-kerma on the patient to the detector air-kerma relates to the patient size in conventional radiography. The incident air-kerma to the patient is provided by the dose area product (DAP) divided by the exposed area ( A exp ) . On the other hand, the standardized exposure index (EI) [1] is related to the detector air-kerma. Thus the ratio of both is expected to be associated to the patient size: EI DAP / A exp ∼ size patient . This hypothesis was tested on 120 adult patients who had an abdominal AP radiography and abdominal computed tomography (CT) scan within 1 year. The DAP, A exp and EI were extracted for every radiography from the dose management platform used in the hospital. The CT images were used to calculate the average WED CT over all axial slices [2] . The WED CT was plotted against the ratio ( EI DAP / A exp ) from the radiography and a curve fit was applied. The methodology was validated on 18 new patients with both an abdominal radiography and CT. The estimated WED ( WED est ) of these patients was found by using their DAP, A exp , EI and the previously fitted curve. The WED est was then compared to the WED as calculated from their CT ( WED CT ) . Results An exponential curve fit was applied to the data with a good correlation of R2 = 0.84 between the WED CT and the ratio EI DAP / A exp . In the validation part, the mean percentage difference between WED est and WED CT of the new patients was −1% and all differences were within ± 10%. Conclusions The proposed and validated methodology allows for the calculation of an attenuation-based patient size metric for conventional radiography using parameters captured by a dose management platform from the DICOM-header.

A CT metal artifact reduction algorithm based on sinogram surgery.

Streak artifacts in computed tomography (CT) images caused by metallic objects limit the wider use of CT imaging technologies. There have been various attempts to improve CT images containing streak artifacts; however, most of them generate additional artifacts or do not completely eradicate existing artifacts. In this paper, we propose a novel algorithm which reduces streak artifacts in CT images. Using CT numbers reconstructed from a given sinogram, we extract the metal part M and the surrounding area C with similar CT numbers. By filling in the area C∪M with the evaluated average CT number of C, we obtain a modified CT image. Using forward projection of the modified CT image, we generate a sinogram containing information about the anatomical structure. We undertake sinogram surgery to remove the metallic effects from the sinogram, after which we repeat the procedure. We perform numerical experiments using various simulated phantoms and patient images. For a quantitative analysis, we use the relative l∞ error and the relative l2 error. In simulated phantom experiments, all l∞ errors and l2 errors approach 10% and 1% of the initial errors, respectively. Moreover, for the patient image simulations, all l∞ errors are decreased by a factor of 20 while the l2 errors are decreased less than 5%. We observe that the proposed algorithm effectively reduces the metal artifacts. In this paper, we propose a metal artifact reduction algorithm based on sinogram surgery to reduce metal artifacts without additional artifacts. We also provide empirical convergence of our algorithm.

Influence of geometry on proximal femoral shaft strains: Implications for atypical femoral fracture.

Atypical femoral fractures (AFF) are characterized as low-energy fractures of the femoral shaft or subtrochanteric region. Femoral geometry is known to play a role in AFF risk; it is hypothesized that high-risk geometries are associated with elevated femoral shaft strain. However, it is not well known which geometric parameters have the greatest effect on strain, or whether interaction between parameters is significant. The purpose of this study was to thoroughly quantify the relationship between femoral geometry and diaphyseal strain, using patient specific finite element (FE) modelling in concert with parametric mesh morphing. Ten FE models were generated from computed tomography (CT) images of cadaveric femora. Heterogeneous material properties were assigned based on average CT intensities at element locations and models were subject to loads and boundary conditions representing the stance phase of gait. Mesh morphing was used to manipulate 8 geometric parameters: neck shaft angle (NSA), neck version angle (NV), neck length (NL), femoral length (FL), lateral bowing angle (L.Bow), anterior bowing angle (A.Bow), shaft diameter (S.Dia), and cortical bone thickness (C·Th). A 2-Level full factorial analysis was used to explore the effect of different combinations of physiologically realistic minimum and maximum values for each parameter. Statistical analysis (Generalized Estimating Equations) was used to assess main effects and first order interactions of each parameter. Six independent parameters and seven interaction terms had statistically significant (p<0.05) effects on peak strain and strained volume. For both measures, the greatest changes were caused by S.Dia, L.Bow, and A.Bow, and/or first order interactions involving two of these variables. As hypothesized, a large number of geometric measures (six) and first order interactions (seven) are associated with changes in femoral shaft strain. These measures can be evaluated radiographically, which may have important implications for future studies investigating AFF risk in clinical populations.

The feasibility of low-concentration contrast and low tube voltage in computed tomography perfusion imaging: an animal study.

Aim: To investigate the feasibility of low-concentration contrast (270 mg/ml) together with low tube voltage (80 kV) and adaptive iterative dose reduction (AIDR)-3D reconstruction in liver computed tomography (CT) perfusion imaging.Method: A total of 15 healthy New Zealand rabbits received two CT scans each. The first scan (control) was acquired at 100 kV and 100 mA with iopromide (370 mg/ml), while the second scan (experimental) was acquired at 80 kV and 100 mA with iodixanol (270 mg/ml) 24 h after the first scan. The obtained images were reconstructed with filtered back projection (FBP) and AIDR-3D in the control and experimental groups respectively. The perfusion parameters (hepatic artery perfusion [HAP], portal vein perfusion [PVP], hepatic perfusion index [HPI], and total liver perfusion [TLP]) and image quality (image quality score, average CT value of abdomen aorta, signal-to-noise ratio [SNR], contrast-to-noise ratio [CNR], and figure of merit [FOM]) were compared using a paired t-test or Mann–Whitney U test between the two groups, when appropriate. The effective radiation dose and iodine intake were also recorded and compared.Results: With the exception of the FOM criteria, the image quality and perfusion parameters were not significantly different between the two groups. The effective radiation dose and iodine intake were 38.79% and 27.03% lower respectively, in the experimental group.Conclusion: Low-concentration contrast (iodixanol, 270 mg/ml) together with low tube voltage (80 kV) and AIDR-3D reconstruction help to reduce radiation dose and iodine intake without compromising perfusion parameters and image quality in liver CT perfusion imaging.

Metal artifact reduction in CT, a phantom study: subjective and objective evaluation of four commercial metal artifact reduction algorithms when used on three different orthopedic metal implants.

Background Metal implants may introduce severe artifacts in computed tomography (CT) images. Over the last few years dedicated algorithms have been developed in order to reduce metal artifacts in CT images. Purpose To investigate and compare metal artifact reduction algorithms (MARs) from four different CT vendors when imaging three different orthopedic metal implants. Material and Methods Three clinical metal implants were attached to the leg of an anthropomorphic phantom: cobalt-chrome; stainless steel; and titanium. Four commercial MARs were investigated: SmartMAR (GE); O-MAR (Philips); iMAR (Siemens); and SEMAR (Toshiba). The images were evaluated subjectively by three observers and analyzed objectively by calculating the fraction of pixels with CT number above 500 HU in a region of interest around the metal. The average CT number and image noise were also measured. Results Both subjective evaluation and objective analysis showed that MARs reduced metal artifacts and improved the image quality for CT images containing metal implants of steel and cobalt-chrome. When using MARs on titanium, all MARs introduced new visible artifacts. Conclusion The effect of MARs varied between CT vendors and different metal implants used in orthopedic surgery. Both in subjective evaluation and objective analysis the effect of applying MARs was most obvious on steel and cobalt-chrome implants when using SEMAR from Toshiba followed by SmartMAR from GE. However, MARs may also introduce new image artifacts especially when used on titanium implants. Therefore, it is important to reconstruct all CT images containing metal with and without MARs.

Three-dimensional printer-generated patient-specific phantom for artificial in vivo dosimetry in radiotherapy quality assurance

Pretreatment intensity-modulated radiotherapy quality assurance is performed using simple rectangular or cylindrical phantoms; thus, the dosimetric errors caused by complex patient-specific anatomy are absent in the evaluation objects. In this study, we construct a system for generating patient-specific three-dimensional (3D)-printed phantoms for radiotherapy dosimetry. An anthropomorphic head phantom containing the bone and hollow of the paranasal sinus is scanned by computed tomography (CT). Based on surface rendering data, a patient-specific phantom is formed using a fused-deposition-modeling-based 3D printer, with a polylactic acid filament as the printing material. Radiophotoluminescence glass dosimeters can be inserted in the 3D-printed phantom. The phantom shape, CT value, and absorbed doses are compared between the actual and 3D-printed phantoms. The shape difference between the actual and printed phantoms is less than 1 mm except in the bottom surface region. The average CT value of the infill region in the 3D-printed phantom is −6 ± 18 Hounsfield units (HU) and that of the vertical shell region is 126 ± 18 HU. When the same plans were irradiated, the dose differences were generally less than 2%. These results demonstrate the feasibility of the 3D-printed phantom for artificial in vivo dosimetry in radiotherapy quality assurance.

Subcutaneous Adipose Tissue Characteristics and Risk of Biochemical Recurrence in Men with High Risk Prostate Cancer

Obesity has become a worldwide epidemic. The interaction of obesity and excess adipose tissue on cancer biology continues to be an area of interest. The purpose of this study was to assess subcutaneous adipose tissue characteristics by computed tomography (CT) as potential imaging biomarkers in patients with high risk prostate cancer receiving radiation treatment (RT). This retrospective study included 185 men with high risk prostate cancer (PSA>20 ng/mL, Gleason score ≥ 8, or clinical extraprostatic extension) treated between 2001 and 2012. All patients received definitive, dose-escalated external beam RT along with a course of neoadjuvant, concurrent, and adjuvant androgen deprivation therapy (ADT). Each patient also had a treatment planning CT that included the L4-L5 vertebral interface and prostate specific antigen (PSA) measurements for at least 1 year following RT. The subcutaneous adipose tissue was contoured on a single axial CT slice at the level of L4-L5. The average CT attenuation, in Hounsfield units (HU), of the structure was calculated and defined as SATHU. SATAREA was defined as the cross-sectional area of the structure (in cm2) that was then normalized by the square of patient height. Biochemical failure (BF) was defined as a PSA rise of 2 ng/mL from the nadir. Freedom from BF (FFBF) was calculated from start time of ADT using the Kaplan-Meier method. Estimates of FFBF were stratified by SATHU and SATAREA quartiles. Median follow-up was 5.3 years. The mean SATHU (± standard deviation) was -99.2 HU (±6.3 HU) and the mean SATAREA was 94.7 cm2/m2 (±42.3 cm2/m2). No significant differences of SATHU and SATAREA were observed among different races or age groups. The 5 and 8-year rates of FFBF across all patients were 82.1% and 74%, respectively. Patients in the lowest quartile of SATHU experienced significantly higher FFBF compared to the other quartiles (Q4 vs. Q1, p=0.029; Q4 vs. Q2, p=0.045; Q4 vs. Q3, p=0.045). No other differences in FFBF were observed between quartiles of SATAREA or other quartiles of SATHU. Using CT imaging as a novel prognostic biomarker, low attenuation of abdominal adipose tissue was associated with a lower rate of biochemical failure in patients with high risk prostate cancer. Further research is needed to elucidate the biological underpinnings of this clinical finding and the role adipose tissue plays in modulating oncologic behavior and outcomes.

Subcutaneous adipose tissue characteristics and the risk of biochemical recurrence in men with high-risk prostate cancer

Purpose/objective(s)To assess subcutaneous adipose tissue characteristics by computed tomography (CT) as potential imaging biomarkers predictive of biochemical recurrence in men with high-risk prostate cancer receiving radiotherapy (RT). Materials and methodsThis retrospective study included men with high-risk prostate cancer (PSA>20ng/ml, Gleason score ≥8, or clinical extraprostatic extension) treated between 2001 and 2012. All patients received definitive, dose-escalated external beam RT along with a course of neoadjuvant, concurrent, and adjuvant androgen deprivation therapy (ADT). Each patient also had a treatment planning CT that included the L4-L5 vertebral interface and prostate specific antigen (PSA) measurements for at least 2 years following RT. The subcutaneous adipose tissue was contoured on a single axial CT slice at the level of L4-L5. The average CT attenuation, in Hounsfield units (HU), of the structure was calculated and defined as SATHU. SATAREA was defined as the cross-sectional area of the structure (in cm2) that was then normalized by the square of patient height. Biochemical failure (BF) was defined as a PSA rise of 2ng/ml from the nadir. Freedom from BF (FFBF) was calculated from start time of ADT using the Kaplan-Meier method. Estimates of FFBF were stratified by SATHU and SATAREA quartiles. ResultsA total of 171 men met the inclusion criteria with a median follow-up of 5.6 years. The mean SATHU (±standard deviation) was −99.2HU (±6.1HU), and the mean SATAREA was 93.2cm2/m2 (±39.4cm2/m2). The 5- and 8-year rates of FFBF across all patients were 81.5% and 73.5%, respectively. Patients in the lowest quartile of SATHU experienced significantly higher FFBF compared to the other quartiles (Q4 vs. Q1, P = 0.017; Q4 vs. Q2, P = 0.045; Q4 vs. Q3, P = 0.044). No other differences in FFBF were observed between quartiles of SATAREA or other quartiles of SATHU. ConclusionLower subcutaneous adipose tissue density was associated with a lower rate of BF following RT with ADT for men with high-risk prostate cancer. Further research is needed to elucidate the biological underpinnings of this clinical finding and the role adipose tissue plays in modulating oncologic behavior and outcomes.

Optimal injection method for long-range computed tomography angiography.

We aimed to obtain high-stable computed tomography (CT) values for CT angiography (CTA). We verified the optimal use of the new protocol for long-range scanning using a contrast material flow phantom (Ichikawa, CT imaging theory. Igaku syoin Publishing, Tokyo, 8; Awai et al., Am J Roentgenol 186(2):379-385, 1) to obtain high-stable CT values (Fig.2). We have developed a novel contrast injection method called the stable line imaging protocol (SLIP). This method involved a gradual reduction in the rate of administration of the contrast medium, which was accompanied by simultaneous administration of saline to compensate for the resultant decrease in the rate of administration. A saline flush was further added after the contrast medium injection. The rate of administration of the saline flush was the same as that of the initial contrast medium. We injected a contrast medium from the injector into the flow phantom. The time-enhancement curve (TEC) data were obtained five times by changing the injection method, and the average CT values were determined. The maximum simulation of the aortic peak enhancement of TEC was defined as pTEC. The time required to keep the CT value more than 80% of the pTEC was defined as the time period of contrast enhancement (p80). The pTEC of a single injection was 295.7±5.3 HU, while that of SLIP was 296.5±2.3 HU; the two values did not differ significantly. The p80 of a single injection was 19.1±0.2s, while that of SLIP was 23.2±0.4s; p80 of SLIP was 18% longer than that of the single injection.

Diagnosis of autoimmune pancreatitis with computed tomography

Objective To investigate the computed tomography (CT) features of autoimmune pancreatitis (AIP). Methods The CT imaging data of 33 patients with AIP confirmed by pathology and/or steroid therapy were retrospectively analyzed. Image analysis including the shape of pancreas, density of lesion, contrast enhancement, the changes of pancreatic duct and biliary duct, peripancreatic appearances and adjacent organ involvement. T test was performed for statistical analysis. Results Among 33 patients with AIP, 23 cases (70%) with pancreatic parenchyma diffuse enlargement, eight cases (24%) with partial enlargement and two cases (6%) with normal pancreas. The lesions appeared hypoattenuating or isoattenuating on plain CT scan. After contrast-enhanced scan, the average CT values of lesions were (75.7±17.0) Hu at arterial phase, which was lower than that of venous phase (90.7±12.0) Hu, and the difference was statistically significant (t=3.378, P=0.002). The lesions demonstrated as progressive enhancement at venous phase. Among 33 patients, the main pancreatic duct was visible in six patients (18%). Sixteen patients (48%) presented with intrahepatic and extrahepatic biliary tract dilatation caused by intrapancreatic common bile duct stenosis. Thickened envelope-like structure around the lesions, presenting as capsule sign was seen in 14 patients (42%). Extra-pancreatic organ involvement was found in seven patients including three cases of kidney involvement. After treated with steroid, seven patients repeated CT which showed different degrees of improvement. Conclusion The main CT findings of AIP are diffuse and partial enlargement of pancreas with progressive enhancement at venous phase, envelope-like structure around pancreas, and stenosis of intrapancreatic common bile duct, which are important in the diagnosis and differential diagnosis of AIP. Key words: Pancreatitis; Autoimmune diseases; Tomography, X-ray computed