Use of Three-Dimensional Printing in Modelling an Anatomical Structure with a High Computed Tomography Attenuation Value: A Feasibility Study

Introduction: Three-dimensional (3D) printing provides an opportunity to develop anthropomorphic computed tomography (CT) phantoms with anatomical and radiological features mimicking a range of patients’ conditions, thus allowing development of individualised, low dose scanning protocols. However, previous studies of 3D printing in CT phantom development could only create anatomical structures using potassium iodide with attenuation values up to 1200 HU which is insufficient to mimic the radiological features of some high attenuation structures such as cortical bone. This study aimed at investigating the feasibility of using 3D printing in modelling cortical bone with a non-iodinated material. Methods: This study had 2 stages. Stage 1 involved a vat photopolymeri-sation 3D printer to directly print cube phantoms with different percentage compositions of calcium phosphate (CP) and resin (approach 1), and approach 2 using a material extrusion 3D printer to develop a cube mould for infilling of the CP with hardener as the phantom. The approach able to create the cube phantom with the CT attenuation value close to that of a tibial mid-diaphysis cortex of a real patient, 1475±205 HU was employed to develop a tibial mid-diaphysis phantom. The mean CT numbers of the cube and tibia phantoms were measured and compared with that of the original CT dataset through unpaired f-test. Results: All phantoms were scanned by CT using a lower extremity scanning protocol. The moulding approach was selected to develop the tibia mid-diaphysis phantom with CT attenuation value, 1434±184 HU which was not statistically significantly different from the one of the original dataset (p = 0.721). Conclusion: This study demonstrates the feasibility to use the material extrusion 3D printer to create a tibial mid-diaphysis mould for infilling of the CP as an anthropomorphic CT phantom and the attenuation value of its cortex matches the real patient’s one.

CT differentiation of gastric ectopic pancreas from gastric stromal tumor

Background Gastric ectopic pancreas (GEPs) is a rare developmental anomaly which is difficult to differentiate it from submucosal tumor such as gastric stromal tumor (GST) by imaging methods. Since the treatments of the GEPs and GST are totally different, a correct diagnosis is essential. Therefore, we retrospectively investigated the CT features of them to help us deepen the understanding of GEPs and GST. Methods This study enrolled 17 GEPs and 119 GST, which were proven pathologically. We assessed clinical and CT features to identify significant differential features of GEPs from GST using univariate and multivariate analyses. Results In univariate analysis, among all clinicoradiologic features, features of age, symptom, tumor marker, location, contour, peritumoral infiltration or fat-line of peritumor, necrosis, calcification, CT attenuation value of unenhancement phase/arterial phase/portal venous phase (CTu/CTa/CTp), the CT attenuation value of arterial phase/portal venous phase minus that of unenhanced phase (DEAP/DEPP), long diameter (LD), short diameter (SD) were considered statistically significant for the differentiation of them. And the multivariate analysis revealed that location, peritumoral infiltration or fat-line of peritumor, necrosis and DEPP were independent factors affecting the identification of them. In addition, ROC analysis showed that the test efficiency of CTp was perfect (AUC = 0.900). Conclusion Location, the presence of peritumoral infiltration or fat-line of peritumor, necrosis and DEPP are useful CT differentiators of GEPs from GST. In addition, the test efficiency of CTp in differentiating them was perfect (AUC = 0.900).

Evaluation of muscle quality and quantity for the assessment of sarcopenia using mid-thigh computed tomography: a cohort study

BackgroundPreviously, sarcopenia was diagnosed based on walking speed, grip strength and muscle mass. However, recent consensus has proposed a concern regarding the use of muscle mass measurement for sarcopenia diagnosis due to lack of accuracy; therefore, new assessment methods in clinical practice are required. We investigated the correlation between computed tomography (CT) and various motor function tests to assess the utility of CT as a potential diagnostic method for sarcopenia.MethodsIn total, 214 patients who were examined at our center during the study period (2016–2017) were included in the study. Single-slice CT scan of the mid-thigh region was performed, from which cross-sectional area (CSA) and CT attenuation value (CTV) of quadriceps femoris were evaluated for each subject. Other assessments included skeletal muscle mass index, muscle strength and physical performance. Furthermore, subjects were classified into four groups as per the Asia Working Group of Sarcopenia (AWGS) 2019 criteria as those with: normal, poor muscle function/strength (poor function), sarcopenia and severe sarcopenia.ResultsCSA and muscle strength exhibited the strongest correlation. Some physical performance tests showed the strongest correlation with CTV. The CSA was significantly lower in women with sarcopenia group and in both men and women with severe sarcopenia (all p < 0.01); furthermore, the CTV was significantly lower in women with poor-function and in both men and women with severe sarcopenia group (all p < 0.01).ConclusionsCSA mostly correlated with muscle strength, whereas CTV mostly correlated with physical performance. CT with measurements of CSA and CTV enables the evaluation of muscle mass and quality simultaneously. CT is believed to be useful in inferring evaluation of motor function and assessment of sarcopenia.

Evaluation of prosthetic complications and tumor recurrence with the single energy metal artifact reduction algorithm in patients with hip tumor prostheses

Background: To evaluate the effectiveness of the single energy metal artifact reduction (SEMAR) algorithm with a second-generation 320-row multi-detector computed tomography (MDCT) on complications and tumor recurrence detection in patients with hip tumor prostheses.Methods: From February 2016 to June 2019, 31consecutive patients with tumor prostheses of the hip joint underwent CT scans. Lesions were confirmed by histology or clinical and imaging follow-up. Images were reconstructed using 2 methods: iterative (IR) algorithm alone and SEMAR algorithm (IR+ SEMAR). Two radiologists graded the image quality visually by a 6-point (from 0 to 5) ordinal scale. Standard deviations (SD) of CT attenuation value defined as the artifact index (AI) were compared between the two reconstructed methods. Paired sample t-test was adopted to compare the AI values on IR and SEMAR images. Wilcoxon matched-pairs signed rank test was performed to compare the visual scores on IR and SEMAR images. A p- value less than 0.05 was considered statistically significant. Results: The artifacts of the SEMAR images were reduced compared to the Non-SEMAR images (113.94 ±128.54 vs 35.98 ± 53.75HU，t=2.867, P < 0.05). 20 and 16 more lesions were detected by observer 1 and observer 2 with SEMAR algorithm respectively. The mean scores of lesions without SEMAR were 1.39 ± 1.45 (observer 1) and 1.55± 1.34 (observer 2); with SEMAR, the scores were significantly higher, 4.42±0.56 (z=-4.752, p < 0.001) and 4.54± 0.72 (z=-4.837, p < 0.001) respectively. Conclusion: The SEMAR algorithm can effectively reduce metal artifacts in patients with hip tumor prostheses and increase the diagnostic accuracy of prosthetic complications and tumor recurrence.

Pericoronary adipose tissue inflammation on coronary computed tomography in patients with vasospastic angina

Background A recent study has demonstrated that coronary spasm is associated with inflammation of peri-coronary adipose tissue (PAT) by using the combination of 18F-fluorodeoxyglucose positron emission tomography and computed tomography (CT). PAT attenuation (FAI) on CT angiography (CTA) has been reported to reflect PAT inflammation. We sought to investigate if FAI on CTA was associated with coronary vasospasm in patients with suspected vasospastic angina (VSA). Methods A total of 88 patients who underwent CTA and acetylcholine provocation test (SPT) for suspected VSA were retrospectively investigated. FAI was assessed by the crude analysis of the mean CT attenuation value of 3 major coronary arteries on CTA. FAI was evaluated for the proximal reference diameter (FAI-Ref) and inner 2mm adipose tissue layer (FAI-2mm) from the vessel wall. Diagnosis of VSA (VSA group) was made by SPT and the subjects with negative SPT without organic coronary lesions served as non-VSA group. Association between VSA diagnosis and FAI was assessed and the predictors of VSA was explored by univariable and multivariable analyses. Results In 45 patients (51.1%), VSA was diagnosed (VSA group). There were no significant differences in baseline characteristics between the VSA and non-VSA groups. RCA-FAI was significantly higher in patients of VSA group than in non-VSA group. RCA-FAI-2mm provided significantly better diagnostic performance for VSA than RCA-FAI-Ref and LCA-derived FAI values. Furthermore, RCA-FAI-2mm showed a significant relationship with the severity of spasm evaluated by most stenotic segment diameter during SPT. (r=−0.28, p&lt;0.001) Multivariable logistic regression analysis revealed that RCA-FAI-2mm was an independent predictor of predicting VSA (P&lt;0.001). Conclusion Coronary spasm may be linked with PAT inflammation detected by CTA-derived RCA-FAI, particularly by inner PAT assessment close to the vessel wall. Representative cases for FAI analyses Funding Acknowledgement Type of funding source: None

Computed Tomography (CT) Attenuation Value in Relation with Body Dimension, Gender and Age in Malay population: A Literature Review

Interaction of CT’s x-ray beams with patient resulted in attenuation process and there are various factors affecting CT attenuation values. The aim of this review is to examine the existed literatures regarding the concept of attenuation in CT and its relationship with body dimension, gender and age in Malay population. Guided by primary question, literature searches were conducted using the established online database; SCOPUS and PubMed. The time frame for literatures was from 2000 to 2019 and only literatures in English language were selected. The size of body dimension has affected the CT attenuation value but it also depending on the type of tissue presence within the region of interest (ROI) such as muscle and fat tissues. Due to larger body framework and higher amount of skeletal muscle mass theoretically males would have higher CT attenuation value than female. CT attenuation value reduces with aging process. Asians including Malay population have smaller body dimension than Caucasians and the mean attenuation value of abdominal region in Asians could differ from 20 HU. Thus, there is a need for future research to investigate the interrelatedness of attenuation in CT (HU) and body dimension within Malay population and close this gap of knowledge.

Visibility of bronchial arteries using virtual and advanced virtual monoenergetic imaging

Background The utility of virtual monoenergetic imaging (VMI) for fine arteries has not been well clarified. Purpose To assess bronchial artery visualization using VMI and noise-optimized advanced VMI (VMI+). Material and Methods Eighty-seven patients with esophageal cancer underwent computed tomography (CT) using a third-generation dual-source system before surgery. Tube voltages were set to 90 kVp and 150 kVp, respectively. Images were reconstructed using VMI and VMI+ with energy levels of 40–120 keV (in 10-keV increments); composite images equivalent to CT images at 105 kVp were also generated. The CT attenuation value and contrast-to-noise ratio (CNR) of bronchial arteries using VMI and VMI+ were compared with those obtained using composite imaging. Two radiologists subjectively analyzed bronchial artery visualization with reference to the composite image. Results CT attenuation values for bronchial arteries using VMI at 40–60 keV and VMI+ at 40 keV and 50 keV were significantly higher than those obtained using composite imaging ( P < 0.05). CNR using VMI at 40–60 keV was significantly higher than that obtained using composite imaging ( P < 0.05), whereas no differences were noted for values obtained using composite imaging between VMI+ at 40 keV and 50 keV. In the subjective analysis, VMI at 40 keV and 50 keV yielded significantly better visibility of bronchial arteries than VMI+ ( P < 0.05). Conclusion VMI and VMI+ at low voltages (40–50 keV) may be useful for bronchial artery visualization. VMI+ may be less effective for fine vessels as bronchial artery visualization.

CT differentiation of gastric ectopic pancreas from gastric stromal tumors

BackgroundGastric ectopic pancreas (GEPs) is a rare developmental anomaly which is difficult to differentiate it from submucosal tumor such as gastrointestinal stromal tumor (GIST) by imaging methods. So we retrospectively investigated the CT features of them to help us make the correct diagnosis.Materials and MethodsThis study enrolled 17 GEPs and 119 GSTs, which were proven pathologically. We assessed clinical and CT features to identify significant differential features of GEPs from GSTs using univariate and multivariate analyses.ResultsIn univariate analysis, among all clinicoradiologic features, features of age, symptom, tumor marker, location, contour, blurred serosa or fat-line of peritumor, necrosis, calcification, CT attenuation value of unenhancement phase/arterial phase/portal venous phase (CTu/CTa/CTp), the CT attenuation value of arterial phase/portal venous phase minus that of unenhanced phase (DEAP/DEPP), long diameter (LD), short diameter (SD) were considered statistically significant for the differentiation of them. And the multivariate analysis revealed that location, blurred serosa or fat-line of peritumor, necrosis and DEPP were independent factors affecting the identification of them.What's more, ROC analysis showed that the test efficiency of CTp was perfect(AUC= 0.900).ConclusionLocation, blurred serosa or fat-line of peritumor, necrosis and DEPP are useful CT differentiators of GEPs from GSTs. In addition, the test efficiency of CTp in differentiating them was perfect (AUC=0.900).

Bone islands incidentally detected on computed tomography: frequency of enostosis and differentiation from untreated osteoblastic metastases based on CT attenuation value

Objective: The frequency of enostosis incidentally found on CT and CT attenuation value to distinguish them from untreated osteoblastic metastases (UOM). Methods: Enostosis group: 46 polytrauma patients underwent thoracoabdominal CT. Inclusion criteria: age range 14–35 years. Exclusion criteria: cancer, previous fractures. UOM group: 20 patients with radiological diagnosis of UOM. Analyzed data: number, size, location and density of enostoses and metastases. The density was measured with the broadest possible region of interest at the center of the lesion by two radiologists independently. Receiver operatingcharacteristic analysis to determine the sensitivity and specificity, area under the curve 95% confidence intervals and cutoff values of CT density to differentiate metastases from enostoses. Results: Patients were 28 ± 7 years old (72% males). 41 (89%) patients had 124 enostoses (2–15 mm) with an average density of 1007 ± 122 Hounsfiled unit (HU, observer1) and 1052 ± 107 (observer2). The most common sites of occurrence were the proximal femur (34%), the pelvis (22%), the acetabulum (20%), the proximal humerus (11%), the vertebrae (11%) and the rib (2%). 13 patients had 1 bone island, 8 patients had 2, 9 cases had 3 and 11 cases had more than 3 enostoses. Overall, 114 UOM were evaluated, their average density was 728 ± 163 HU (observer1) and 712 ± 178 HU (observer2). The area under the curve value of mean density to distinguish enostoses from UOM was 0,982. Using a cut-off of 881 HU for mean density, sensitivity was 98% and specificity 95%. Conclusion: The frequency of enostosis in this study is 89%. The average density identified can help to distinguish enostoses from UOM. Advances in knowledge: We report the exact frequency of enostosis.