Control of whole-body FDG-positron emission tomography image quality by adjusting the acquisition time: A new physical image quality index and patientdependent parameters for clinical imaging

Objective: This study aimed to establish a methodology for obtaining visually equivalent image quality regardless of patient size by controlling the acquisition time of positron emission tomography (PET) studies. Methods: In Part 1, we determined the physical image quality index with the highest correlation with visual assessment in 30 patients. In Part 2, 100 patients were scanned to identify the patient-dependent parameters that were most correlated with the physical image quality index. These parameters were calculated from the combination of the administered activity of 18F-FDG and weight. We drew an approximate curve from these parameters and prepared a scatter plot of the physical image quality index. In Part 3, we checked whether the image quality was constant by controlling the acquisition time in 189 patients. The approximation formula we obtained under (2) was used to control the acquisition time. The physical image quality index was a constant value, and the patient-dependent parameter was calculated from the patient’s physique. Results: The physical image quality index with the highest correlation with visual evaluation was the noise equivalent count weight (NECweight) (correlation coefficient: 0.90). The patient-dependent index most correlated with NECweight was activity/weight3 (A/W3) (coefficient of determination: 0.978). The verification of the acquisition time to obtain a certain image quality showed an average of 0.60 ± 0.034 Mcounts/m∙kg, and a similar image quality was obtained independent of the individual physiques. Conclusions: Calculating NECweight and A/W3 enable the determination of the appropriate acquisition time for stable image quality before the PET study

Prevalence of Femoroacetabular Impingement Features in Japanese Young Adults without Symptoms: Hip Joint Morphology Using Radial Reformation from Computed Tomography

Purpose: To determine the prevalence of femoroacetabular impingement (FAI) morphology in asymptomatic Japanese young adults using multi-detector computed tomography (MDCT) scan. Materials and Methods: A total of 170 subjects (85 men; age, 19–39 years) without hip-related problems were included. Radial slices of 2-mm thickness at 30° intervals were reconstructed perpendicular to the central axis of the femoral head and neck for both hips. Alpha (α) angles, acetabular (AC) depths, and lateral centre-edge (LCE) angles were measured; maximum value of measured α angles was defined as max α angle, and minimum value of measured AC depths was defined as min AC depth. Max α angle > 55° was considered positive for cam-type FAI feature and min AC depth 40° was considered positive for pincer-type FAI feature. Differences among planes, right-left correlations, and sex differences in FAI abnormalities were assessed. Results: The α angles at 1- and 2-o’clock positions in men and at 2-o’clock position in women were significantly greater than those at other positions. AC depths at 2-o’clock position were smallest in men and women. Max α angles and min AC depths and LCE angles showed strong right-left correlations. Max α angles and the numbers of hips with cam features were significantly higher in men than in women. The prevalence of pincer features was similar between men and women. Conclusion: The prevalence of cam type deformity is higher in men. Our results in Japanese populations were similar to those reported previously for Caucasians

Synthesized effective atomic numbers for commercially available dual-energy CT

Purpose: The objective of this study was to assess synthesized effective atomic number (Zeff) values with a new developed tissue characteristic phantom and contrast material of varying iodine concentrations using single-source fast kilovoltage switching dual-energy CT (DECT) scanner. Methods: A newly developed multi energy tissue characterisation CT phantom and an acrylic phantom with various iodine concentrations of were scanned using single-source fast kilovoltage switching DECT (GE-DECT) scanner. The difference between the measured and theoretical values of Zeff were evaluated. Additionally, the difference and coefficient of variation (CV) values of the theoretical and measured values were compared with values obtained with the Canon-DECT scanner that was analysed in our previous study. Results: The average Zeff difference in the Multi-energy phantom was within 4.5%. The average difference of the theoretical and measured Zeff values for the acrylic phantom with variation of iodine concentration was within 3.3%. Compared to the results for the single-source Canon-DECT scanner used in our previous study, the average difference and CV of the theoretical and measured Zeff values obtained with the GE-DECT scanner were markedly smaller. Conclusions: The accuracy of the synthesized Zeff values with GE-DECT had a good agreement with the theoretical Zeff values for the Multi-Energy phantom. The GE-DECT could reduce the noise and the accuracy of the Zeff values than that with Canon-DECT for the varying iodine concentrations of contrast medium. Advances in knowledge: The accuracy and precision of the Zeff values of the contrast medium with the GE-DECT could be sufficient with human equivalent materials

Accelerated Splenic Enlargement after Splenic Trauma: Influence of Splenic Arterial Embolization

Splenic injury is common in blunt trauma. As post-injury splenic volume changes are unclear, the aim of this study was to elucidate such changes. This retrospective study included 18 patients (14 males, median age 24.5 years) with a splenic injury treated between January 2009 and December 2016. All underwent computed tomography (CT) during admission to our hospital and at the last follow-up visit. The splenic volumes on the first and last enhanced delayed-phase CT scans were compared. The fluid response, transfusion, injury severity score, trauma grade, and extent of splenic artery embolization (SAE) were obtained from medical records. The volume change was assessed with a Mann-Whitney U-test. The volume change in patients treated conservatively was also evaluated to study the natural course after injury. On the first and last scans, the median splenic volume was 105.8 (interquartile range [IQR] 65.4–139.7) and 123.6 (IQR 102.0–225.0) cm3, respectively. The volume increased by 67 (-0.4 ± 120.0) %. SAE was the only factor significantly related to the volume change (p < 0.05). The median follow-up period was 13 (IQR 6–20) days. In conservatively treated patients, the splenic volume change was correlated with the interval between the first and last CT studies. Our findings suggest that the volume of the injured spleen increases in the natural course after trauma. SAE resulted in a decrease in the splenic volume

Content-based CT image retrieval system using deep learning: Preliminary assessment of its accuracy for classifying lesion patterns and retrieving similar cases among patients with diffuse lung diseases

Practical image retrieval systems must fully use image databases. We investigated the accuracy of our content-based computer tomography (CT) image retrieval system (CB-CTIRS) for classifying lesion patterns and retrieving similar cases in patients with diffuse lung diseases. The study included 503 individuals, with 328 having diffuse lung disease and 175 having normal chest CT scans. Among the former, we randomly selected ten scans that revealed one of five specific patterns [consolidation, ground-glass opacity (GGO), emphysema, honeycombing, or micronodules: two cases each]. Two radiologists separated the squares into six categories (five abnormal patterns and one normal pattern) to create a reference standard. Subsequently, each square was entered into the CB-CTIRS, and the F-score used to classify squares was determined. Next, we selected 15 cases (three per pattern) among the 503 cases, which served as the query cases. Three other radiologists graded the similarity between the retrieved and query cases using a 5-point grading system, where grade 5 = similar in both the opacity pattern and distribution and 1 = different therein. The F-score was 0.71 for consolidation, 0.63 for GGO, 0.74 for emphysema, 0.61 for honeycombing, 0.15 for micronodules, and 0.67 for normal lung. All three radiologists assigned grade 4 or 5 to 67.7% of retrieved cases with consolidation, emphysema, or honeycombing, and grade 2 or 3 to 67.7% of the retrieved cases with GGO or micronodules. The retrieval accuracy of CB-CTIRS is satisfactory for consolidation, emphysema, and honeycombing but not for GGO or micronodules

Improved Detectability of Hyper-Dense Nodules Using Dual-Energy Computed Tomography Scanning: Phantom Study Using Simulated Liver Harboring Nodules

The purpose of this study was to evaluate the detectability of hyper-dense nodules using dual-energy computed tomography (DECT) in a phantom. Arterial-phase hepatic dynamic computed tomography (CT) was conducted on small, medium, and large liver-simulating phantoms harboring simulated hypervascular tumors. We acquired 150 single-energy CT (SECT) and 150 DECT scans and measured the contrast-to-noise ratio (CNR) of the nodules. Alternative free response receiver observer characteristic (AFROC) curves of five radiologists’ readings of the SECT and DECT scans were compared to assess detectability of the hyper-dense nodules. For all phantoms, the CNR of nodules measured using DECT was significantly higher than that by using SECT (p < 0.001, all). In the AFROC study, DECT showed a significantly larger area under the curve than that with SECT (0.778 vs 0.499, p = 0.012). Detectability of high-density nodules was better with DECT scans than with SECT scans

Predicting Blood Flow from the Superior Mesenteric Artery to the Celiac Arterial Region on CT Angiography in Patients with Median Arcuate Ligament Syndrome

Purpose: This study aimed to assess whether computed tomography (CT) findings can be used to predict blood flow from the superior mesenteric artery (SMA) to the celiac artery (CA) region in patients with median arcuate ligament syndrome (MALS). Materials and methods: Two radiologists who reviewed 1,290 conventional SMA angiograms and CT scans identified 36 patients with MALS. MALS was classified by their blood flow angiography findings as type A (CA region not or barely visualized) and type B (CA region clearly visualized). The association between patient age, sex, post-stenotic dilatation ratio of the celiac axis, maximum diameter of the pancreaticoduodenal arcade (PDA), and MALS classification based on SMA angiography was assessed. Results: Of 36 MALS patients, 17 had MALS type A and 19 had MALS type B. The mean of the maximum diameter of the PDA in MALS type A was 1.6 ± 0.9 mm (SD) and 4.3 ± 1.3 mm in MALS type B. The poststenotic dilatation ratio of the celiac axis was 2.4 ± 1.2 in MALS type A and 2.2 ± 1.4 in MALS type B. Only maximum diameter of the PDA was a predictor of MALS type B (odds ratio, 15.7; 95% confidence interval, 2.3–108.1). Conclusion: The maximum diameter of the PDA on CT angiography can be used to predict the blood flow from the SMA to the CA region in patients with MALS

Diagnostic Performance of Positron Emission Tomography for the Presurgical Evaluation of Patients with Non-lesional Intractable Partial Epilepsy : Comparison among 18F-FDG, 11C-Flumazenil, and 11C-Flumazenil Binding Potential Imaging Using Statistical Imaging Analysis

To compare the diagnostic performance of 18F-FDG PET, 11C-FMZ PET, and 11C-FMZ BP imaging for the evaluation of patients with intractable partial epilepsy whose MRI findings are normal by using statistical imaging analysis. Ten patients underwent comprehensive presurgical evaluation, including PET studies, to assess the epileptic foci. The extent of cortical resection was based on the results of intracranial video-electroencephalography (IVEEG) monitoring and brain mapping under stimulation. The images of 10 patients and 30 controls were spatially normalized to templates generated in-house by non-rigid registration and the standardized images of the patients and controls were statistically compared. Epileptic focus candidates were visualized on a color map of axial images of each template and the focus site was identified in candidates for lobar location. In patients with Engel I postoperative seizure outcomes we assessed the sensitivity and specificity of the imaging methods for lobar focus localization. We also compared the concordance scores of patients with Engel I and Engel II-IV postoperative seizures. The sensitivity and specificity for lobar focus localization on 18F-FDG PET scans was 90.0% and 84.8%, respectively; it was 30.0% and 81.4% for 11C-FMZ PET, 40.0% and 66.7% for 11C-FMZ BP images, and 100.0% and 51.4% for 18F-FDG PET/11C-FMZ PET/11C-FMZ BP images. In one patient the epileptic focus not detected on 18F-FDG PET scans was shown on 11C-FMZ BP images. In patients with Engel I post-treatment seizures the concordance scores were significantly higher for 18F-FDG PET than 11C-FMZ PET and 11C-FMZ BP images (p < 0.05). With respect to sensitivity and specificity, 18F-FDG PET was superior to 11C-FMZ PET and 11C-FMZ BP imaging. However, in some patients with normal MRI results, 11C-FMZ BP studies may complement 18F-FDG PET findings in efforts to identify the epileptogenic lobar regions

Hybrid Surgery for Portosystemic Encephalopathy in a Patient with Liver Cirrhosis: a case report

Regarding the treatment for a portosystemic shunt, surgical or interventional radiological closure of the shunt was established. Interventional radiology including balloon-occluded retrograde transvenous obliteration can worsen portal hypertension and create a large thrombus close to the major venous system in the case of a huge portosystemic shunt. In contrast, it is also difficult to treat some cases through surgery alone when huge complicated shunts exist very deep in the body. Herein, we report a successful case of surgical shunt ligation for portosystemic encephalopathy in a hybrid operation room that enabled intraoperative angiography and computed tomography. A 62-year-old woman with chronic hepatitis C was referred to our hospital due to high levels of serum ammonia and hepatic encephalopathy. She had a massive, complicated portosystemic shunt from the inferior mesenteric vein to the left renal vein but did not have esophageal or gastric varices. It was difficult to occlude the portosystemic shunt by interventional radiologic techniques because the shunt had an extremely large amount of blood flow and many collateral routes. We performed the shunt ligation in the hybrid operation room. Intraoperative angiography provided detailed information about the portosystemic shunt, such as direction or volume of blood flow and collateral routes in real time. Her encephalopathy disappeared completely and she remains healthy with improved liver functional reserve to date. In conclusion, this is a successful case of a hybrid operation for an extremely large and complicated portosystemic shunt, providing for intraoperative angiography as a safe and reliable surgical treatment for portosystemic encephalopathy in patients with liver cirrhosis