Clinical impact of low tube voltage computed tomography during hepatic arteriography with low iodine to detect hepatocellular carcinoma before transarterial chemoembolization.

PURPOSE: This study aimed to evaluate the clinical impact of low tube voltage computed tomography (CT) during hepatic arteriography (CTHA) using low iodine contrast to detect hepatocellular carcinoma (HCC). MATERIALS AND METHODS: CTHA images were obtained using a dual-spin technique (80 kVp and 135 kVp) with 30 ml of low-dose iodine contrast (75 mgI/ml). Three radiologists reviewed 135 kVp and 80 kVp CTHA images to diagnose HCC, recording their confidence scores and evaluations of sharpness, noise, artifact, and overall image quality. Lesion-to-liver contrast ratios and objective noise were measured by a non-reader radiologist. RESULTS: We included 23 patients (body mass index, 23.6 ± 2.6 kg/m2) with 89 HCCs. The mean radiation dose index volume was 21.3 mGy at 135 kVp and 9.4 mGy at 80 kVp (P < 0.001). The overall sensitivity and positive predictive value for diagnosing HCCs at 80 kVp vs. 135 kVp were 0.787 vs. 0.730 and 0.712 vs. 0.756, respectively. The lesion-to-liver contrast ratio at 80 kVp was significantly higher than at 135 kVp in the first (3.1 vs. 2.0; P = 0.008) and second phase (3.1 vs. 2.3; P = 0.016). Objective noise was significantly higher at 80 kVp than at 135 kVp in the first (15. 6 ± 4.9 vs. 11.0 ± 3.1; P < 0.001) and second (16.9 ± 5.2 vs. 15.0 ± 7.3; P = 0.046) phases. CONCLUSION: An 80 kVp CTHA, with lower-dose iodine, improved the sensitivity and reduced the radiation dose, despite a decreased positive predictive value in comparison with a 135-kVp CTHA with the same iodine dose.

Effect of Portal Vein and Hepatic Artery Occlusion on Radiofrequency Ablation: Animal Experiment Comparing MR and Histology Measurements of the Ablation Zones.

PURPOSE: This animal experimental study evaluated how hepatic artery and portal vein transient occlusion affects the ablation zone of hepatic radiofrequency ablation (RFA). MATERIAL AND METHODS: Twenty-one rabbits were divided into three groups of seven each: (1) control, (2) hepatic artery occlusion, and (3) portal vein occlusion by a balloon catheter. For each rabbit, two or three RFA sessions were performed using an electrode needle. Ablation time, temperature around the tip of RFA needle at the end of RFA, ablation volume on fat-suppressed T1-weighted image in the hepatobiliary phase, and coagulative necrosis area on histopathology were measured and compared between the three groups using the Kruskal-Wallis paired Mann-Whitney U tests. RESULTS: In 43 RFA sessions (group 1, 15; group 2, 14; group 3, 14), mean tissue temperature in group 3 (77.0 °C ± 7.7 °C) was significantly higher compared to groups 1 (59.2 °C ± 18.8 °C; P = 0.010) and 2 (67.5 °C ± 9.9 °C; P = 0.010). In addition, mean ablation volume and coagulative necrosis in group 3 (2.10 ± 1.37 mm3 and 0.86 ± 0.28 mm2, respectively) were larger compared to groups 1 (0.84 ± 0.30 mm3; P < 0.001 and 0.55 ± 0.26 mm2; P = 0.020, respectively) and 2 (0.89 ± 0.59 mm3; P = 0.002 and 0.60 ± 0.22 mm2; P = 0.024, respectively). CONCLUSION: Portal vein occlusion potentially boosts tissue temperature, ablation volume, and area of histopathologically proven coagulative necrosis during hepatic RFA in the non-cirrhotic liver.

Histologic Distribution and Characteristics on MR Imaging of Ultrasmall Superparamagnetic Iron Oxide in Ethyl-nitrosourea-induced Endogenous Rat Glioma.

PURPOSE: (1) To evaluate the enhancement patterns of an ultrasmall superparamagnetic iron oxide contrast agent (USPIO-CA) compared with those of a gadolinium-based contrast agent (Gd-BCA). (2) To compare the histologic distribution of USPIO-related iron particles (USPIO-IPs) with the USPIO-enhancement area in the early vascular and in the cellular imaging phase (E- and L-phase, respectively) after intravenous CA administration. METHODS: We performed USPIO-enhanced MRI of N-ethyl-N-nitrosourea (ENU)-induced endogenous rat glioma, including spin-echo (SE) T1-weighted images (T1WIs) and gradient-recalled-echo (GRE) T2-weighted images (T2WIs), before and at 3-6 h after USPIO-CA administration for E-phase images. For L-phase images, MRI was performed at 16-19 and 62-69 h after administration. Two observers determined the USPIO-enhancement area on E-phase images and Gd-enhancement areas. We compared the USPIO-enhancement size (USPIO-ES) and Gd-ES on SE T1WIs, and the hypo-intense USPIO-ES on GRE T2WIs and Gd-ES using the Wilcoxon signed-rank test. In addition, two raters visually evaluated the correspondence between the histologic distribution of USPIO-IPs and the USPIO-enhancement area on corresponding GRE T2WIs at each phase using a 3-rating scale. RESULTS: Significantly smaller hyper-intense, hypo-intense and combined hyper-/hypo-intense areas were observed on USPIO-enhanced SE T1WIs compared with Gd-enhanced images (all P < 0.001). The hypo-intense USPIO-ES on GRE T2WIs was significantly smaller than the Gd-ES (P = 0.001). The distribution of USPIO-IPs on histopathological specimen and USPIO-enhancement on GRE T2WIs exhibited poor agreement in 5 of 9 tumors with enhancement from rats sacrificed early. The distribution of microglia containing USPIO-IPs corresponded with the pattern of USPIO-enhancement in the 2 tumors with late enhancement. CONCLUSION: The enhancement pattern and size of USPIO-CA in a rat glioma model were statistically different from those of Gd-BCA. Our histological data suggests that USPIO-enhanced MRI offers vascular bed imaging in E-phase and might depict the intra-tumoral distribution of immune effector cells in L-phase.

Noncontrast MRI of acute abdominal pain caused by gastrointestinal lesions: indications, protocol, and image interpretation.

Gastrointestinal tract lesions are major causes of acute abdominal pain. A rapid, accurate, and reliable diagnosis is required to manage patients. Magnetic resonance imaging (MRI) is a nonionizing modality that is beneficial for pregnant women, children, and young adults who are sensitive to ionizing radiation. For patients with renal impairment who are not accurately diagnosed with noncontrast computed tomography, noncontrast MRI can serve as an alternative diagnostic modality. MRI protocols used for acute abdominal pain are supposed to be optimized and prioritized to shorten scanning times. Single-shot T2-weighted and fat-suppressed T2-weighted imaging are important pulse sequences that are used to reveal pathology and inflammation in the gastrointestinal tract. Diffusion-weighted imaging clearly depicts inflammation and abscesses as hyperintense lesions. Most acute gastrointestinal tract lesions, including inflammation, ischemia, obstruction, and perforation, demonstrate bowel wall thickening. Bowel obstruction and adynamic ileus present bowel dilatation, and perforation and penetration show bowel wall defects. MRI can be used to reveal these pathological findings with some characteristics depending on their underlying pathophysiology. This review article discusses imaging modalities for acute abdominal pain, describes a noncontrast MRI protocol for acute abdominal pain caused by gastrointestinal tract lesions, and reviews MRI findings of acute gastrointestinal tract lesions.

Optimization of pulse sequences in ultrafast magnetic resonance imaging for the diagnosis of acute abdominal pain caused by gastrointestinal disease.

BACKGROUND: Magnetic resonance imaging (MRI) is widely used to diagnose acute abdominal pain; however, it remains unclear which pulse sequence has priority in acute abdominal pain. PURPOSE: To investigate the diagnostic accuracy of MRI and to assess the conspicuity of each pulse sequence for the diagnosis of acute abdominal pain due to gastrointestinal diseases. MATERIAL AND METHODS: We retrospectively enrolled 60 patients with acute abdominal pain who underwent MRI for axial and coronal T2-weighted (T2W) imaging, fat-suppressed (FS)-T2W imaging, and true-fast imaging with steady-state precession (True-FISP) and axial T1-weighted (T1W) imaging and investigated the diagnosis with endoscopy, surgery, histopathology, computed tomography, and clinical follow-up as standard references. Two radiologists determined the diagnosis with MRI and rated scores of the respective sequences in assessing intraluminal, intramural, and extramural abnormality using a 5-point scale after one month. Diagnostic accuracy was calculated and scores were compared by Wilcoxon-signed rank test with Bonferroni correction. RESULTS: Diagnostic accuracy was 90.0% and 93.3% for readers 1 and 2, respectively. Regarding intraluminal abnormality, T2W, FS-T2W, and True-FISP imaging were superior to T1W imaging in both readers. FS-T2W imaging was superior to True-FISP in reader 2 (P < 0.0083). For intramural findings, there was no significant difference in reader 1, whereas T2W, FS-T2W, and True-FISP imaging were superior to T1W imaging in reader 2 (P < 0.0083). For extramural findings, FS-T2W imaging was superior to T2W, T1W, and True-FISP imaging in both readers (P < 0.0083). CONCLUSION: T2W and FS-T2W imaging are pivotal pulse sequences and should be obtained before T1W and True-FISP imaging.

MR Imaging-based Evaluation of Mesenteric Ischemia Caused by Strangulated Small Bowel Obstruction and Mesenteric Venous Occlusion: An Experimental Study Using Rabbits.

PURPOSE: This study assessed the MRI findings of strangulated small bowel obstruction (SBO) and mesenteric venous occlusion (MVO) in a rabbit model using 3T MRI. MATERIALS AND METHODS: Twenty rabbits were included in this study. The strangulated SBO and MVO models were generated via surgical procedures in nine rabbits, and sham surgery was performed in two rabbits. The success of generating the models was confirmed via angiographic, macroscopic, and microscopic findings after the surgical procedure. MRI was performed before and 30 min after inducing mesenteric ischemia. T1-weighted images (T1WIs), T2-weighted images (T2WIs), and fat-suppressed T2WIs (FS-T2WIs) were obtained using the BLADE technique, and fat-suppressed T1WIs (FS-T1WIs) were obtained. The signal intensities of the affected bowel before and after the surgical procedures were visually categorized as high, iso, and low intense compared with the findings for the normal bowel wall on all sequences. Bowel wall thickness was measured, and the signal intensity ratio (SI ratio) was calculated using the signal intensities of the bowel wall and psoas muscle. RESULTS: Angiographic, macroscopic, and microscopic findings confirmed that all surgical procedures were successful. The ischemic bowel wall was thicker than the normal bowel. The bowel wall was thicker in the MVO model (3.17 ± 0.55 mm) than in the strangulated SBO model (2.26 ± 0.46 mm). The signal intensity and SI ratio of the bowel wall were significantly higher after the procedure than before the procedure on all sequences in both models. The mesentery adjacent to the ischemic bowel loop exhibited a high signal intensity in all animals on FS-T2WIs. CONCLUSION: Non-contrast MRI can be used to evaluate mesenteric ischemia caused by strangulated SBO and MVO. FS-T2WIs represented the best modality for depicting the high signal intensity in the bowel wall and mesentery caused by ischemia.

Change in hepatic hemodynamics assessed by hepatic arterial blood pressure and computed tomography during hepatic angiography with the double balloon technique.

PURPOSE: To assess the change in hepatic arterial blood pressure (HABP) and computed tomography during hepatic arteriography (CTHA) using the double balloon technique. MATERIALS AND METHODS: Nine patients with hepatocellular carcinoma (HCC) were enrolled. We inserted a 5.2-Fr balloon catheter into the common or proper hepatic artery and a 1.8-Fr microballoon catheter into the lobar or segmental artery feeding the HCC. HABPs were measured with the 1.8-Fr microballoon catheter (usual-HABP), with the 1.8-Fr balloon inflated (B-HABP), and with both the 5.2-Fr and 1.8-Fr balloons inflated (BB-HABP). CTHAs were performed via a 1.8-Fr microcatheter (usual-CTHA), with the 1.8-Fr balloon inflated (B-CTHA selective), with both the 5.2-Fr and 1.8-Fr balloons inflated (BB-CTHA selective), and via the 5.2-Fr catheter with the 1.8-Fr balloon inflated (B-CTHA whole) and with both the 5.2-Fr and 1.8-Fr balloons inflated (BB-CTHA whole). RESULTS: In all cases, B-HABP was lower than usual-HABP. There was a decrease in BB-HABP in comparison with B-HABP in cases with occlusion of the proper hepatic artery. The contrast effect of B-CTHA selective increased in four cases. The contrast effect on B-CTHA whole remained in all cases. CONCLUSION: This technique can be useful in decreasing HABP and collateral blood flow from the adjacent hepatic segment.

Transcatheter Arterial Embolization for Postoperative Bleeding Following Abdominal Surgery.

PURPOSE: We aimed to estimate the usefulness of transcatheter arterial embolization (TAE) in patients with postoperative abdominal hemorrhage and to evaluate the effects of pancreatic fistula on clinical outcomes and angiographic findings. MATERIALS AND METHODS: We enrolled 22 patients (20 males and 2 females; mean age 63 years; range 25-86 years), who underwent transarterial angiography for postoperative hemorrhage after abdominal surgery. This group corresponded to 28 procedures. Technical and clinical success rates were calculated, and clinical findings and outcomes were compared between patients with and without a pancreatic fistula. RESULTS: Pre-interventional CT was performed in all patients before first angiography, and the location of the bleeding was identified in all but one patient. Active arterial bleeding, identified by extravasation of contrast agent (n = 12), pseudoaneurysm formation (n = 12), and arterial wall irregularity (n = 2) were detected in 28 angiographic procedures, and embolization was performed in 26 instances. Various embolization techniques such as isolation, packing, embolization, and stentgraft implantation were performed. The technical and clinical success rates were 96% (25/26 procedures) and 82% (18/22 patients), respectively. In hemodynamically unstable patients (shock index: heart rate/systolic blood pressure > 1), a 92% (12/13 cases) technical success rate was achieved. There were no significant differences in any evaluated parameters between patients with and without pancreatic fistula. CONCLUSION: TAE is a safe and effective for treating postoperative hemorrhage even in patients with hemodynamic instability and pancreatic fistula. Additionally, pre-interventional CT is useful for effective, consecutive interventions.