Keiji Matsunaga

Diffusion-weighted imaging of malignant breast tumors: the usefulness of apparent diffusion coefficient (ADC) value and ADC map for the detection of malignant breast tumors and evaluation of cancer extension.

The authors used breast diffusion-weighted imaging (DWI) to diagnose breast cancer and identify cancer extension. Isotropic DWI was performed with EPI. The apparent diffusion coefficient (ADC) value was calculated and displayed on an ADC map. The authors compared between the distribution of low ADC values and pathologic cancer extension. The mean ADC value of breast cancer was 1.12 ± 0.24 × 10−3 mm2/s, which was lower than that of normal breast tissue. The ADC value for invasive ductal carcinoma was lower than that of noninvasive ductal carcinoma. The sensitivity of the ADC value for breast cancer using a threshold of less than 1.6 × 10−3 mm2/s was 95%. Seventy-five percent of all cases showed precise distribution of low ADC value as cancer extension. The causes of underestimation were susceptibility artifact from bleeding and the limit of spatial resolution. Benign proliferative change showed a low ADC value. The authors conclude that DWI has a potential for clinical appreciation in detecting breast cancer.

Diaphragmatic hernia after radiofrequency ablation therapy for hepatocellular carcinoma

3Department of Radiology, Kitasato University School of Medicine, Sagamihara, Kanagawa 228-8555, Japan. ercutaneous radiofrequency ablation is a novel thermal ablation technique for achieving coagulative necrosis of liver tumors with fewer treatment sessions than percutaneous ethanol injection therapy requires [1, 2]. Several recent developments in radiofrequency ablation technology, such as a high-power (150–200 W) radiofrequency generator, a method for conducting radiofrequency ablation during occlusion of hepatic blood flow, and saline-enhanced radiofrequency ablation techniques, have made it possible to necrotize a larger volume of tissue—3 cm or more in diameter—during a single ablation procedure [3]. Most of the complications after radiofrequency ablation have been minor, but some severe and fatal complications have been reported [4, 5]. In a multicenter study in 2,320 patients with 3,554 lesions [4], six patients (0.3%) died after radiofrequency ablation, including two caused by multiorgan failure following intestinal perforation; one case each of septic shock, tumor rupture, liver failure after bile duct stenosis; and sudden death of unknown cause. Fifty cases (2.2%) of additional major complications were also reported, including 12 (0.5%) of peritoneal bleeding, 12 of tumor seeding, six of hepatic abscess, five of gastrointestinal wall perforation, three of hemothorax, two of rapid hepatic decompensation, and one case each of diaphragmatic paresis, common bile duct stenosis, cardiac arrest, pulmonary embolism, pneumothorax, large biloma, multisegmental hepatic infarction, acute cholestasis, and septicemia. Thermal damage has been documented as a specific complication of radiofrequency ablation. We recently encountered a patient with a diaphragmatic hernia due to thermal damage of the diaphragm. A defect of the diaphragm occurred after radiofrequency ablation for hepatocellular carcinoma (HCC) and remained quiescent for 18 months until bowel herniated through it. To our knowledge, this is the first case in the literature to report diaphragmatic hernia as a complication of radiofrequency ablation. The clinical presentation was acute abdominal pain, whereas MDCT clearly indicated a diaphragmatic defect.

Acquisition Protocols and Correction Methods for Estimation of the Heart-to-Mediastinum Ratio in 123I-Metaiodobenzylguanidine Cardiac Sympathetic Imaging

Septal penetration of high-energy photons affects quantitative results in imaging of 123I-labeled tracers. We investigated acquisition protocols (collimator choice and energy window setting) and correction methods for estimating the heart-to-mediastinum (H/M) ratio in cardiac 123I-metaiodobenzylguanidine (MIBG) imaging. Methods: Four hours after 123I-MIBG injection, 40 patients successively underwent planar anterior chest imaging with the medium-energy (ME) (ME method) and low-energy high-resolution (LEHR) (LEHR method) collimators. A 20% energy window was used for both collimators. Another 40 patients were imaged successively with the ME collimator and a 20% window (ME method), the low-medium-energy (LME) collimator and a 20% window (LME20 method), and the LME collimator and a 15% window (LME15 method). The H/M ratios obtained by the LEHR, LME20, and LME15 methods were corrected using their correlations with the H/M ratio obtained by the ME method (empiric correction). The 123I-dual-window (IDW) correction was also applied to remove the influence of high-energy photons. Results: Without correction, severe underestimation of the H/M ratio was shown for the LEHR method using the ME method as a standard, and this underestimation increased with increasing H/M ratios. Underestimation substantially decreased using the LME20 method and further using the LME15 method. Empiric correction reduced the error in the H/M ratio by the LEHR method, but the error was still evident. After empiric correction, the H/M ratios with the LME collimator were comparable to those with the ME collimator. The IDW correction only partially reduced underestimation by the LEHR method and caused a small overestimation for the LME15 method. Conclusion: The use of an LME collimator appears to be acceptable for cardiac 123I-MIBG imaging as an alternative to an ME collimator, and the application of a 15% energy window is recommended when an LME collimator is used. Empiric correction is also expected to improve exchangeability between H/M ratios calculated with ME and LME collimators. Neither the use of an LEHR collimator nor the use of IDW correction is recommended.

Usefulness of the navigator-echo triggering technique for free-breathing three-dimensional magnetic resonance cholangiopancreatography

PURPOSE To prospectively compare the navigator-echo triggering technique (navigator technique) and the conventional respiratory triggering technique using bellows (bellows technique) for free-breathing three-dimensional (3D) magnetic resonance cholangiopancreatography (MRCP) under clinical conditions. MATERIALS AND METHODS Forty patients referred for evaluation of biliary or pancreatic diseases underwent 3D MRCP examination using both navigator and bellows techniques. Two independent radiologists visually evaluated the image quality of 12 segments of the pancreaticobiliary tree in a blinded manner. In addition, the clarity of the lesion was compared between the two techniques in a side-by-side manner. RESULT MRCP images were successfully acquired using both techniques in all patients. No significant difference in acquisition time was found between the two techniques. The image quality was significantly better using the navigator technique than using the bellows technique for the following seven segments: the head, body, and tail of the pancreatic duct; right hepatic duct; anterior and posterior segments of the right hepatic duct; and cystic duct. The other segments (common hepatic and bile duct, left hepatic duct, medial and lateral segments of left hepatic duct, gallbladder) showed no significant difference. The clarity of lesion depiction was significantly better using the navigator technique than using the bellows technique. CONCLUSION Respiratory-triggered 3D MRCP using the navigator technique was shown to be feasible in routine clinical practice. The navigator technique improved the image quality of free-breathing 3D MRCP compared with the bellows technique. The clarity of lesion visualization was also better using the navigator technique than using the bellows technique.

Motion artifact reduction of diffusion‐weighted MRI of the liver: Use of velocity‐compensated diffusion gradients combined with tetrahedral gradients

To assess the effect of motion artifact reduction on the diffusion‐weighted magnetic resonance imaging (DWI‐MRI) of the liver, we compared velocity‐compensated DWI (VC‐DWI) and VC‐DWI combined with tetrahedral gradients (t‐VC‐DWI) to conventional DWI (c‐DWI) in the assessment of apparent diffusion coefficients (ADCs) of the liver.

Optimal techniques for magnetic resonance imaging of the liver using a respiratory navigator-gated three-dimensional spoiled gradient-recalled echo sequence

PURPOSE To optimize the navigator-gating technique for the acquisition of high-quality three-dimensional spoiled gradient-recalled echo (3D SPGR) images of the liver during free breathing. MATERIALS AND METHODS Ten healthy volunteers underwent 3D SPGR magnetic resonance imaging of the liver using a conventional navigator-gated 3D SPGR (cNAV-3D-SPGR) sequence or an enhanced navigator-gated 3D SPGR (eNAV-3D-SPGR) sequence. No exogenous contrast agent was used. A 20-ms wait period was inserted between the 3D SPGR acquisition component and navigator component of the eNAV-3D-SPGR sequence to allow T1 recovery. Visual evaluation and calculation of the signal-to-noise ratio were performed to compare image quality between the imaging techniques. RESULT The eNAV-3D-SPGR sequence provided better noise properties than the cNAV-3D-SPGR sequence visually and quantitatively. Navigator gating with an acceptance window of 2mm effectively inhibited respiratory motion artifacts. The widening of the window to 6mm shortened the acquisition time but increased motion artifacts, resulting in degradation of overall image quality. Neither slice tracking nor incorporation of short breath holding successfully compensated for the widening of the window. CONCLUSION The eNAV-3D-SPGR sequence with an acceptance window of 2mm provides high-quality 3D SPGR images of the liver.

Imipenem/cilastatin sodium (IPM/CS) as an embolic agent for transcatheter arterial embolisation: a preliminary clinical study of gastrointestinal bleeding from neoplasms

PurposeTo evaluate the feasibility and usefulness of imipenem/cilastatin sodium (IPM/CS) as an embolic agent for intestinal bleeding from neoplasms.Materials and methodsSeven patients who underwent 11 transarterial embolisations (TAEs) using IPM/CS as an embolic material for duodenal or small/large intestinal tumour bleeding from January 2004 to December 2011 were retrospectively evaluated. A mixture of IPM/CS and contrast medium was introduced through the microcatheter positioned at the feeding artery to the tumour until extravasation disappeared or stasis of blood flow to the tumour staining was observed.ResultsHaemostasis was obtained in all patients. Therefore, the technical success rate was 100%. Rebleeding was observed in four patients. All of them underwent repeat TAE using IPM/CS, and haemostasis was obtained successfully. No complication was identified following laboratory and clinical examinations. No haemorrhagic death occurred. Haemorrhagic parameters, including blood haemoglobin and the amount of blood transfusion, improved after TAE.ConclusionThe safety, feasibility, and effectiveness of TAE using IPM/CS as an embolic material for intestinal bleeding from neoplasms were suggested by this study. The mild embolic effect of IPM/CS may be adequate for oozing from tumours. Although rebleeding may occur after embolotherapy using IPM/CS, repeat embolisation is effective as treatment for rebleeding.

Correction of collimator-dependent differences in the heart-to-mediastinum ratio in 123I-metaiodobenzylguanidine cardiac sympathetic imaging: Determination of conversion equations using point-source imaging

BackgroundSeptal penetration causes collimator-dependent differences in the heart-to-mediastinum (H/M) ratio in 123I-metaiodobenzylguanidine (MIBG) cardiac imaging. We investigated generally applicable methods to correct such differences.Methods and ResultsFour hours after 123I-MIBG injection, 40 patients underwent anterior chest imaging successively with medium-energy (ME) and various non-ME collimators. The H/M ratios obtained with the non-ME collimators before and after 123I-dual-window penetration correction were compared with the ME-derived standard values to determine patient-based conversion equations for empiric and combined corrections, respectively. A 123I point source was imaged with various collimators, and the central ratio, the ratio of count in a small central region of interest to count in a large one, was calculated. The method of predicting the conversion equations from the central ratios was determined. Correction using the patient-based conversion equations removed systematic underestimation of the H/M ratios obtained with the non-ME collimators, and combined correction depressed residual random errors to some degree. Point-source-based equations yielded results comparable to the patient-based equations.ConclusionsEmpiric and combined corrections effectively reduce collimator-dependent differences in the H/M ratio. The conversion equations can be predicted from simple point-source imaging, which would allow to apply these corrections to data obtained with various collimators.

Evaluation of a respiratory navigator-gating technique in Gd-EOB-DTPA-enhanced magnetic resonance imaging for the assessment of liver tumors

OBJECTIVES We investigated the clinical usefulness of respiratory navigator-gating technique for the assessment of liver tumors in Gd-EOB-DTPA-enhanced magnetic resonance (MR) imaging. METHODS Eighty patients who underwent Gd-EOB-DTPA-enhanced MR imaging to evaluate known or suspected liver tumors were enrolled. Three-dimensional spoiled gradient-recalled echo images of the liver were acquired in the hepatobiliary phase by the following three methods: breath-hold imaging, navigator-gated low-resolution imaging, and navigator-gated high-resolution imaging. Navigator-gated imaging was performed during free breathing. Spatial resolution was identical between breath-hold imaging and gated low-resolution imaging. Signal intensities in the liver, muscle, and spleen were measured in 20 patients. Image quality was visually evaluated in all 80 patients. The detection rate and lesion conspicuity were assessed for 71 malignant liver lesions identified in 29 patients. RESULTS The liver-to-muscle and liver-to-spleen signal ratios were significantly lower for gated images compared to breath-hold images. Images of acceptable quality were obtained in most patients by all three methods, and the overall image quality of axial images did not differ significantly among the imaging methods, although superior reformatted coronal images were obtained by gated high-resolution imaging. The detection rates of malignant liver lesions were similar among the three imaging methods, although lesion conspicuity was significantly better for breath-hold imaging compared to gated imaging. CONCLUSIONS Navigator-gated imaging provided image qualities and detection rates of malignant liver lesions comparable to breath-hold imaging in Gd-EOB-DTPA-enhanced MR imaging; however, no additional benefits of high-resolution imaging were proven for lesion evaluation.

Intraperitoneal bleeding due to rupture of the left gastric vein (LGV) in a patient with liver cirrhosis: a case report

Intraperitoneal bleeding from ruptured ectopic varices is a rare and fatal complication in patients with portal hypertension. Although laparotomy with high mortality is performed, it is difficult to detect correct bleeding site and save the patient. This is probably the first case report of rupture from left gastric vein revealed by transjugular intrahepatic portosystemic shunt (TIPS). We propose the use of TIPS for diagnosing and treating intraperitoneal bleeding from ectopic varices.