Junichi Hachiya

Diffusion-weighted MR imaging with single-shot echo-planar imaging in the upper abdomen: preliminary clinical experience in 61 patients

AbstractBackground: To determine the potential ability of diffusion-weighted magnetic resonance (MR) imaging with single-shot echo-planar imaging (DW imaging) in the upper abdomen by apparent diffusion coefficient (ADC) and signal:intensity ratio (SIR) measurements. Methods: DW imaging was performed in 61 clinical patients. ADCs in the liver, pancreas, spleen, kidney, and different pathological conditions were calculated. Spleen-to-liver SIR and segmental intensity difference of the liver (SID) were also calculated. Results: The mean ADCs (mm2/s) were 2.28 × 10−3± 0.07 in the liver, 1.44 × 10−3± 0.05 in the spleen, 1.94 × 10−3± 0.19 in the pancreas, and 5.76 × 10−3± 0.06 in the kidney. The mean ADC of cirrhotic liver was 1.96 × 10−3± 0.62, which was lower than that of normal liver. Other pathologic conditions also showed ADCs different from those of normal tissues. All DW images showed significantly higher spleen-to-liver SIRs and SIDs than did T2-weighted images (p < 0.05). Conclusion: The mean ADCs obtained with DW imaging were different in each upper abdominal organ and with each pathologic condition. DW images showed better soft tissue contrast than did T2-weighted images with regard to SIR and CNR in depicting and characterizing upper abdominal disorders.

Diagnosis of anomalous pancreaticobiliary junction : Value of magnetic resonance cholangiopancreatography

BACKGROUND Anomalous pancreaticobiliary junction (a long common channel), with or without congenital choledochal cyst, is frequently associated with biliary tract carcinoma. We assessed the diagnostic value of magnetic resonance cholangiopancreatography (MRCP) for patients with anomalous pancreaticobiliary junction (PBJ). METHODS In 159 adult patients with pancreatobiliary disease, breath-hold (1 to 18 seconds) MRCP was performed according to a half-Fourier acquisition single-shot turbo spin-echo sequence. In all patients the length of the common channel demonstrated by MRCP was compared with that demonstrated by endoscopic retrograde cholangiopancreatography. In 11 patients with anomalous PBJ (the common channel > or = 15 mm on endoscopic retrograde cholangiopancreatography), the diagnostic accuracy of MRCP for associated biliary diseases was evaluated. RESULTS No complications were encountered in performing MRCP. On MRCP, the length of the common channel was calculated to be 15 mm or longer in nine (82%) of 11 patients with anomalous PBJ. In patients with normal PBJ, MRCP identified PBJ with the channel measuring 0 mm in length. MRCP allowed detailed visualization of congenital choledochal cyst (all seven patients) but failed to depict carcinoma (one patient) and mucosal hyperplasia (five patients) of the gallbladder. CONCLUSIONS MRCP is a noninvasive and accurate imaging method for diagnosing anomalous PBJ and congenital choledochal cyst.

Determinations of organ doses and effective dose equivalents from computed tomographic examination

The organ or tissue doses were determined with a phantom measurement for 12 types of CT scanners widely used in Japan. Two types of thermoluminescent dosimeters were used for the dose determinations in a Rando woman phantom. The effective dose equivalents recommended by the International Commission on Radiological Protection were calculated using the measured organ or tissue doses. It was found that the CT scanners currently available give quite different organ or tissue doses. When selecting the optimum technical factors for scanning, therefore, it is important to take into consideration the balance of the image quality and the radiation exposure to patients.

Magnetic resonance cholangiography using half-Fourier acquisition for diagnosing choledocholithiasis.

Objective:Magnetic resonance cholangiography (MRC), using a half-Fourier acquisition single-shot turbo spin-echo (HASTE) sequence, noninvasively provides very rapid (1–2 s) and high-quality images of the biliary tract. We assessed the diagnostic usefulness of HASTE-MRC for choledocholithiasis.Methods:A total of 101 patients with suspected choledocholithiasis underwent MRC, ultrasonography, and endoscopic retrograde cholangiopancreatography (ERCP). In 97 patients in whom ERCP fully depicted the common bile duct, we retrospectively analyzed the capability of MRC to image the common bile duct and to diagnose choledocholithiasis, in comparison with that of ultrasonography.Results:In 34 patients, ERCP demonstrated bile duct stones, which were confirmed at endoscopic or surgical treatment. The common bile duct was fully delineated in 98% by MRC and in 70% by ultrasonography. MRC (91%) was more sensitive than ultrasonography (71%) for detecting choledocholithiasis (p < 0.05). MRC demonstrated bile duct stones in all patients with stones ≥11 mm but missed calculi in the 29% of patients with small (3–5 mm) stones. MRC was capable of detecting choledocholithiasis regardless of bile duct caliber. The specificity of MRC (100%) was higher than that of ultrasonography (95%).Conclusion:HASTE-MRC, a fast and noninvasive procedure, can accurately diagnose choledocholithiasis although the detectability for small stones is limited.

Breath-held MR cholangiopancreatography with half-averaged single shot hybrid rapid acquisition with relaxation enhancement sequence : Comparison of fast GRE and SE sequences

PURPOSE Our goal was to determine whether half-averaged single shot hybrid rapid acquisition with relaxation enhancement (single shot hybrid RARE) sequence can improve image quality, duct conspicuity, signal intensity ratio (SIR), and contrast-to-noise ratio (CNR) of MR cholangiopancreatography (MRCP) by comparing it with two other MRCP sequences: fast SE (FSE) and contrast-enhanced Fourier-acquired steady-state technique (CE-FAST). METHOD MRCP with three sequences was obtained in 46 people (10 volunteers, 36 patients with pancreatobiliary disease). Overall image quality and duct conspicuity were graded. SIR and CNR were also measured. RESULTS Overall image quality was graded excellent or good in all 46 patients (100%) with single shot hybrid RARE, in 38 of 46 (83%) with FSE, and in 5 of 46 (11%) with CE-FAST. Duct conspicuity was the best in single shot hybrid RARE statistically. SIR was the highest in FSE, while CNR was highest statistically in single shot hybrid RARE of three sequences. CONCLUSION Single shot hybrid RARE can provide consistently higher quality MRCP than FSE and CE-FAST because sequential images by single shot hybrid RARE minimize respiratory, bowel, and cardiac motion artifacts.

Diffusion-weighted MRI of subdural and epidural empyemas

We reviewed diffusion-weighted images (DWI) from eight patients with subdural and four with epidural empyemas to assess the possibility of differentiating between these lesions by DWI. The signal intensities of the empyemas on DWI, and maps of the apparent diffusion coefficient (ADC) were analysed in seven patients. In seven of the eight patients with subdural empyema, the lesions appeared as areas of high signal. The ADC maps confirmed that these areas were the result of restricted diffusion. (In the remaining patient, the lesion showed a mixture of high and low signal.) The epidural empyemas contained areas of low signal in all four patients; part of the empyema was isointense or gave high signal in two. DWI may be an adjunct to conventional sequences for differentiating between subdural and epidural empyemas.

Comparison between endorectal coil and pelvic phased-array coil magnetic resonance imaging in patients with anorectal tumor

BACKGROUND Magnetic resonance imaging (MRI) has been used as one of the diagnostic tools in the preoperative evaluation of rectal cancer. However, the usefulness of endorectal coil (ERC) compared with phased array coil (PA) MRI is still unknown. PATIENTS AND METHODS Nineteen patients with rectal (17 patients) and anal (2 patients) tumors undergoing both ERC-MRI and PA-MRI preoperatively were included in the study. Seventeen patients had advanced stage tumors, and the remaining 2 had early stage tumors. The diagnostic accuracy of depth tumor invasion and lymph node metastasis were compared with reference to the histopathologic findings as the gold standard. RESULTS ERC-MRI was evaluable in only 10 (52.6%) of 19 patients, because of difficulties in ERC placement, whereas PA-MRI could be obtained in all patients (100%). In 10 patients examined by both modalities, the diagnostic accuracy of depth of tumor invasion was 80% by ERC-MRI and 80% by PA-MRI. In lymph node staging, ERC yielded sensitivity of 100%, specificity of 62.5%, and overall accuracy of 70.0%. The corresponding values for PA-MRI were 50%, 100% and 90.0%, respectively. These figures were not significantly different between the two modalities. CONCLUSIONS ERC-MRI and PA-MRI showed similar diagnostic accuracy. ERC-MRI may be abandoned in the preoperative staging of patients with locally advanced anorectal tumors because of its limited clinical utility.

Transient hepatic attenuation differences on dynamic computed tomography.

Transient hepatic attenuation differences (THAD) are occasionally noted on dynamic CT in patients with portal vein obstruction, arterioportal shunt, liver tumor, and liver abscess. We report four additional cases of THAD with unreported and/or unexplained etiology.

Preoperative staging by multidetector-row computed tomography in patients with rectal carcinoma

BACKGROUND Multidetector-row computed tomography (MDCT, or multi-slice CT) has been introduced in 2000. So far, there has been no published study on this modality in patients with rectal carcinoma. METHODS Twenty patients with rectal carcinoma were preoperatively examined by MDCT and conventional CT (CCT). Diagnostic accuracies of both modalities were compared regarding the evaluation of depth of tumor invasion (Tis/T1/T2, T3, T4) and lymph node metastasis based on the pathologic findings. RESULTS Although CCT detected a tumor in 13 (65%) of 20 patients, MDCT revealed a tumor in all 20 patients (P = 0.004). Regarding depth of tumor invasion, the concordance rate was significantly higher for MDCT (20/20: 100%) than for CCT (12 of 20: 60%; P = 0.002). Regarding lymph node metastasis, the overall accuracy was 70.0% in CCT, and also 70.0% in MDCT. CONCLUSIONS MDCT was superior to CCT in the evaluation of depth of tumor invasion, but was equal to CCT in the evaluation of lymph node metastasis.

A prospective comparison between multidetector-row computed tomography and magnetic resonance imaging in the preoperative evaluation of rectal carcinoma

BACKGROUND Multidetector-row computed tomography (MDCT, or multislice CT) is a new modality with four detectors, which makes examination time shorter and produces higher resolution and multiplanar reformation of the images. Its diagnostic role in patients with rectal carcinoma has not been determined. METHODS Twenty-one patients with rectal carcinoma were preoperatively examined by both MDCT and magnetic resonance imaging (MRI). Diagnostic accuracies of both modalities were compared regarding depth of tumor invasion and lymph node metastasis based on the pathologic findings. RESULTS Both examinations detected all tumors. Regarding depth of tumor invasion, the concordance was 95.2% (20 of 21) for MDCT and 100% (21 of 21) for MRI. Regarding lymph node metastasis, the overall accuracy was 61.9% for MDCT and 70.0% for MRI. CONCLUSIONS Multidetector-row computed tomography was equal to MRI in the preoperative local staging of rectal carcinoma.