Takeshi Yoshizako

Usefulness of Diffusion-Weighted Imaging and Dynamic Contrast-Enhanced Magnetic Resonance Imaging in the Diagnosis of Prostate Transition-Zone Cancer

Background: Conventional T2-weighted (T2-WI) magnetic resonance imaging (MRI) has poor sensitivity for prostate transition-zone (TZ) cancer detection. Purpose: To retrospectively evaluate the clinical value of diffusion-weighted MRI (DW-MRI) and dynamic contrast-enhanced MRI (DCE-MRI) in combination with T2-WI for the diagnosis of TZ cancer. Material and Methods: Twenty-six TZ cancers in 23 patients with at least one tumor (tumor size >10 mm) located predominantly in the TZ were included in the study. Sixteen peripheral-zone (PZ) cancers in 12 patients with PZ cancer but without TZ cancer (control group) were selected by step-section pathologic maps. All patients underwent MRI and radical prostatectomy. MRI was obtained by a 1.5T superconducting system with a phased-array coil. Imaging sequences were T2-WI with fat saturation (FST2-WI), DW-MRI (single-shot echoplanar image, b=0 and 1000 s/mm2, apparent diffusion coefficient [ADC] map findings), and DCE-MRI (3D fast spoiled gradient recalled [SPGR], contrast medium [0.2 mmol/kg], total injection time 5 s, image acquisition 30, 60, and 90 s). Sensitivity, specificity, accuracy, and positive predictive value (PPV) for the diagnosis of TZ cancer were evaluated in four protocols: A) FST2-WI alone, B) FST2-WI plus DW-MRI, C) FST2-WI plus DCE-MRI, D) FST2-WI plus DW-MRI plus DCE-MRI. Results: Sensitivity, specificity, accuracy, and PPV in protocol A (FST2-WI alone) were 61.5%, 68.8%, 64.3%, and 76.2%, respectively. FST2-WI plus DW-MRI (protocol B) improved the sensitivity, specificity, accuracy, and PPV. In FST2-WI plus DW-MRI plus DCE-MRI (protocol D), the number of true-negative lesions increased and false-positive lesions decreased, and the sensitivity, specificity, accuracy, and PPV were 69.2%, 93.8%, 78.6%, and 94.7%, respectively. There was a significant difference between protocols A and D (P<0.05). Conclusion: Adding DW-MRI to FST2-WI in the diagnosis of prostate TZ cancer increased the diagnostic accuracy. The addition of DCE-MRI may be an option to improve the specificity and PPV of diagnosing TZ cancer with FST2-WI and DW-MRI.

Diffusion-weighted MRI for evaluating perianal fistula activity: Feasibility study

PURPOSE To assess the feasibility of using diffusion-weighted magnetic resonance (MR) imaging (DWI) for evaluating perianal fistula activity. MATERIALS AND METHODS This study retrospectively assessed 24 patients with clinically suspected perianal fistula who underwent a total of 28 MR examinations after conservative treatment with antibiotics. DWI was performed at 1.5 T, using b-values of 0 and 1000 s/mm(2). Apparent diffusion coefficient (ADC) maps were created and ADCs of the lesions were measured. Lesions were classified into two groups based on the need for surgery and surgical findings: positive inflammation activity (PIA) and negative inflammation activity (NIA). ADCs of both groups were compared using an unpaired t-test, and Receiver Operating Characteristic (ROC) analysis was performed. RESULTS The ADC (in 10(-3) mm(2)/s) of the PIA group (0.908±0.171) was significantly lower (P=0.0019) than that of the NIA group (1.124±0.244). The area under the ROC curve was 0.749. An optimal cut-off ADC of 1.109 yielded a sensitivity of 95.7%, a specificity of 50%, a positive predictive value of 71%, and a negative predictive value of 90%. CONCLUSION DWI is a feasible method for evaluating perianal fistula activity. The diagnostic performance of this technique should be established in future, larger prospective studies.

Comparison of utility of tumor size and apparent diffusion coefficient for differentiation of low- and high-grade clear-cell renal cell carcinoma

Background: There is a significant correlation between tumor size and tumor grade for clear-cell renal cell carcinoma (RCC) in pathology. Thus, apparent diffusion coefficient (ADC) of clear-cell RCC might be influenced by tumor size. Purpose: To compare the utility of tumor size and ADC for distinguishing low-grade from high-grade clear-cell RCC. Material and Methods: Forty-nine patients undergoing preoperative magnetic resonance imaging were retrospectively assessed. ADC values were calculated using b-value combinations of 0 and 800 s/mm2 at 1.5 T. Two radiologists in consensus measured ADC values via small region of interest (ROI) (mean ROI area, 88.8 mm2; range, 80–108 mm2) placement on an area of solid tumor on a single slice. Maximum tumor diameter was measured at the maximum tumor area. A single pathologist reviewed all pathological slides to determine the nuclear grade according to the Fuhrman classification. The utility of ADC, tumor size, and ADC/size ratio for distinguishing low-grade from high-grade tumors was assessed. Receiver-operating characteristic (ROC) analysis and regression analysis of the each index were performed. The correlation between ADC and tumor size was also investigated. Results: The 49 clear-cell RCC included 34 low-grade and 15 high-grade tumors. The differences of ADC, tumor size, and ADC/size ratio between high-grade and low-grade tumors were statistically significant (P <0.05). The area under the ROC curve of ADC, tumor size, and ADC/size ratio were 0.802, 0.763, and 0.804 respectively. However, using regression analysis, only ADC (P <0.05) was statistically significant index as independent risk factors for high-grade clear-cell RCC. Moreover, weak significant correlation was observed between tumor size and ADC (R2 = 0.3865, P <0.01). Conclusion: There was a weak significant correlation between tumor size and ADC value of clear-cell RCC. Using ROC and regression analysis, ADC was statistically significant index for distinguishing low-grade from high-grade clear-cell RCC more than tumor size and ADC/size ratio.

Risk factors influencing chest tube placement among patients with pneumothorax because of CT-guided needle biopsy of the lung

Introduction: The purpose of this study was to evaluate the risk factors for developing a pneumothorax requiring chest tube placement in patients undergoing CT‐guided needle biopsy of the lung.

MR imaging of vertebral metastases: evaluation of fat saturation imaging

OBJECTIVE To compare conventional T1-weighted imaging (SE-T1) and chemical shift fat-saturation T1-weighted imaging (FS-T1) in the diagnosis of bone metastases. SUBJECTS Twenty-two patients (101 vertebrae) with non-neoplastic lesions (Group 1) and 21 patients (72 vertebrae) with spinal metastases (Group 2) were evaluated with both images. RESULTS The signal intensity (SI) distribution of Groups 1 and 2 on SE-T1 showed various patterns, and SI measurement was not significantly different between the two groups. On FS-T1, all non-neoplastic lesions had a low-intensity homogeneous appearance; however, the metastases had mixed to high SI. The SI measurement data of Group 2 was significantly (P < 0.0001) higher than that of Group 1. CONCLUSION FS-T1 was useful in evaluating vertebral metastases.

Apparent diffusion coefficient of line scan diffusion image in normal prostate and prostate cancer—comparison with single-shot echo planner image

PURPOSE This retrospective study was designed to evaluate the apparent diffusion coefficient (ADC) of line scan diffusion images (LSDI) in normal prostate and prostate cancer. Single-shot echo planner images (SS-EPI) were used for comparison. MATERIALS AND METHODS Twenty prostate tumors were examined by conventional MRI in 14 patients prior to radical prostatectomy. All patients were examined with a 1.5-T MR imager (Signa CV/i ver. 9.1 GE Medical System Milwaukee, WI, USA). Diffusion-weighted MR imaging (DWI) using LSDI was performed with a pelvic phased-array coil, with b values of 5 and 800 s/mm². DWI using SS-EPI was performed with a body coil, with b values of 0 and 800 s/mm². The ADCs of each sequence for 14 normal prostate and 20 prostate cancers were histopathologically assessed. Signal-to-noise ratio (SNR) on DWI was estimated and compared for each sequence. RESULTS The mean ADCs (±S.D.) of normal peripheral zones (PZ), transition zones (TZ) and cancer (in 10⁻³ mm²/s) that used LSDI were 1.42±0.12, 1.23±0.10 and 0.79±0.19, respectively. Those that used SS-EPI were 1.76±0.26, 1.38±0.20 and 1.05±0.27, respectively. Using unpaired t test (P<.05), we found a significant difference in each sequence between normal tissue (both PZ and TZ) and the cancer. Paired t test (P<.05) also registered a significant difference between LSDI and SS-EPI. Mean SNR for DWI using LSDI was 16.49±5.03, while the DWI using SS-EPI was 18.85±9.26. The difference between the SNR of each sequence was not statistically significant by paired t test. CONCLUSION We found that ADCs using LSDI and SS-EPI showed similar tendencies in the same patients. However, in all regions, LSDI ADCs had smaller standard deviations than SS-EPI ADCs.

Two-dimensional time-of-flight MR venography: assessment with detection of chronic deep venous thrombosis in combination with magnetization transfer contrast.

PURPOSE The purpose of this study was to determine the optimum imaging parameters for 2D-TOF MR venography (MRV) of the pelvis and suprapopliteal deep venous system in combination with off-resonance magnetization transfer constant (MTC) and to evaluate the use of MRV in patients suspected of having chronic deep venous thrombosis (DVT) by comparing its accuracy with that of conventional venography (CV). METHOD MRV was performed in 10 normal subjects to determine the optimum imaging parameters. Systematically varied scan parameters included flip angles ranging from 30 to 120 degrees by 10 degrees increments. Best TR was calculated by using the theoretical relation between the optimal TR and flow velocity. We then evaluated the use of MRV in 26 patients (total 52 deep venous systems) suspected of having chronic DVT by comparing its accuracy in evaluating the intrapelvic and suprapopliteal deep venous system with that of CV. RESULTS The optimal imaging parameters for intrapelvic and suprapopliteal venous system MRV were found to be a flip angle of 60 degrees and a pulse sequence of 35/6.9 (TR ms/TE ms) combined with an off-resonance MTC technique. All the main veins of the intrapelvic and suprapopliteal venous systems were clearly demonstrated in each subject. The sensitivity of MRV was 100% and its specificity was 100% for diagnosis of pelvic venous stenosis. The collateral vessels were demonstrated with MRV in all patients. CONCLUSION 2D-TOF off-resonance MTC MRV of the pelvis and the suprapopliteal lower extremities is suitable for evaluation of intrapelvic branches and suprapopliteal deep venous system and chronic DVT.

Power Doppler ultrasonography for assessment of rheumatoid synovitis: comparison with dynamic magnetic resonance imaging

PURPOSE The aim of this study was to compare the effectiveness of power Doppler ultrasonography (PDUS) with that of dynamic magnetic resonance imaging (MRI) for detecting active synovitis in the hands of rheumatoid arthritis (RA) patients. MATERIALS AND METHODS PDUS and dynamic MRI were performed for a total of 220 finger joints with active RA. Each synovial blood flow by PDUS and dynamic MRI was measured and categorized into four grades. RESULTS Taking dynamic MRI as a reference, PDUS showed a sensitivity of 94%, a specificity of 95%, and an accuracy of 95%. CONCLUSION PDUS is useful for detection of active synovitis in the overall-grade RA patients.

Magnetic resonance imaging features of angiomyofibroblastoma-like tumor of the scrotum with pathologic correlates

Various tumors can occur in the scrotum. Among them, angiomyofibroblastoma-like tumors are very rare mesenchymal tumors. We report a case of an angiomyofibroblastoma-like tumor that arose in the right half of the scrotum in a 72-year-old man. It is difficult to separate angiomyofibroblastoma-like tumors from other malignant tumors invading the male genital tract on the basis of clinical characteristics and magnetic resonance imaging findings.

Low b-value diffusion-weighted imaging for diagnosing strangulated small bowel obstruction: A feasibility study

To assess the feasibility of low b‐value diffusion‐weighted imaging (DWI) for diagnosing strangulated small bowel obstruction (SBO).