Chan Kyo Kim

Value of Diffusion-weighted Imaging for the Prediction of Prostate Cancer Location at 3t Using a Phased-array Coil: Preliminary Results

Objectives:To retrospectively evaluate the imaging quality of diffusion-weighted imaging (DWI), compare the apparent diffusion coefficient (ADC) values for malignant and benign tissues in the peripheral zone (PZ) and transition zone (TZ), and evaluate whether T2-weighted imaging (T2WI) with DWI could improve the prediction of prostate cancer location when compared with T2WI at 3T using a phased-array coil. Materials and Methods:Thirty-seven patients underwent T2WI and DWI before radical prostatectomy. The DWI technique with b = 0 and b = 1000 s/mm2 was used. ADC values were measured in benign and malignant tissues in the PZ or TZ. The prediction of prostate cancer location was evaluated in the PZ and TZ using T2WI and T2WI with DWI, respectively. Two readers in consensus recorded the presence of prostate cancer at magnetic resonance imaging and rated the imaging quality of DWI. Results:For the prediction of 68 prostate tumors, the overall sensitivity and positive predictive value of T2WI with DWI were 84% and 86%, whereas those of T2WI were 66% and 63%, respectively (P < 0.05). The mean ADC values of malignant and benign tissues in the PZ and TZ were 1.30 ± 0.26 and 1.96 ± 0.20, and 1.35 ± 0.24 and 1.75 ± 0.23 × 10−3mm2/s, respectively (P < 0.01). The overall imaging quality was satisfactory or better in 97% of patients. Conclusion:DWI is a feasible technique that can be used for the differentiation of malignant and benign tissues in the PZ and TZ. Additionally, T2WI with DWI is superior to T2WI alone for the prediction of prostate cancer location.

Detection of hepatocellular carcinomas and dysplastic nodules in cirrhotic liver accuracy of ultrasonography in transplant patients

The purpose of this study was to assess the usefulness of ultrasonography in the detection of hepatocellular carcinomas and dysplastic nodules in patients with liver cirrhosis. Pretransplantation sonograms in 52 patients with liver cirrhosis who underwent orthotopic liver transplantation were evaluated retrospectively. The numbers of hepatocellular carcinomas and dysplastic nodules were assessed in the explanted liver specimens and compared with pretransplantation ultrasonographic results. Eighteen hepatocellular carcinomas in 16 patients and 20 dysplastic nodules in 11 patients were present in the explanted livers. The size of hepatocellular carcinomas ranged from 0.6 to 5.0 cm (mean, 2.1 cm) in diameter, and that of dysplastic nodules ranged from 0.5 to 1.7 cm (mean, 1.0 cm) in diameter. Pretransplantation ultrasonography enabled detection of 6 of 18 hepatocellular carcinoma and 0 of 20 dysplastic nodule lesions; lesion detection sensitivity for hepatocellular carcinomas and dysplastic nodules was 33% and 0%, respectively. Patient sensitivity and specificity for hepatocellular carcinomas were 38% (6 of 16) and 92% (33 of 36), and those for dysplastic nodules were 0% and 95% (39 of 41), respectively. On the basis of our results, ultrasonography is insensitive for detection of hepatocellular carcinomas and dysplastic nodules in patients with advanced liver cirrhosis.

High-b-Value Diffusion-Weighted Imaging at 3 T to Detect Prostate Cancer: Comparisons Between b Values of 1,000 and 2,000 s/mm2

OBJECTIVE The objective of our study was to investigate the diagnostic performance of 3-T MRI of the prostate using diffusion-weighted imaging (DWI) with high b values (1,000 and 2,000 s/mm2) and a phased-array coil in predicting localized prostate cancer. MATERIALS AND METHODS Forty-eight patients underwent single-shot echo-planar DWI at 3 T, followed by radical prostatectomy. DWI was performed at high b values of 1,000 and 2,000 s/mm2. Apparent diffusion coefficient (ADC) maps were analyzed by visual and quantitative assessment for tumor and benign tissue in the peripheral and transition zones. The visual and quantitative results of ADC maps obtained at b values of 1,000 and 2,000 s/mm2 were compared with the histopathologic findings. RESULTS To predict localized prostate cancer, the sensitivity of ADC maps obtained at a b value of 1,000 versus 2,000 s/mm2 was 88% and 71%, respectively, and the accuracy was 89% and 86% (p<0.01). The mean ADC values of tumors in both the peripheral and transition zones were significantly lower than those of benign tissues at both b values of 1,000 and 2,000 s/mm2 (p<0.001). CONCLUSION Prostate DWI performed at 3 T using high b values was able to improve differentiation of tumors from benign tissue. DWI performed using a b value of 1,000 s/mm2 was more sensitive and more accurate in predicting localized prostate cancer than DWI performed using a b value of 2,000 s/mm2.

Localization of prostate cancer using 3T MRI: comparison of T2-weighted and dynamic contrast-enhanced imaging.

Objective: To compare dynamic contrast-enhanced imaging and T2-weighted imaging using a 3T MR unit for the localization of prostate cancer. Methods: Twenty consecutive patients with biopsy-proven prostate cancer underwent both T2-weighted imaging and dynamic contrast-enhanced imaging. At T2-weighted imaging and dynamic contrast-enhanced imaging, the presence or absence of prostate cancer confined within the prostate without extracapsular or adjacent organ invasion was evaluated in the peripheral zones of base, mid-gland, and apex on each side. Final decisions on prostate cancer localization were made by consensus between two radiologists. Degrees of depiction of tumor borders were graded as poor, fair, or excellent. Results: Prostate cancer was pathologically detected in 64 (53%) of 120 peripheral zone areas. The sensitivity, specificity, and accuracy for prostate cancer detection were 55%, 88% and 70% for T2-weighted imaging and 73%, 77%, and 75% for dynamic contrast-enhanced imaging, respectively. Three cancer areas were detected only by T2-weighted imaging, 15 only by dynamic contrast-enhanced imaging, and 34 by both T2-weighted imaging and dynamic contrast-enhanced imaging. A fair or excellent degree at depicting tumor border was achieved in 67% by T2-weighted imaging and in 90% by dynamic contrast-enhanced imaging (P < 0.05). Conclusions: Dynamic contrast-enhanced imaging at 3T MRI is superior to T2-weighted imaging for the detection and depiction of prostate cancer and thus is likely to be more useful for preoperative staging.

Diffusion-weighted imaging of the prostate at 3 T for differentiation of malignant and benign tissue in transition and peripheral zones: Preliminary results

Objective: To evaluate prospectively the use of apparent diffusion coefficients (ADCs) for the differentiation of malignant and benign tissue in the transition (TZ) and peripheral (PZ) zones of the prostate diffusion-weighted imaging (DWI) at 3 T magnetic resonance imaging (MRI) using a phased-array coil. Methods: The DWI at 3-T MRI was performed on a total of 35 patients before radical prostatectomy. A single-shot echo-planar imaging DWI technique with b = 0 and b = 1000 s/mm2 was used. The ADC values were measured in both benign and malignant tissues in the PZ and TZ using regions of interest. Differences between PZ and TZ ADC values were estimated using a paired Student t test. Presumed ADC cutoff values in the PZ and TZ for the diagnosis of cancer were assessed by receiver operating characteristic analysis. Results: The ADC values of malignant tissues were significantly lower than those of benign tissues in the PZ and TZ (P < 0.001; 1.32 ± 0.24 × 10−3 mm2/s vs 1.97 ± 0.25 × 10−3 mm2/s, and 1.37 ± 0.29 × 10−3 mm2/s vs 1.79 ± 0.19 × 10−3 mm2/s, respectively). For tumor diagnosis, cutoff values of 1.67 × 10−3 mm2/s (PZ) and 1.61 × 10−3 mm2/s (TZ) resulted in sensitivities and specificities of 94% and 91% and 90% and 84%, respectively. Conclusions: The DWI of the prostate at 3T MRI using a phased-array coil was useful for the differentiation of malignant and benign tissues in the TZ and PZ.

Comparison of phased-array 3.0-T and endorectal 1.5-T magnetic resonance imaging in the evaluation of local staging accuracy for prostate cancer.

Objective: To retrospectively evaluate local staging accuracy for prostate cancer at 3.0-T magnetic resonance imaging (MRI) by comparing with that at 1.5-T MRI. Methods: Two groups, each consisting of 54 patients, were included by matching for age, prostate specific antigen, and Gleason score. Before radical prostatectomy, 1 group underwent 3.0-T MRI using a phased-array coil, and the other 1.5-T MRI using an endorectal coil. T2-weighted MR images at 3.0 and 1.5 T were analyzed in consensus by 2 radiologists, and their staging accuracy was compared with histology. Artifact and overall image quality were compared at both 3.0 and 1.5 T. Results: Accuracy for T3 stage at 3.0 and 1.5 T were 72% (39/54) and 70% (38/54), respectively (P > 0.05). The 3.0-T MRI had a lower incidence of MR artifacts than the 1.5-T MRI (P < 0.05). However, overall imaging quality at both 3.0 and 1.5 T had no significant difference (P > 0.05). Conclusions: The 3.0-T phased-array MRI is equivalent to the 1.5-T endorectal MRI in evaluating local staging accuracy for prostate cancer without significant loss of imaging quality.

MRI Techniques for Prediction of Local Tumor Progression After High-Intensity Focused Ultrasonic Ablation of Prostate Cancer

OBJECTIVE The purpose of this study was to evaluate the diagnostic performance of dynamic contrast-enhanced MRI (DCE-MRI) and of T2-weighted MRI with diffusion-weighted imaging (DWI) for predicting local tumor progression after high-intensity focused ultrasonic ablation of localized prostate cancer. MATERIALS AND METHODS Twenty-seven patients who had increased levels of prostate-specific antigen after high-intensity focused ultrasonic ablation underwent MRI and endorectal biopsy. The MR images and biopsy results were correlated for six prostate sectors. Residual or recurrent prostate cancer after treatment was defined as local tumor progression if the biopsy results showed cancer foci. Two readers blinded to the clinical findings and biopsy results used a 5-point scale to independently assess DCE-MR images and T2-weighted and diffusion-weighted MR images. The results were compared by use of the McNemar test with Bonferroni correction, generalized estimating equations, and receiver operating characteristic analysis. RESULTS After high-intensity focused ultrasonic ablation, local tumor progression was pathologically detected in 54 (33%) of 162 sectors in 18 patients. The sensitivities of DCE-MRI and T2-weighted MRI with DWI were 80% and 63% for reader 1 (p = 0.004) and 87% and 70% for reader 2 (p = 0.004). The specificities of DCE-MRI and T2-weighted MRI with DWI were 68% and 78% for reader 1 (p = 0.002) and 63% and 74% for reader 2 (p < 0.001). The accuracy rates of DCE-MRI and T2-weighted MRI with DWI were 72% and 73% for reader 1 (p > 0.05) and 71% and 73% for reader 2 (p > 0.05). The areas under the receiver operating characteristic curve for DCE-MRI and T2-weighted MRI with DWI were 0.77 and 0.77 for reader 1 and 0.85 and 0.81 for reader 2. CONCLUSION For prediction of local tumor progression of prostate cancer after high-intensity focused ultrasonic ablation, DCE-MRI was more sensitive than T2-weighted MRI with DWI, but T2-weighted MRI with DWI was more specific than DCE-MRI.

Prospective evaluation of 3-T MRI performed before initial transrectal ultrasound-guided prostate biopsy in patients with high prostate-specific antigen and no previous biopsy.

OBJECTIVE The purpose of our study was to prospectively evaluate whether MRI before an initial transrectal ultrasound-guided biopsy contributed to detection of prostate cancer in patients with high prostate-specific antigen (PSA) level and no previous biopsy. SUBJECTS AND METHODS Men with an abnormal digital rectal examination or high PSA level were enrolled in this prospective randomized study. Participants were randomly allocated into two groups; the MRI group underwent 3-T MRI and then a transrectal ultrasound-guided biopsy with knowledge of the cancer location. The non-MRI group did not undergo MRI before transrectal ultrasound-guided biopsy. The cancer detection rate and positive core rate were obtained to compare the MRI and non-MRI groups. RESULTS The MRI and non-MRI groups contained 44 and 41 patients, respectively. There was no significant difference between the two groups with respect to age, PSA, and prostate volume. The MRI group (13/44, 29.5%) had a significantly higher cancer detection rate than the non-MRI group (4/41, 9.8%) (p = 0.03). The MRI group (52/527, 9.9%) had a significantly higher positive core rate than the non-MRI group (11/432, 2.5%) (p = 0.00). Regarding cancer detection rate and positive core rate, odds ratios were 3.9 (95% CI, 1.1-13.1) and 4.2 (95% CI, 2.2-8.1), respectively. CONCLUSION In patients with PSA level and no previous biopsy, 3-T MRI that is performed before transrectal ultrasound-guided biopsy may contribute to the detection of prostate cancer.

Assessment of Response to Radiotherapy for Prostate Cancer: Value of Diffusion-Weighted MRI at 3 T

OBJECTIVE The objective of our study was to investigate the changes of apparent diffusion coefficient (ADC) values in prostate cancers before and after radiotherapy at 3 T using a phased-array coil. MATERIALS AND METHODS Forty-nine patients with biopsy-proven prostate cancer who received radiotherapy underwent diffusion-weighted imaging (DWI) at 3 T and were included in the study. Biopsies in all patients were performed before the initial MRI examination (range, 15-35 days before MRI; mean, 23.4 days). All 49 patients underwent DWI (b values = 0 and 1,000 s/mm(2)) before and 1-5 months after the completion of radiotherapy. The changes in ADC values were measured for cancers and benign tissues before and after therapy. Additionally, the changes in serum prostate-specific antigen (PSA) levels were evaluated before and after therapy. RESULTS A total of 57 cancers (peripheral zone, n = 45; transition zone, n = 12) were found in 46 patients. For the tumors, the mean ADC value after therapy (1.61 x 10(-3) mm(2)/s) was increased compared with the mean ADC value before therapy (1.0 x 10(-3) mm(2)/s) (p < 0.001). After radiotherapy, the mean ADC values of benign peripheral zones and of benign transition zones were statistically significantly decreased compared with those before radiotherapy (p < 0.05). Before treatment, a significant difference of ADC values between the tumors and benign tissues was found (p < 0.001), whereas there was no significant difference of ADC values between them after treatment (p > 0.1). The median PSA level after therapy (0.49 ng/mL) was decreased compared with the median PSA level before therapy (20.0 ng/mL). CONCLUSION With the use of a 3-T MR scanner, our preliminary results suggest that ADC values may be useful as an imaging biomarker for monitoring therapeutic response of prostate cancer to radiotherapy.

Update of prostate magnetic resonance imaging at 3 T.

More recently, 3-T magnetic resonance (MR) scanner become more clinically available, and clinical application of 3-T MR imaging (MRI) of the abdomen and pelvis is now feasible and being performed at many institutions. However, few prostrate 3-T MRI studies have been published. The increase in signal-to-noise ratio at 3 versus 1.5 T clearly improves spatiotemporal and spectral resolutions of the prostate. Thus, we asked whether 3-T MRI improves the localization and staging of prostate cancer versus 1.5-T MRI. To answer this question, this article reviews the current limitations of prostate 1.5-T MRI and addresses its pros and cons. Moreover, we present preliminary results of prostate 3-T MRI and introduce our experience for prostate 3-T MRI using a phased-array coil, with an emphasis on imaging sequences, for example, T2-weighted, dynamic contrast-enhanced, diffusion-weighted, and MR spectroscopic imaging.