Yasuyuki Hamada

Kumamoto Kinoh Hospital, Kumamoto, Kumamoto Prefecture, Japan

Are you Yasuyuki Hamada?

Claim your profile

Publications (9)12.56 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: The objective of this study was to assess whether adding isovoxel 3-dimensional T2-weighted imaging (volume isotropic T2-weighted acquisition [VISTA]) to multiparametric magnetic resonance imaging (mp-MRI) improves the ability to diagnose the extracapsular extension (ECE) of prostate cancer.
    Journal of computer assisted tomography. 10/2014;
  • [Show abstract] [Hide abstract]
    ABSTRACT: Normalization of the apparent diffusion coefficient (ADC) may overcome ADC variability attributable to different patient and/or technical factors. The purpose of this study was to compare the efficacy of ADC and the normalized ADC (nADC) for differentiating between prostate cancer with a Gleason score (GS) = 6 and GS > 6 and to identify an optimum reference for nADC calculations.
    Japanese journal of radiology 10/2014; · 0.73 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: OBJECTIVE. The purpose of our study was to identify low-risk prostate cancer on the basis of the D'Amico clinical risk score in patients with prostate-specific antigen (PSA) levels 10 ng/mL or less who had undergone radical prostatectomy by comparing apparent diffusion coefficient (ADC) with transrectal ultrasound (TRUS)-guided target biopsy. MATERIALS AND METHODS. In the preliminary study, we used receiver operating characteristic (ROC) analysis and determined the cutoff ADC to identify prostate cancer with a Gleason score of 6 or less for 117 patients. In the primary study, we assessed the combination of routine MRI (T2-weighted and diffusion-weighted imaging) plus the cutoff ADC value ("method A") to identify low-risk prostate cancer for another 89 patients. Their diagnostic value was compared with that of routine MRI combined with the Gleason score obtained from TRUS-guided target biopsies ("method B"). RESULTS. The preliminary study showed that a mean ADC of 1.04 × 10(-3) mm(2)/s was the best cutoff. In the primary study, accuracy was statistically higher with method A for each reader (p = 0.041). CONCLUSION. In patients with PSA levels 10 ng/mL or less, the combination of MRI findings plus the cutoff ADC is significantly more accurate for the identification of low-risk prostate cancer than is the combination of MRI followed by TRUS-guided target biopsy.
    American Journal of Roentgenology 05/2014; 202(5):1051-7. · 2.90 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Objective To assess the clinical negative predictive value (NPV) of multiparametric MRI (mp-MRI) for prostate cancer in a 5-year follow-up. Materials and Methods 193 men suspected of harboring prostate cancer with negative MRI findings were included. Patients with positive transrectal ultrasound (TRUS)-guided biopsy findings were defined as false-negative. Patients with negative initial TRUS-guided biopsy findings were followed up and only patients with negative findings by digital rectal examination, MRI, and repeat biopsy and no increase in PSA at 5-year follow-up were defined as “clinically negative”. The clinical NPV of mp-MRI was calculated. For quantitative analysis, mean signal intensity on T2-weighted images and the mean apparent diffusion coefficient value on ADC maps of the initial MRI studies were compared between peripheral-zone (PZ) cancer and the normal PZ based on pathologic maps of patients who had undergone radical prostatectomy. Results The clinical NPV of mp-MRI was 89.6% for significant prostate cancer. Small cancers, prostatitis, and benign prostatic hypertrophy masking prostate cancer returned false-negative results. Quantitative analysis showed that there was no significant difference between PZ cancer and the normal PZ. Conclusion The mp-MRI revealed a high clinical NPV and is a useful tool to rule out clinically significant prostate cancer before biopsy.
    European Journal of Radiology. 01/2014;
  • [Show abstract] [Hide abstract]
    ABSTRACT: PURPOSE To identify low-risk prostate cancer we retrospectively determined the optimal cutoff apparent diffusion coefficient (ADC) and compared the diagnostic value of the combination of routine MRI studies (T2- and diffusion-weighted images) plus the cutoff ADC with that of MRI followed by transrectal ultrasound (TRUS)-guided target biopsy in patients with PSA levels ≤ 10 ng/ml. METHOD AND MATERIALS In the preliminary study we used receiver operating characteristic (ROC) analysis and determined the cutoff ADC optimal for the identification of prostate cancer with a Gleason score (GS) ≤ 6 in 120 consecutive patients with PSA levels ≤ 10 ng/ml who had undergone radical prostatectomy. Our primary study included another 89 consecutive patients with PSA levels ≤ 10 ng/ml who were also treated by radical prostatectomy for pathologically-proved prostate cancer. Two radiologists independently assessed the combination of routine MRI studies plus the results of the cutoff ADC value (method A) for its diagnostic effectiveness in identifying prostate cancer classified as low-risk by the D’Amico clinical risk score (T stage ≤ T2a, GS ≤ 6, PSA ≤ 10 ng/ml). Their findings were then compared with the diagnostic value of routine MRI combined with the GS obtained from TRUS-guided target biopsies (method B) to identify the superior diagnostic method. RESULTS Our preliminary study showed that a mean ADC of 1.04 x 10-3 mm2/sec was the optimal cutoff for identifying prostate cancer with a GS ≤ 6 with an area under the ROC curve of 0.707. Under method A, sensitivity, specificity, PPV, NPV, and accuracy were 71.4%, 97.3%, 83.3%, 94.8%, and 93.3% for reader 1, and 71.4%, 94.7%, 71.4%, 94.7%, and 91.0% for reader 2, respectively. Under method B they were 57.1%, 89.3%, 50.0%, 91.8%, and 84.3% (reader 1) and 57.1%, 85.3%, 42.1%, 91.4%, and 80.9% (reader 2). For each reader accuracy was statistically higher with method A (p = 0.041). CONCLUSION In patients with PSA levels ≤ 10 ng/ml, the combination of MRI findings plus the cutoff ADC is significantly more accurate for the identification of low-risk prostate cancer than is the combination of MRI followed by TRUS-guided target biopsy. CLINICAL RELEVANCE/APPLICATION MRI study combined with ADC evaluation is highly useful for the detection of low-risk prostate cancer in patients with PSA levels ;10 ng/ml and avoids unnecessary invasive procedures including biopsy.
    Radiological Society of North America 2013 Scientific Assembly and Annual Meeting; 12/2013
  • [Show abstract] [Hide abstract]
    ABSTRACT: To assess the diagnostic performance of diffusion-weighted magnetic resonance (MR) imaging (DWI) for prostate cancer detection, using different b-values. A total of 201 patients who underwent MR imaging before total prostatectomy were evaluated. MR images were independently assessed by three radiologists. Three combinations of sequences were separately evaluated, as follows: group 1 [T2-weighted images (T2WI) alone], group 2 (T2WI and DWI with a b-value of 1,000 s/mm2), group 3 (T2WI and DWI with a b-value of 2,000 s/mm2). Whole-mount-section histopathological examination was the reference standard. Areas under the receiver operating characteristic curve (AUCs) and diagnostic performance parameters were determined. The sensitivity, specificity, and AUC for the detection of prostate cancer were as follows: 52.2%, 80.7%, and 0.694 in group 1; 61.2%, 82.6%, and 0.755 in group 2; 73.2%, 89.7%, and 0.842 in group 3. Group 3 achieved the highest diagnostic performance, followed by group 2 (P<0.05). In the transition zone, the specificity was lower (P<0.001) for group 2 (82.2%) than for group 1 (86.2%). The addition of diffusion-weighted images with a b-value of 2,000 s/mm2 to T2WI can improve the diagnostic performance of MR imaging in prostate cancer detection.
    European Radiology 01/2011; 21(1):188-96. · 4.34 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: We assessed the outcome after radical prostatectomy and pelvic lymphadenectomy for lymph node positive prostate cancer retrospectively. Furthermore, we compared the efficacy of immediate androgen deprivation adjuvant therapy in node positive patients who have undergone radical prostatectomy. We investigated 62 patients who have undergone radical prostatectomy and pelvic lymphadenectomy and have been found to have lymph node positive prostate cancer at our facility between January 1992 and January 2008. We researched the clinical stages, the pathological stages and Gleason scores for pathological pN1 + prostate cancer, retrospectively. The serum PSA levels were followed up every 6 months, and we considered that biochemical progression was PSA >0.4 ng/ml. We classified the groups treated with or without immediate androgen deprivation adjuvant therapy, the biochemical progression free survival and cause specific survival were analyzed by the Kaplan-Meier method, and the statistical significance was determined by the log rank test. The rate of lymph node positive patients who have undergone radical prostatectomy was 7.1%. The rate of 8 or greater in Gleason score of all the lymph node positive patients was 68.3%. The 5-year prostate cancer specific survival and 5-year biochemical progression free survival rates were 90.3 and 67.4% of all the patients. The biochemical progression free survival rate of the group of patients who have received immediate androgen deprivation therapy after radical prostatectomy was significantly higher than that of the group of patients who have not received immediately androgen deprivation therapy. It may be suggested that early androgen deprivation adjuvant therapy benefits patients with nodal metastases who have undergone radical prostatectomy and lymphadenectomy, compared with those who received deferred treatment, although in a retrospective nonrandomized study.
    Nippon Hinyōkika Gakkai zasshi. The japanese journal of urology 07/2009; 100(5):570-5.
  • [Show abstract] [Hide abstract]
    ABSTRACT: Advances in high-precision radiation therapy techniques for patients with prostate cancer permit selective escalation of the radiation dose delivered to the dominant intraprostatic lesion and improve the therapeutic ratio. We evaluated the value of diffusion-weighted imaging (DWI) for dominant intraprostatic lesion assessment. The study population consisted of 23 patients with early prostate cancer. Before undergoing total prostatectomy, they were evaluated by means of magnetic resonance imaging, including DWI. T2-weighted imaging (T2WI) with and without DWI were retrospectively assessed by six independent observers. Imaging findings were compared with pathologic results from whole prostate specimens on a lesion-by-lesion basis. Pathologic study identified 43 lesions in 23 patients. On magnetic resonance imaging, the six observers correctly identified 11-22 of 43 lesions (sensitivity, 26-51%) on T2WI alone and 20-31 (sensitivity, 47-72%) on T2WI plus DWI. Positive predictive values were 42-73% on T2WI alone and 58-80% on T2WI plus DWI. For all observers, detection was higher on combined T2WI and DWI than on T2WI alone. Because the addition of DWI to T2WI improves the detectability of prostate cancer, DWI may offer a promising new approach for radiation therapy planning.
    International journal of radiation oncology, biology, physics 12/2008; 74(2):399-403. · 4.59 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: There were many case reports about bladder tamponade resulting from clots of blood. However, there were few reports about the clinical study that result from collecting cases of bladder tamponade. Thus, we performed a retrospective study about bladder tamponade resulting from clots of blood that we had managed. We investigated 20 patients who had bladder tamponade and were consulted at our facility between October 2002 and September 2005. We researched causes of the bleeding, characteristics of the patients, the laboratory data of coagulation system and treatments of our experience in managing patients. There were 17 males and 3 females. The average age of the patients was 74.0 years old. 8 cases took anticoagulant drugs, 6 cases had medical history of cerebral infarction or cardiac infarction, 4 cases took anticholinergic drugs and 9 cases had benign prostate hypertrophy or urethral stricture. Bleeding was due to bladder tumor in 9, prostate cancer in 1, radiation cystitis in 3, chronic cystitis in 1, malignant lymphoma in 1, idiopathic causes in 3 and unknown causes in 2 cases. Except 1 case, in all cases, evacuation of the clots was the first procedure followed by saline irrigation. This initial line of treatment was able to control the hemorrhage in 40% of the patients. For the remaining cases, transurethral coagulation and resection of bladder tumor were used as the second line treatment, and furthermore, radical cystectomy was performed in 1 case. Surgical treatments were required in 12 cases. Blood transfusion was required in 4 cases. According to progress aging society, the amounts of taken anticoagulant drugs and the patients who had lower urinary tract dysfunction may increase. It may be suggested that the cases of bladder tamponade resulting from clots of blood without bladder tumor or radiation cystitis tend to increase.
    Nippon Hinyōkika Gakkai zasshi. The japanese journal of urology 08/2006; 97(5):743-7.