Biomedical subjects

Iori Sumida

Publications and source records attributed to Iori Sumida.

9 recordsLinked to original sources

PubMed2006

Dosimetric consideration of individual 125I source strength measurement and a large-scale comparison of that measured with a nominal value in permanent prostate implant brachytherapy.

PURPOSE: We investigated the difference between measured and manufacturer's nominal source strength in a large sample of a single model of (125)I seeds. Physical characteristics of single seed measurement by the well-type ionization chamber were also investigated to provide dosimetric data. MATERIALS AND METHODS: A well-type ionization chamber with a single seed holder was used to measure source strength of all 1935 (125)I seeds implanted in the initial 28 patients in our hospital. Physical characteristics including linearity of readings for different integral time intervals, reproducibility, isotropy, and axial positional sensitivity were assessed. To calculate the source strength, the integral charge during 30 s was measured and converted to air kerma strength. The nominal activity stated by the manufacturer was compared with the measured value. RESULTS: Linearity, reproducibility, and isotropy of the well-type ionization chamber were within 0.2%. Measured source strength was on average 2.1% (range -7.6% to +7.2%), lower than the nominal value. Standard deviation of all measured seeds was 2.0%. The maximum difference between the measured and the manufacturer's nominal source strength in each patient was -3.7%. The standard deviation averaged 1.6%. CONCLUSION: The nominal source strength of the (125)I seeds agreed well with the measured value. Our study can be helpful as guidance for individual (125)I seed source strength measurement.

Brachytherapy↗

PubMed2006

High-dose-rate brachytherapy without external beam irradiation for locally advanced prostate cancer.

BACKGROUND AND PURPOSE: High-dose-rate brachytherapy (HDR-BT) had been used only in combination with external beam irradiation (EBI) until our previously reported first trial of HDR-BT alone without EBI. The purpose of the current report is to evaluate the feasibility, toxicity and efficacy of this regimen, with more patient accrual and longer follow-up. MATERIAL AND METHODS: From 1995 through 2004, 111 patients with localized prostate cancer were treated with HDR-BT without EBI. Fifteen patients were considered as low-risk, 28 as intermediate-risk, and 68 as high-risk. The prescribed dose was 48 Gy/8 fractions/5 days or 54 Gy/9 fractions/5 days. Median follow-up time was 27 months (range 5-119). RESULTS: All the patients completed the treatment regimen. The 3- and 5-year PSA failure-free rates were 83% and 70%, and the local control rates 100% and 97%. The maximum toxicities observed were Grade 3 by CTCAE v3.0 (6 acute, 1 chronic). CONCLUSIONS: HDR-BT without EBI was feasible and its toxicity acceptable. Short-term tumor control was promising, even for locally advanced cases. More patient accrual and longer follow-up are needed to confirm the efficacy of this novel approach.

Aged↗

PubMed2006

High-dose-rate brachytherapy combined with long-term hormonal therapy for high-risk prostate cancer: results of a retrospective analysis.

PURPOSE: High-dose-rate (HDR) brachytherapy combined with hormonal therapy (HTx), without the addition of external beam radiation therapy (EBRT) for high-risk prostate cancer was evaluated retrospectively. MATERIALS AND METHODS: Between May 1995 and April 2002, 35 patients with prostate cancer [Stage > or = T2b (UICC 1997) or tumor grading=3 or prostate-specific antigen (PSA) level > or = 20 ng/mL] were treated with HDR brachytherapy combined with HTx. Most patients (74%) had two or more of these factors. All patients received Iridium-192 HDR brachytherapy with a total dose of 54 Gy/9 fractions/5 days (48 Gy/8 fractions/5 days for the first 6 cases) in one implant session. The median neoadjuvant HTx [luteinizing hormone-releasing hormone (LH-RH) agonist and antiandrogen] period was 7 months. The median adjuvant HTx (ATH) (LH-RH agonist) period was 40 months, and median follow-up was 57 months (range, 23-117 months). RESULTS: The 5-year actuarial biochemical control, local control, and disease-free rates were 62%, 96%, and 76% respectively. No patients experienced local and/or regional relapse without distant progression. The 5-year actuarial cause-specific survival and overall survival rates were 89% and 87%, respectively. The acute and late toxicity were moderate and well tolerated. CONCLUSION: HDR brachytherapy plus long-term HTx is at least as effective as conventional EBRT plus long-term HTx.

Aged↗

PubMed2006

A pilot study of wider use of accelerated partial breast irradiation: intraoperative margin-directed re-excision combined with sole high-dose-rate interstitial brachytherapy.

BACKGROUND: Accelerated partial breast irradiation (APBI) is generally limited to patients at extremely low risk of local recurrence. The significance of the risk factors, however, depends on the extent of surgery, radiation, and systemic therapy. In Japan, wide excision is generally supplemented by intraoperative margin-directed re-excision if the frozen section examination yields positive results. This approach combined with conventional radiotherapy achieved an excellent 10-year local control rate of 93%, and young age and ductal carcinoma in situ were not risk factors for local recurrence. To reduce the treatment duration, high-dose-rate interstitial brachytherapy (HDRIB) was employed. The first APBI phase I / II trial in Japan was conducted to determine if wider indications for early breast cancer patients were appropriate. METHODS: The subjects comprised 20 patients including those with extensive intraductal component (n=7), ductal carcinoma in situ (n=2), positive final margins (n=3), and of younger age (< or = 45 years; n=5). Breast-conserving surgery using an intraoperative re-excision approach was followed by intraoperative implantation of applicators. Sole HDRIB of a 36-42 Gy in 6-7 fractions was delivered postoperatively over 3-4 days. Tumors were staged as follows: cT1 (n=12), cT2 (n=8), cN0 (n=20). Systemic therapy was used in 16 patients (80%). The median follow-up period was 52 months (range, 26-86 months). RESULTS: Te five-year crude local, distant control, and Kaplan-Meier cause-specific survival rates were 95%, 95%, and 89%, respectively. Fat necrosis developed in 1 patient. CONCLUSIONS: Sole HDRIB with intraoperative margin-directed re-excision was feasible under wider indications compared to other contemporary APBI series, and achieved acceptable and similar results to these series in terms of the local control rate and complications.

Adult↗

PubMed2005

Optimization of dose distribution for HDR brachytherapy of the prostate using Attraction-Repulsion Model.

PURPOSE: To optimize dose distribution for high-dose-rate brachytherapy for prostate cancer, we have developed a new algorithm named Attraction-Repulsion Model (ARM). In this study, we compared the ARM with geometric optimization (GO). METHODS AND MATERIALS: The ARM was used to optimize the dose distribution by finding the best dwell time combination. ARM requires grids inside the clinical target volume (CTV) and critical organs. These grids generate attraction or repulsion based on specific dose constraints. After calculations were performed repeatedly until the attraction and repulsion forces reached equilibrium, the optimal dwell time distribution was established. We compared the ARM with GO for 10 patients using dose-volume histograms. RESULTS: The CTV ranged from 23 to 48 cc, and the CTV V150 ranged from 52% to 79%, and 23% to 44% for GO and ARM, respectively. This indicates that the dose homogeneity indices, as well as the conformal indices, were higher for ARM than for GO. The urethra V150 was 0-99% and 0-1% for GO and ARM, respectively. CONCLUSION: The ARM proved to be superior to GO in minimizing the dose to normal structures and in improving dose homogeneity for the target while reducing the dose to normal tissues.

Algorithms↗

PubMed2004

An optimization algorithm of dose distribution using attraction-repulsion model (application to low-dose-rate interstitial brachytherapy).

PURPOSE: To optimize dose distribution for prostate cancer in low-dose-rate interstitial brachytherapy, we have developed a new algorithm named the Attraction-Repulsion Model. The purpose was to find the optimal source configuration. METHODS AND MATERIALS: The Attraction-Repulsion Model is used to optimize the dose distribution by finding the best seed configuration. We arranged grids at intervals of a certain space inside and established target and critical organs as areas of interest. We can make an attribute for grids, and the grids show attraction or repulsion depending on dose delivered from source. Source position is changed by the forces that the grids impose to the sources. A calculation was done repeatedly until the attraction and repulsion forces reached a balance. The optimal configuration was established when the sources reached a stable distribution in time. To evaluate the optimization plan, dose-volume histograms were used. RESULTS: Source configuration can be optimized automatically. The calculation time was approximately 5 min. The V100, V150, V200, and D90 of the target were 95%, 39%, 9%, and 157 Gy, respectively. V150 of the urethra and V80 of the rectum were 2% and 0%, respectively. CONCLUSION: This method can optimize the dose distribution objectively.

Algorithms↗

PubMed2002

[Canon's flat-panel detector].

We measured and evaluated digital, pre-sampling and overall imaging properties (characteristic curve, modulation transfer function (MTF), Wiener spectrum (WS), noise equivalent quanta (NEQ) ) for Cannon's flat-panel detector (FPD), Fuji computed radiography (FCR) and screen-film (S/F) systems, respectively. First, the digital and overall characteristic curves of FPD and FCR systems were more wide dynamic range than that of the S/F system. Second, the pre-sampling and overall MTF of FPD system were better than those of FCR system a little at lower spatial frequencies than 0.8 mm(-1), but the overall MTF of FPD and FCR systems were worse than that of S/F system a little at all spatial frequencies. Third, the digital and overall WS of FPD system were similar or better than those of FCR system, but the overall WS of FPD and FCR systems were worse than that of S/F system. Fourth, the pre-sampling and overall NEQ of FPD system were better than those of FCR system a little at lower spatial frequencies than 1.6 mm(-1), but the overall NEQ of FPD and FCR systems were worse than that of S/F system at all spatial frequencies. Comparison of chest phantom images showed that the FPD produced images with quality comparable to or higher than those of the FCR system. From these results, we can expect that the FPD is useful machine by using digital image processing and so on in the radiology department.

Image Processing, Computer-Assisted↗

PubMedDate not supplied

CyberKnife stereotactic irradiation for metastatic brain tumors.

BACKGROUND: The CyberKnife provides a new technique for performing frameless stereotactic irradiation. So far, few reports have been published on clinical outcomes obtained with the CyberKnife. This report summarizes our clinical experience with CyberKnife irradiation for metastatic brain tumors. MATERIALS AND METHODS: Seventy-seven lesions (48 patients) were evaluated and analyzed, and 66 lesions in 41 patients were treated with stereotactic radiosurgery (SRS). The prescribed dose was 9 to 30 Gy. RESULTS: Freedom from progression of the tumors was more likely with a prescribed dose of at least 24 Gy than with one of less than 20 Gy (p=0.0244; log-rank test). The CR (complete response) rate was significantly higher when D99 was at least 24 Gy (p=0.0045). There were no severe side effects. CONCLUSION: Stereotactic irradiation with the CyberKnife for metastatic brain tumors is effective and safe. D99 should be at least 24 Gy for CyberKnife SRS treatment.

Brain Neoplasms↗

PubMedDate not supplied

Quantitative evaluation of changes in irradiated lung fields after stereotactic irradiation by the Polygon Method.

PURPOSE: To evaluate areas of change in lung after thoracic stereotactic irradiation (STI). MATERIALS AND METHODS: We developed a method of evaluation named the Polygon Method, to measure the irradiated lung fields of 12 lung tumors treated by STI. Before treatment, each targeted field was divided into several circular zones of 2 cm in width centered at the tumor on high resolution computed tomography, and the areas of each zone before and after treatment were compared. RESULTS: Six months after treatment, the areas of the zone within 2 cm from the tumor decreased, and the mean ratio of areas after and before STI was 0.849 (range, 0.515 to 1.052, p=0.0254). By contrast, the areas of zones located at 4 to 6, 6 to 8, 8 to 10, and more than 10 cm from the tumor tended to increase, with mean ratios of 1.059, 1.058, 1.089 (p=0.0374), and 1.084, respectively. CONCLUSION: After thoracic STI, volume loss in the lung is limited to the field in close proximity to the tumor, while compensatory expansion of the lung occurs in fields distant from the tumor.

Adenocarcinoma↗