This study shows detailed characteristics of realistic radiotherapy photon beams: dose distribution, energy spectra, angular spread, fluence profiles and mean energy profiles. It provides more comprehensive information for radiotherapy photon beams including incident photons and primary photons as well as contaminating electrons and positrons in a radiation beam for different field sizes and beam energies. The EGSnrc Monte Carlo code, BEAMnrc has been used to simulate 4 and 10 MV photon beams from a Varian Clinac 2100C accelerator. A simulated realistic beam is stored in a phase space files, which contains details of each particle's complete history including where it has been and where it has interacted. The phase space files are used to calculate depth-dose components from different particles and surface dose and contribution from different particles to surface dose across the filed. Energy spectra, angular spread, fluence profiles and mean energy profiles at the phantom surface for each particle are also obtained using the phase space information. The accuracy of a simulated beam is validated by the excellent agreement between the Monte Carlo calculated and measured dose distributions except for 10 MV at the 40×40 cm² field in the build-up region. Measured depth-dose curves are obtained from depth-ionization curves by accounting for the stopping-power ratios for realistic beams. At 4 MV, the contaminant charged particles contribute 6% to 26% of maximum dose at the surface when the field size increases from 10×10 to 40×40 cm². Similarly, their contributions at 10 MV are up to 7% and 23% of maximum dose at the surface for 10×10 cm² and 40×40 cm² fields, respectively. However, the fluence of these contaminant charged particles is less than 1.0% of incident photon fluence in all cases.

View full abstract

Purpose: The purpose of this study was to evaluate the CT appearance of radiation injury to the lung and clinical symptoms after SRT (stereotactic radiation therapy) for small lung cancers.
Methods and Materials: In this analysis, 35 patients with 39 primary or metastatic lung cancers were enrolled. The follow-up at the time of evaluation ranged from 6 to 44 months (median 18 months). SRT was performed by 3D conformal method which focuses a single high dose to the tumor. We evaluated the CT appearance of acute radiation pneumonitis (within 6 months) and radiation fibrosis (after 6 months) after SRT. Clinical symptoms were evaluated by CTCAE ver.3.0.
Results: CT appearance of acute radiation pneumonitis was classified as follows; 1) diffuse consolidation in 12 lesions (30.7%), 2) patchy consolidation and ground-grass opacities (GGO) in 6 lesions (15.4%), 3) diffuse GGO in 5 patients (12.8%), 4) patchy GGO in 1 lesion (2.6%), 5) no evidence of increasing density in 15 lesions (38.5%). CT appearance of radiation fibrosis was classified as follows; 1) modified conventional pattern (consolidation, volume loss and bronchiectasis similar to, but less extensive than conventional radiation fibrosis) in 18 lesions (46.2%), 2) mass-like pattern (focal consolidation limited around the tumor) in 10 lesions (25.6%), 3) scar-like pattern (linear opacity in the region of the tumor associated with volume loss) in 11 lesions (28.2%). Eleven of 15 lesions which had no evidence of increasing density of acute radiation pneumonitis progressed to scar-like pattern of radiation fibrosis. Most of these patients had pulmonary emphysema. Patients who were diagnosed more than Grade 2 pneumonitis were significantly more in diffuse consolidation pattern than in other pattern (p=0.00085). Patients who were diagnosed more than Grade 2 pneumonitis were significantly less in no evidence of increase density pattern than in other pattern (p=0.0026).
Conclusion: CT appearance after SRT was classified into five patterns of acute radiation pneumonitis and three patterns of radiation fibrosis. Most of patients who were classified into no evidence of increasing density of acute radiation pneumonitis progressed to scar-like pattern of radiation fibrosis, and had pulmonary emphysema. Most of these patients were not also diagnosed more than grade 2 pneumonitis, therefore we are able to suggest these patients were good candidate for SRT.

View full abstract

Purpose: To evaluate biochemical failures after radical external beam radiotherapy for prostate cancer.
Material and Methods: A total of 143 patients with prostate cancer (5 cases in stage A2, 95 in stage B and 43 in stage C; 18 in low risk group, 37 in intermediate risk group, 67 in high risk group and 21 in unknown group) were included in this study. Patients of stage A2 and B underwent external irradiation of 46 Gy to the prostate gland and seminal vesicle and additional 20 Gy to the prostate gland, while patients of stage C underwent external irradiation of 66 Gy to the prostate gland and seminal vesicle including 46 Gy to the pelvis. Neoadjuvant hormonal therapy was done in 66 cases, and long-term hormonal therapy in 75 cases; two cases were treated with radiation therapy alone.
Results: The 3-year relapse free survival rates by stage A2, B and C were 100%, 96.7% and 88.1%, respectively. The 3-year relapse free survival rates by low, intermediate and high risk groups were 100%, 92.3% and 89.7%, respectively. Biochemical failure was noted in nine cases during the average observation term of 32.2 months; in this group the median of PSA value was 2.6 ng/ml, the doubling time was 8.6 months, and the term of biochemical failure was 33.2 months. Six of eight cases with biochemical failure were the neoadjuvant hormonal therapy group, but bNED curve showed no significant difference between neoadjuvant and long-term hormonal groups.
Conclusion: It is supposed that unnecessary hormonal therapies were performed based on the nonspecific diagnosis of biochemical failure after radical radiotherapy in our group of patients. A precise criterion of biochemical failure after radical radiotherapy for prostate cancer is necessary.

View full abstract

We have redeveloped a high-energy X-ray spectra estimation method reported by Iwasaki et al (Radiat Phys Chem 67: 81, 2003). The method is based on the iterative perturbation principle to minimize differences between measured and calculated transmission curves, originally proposed by Waggener et al (Med Phys 26: 1269, 1999). Estimating spectra of 4-15 MV X-ray beams from a linear accelerator, we describe characteristic features of the redeveloped method with regard to parameters including the pre-spectrum, energy bin width, measured transmission data, interpolated transmission data, and crevice.

View full abstract

Locally advanced non-small cell lung cancer is often inoperable. It is difficult to choose the optimal therapy for locally advanced lung carcinoma with malignant airway obstruction. We applied Neodymiumyttrium-aluminum garnet (Nd-YAG) laser therapy combined with external beam radiotherapy. Seven patients were treated with Nd-YAG laser and 60 Gy and more of conventional radiotherapy. All patients had malignant airway obstructions and severe dyspnea at the beginning of Nd-YAG laser therapy. These patients received good to excellent palliation and were able to have normal daily lifes after the treatments. The Nd-YAG laser combined with external radiotherapy may be one of the most useful treatment for locally advanced lung cancer with malignant airway stenosis to improve quality of life.

View full abstract

Purpose: To report treatment results of floor of mouth cancer with definitive radiotherapy.
Materials and Methods: Sixty-five patients with newly diagnosed floor of mouth cancer received definitive (chemo-) radiotherapy at the department of Radiation Oncology at Aichi Cancer Center. Thirty-five patients were treated with only external irradiation, 28 patients with the combination of external irradiation and brachytherapy, and 2 patients with only brachytherapy. Twenty-nine patients received chemotherapy. Systemic chemotherapy was done for 22 patients with advanced disease (both locally-advanced and neck lymph node metastases), and intra-arterial chemotherapy for 7 patients with locally advanced disease.
Results: Five-year overall survival rate (OS) was 59% and 5-year progression free survival rate was 49%. Five-year OS for stage I + II was 69% and that for stage III + IV was 51%. We found 23 recurrences, which were divided into 10 in floor of mouth, 7 in neck lymph nodes, 2 in both, and 4 in distant areas. Late complications were found in 30 patients. Thirteen patients had developed mandibular osteomyelitis, 7 of which required surgical intervention. Soft tissue necrosis was found in 12 patients, and only one received surgery. Double cancers were found in 25 patients. There were 7 oral cancers and 6 esophageal cancers.

View full abstract

Objective: Transperineal I-125 seed brachytherapy for prostate cancer is rapidly expanding in Japan. Seed migrations to lung and abdomen are well known complication in the seed brachytherapy. The rate of incidence and the predisposing factors were studied.
Material and Method: From April 2004 through January 2005, 36 patients underwent transperineal I-125 seed brachytherapy for prostate cancer. In all patients loose I-125 seeds were inserted with Mick applicator according to modified peripheral loading pattern. One day, 1 week, and 1 month after the procedure, posteroanterior and lateral chest X-rays and abdominal X-ray were performed.
Results: Abdominal and chest seed migrations were seen in 11 (30.6%) and 14 (38.9%) patients, respectively. In total, 20 patients (55.6%) showed seed migrations. Forty-two I-125 seeds migrated out of 2,508 implanted seeds. Most of the migrations were seen until 1 month after the procedure. The preplanned number of the extraprostatic seeds had a statistically significant influence upon the incidence of seed migration.
Conclusions: Seed migration is not a rare phenomenon in transperineal I-125 seed brachytherapy for prostate cancer. To confirm seed migration, X-ray examinations 1 month after the procedure are suited. At the preplanning, the number of extraprostatic seeds should be limited to minimal to decrease the incidence of seed migration. In future, the introduction of linked I-125 seeds is preferred.

View full abstract

To ascertain the basic structural characteristics of radiation oncology facilities in Japan, we conducted a national survey on their status in 2003. Responses were obtained from 100% of potential facilities and 726 facilities delivered radiation therapy for 149,793 new patients.
The numbers of full time employee (FTE) JASTRO-certified oncologists, radiation oncologists, radiation therapists, physicists and radiation therapy nurses were 369, 941, 1,555, 70 and 717, each. The cooperative efforts of radiation oncologists and staff members of facilities are critical to the success of Radiation therapy.

View full abstract

The purpose of this study was to quantify 1 cm dose equivalent rate of patients with localized prostate cancer treated with ¹²⁵I seed implantation, to evaluate predictive factors for the measured dose and to assess radiation safety to the general public.
Ionization chamber, which is authorized to detect the photons with an energy lower than 30 keV, was used to measure the photons emitted by I-125 with a mean energy of 27.4 keV. Measurements of the 1 cm dose equivalent rate were taken at one meter perpendicular from the skin surface in the anterior, lateral and caudal directions in the supine position for 70 patients treated with ¹²⁵I seed implantation.
As a result, the 1 cm dose equivalent rate measured from the anterior direction was the highest and correlated with the depth of the prostate from the patient's surface. In 7 patients, the 1 cm dose equivalent rate at 1 meter from the anterior skin surface exceeded 1.8 μSv/h of the limitation of discharge criteria, but their total seed activity was less than 1,300 MBq. Their depth of prostate from the skin surface was thin compared with the depth of the remaining patients, whose dose rate was 1.8 μSv/h or less. This result gives a warning that the 1 cm dose equivalent rate from a thin patient could exceed 1.8 μSv/h even if a patient contains less overall seed activity than the limit of the criteria, so adequate instructions are needed to minimize the exposure to the public.
The estimated value of the patient's peripheral dose equivalent rate from our data was 0.0008 μSv · m²/MBq/h, which was much lower than the effective dose rate constant of 0.0014 μSv · m²/MBq/h adopted as a evaluation of radiation exposure of ¹²⁵I seed source in Japan. The mean value of the 1 cm dose equivalent rate per 1 MBq at 1 meter from the anterior skin surface was 0.0015 μSv · m²/MBq/h, which was nearly equal to the effective dose rate constant adopted in Japan.
Therefore, these data suggest that radiation safety to the general public is kept with in Japanese discharge criteria calculated from the effective dose rate constant of ¹²⁵I seed source.

View full abstract