For irradiation, a rectangular cone for electron beams was newly designed to utilize scattered electrons. A blind tube had a hole placed on the lateral wall and a metal plate placed at the end of tube set at an oblique angle to incident electron beams. We investigated the possible application of this cone for electron beam therapy through the Monte Carlo simulation and experiment. The results show tendency agreement on the dose distribution at the surface of a water phantom and also the depth dose distribution. The maximum output of scattered electrons was about 0.41 Gy/min with the maximum input 6.3 Gy/min. We adjusted the dose distributions for the treatment of intra cavity or the shallow lesion with a configuration scattering plate angle. Therefore, it is expected that the scattered electrons produced by the novel cone can be applied as a new treatment beam.

View full abstract

We introduced an image mixing camera system at Akita University Hospital in 1999. We evaluated portal film matching rate by using this mixing camera system from January to December 1998. Of 166 cases of radiation therapy, 17 cases were selected at random and we used this system and compared it with the visual verification of portfilms, a traditional way of examination. These 17 cases examined in a traditional way were the cases that were considerd to have no problem in terms of matching (within-10 mm distance). As a result of using this mixing camera system, we found that only 2 cases out of 17 were actually fully (100%) matched. We consider that difference in magnification of portfilm and linacgraphy was one of the reasons for mismatch. Our image mixing camera system can check each other at equal magnification. Therefore this device will play an important role in radiation therapy in terms of increasing the accuracy of treatment (Quality Assurance).

View full abstract

Although transperineal low-dose-rate interstitial radiation using a Syed-Neblett template has been reported, the same method by high dose rate has been rarely reported. The practical procedures involved in the transperineal high-dose-rate Ir-192 interstitial radiation by the Syed-Neblett template was described. In the ideal applicator alignment, the vaginal mucosal doses in the high-dose-rate irradiation were calculated by geometrical optimization or equal weighting. The Ir-192 source was assumed to move by 1cm steps and the reference line was located 5 mm laterally to the outermost applicator. The mean reference line dose was settled to 6 Gy. The vaginal mucosal doses remained at around 8 Gy even with an increase of applicator number and with various dwell positions and dwell times, provided that geometrical optimization was performed. The simultaneous use of tandem and obturator applicators did not bring about a high vaginal mucosal dose. The dose homogeneity index was also improved in the case undergoing geometrical optimization. In the transperineal high-dose-rate interstitial radiation, tandem and obturator applicators could be used simultaneously.

View full abstract

The effects of polaprezinc (an insoluble zinc complex of L-carnosine) on taste abnormalities were investigated in 22 patients receiving radiation therapy to head and neck malignancies. The total doses to the tongue were 25.5-46.0 Gy (mean, 37.9 Gy). All patients received 75 mg of polaprezinc two times a day with an interval of 0-1, 561 days (mean, 305.3 days) after the completion of radiation therapy. The duration of the drug administration was 25-353 days (mean, 96.9 days). Twenty patients (90.9%) were aware of an improvement of a partial or complete loss of taste. Polaprezinc is effective in improving loss of taste after radiation therapy.

View full abstract

The dose rate effect, low dose rate radiotherapy (LDR) /high dose rate radiotherapy (HDR), was calculated using the isoeffect ICRU rectal dose by intracavitary radiotherapy (ICRT) for uterine cervix cancer. The subjects analyzed consisted of 78 LDR and 74 HDR patients whose ICRU rectal dose could be calculated and whose local control as stage cases could be evaluated. The point A dose in ICRT was 45-55 Gy/3 fractions/3 weeks for LDR and 30 Gy/6 fractions/3 weeks for HDR. The dose effect relationships associated with local control at each whole pelvis external radiation dose were calculated using the double integration method and Probit analysis, and the 50% and 90% local control ICRU rectal doses were calculated from this relationship. Finally, the dose rate effect LDR/HDR was determined from 50% and 90% local control doses. The dose rate effect calculated from the 50% local control dose was 1.24 and that from the 90% local control dose was 1.14.

View full abstract

The improvement of spatial dose distribution is one of the means to make feasible the local control of malignancies, which is the goal of radiotherapy. We have modified the inverse planning introduced by Brahme in the late 1980's and developed a new high-performance calculation method, confirming its validity in a case of head and neck tumor. The employed prescription of dose distribution conforms to DICOM-RT, and the object function comprises degrees of dose dissatisfaction regulating PTV and OARs. The treatment parameters are defined as the intensity modulated beam weight distribution for all portal beams. A multiplestep gradient method is used to optimize dose distribution. Graphic display for each term of the object function allows visual estimation of its convergency. Initial values for each local search are chosen from a solution of the prior search, while slightly tuning the prior prescription. We have confirmed the availability of this method by applying it to a case of oropharynx carcinoma, in which we used fixed five ports on a 2D image. Convergence was met after twenty iterations for the first search, while the second search required only five iterations. The DVH analysis revealed that OAR exposure can be reduced if we allow increased dose non-uniformity in PTV. Inverse planning has been clinically applied chiefly with a 2.5 dimensional technique to prostate carcinoma as well as head and neck tumors. We believe that three dimensional implementation with high degrees of beam direction freedom is required so as to be applied to such cases as hepatocholangio-pancreatic malignancies where dose optimization is expected to accompany greater difficulties. Global search strategy seems to run the risk of vast calculation time. The advantages of the proposed multiple-step gradient method with prescription tuning capability are fast calculation and reduced risk for local minimum problems. It is highly expected that 3D inverse planning being developed will become a competent rival to proton therapy.

View full abstract

Purpose: To improve the local control of stage II-III esophageal cancer, we tried concurrent chemoradiotherapy with low-dose continuous infusion of 5-fluorouracil (5-FU) during the entire course of conventional radiotherapy. Material and Methods: Forty-three eligible patients with stage II-III esophageal cancer were treated with conventional radiotherapy up to 60-70 Gy concurrently with continuous infusion of 5-FU (300mg/m² per 24 hours) for 5 days per week given over 5 to 7 weeks. All patients were followed up more than 5 years after starting the treatments. Results: Although there were two treatment-related deaths, 88% of the patients (38/43) could complete the planned course of chemoradiotherapy. Response rate was 90%. The median survival time was 12.2 months, and the 2-and 5-year overall survival rates were 33% and 15%, respectively. Conclusion: Low-dose continuous infusion of 5-FU given during the entire course of conventional radiotherapy is feasible and seems to offer better results than radiotherapy alone in the treatment of stage II-III esophageal cancer.

View full abstract

Purpose: To improve the local control of stage III non-small cell lung cancer, we tried concurrent chemoradiotherapy with daily low-dose cisplatin during the first 5 weeks of conventional radiotherapy. Material and Methods: Ten consecutive patients with stage III non-small cell lung cancer were treated with chemoradiotherapy with 66 Gy in conventional fractionation and concurrent daily low-dose cisplatin (4mg/m²), which was given 5 days per week (from Monday to Friday) for the first 5 weeks. Results: There was no case with>grade 3 toxicity. The median survival was 14.6 months, and the 2-year local progression-free survival rate was 35%. Conclusion: Daily low-dose cisplatin combined with conventional radiotherapy was considered to be feasible and to have the possibility to offer better local control than radiotherapy alone in the treatment of stage III non-small cell lung cancer.

View full abstract

Oral leukoplakia is known as a premalignant lesion. It often recurs and malignant transformation occurs in spite of various treatments such as surgical removal or laser excision. We experienced a case of oral leukoplakia treated by radiation therapy, which was effective for the purpose of pain relief. This case is an 85 year old woman who suffered from leukoplakia on the right buccal mucosa. She was treated by laser excision four times and had been medicated by vitamin A for 4 years before radiation therapy. However, leukoplakia often recurred with pain, so we treated it by radiation therapy in June 1996. Total delivered irradiated dose was 40Gy/20 fr/32 days. 3 years and 7 months after radiation therapy, neither recurrence nor malignant transformation occurred, and no late radiation complication existed so far. Radiation therapy was effective in this case for the purpose of pain relief and diminution of the lesion, so if patient is elderly and if we can obtain informed consent, radiation therapy is thought to be a usefull for treating recurrent oral leukoplakia.

View full abstract

A national survey about the current management of the hospital ward by radiation oncologists in Japan was performed in 2000. The number of radiation oncologists was too small to cover the whole inpatients who received radiotherapy. Therefore, the increase in the number of radiation oncologist and the special ward for palliative care are waited.

View full abstract

We developed and herein introduce a new microscopic system for automatic acquisition of timelapse images of both brightfield images and four kinds of fluorescence images. We combined an inverted incident-light fluorescence microscope with an incubation system, a Hoffman Modulation Contrast device, a color chilled 3CCD camera, and an automatic excitation-filter exchanger. The light source switching for brightfield imaging was controlled automatically by a computer. Cells were maintained in 5% CO₂ plus 95% air at 37°C on a microscopic stage with an incubation system, which consists of a gas-regulatory system and two separate temperature-control devices.
The fluorescence of annexin V (AV)-enhanced green fluorescent protein (EGFP), AV-fluorescein isothiocyanate, and propidium iodide (PI) diminished 3%, 77%, and 28%, respectively, at 24 hours during time-lapse observation using this system.
Time-lapse observation of individual Jurkat cells using this system confirmed that anti-Fas antibody-mediated apoptotic cells occurred at first budding and were stained with AV-EGFP alone, and thereafter were also stained with PI when the cells became flat as a result of ruptures of the plasma membrane. These results present direct evidence that apoptotic cells undergo secondary necrosis, which could be recognized based on PI staining. There was a significantly long time interval between the staining of individual cells with AVEGFP, indicating apoptosis, and the staining of these cells with PI, which indicated the occurrence of secondary necrosis. On the other hand, most of the cells that underwent necrosis were detected simultaneously with AVEGFP and PI.
The microscopic system we developed allows time-lapse and simultaneous observation of individual cells for changes in both morphology and staining pattern of fluorescent dyes that allow the visualization of cellular function. This system might be a useful tool for research in radiation biology.

View full abstract