X-rays were discovered on 8 November 1895 by Professor Wilhelm Röntgen, Professor of Physics at the University of Würzburg in Bavaria. It is therefore very appropriate to publish at the time of the centennial a brief resume of this momentous discovery which has led to so many advances not only in the field of radiodiagnosis and radiation therapy, but also in industrial fields such as non-destructive testing and detection of art forgeries, and in microscopy, and astronomy. This particular paper concentrates on the actual discovery by Röntgen, together with a commentary on early apparatus, and extensive reviews of other aspects have been published elsewhere^{1), 2)} as well as a book containing some 700 illustrations³⁾ of applications of X-rays in the early years in medicine and industry.

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Radiation therapy contribute greatly to the treatment of head and neck cancer, becausei t maintains the normal anatomy, minimizes functional loss, and facilitates a patient's return to work. Brachytherapy using small radiation sources is an indispensable modality for the treatment of cancer of the oral region, in which emphasis should be laid on the maintenance of normal anatomy and function and a high quality of life. Brachytherapy was performed in 62% of the radiation therapy patients with cancer of the oral region. Interstitial brachytherapy with radium, ¹⁹²Ir-hairpin was administered to more than 80% of the patients with tongue cancer and ¹⁹⁸Augrain was frequently used for other site of the oral region. Introduction of the remote afterloading system (RALS) has completely eliminated the possibility of personnel exposure and increased the indication for brachytheapy. There is a lot of work to be done in the near future, including the establishment of dose-time relationship for RALS and the development of related apparatus and instruments and the standardization of dose assesment.

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We evaluated the effects of fractioned intervals on normal tissue recovery from radiation injury after neutron exposure. Doses ranging from 9 to 25 Gy of 30 MeV deuteronberyllium neutrons (0.7Gy/min.) were imposed on the hind legs of C3H/He female mice in single or in two equally divided doses at various intervals ranging from 6 hours to 14 days. The effective doses 50% for early skin shrinkage measured at around 40 to 50 days, late skin contraction and leg contracture at 250 days after irradiation were evaluated. With recovery ratios, (D2-D 1)/D 1, the patterns obtained were similar to those observed in the isoeffect curves. However, with one or two day intervals, they remarkably decreased to less than 10% irrespective of the response evaluated especially in late skin contraction. This might indicate the induction of hypersensitivity and/or very little recovery at these intervals. Therefore, fractioned intervals of more than five days and around one and/or two days seem less beneficial from the view point of normal tissue recovery.

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Over the past two years, we have attempted to practice radiotherapy in accordance with the principle of informed consent. The procedure used in our radiotherapy, which consists of informing the patient of the seriousness of his or her disease (malignant and benign) and receiving signed consent forms, is a new system in Japan. This is a report of our experience with this system and its advantages and disadvantages. We are satisfied with the clinical results of the attempt. Radiotherapy in accordance with informed consent has now become routine at our hospital. We feel that this practice will produce the mutual enhancement of our responsibility to patients and their trust in us, and improve cure rates. In promoting mutual understanding between our patients and ourselves, we must keep in mind that we, radiation oncologists, are not only radiotherapists but also health-care providers in our capacity as medical and surgical doctors. It is also necessary to achieve the best radiotherapeutic system in Japan.

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Between 1980 and 1994, 36 patients with loco-regional recurrent esophageal cancer were treated with radiation therapy (RT) at Kyoto University Hospital. Local response and survival rates of the patients were analyzed. The 2-and 5-year cumulative survival rates of the patients were both 13%. Pretreatment and treatment parameters were evaluated in an univariate analysis for the endpoint of survival rates. Tumor size (≤3cm vs.>3cm) and initial treatment (surgery vs.RT) were significant variables for survival rates. In addition to the parameters, interval between initial treatment and recurrence (≤6 months vs.>6 months), distant metastasis at the time of recurrence, and recurrent sites (mediastinal lymph nodes, neck lymph nodes vs. esophagus, abdominal lymph nodes) also affected the survival rate, although not significantly. In terms of treatment methods, all three tumors treated with accelerated hyperfractionation showed CR. On the other hand, RT with chemotherepy did not improve the prognosis. In conclusion, aggresive RT is indicated for patients with recurrent esophageal cancer who were initially treated with surgery and had only mediastinal or neck lymph nodes recurrence of ≤3cm in diameter.

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Purpose: During the past 10 years, five infants with Kasabach-Merritt syndrome (K-M) received radiation therapy were reported. We investigated whether radiation therapy for K-M was useful and what the unfavorable factors of K-M were.
Material and treatment: During the past 10 years, we have treated five infants with K-M. The syndrome occurred at ages ranging from birth to 4 months. The incidence of female to male ratio was 3: 2. Among 5 cases, the site of hemangioma was as follows; shoulder, anterior chest wall, lower abdominal wall, face and neck and inguinal site. All 5 cases received medication to control the coagulopathy including prednisone and blood transfusion at first. Because the platelet count and the bleeding tendency did not improve in any case, these cases received radiation therapy.Total dose ranged from 5 to 10Gy and fraction-size ranged from 0.5 to 1.75Gy. Irradiation session was 2 or 3 times per week.
Results: In 5 cases, 4 cases showed cure of bleeding tendency and disappearance of tumor, andsur vived. In these 4 cases, normalization of platelet count was obtained at the early phase of dose ranging from 3 to 5 Gy by radiation therapy. In the remaining case, bleeding tendency was improved at the late phase by initial radiation therapy, however, after that immediately relapsed. In this case, the salvage radiation therapy was not effective and she died from airway obstruction. This case was of neonatal age and had bulky neck tumor.
Conclusion: We recognized that radiation therapy was effective for K-M.
A serious case was of neonatal age and had bulky neck tumor. It was estimated that the unfavorable factors of K-M were neonatal case and bulky neck tumor case.

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Twenty-four patients who received radical radiotherapy for superficial esophageal cancers between October, 1982 and September, 1994 (“ep” in 1, “mm” in 4, “sm” in 19) were evaluated. The median age of the patients was 71 years (57-84), the median follow-up period was 48 months (4 months to 12 years and 3 months), and the male-female ratio was 23: 1.
Radiotherapy was performed by external irradiation alone in 15 patients and external irradiation plus intraluminal irradiation in 9 patients. The cummulative survival rate were calculated by the Kaplan-Meier method.
(1) Local recurrence was observed in 7 patients, of whom 4 had recurrence inside the irradiation field and 3 had recurrence outside the irradiation field.
(2) Local recurrence was observed in all “sm” patients, but not at all in the “ep” and “mm” paients.
(3) The 2-year and 5-year local control survival rates were 75.0% and 62.5%, respectively.
(4) Death was observed in 13 patients, of whom 3 died of esophageal cancer, 4 died of other cancers, and 6 died of other diseases.
(5) The 2-year and 5-year survival rates and primary disease survival rates were 76.7% and 36.5%, respectively, and 90.9% and 79.8%, respectively.
(6) As delayed complications, esophageal constriction, ulcer, and bronchial ulcer were noted in 1 each (total 3 cases, 12.5%), but the ulcer proved manageable by subsequent treatment.
Although superficial cancers evaluated in this study had disadvantages for radical radiotherapy, such as the high incidence of multiple cancers and complications, a satisfactory primary disease survival rate was obtained. Concerning local control, however, recurrence was often observed in the “sm” group, and improvements in local control and the establishment of treatments according to the depth of invasion and the presence or absence of lymph node metastasis are considered to be needed.

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To assess the dose-modifying factors for skin ulceration, the hind legs of mice were irradiated using gamma-rays of various doses in single exposures. The skin ulceration began to occur 2 months after irradiation, after early skin reactions such as wet desquamation, had healed completely. No new skin ulceration was observed more than 8 months after irradiation even though the observations were continued until 12 months post-irradiation. The ulceration dose 50 (UD 50), a dose required to produce skin ulceration in from 2 to 8 months in 50% of the tested animals, was calculated for each treatment schedule. The preliminary shaving procedure reduced the UD 50 dose to 0.85 that of the untreated controls. The ventral aspect of the hind leg was more radioresistant to single-dose irradiation than was to the dorsal aspect. The UD 50 for the ventral aspect was 1.29 times that for the dorsal aspect when the skin had been previously shaved, and 1.46 times that for the unshaved control legs. The UD 50 was 7 and 14% larger when mice were kept in the dorsal rather than the abdominal position during irradiation, for the preliminarily shaved and unshaved skin, respectively.

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Apoptosis is the predominant form of cell death and occurs under variety of physiological and pathological conditions. In the present study, we detected the apoptotic cells and S phase cells in rat tongue epithelium in both normal and irradiated conditions. After 24 hours from irradiation, cell cycle arrest was obvious and the number of apoptotic cell reached the maximum level; however there was no detectable DNA fragmentation in basal cells.

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Mouse hind legs were exposed to single and multi-fractionated gamma rays with various time intervals between doses, and the ventral aspects of the legs were observed for ulceration from 2 to 8 months following irradiation. The doses necessary to produce ulcer (s) in 50% and 10% of the tested animals (UD 50 and UD 10, respectively) were calculated for each treatment schedule. Using these isoeffect doses, recovery curves and time-dose relationships of the target cells were assessed for ulceration. On the time interval-isoeffect dose curve, the isoeffect doses increased, decreased and increased again with increasing time intervals for two and four fractionation treatment schedules. The first peak was at 0.5 (or 0.5) day fractionation interval, and the trough at 4 (or 5) day intervals for 2 (or 4) fractions, when either the 10 or 50% ulceration was used as an end point. Applying the α/β model on UD 10 and UD 50, the flexured ose of the dose-response curve for the critical target cells for ulceration was calculated to be 0.23 Gy and 0.89 Gy, respectively.

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A linac system (Mitsubishi ML15MV) was modified in the following manner so as to enable stereotatactic rediotherapy. A small CCD (charge-coupled device) video-camera, beam's eye monitor, is mounted in the gantry of the linac at the place optically identical to the linac x-ray source.
Standard parts of the Leksell stereotactic system were used for localizing the target point on the patient's head. A positioning device-a target pointer consisting of two sets of cross hairsis attached, for positioning purpose, to the arc of the stereotactic system. The target pointer always indicates the center of the arc, regardless of the direction in which the target pointer or the arc is oriented. The monitor system and the target pointer are used together to maintain the center of the arc on the isocenter of the linac. This method enables us to perform precise positioning without having to use a special head-supporting stand.

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