• Radiation Oncology Journal
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• v.19 no.1
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• pp.74-80
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• 2001

Purpose : Irradiation cones by using backscatter electrons are made for the treatment of superficial small lesions of skin, oral cavity, and rectum where a significant dose gradient and maximum surface dose is desired. Methods and Materials : Backscatter electrons are produced from the primary electron beams from the linear accelerators. The design consists of a cylindrical cone that has a thick circular plate of high atomic number medium (Pb or Cu) attached to the distal end, and the plate can be adjusted the reflected angle. Primary electrons strike the metal plate perpendicularly and produce backscatter electrons that reflect through the lateral hole for treatment. Using film and a parallel plate ion chamber, backscatter electron dose characteristics are measured. Results : The depth dose characteristic of the backscatter electron is very similar to that of the hard x-ray beam that is commonly used for the intracavitary and superficial lesions. The basckscatter electron energy is nearly constant and effectively about 1.5 MeV from the clinical megavoltage beams. The backscatter electron dose rate of $35\~85\;cGy/min$ could be achieved from modern accelerators without any modification. and the depth in water of $50\%$ depth dose from backscatter electron located at 6mm for $45^{\circ}$ angled lead scatter. The beam flatness is dependent on the slit size and the depth of treatment, but is satisfactory to treat small lesions. Conclusions : The measured data for backscatter electron energy, depth dose flatness dose rate and absolute dose indicates that the backscatter electrons are suitable for clinical use.

• Radiation Oncology Journal
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• v.11 no.2
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• pp.347-354
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• 1993

This is a retrospective analysis of 67 patients with histologically proven invasive carcinoma of uterine cervix treated with surgery followed by adjuvant radiotherapy at Inje University Seoul Paik Hospital between october 1983 and september 1991, Postoperative radiotherapy was carried out in patients with high risks of locoregional recurrence such as positive pelvic lymph node (38 pts), large tumor size more than 3 cm (22 pts), cervical stromal invasion more than 2/3 (46 pts), parametrial involvement (9 pts), positive resection margin (14 pts), endo/myometrial extension (10 pts), and angiolymphatic invasion (13 pts). Stage I A, I B, and IIA were 2 $(3\%),$ 39 $(58.2\%),\;and\;26\;(38.8\%),$ respectively. Median follow-up period was 48 months with ranges from 13 to 115 months. All 67 patients were treated externally with standard pelvic field with radiation dose ranging from 4080 to 6120 cGy in 4~6 weeks period of time. Of these, 45 patients received intracavitary radiotherapy. The overall survival rate and disease free survival rate at 5-year were $88.0\%\;and\;82.1\%,$ respectively. The survival rates by stage were $87.1\%$ in IB and $88.4\%$ in IIA. Local control rate was $80.6\%(58\;pts).$ The treatment failure was noted in 12 of 67 patients $(17.9\%):$ locoregional failure in $7(10.4\%),$ distant metastasis in 3 $(4.5\%),$ and locoregional and distant metastasis in $2(3\%),$ The univariate analysis of prognostic factors disclosed endo/myometrial extension as a significant factor of survival and recurrence $(70.0\%\;vs\;91.1\%\;P<0.05\;&\;30.0\%\;vs\;15.8\%,\;respectively).$ The complication of postoperative radiothrapy was not significant and all patient were well tolerated. In conclusion, postoperative radiotherapy in patients with high risks of locoreginal recurrence is relatively well tolerated and it gives significantly improved survival rate especially in patients with positive lymph nodes, bulky tumor size $(\geqq3\;cm),$ parametrial involvement, cervical stromal invasion more than 2/3, positive resection margin and angiolymphatic invasion.

• Radiation Oncology Journal
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• v.10 no.2
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• pp.267-275
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• 1992

Remote afterloading high dose rate brachytherapy (HDRB) is a new technology and needs new biological principle for time and dose schedule. Here, authors attempt to evaluate the technique and clinical outcome in 116 patients, 590 procedures peformed at Asan Medical Center for 3 years. From Sep. 1989 to Aug 1992, 471 procedures of intracavitary radiation in 58 patients of cervical cancer and 26 of nasopharyngeal cancer,79 intraluminal radiation in 12 of esophageal cancer, 11 of endobronchial cancer and 1 Klatskin tumor and 40 interstitial brachytherapy in 4 of breast cancer, 1 sarcoma and 1 urethral cancer were performed. Median follow-up was 7 months with range $1\~31$ months. All procedures except interstitial were performed under the local anesthesia and they were all well tolerated and completed the planned therapy except 6 patients. 53/58 patients with cervical cancer and 22/26 patients with nasopharynx cancer achieved CR. Among 15 patients with palliative therapy, $80{\%}$ achieved palliation. We will describe the details of the technique and results in the text. To evaluate biologic effects of HDRB and optimal time/dose/fractionation schedule, we need longer follow-up. But authors feel that HDRB with proper fractionation schedule may yield superior results compared to the low dose rate brachytherapy considering the advantages of HDRB in safety factor for operator, better control of radiation dose and volume and patients comfort over the low dose brachytherapy.

• Journal of Yeungnam Medical Science
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• v.6 no.1
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• pp.87-98
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• 1989

Clinical estimation of bladder and rectal doses from high dose rate intracavitary irradiation in carcinoma of the cervix uteri has been initiated on a routine basis in an effort to obtain the optimum radiotherapeutic dose. Simulation films with contrast media are used to image the bladder and rectum, and dose rates are estimated at various interesting points with the aid of treatment planning computer, NEC Therac-2300. Fifty-three patients have been reviewed in order to ascertain the correlation between radiation dose at interesting points in the bladder and rectum and the dose at Point A and B. The dose ratio between doses at Point A 'and interesting points is an important clinical factor in evaluating the treatment planning. This also serves as documentation of the dose to normal structures within the treatment volume. Authors conclude that obtained data are within acceptable ranges and routine simulation films of the bladder and rectum after administration of contrast media with dose calculations at interesting points provide important information for optimizing radiotherapy planning in the treatment of cervical carcinoma without increased time and effort or patient's discomfort.

• Progress in Medical Physics
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• v.15 no.3
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• pp.134-139
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• 2004

This study was aimed to develop a new ovoid applicator for vaginal high-dose rate intracavitary radiation therapy, evaluate uniformity of dose distribution, and assess clinical applicability. The authors evaluated dose uniformity of vaginal mucosa according to 5-different ovoid-separation using 2-channel and modified 3-channel ovoid applicator. There were no significant differences in the dose distribution along the vaginal mucosa with 2 and 2.5 cm separations, but there were between the 2-channel and 3-channel ovoid applicator with a separation of 3 cm or more. Although a low dose area was shown between two ovoid applicators with the 2-channel ovoid applicator, the dose distribution along the vaginal mucosa with the 3-channel ovoid applicator was very uniform.

• Radiation Oncology Journal
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• v.11 no.2
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• pp.355-361
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• 1993

Since May 1991, authors have conducted a pilot study to determine the feasibility and evaluate the effect of concurrent radiation therapy and chemotherapy with 5-FU and Cis-platinum for locally advanced cervical cancer (stage IIB-IVA). Radiation therapy consisted of external irradiation to whole pelvis (4140 cGy/23 fx) in 4.5 weeks followed by high dose rate intracavitary radiation therapy (HDR ICRT) to deliver a dose of 30 to 35 Gy to A point in 6 to 7 fractions. After the intracavitary radiation therapy, parametrial boost was delivered for B point dose of 60 Gy in Stage IIB and 65 Gy in stage IIIB. 5-FU (1000 $mg/m^2/24hr$ for 96 hour iv infusion) and Cis-platinum (20 $mg/m^2/day$ IV bolus for 3 days) were given during the second week of external RT and the second course chemotherapy administered at the first HDR ICRT with the same method as the first chemotherapy. Sixteen patients (10 stage IIB,4 stage IIIB,2 stage IVA) were registered to this protocol. Among these 16 patients, two refused treatment after 2 fractions of external irradiation, and one could not continue intracavitary irradiation because of treatment related genitourinary toxicity. So 14 patients were evaluated for toxicity and 13 patients were evaluated for response analysis. Five of 14 patients developed grade 3 gastrointestinal toxicity but 4 of them recovered at the completion of treatment. One stage IIIB patient with inguinal lymph node metastasis who received higher dose of radiation in spite of initial poor performance status did not recover from gastrointestinal toxicity at the completion of treatment. And she died of distant metastasis at one month after the completion of treatment. Two of 14 evaluable patients showed weight loss, more than $10\%$ of initial weight. One patient developed grade 3 leukopenia. In this study, the average total treatment period of completely treated patients was 75 days and three of them took more than 80 days (84, 84, 89 days). Toxicities were generally acceptable and there were no treatment related death. At the last follow-up, complete response was achieved in $62\%(8/13)$ and especially of nine patients with stage IIB, eight patients showed complete response. This study suggests that concurrent radiation therapy and chemotherapy (5-FU and Cis-platinum) is tolerable and effective. Further follow-up is needed to determine whether this protocol will have a favorable impact on survival and to evaluate the late effect on normal tissues. In future, prospective randomized trials are needed to compare the standard radiation therapy alone with concurrent chemotherapy and radiation therapy for locally advanced cervical carcinoma.

• Radiation Oncology Journal
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• v.23 no.3
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• pp.143-156
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• 2005

Background: The best dose-fractionation regimen of the definitive radiotherapy for cervix cancer remains to be clearly determined. It seems to be partially attributed to the complexity of the affecting factors and the lack of detailed information on external and intra-cavitary fractionation. To find optimal practice guidelines, our experiences of the combination of external beam radiotherapy (EBRT) and high-dose-rate intracavitary brachytherapy (HDR-ICBT) were reviewed with detailed information of the various treatment parameters obtained from a large cohort of women treated homogeneously at a single institute. Materials and Methods: The subjects were 743 cervical cancer patients (Stage IB 198, IIA 77, IIB 364, IIIA 7, IIIB 89 and IVA 8) treated by radiotherapy alone, between 1990 and 1996. A total external beam radiotherapy (EBRT) dose of $23.4\~59.4$ Gy (Median 45.0) was delivered to the whole pelvis. High-dose-rate intracavitary brachytherapy (HDR-IBT) was also peformed using various fractionation schemes. A Midline block (MLB) was initiated after the delivery of $14.4\~43.2$ Gy (Median 36.0) of EBRT in 495 patients, while In the other 248 patients EBRT could not be used due to slow tumor regression or the huge initial bulk of tumor. The point A, actual bladder & rectal doses were individually assessed in all patients. The biologically effective dose (BED) to the tumor ($\alpha/\beta$=10) and late-responding tissues ($\alpha/\beta$=3) for both EBRT and HDR-ICBT were calculated. The total BED values to point A, the actual bladder and rectal reference points were the summation of the EBRT and HDR-ICBT. In addition to all the details on dose-fractionation, the other factors (i.e. the overall treatment time, physicians preference) that can affect the schedule of the definitive radiotherapy were also thoroughly analyzed. The association between MD-BED $Gy_3$ and the risk of complication was assessed using serial multiple logistic regression models. The associations between R-BED $Gy_3$ and rectal complications and between V-BED $Gy_3$ and bladder complications were assessed using multiple logistic regression models after adjustment for age, stage, tumor size and treatment duration. Serial Coxs proportional hazard regression models were used to estimate the relative risks of recurrence due to MD-BED $Gy_{10}$, and the treatment duration. Results: The overall complication rate for RTOG Grades $1\~4$ toxicities was $33.1\%$. The 5-year actuarial pelvic control rate for ail 743 patients was $83\%$. The midline cumulative BED dose, which is the sum of external midline BED and HDR-ICBT point A BED, ranged from 62.0 to 121.9 $Gy_{10}$ (median 93.0) for tumors and from 93.6 to 187.3 $Gy_3$ (median 137.6) for late responding tissues. The median cumulative values of actual rectal (R-BED $Gy_3$) and bladder Point BED (V-BED $Gy_3$) were 118.7 $Gy_3$ (range $48.8\~265.2$) and 126.1 $Gy_3$ (range: $54.9\~267.5$), respectively. MD-BED $Gy_3$ showed a good correlation with rectal (p=0.003), but not with bladder complications (p=0.095). R-BED $Gy_3$ had a very strong association (p=<0.0001), and was more predictive of rectal complications than A-BED $Gy_3$. B-BED $Gy_3$ also showed significance in the prediction of bladder complications in a trend test (p=0.0298). No statistically significant dose-response relationship for pelvic control was observed. The Sandwich and Continuous techniques, which differ according to when the ICR was inserted during the EBRT and due to the physicians preference, showed no differences in the local control and complication rates; there were also no differences in the 3 vs. 5 Gy fraction size of HDR-ICBT. Conclusion: The main reasons optimal dose-fractionation guidelines are not easily established is due to the absence of a dose-response relationship for tumor control as a result of the high-dose gradient of HDR-ICBT, individual differences In tumor responses to radiation therapy and the complexity of affecting factors. Therefore, in our opinion, there is a necessity for individualized tailored therapy, along with general guidelines, in the definitive radiation treatment for cervix cancer. This study also demonstrated the strong predictive value of actual rectal and bladder reference dosing therefore, vaginal gauze packing might be very Important. To maintain the BED dose to less than the threshold resulting in complication, early midline shielding, the HDR-ICBT total dose and fractional dose reduction should be considered.

• Radiation Oncology Journal
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• v.24 no.1
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• pp.44-50
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• 2006

Puroose: This study evaluated the late rectal complications in cervix cancer patients following treatment with external beam radiotherapy (EBRT) and high dose rate intracavitary radiation (HDR ICR). The factors affecting the risk of developing late rectal complications and its incidence were analyzed and discussed. Materials and Methods: The records of 105 patients with cervix cancer who were treated with radical radiotherapy using HDR ICR between July, 1995 and December, 2001 were retrospectively reviewed. The median dose of EBRT was 50.4Gy $(41.4{\sim}56.4 Gy)$ with a daily fraction size of 1.8Gy. A total of $5{\sim}7$ (median: 6) fractions of HDR ICR were given twice weekly with a fraction size of $4{\sim}5 Gy$ (median: 4Gy) to A point using an Ir (Iridium)-192 source. The median dose of ICR was 24 Gy $(20{\sim}35 Gy)$. During HDR ICR, the rectal dose was measured in vivo by a semiconductor dosimeter. The median follow-up period was 32 months, ranging from 5 to 84 months. Results: Of the 105 patients, 12 patients (11%) developed late rectal complications: 7 patients with grade 1 or 2, 4 patients with grade 3 and 1 patient with grade 4. Rectal bleeding was the most frequent chief complaint. The complications usually began to occur $5{\sim}32$ (median: 12) months after the completion of radiotherapy. Multivariate analysis revealed that the measured cumulative rectal BED over 115 Gy3 (Deq over 69 Gy) and the depth (D) of a 5 Gy isodose volume more than 50 mm were the independent predictors for late rectal complications. Conclusion: With evaluating the cumulative rectal BED and the depth of a 5 Gy isodose volume as predictors, we can individualize treatment planning to reduce the probability of late rectal complications.

• Journal of radiological science and technology
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• v.39 no.2
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• pp.163-170
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• 2016

To evaluate whether the difference in geometrical characteristics between high-dose-rate (HDR) $^{192}Ir$ sources would influence the dose distributions of intracavitary brachytherapy. Two types of microSelectron HDR $^{192}Ir$ sources (classic and new models) were selected in this study. Two-dimensional (2D) treatment plans for classic and new sources were generated by using PLATO treatment planning system. We compared the point A, point B, and bladder and rectum reference points based on ICRU 38 recommendation. The radial dose function of the new source agrees with that of the classic source except difference of up to 2.6% at the nearest radial distance. The differences of anisotropy functions agree within 2% for r=1, 3, and 5 cm and $20^{\circ}$ < ${\theta}$ < $165^{\circ}$. The largest discrepancies of anisotropy functions reached up to 27% for ${\theta}$ < $20^{\circ}$ at r=0.25 cm and were up to 13%, 10%, and 7% at r=1, 3, and 5 cm for ${\theta}$ > $170^{\circ}$, respectively. There were no significant differences in doses of point A, point B, and bladder point for the treatment plans between the new and classic sources. For the ICRU rectum point, the percent dose difference was on average 0.65% and up to 1.0%. The dose discrepancies between two treatment plans are mainly affected due to the geometrical difference of the source and the sealed capsule.

• Radiation Oncology Journal
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• v.14 no.1
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• pp.33-39
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• 1996

Purpose : This study was done to analyze survivals, patterns of failure, and complications of early uterine cervix cancer after curative radiotherapy. Materials and Methods : Eighty patients with uterine cervix cancer FIGO Stage IB (48 cases) and Stage IIA (32 cases) treated with radiotherapy were analyzed retrospectively. Patients were treated from November 1985 to May 1993, and minimum follow up period was 24 months and 6 cases were lost to follow up. All of them were treated with external radiotherapy and different fractions of high dose rate intracavitary radiotherapy, Survival rates, failure patterns, complication rates and degrees of severity were analyzed according to several factors. Results : Overall 5 year survival rate and relapse free survival rate were $72.3\%$, and $72.8\%$ respectively. Prognostic factors were stage, size, pathology, RT response and there was no significant survival difference among the reasons of radiotherapy choice. There were 19 cases of treatment failure, another 3 cases were not tumor related death, and most of treatment related failure occurred within 24 months Late complication rate of bladder and rectum were $8.8\%,\;15\%$ respectively, frequency and severity of complication were correlated with ICR fractionation dose and total dose. Conclusion : These results showed that survival rates of early stage radiation treated cervix cancer patients were comparable to surgical series, but more aggressive treatment methods needed for stage IIA poor prognostic patients. To decrease late complication, choice of proper ICR dose and meticulous vaginal packing is needed.