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A Study of Three-dimension Tissue Equivalent Compensator for 6MV X-Rays.

Journal of the Korean Society for Therapeutic Radiology.1989;7(1):133-140.

Three-dimension paraffin compensator was designed to construct the tissue equivalent compensator for irregular body contours and obiliques beam incidence. The ratio of compensator thickness to tissue deficit was depended on field size, depth and air gap because the scattered dose loss. The ratio of compensator-tissue was optimized 0.79, 0.73, 0.61 and 0.50 in 6MV x-rays as function of field size 4x4, 10x10, 20x20 and 30x30 cm2 respectively in our study. Using this tissue equivalent compensator, it can be got 2% difference of dose at same mid-plane in phantom study.
Incidence ; Paraffin

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A Study on Design and Application of Tissue Compensator for 6MV X-rays.

Kyu Young CHAI ; Eun Kyung CHOI ; Woong Ki CHUNG ; Wee Saing KANG ; Sung Whan HA ; Charn Il PARK

Journal of the Korean Society for Therapeutic Radiology.1989;7(1):123-132.

A radiation beam incident on an irregular or sloping surface produces the non-uniformity of absorbed dose. The use of a tissue compensator can partially correct this dose inhomogeneity. The tissue compensator is designed based on the patient's three dimensional contour. After required compensator thickness was determined according to tissue deficit at 25 cmx 25 cm field size, 10 cm depth for 6MV x-rays, tissue deficit was mapped by isoheight technique using laser beam system. Compensator was constructed along the designed model using 0.5 mm lead sheet or 5 mm acryl plate. Dosimetric verification were performed by film dosimetry using humanoid phantom. Dosimetric measurements were normalized to central axis full phantom readings for both compensated and non-compensated field. Without compensation, the percent differences in absorbed dose ranged as high as 12.1% along transverse axis, 16.8% along vertical axis. With the tissue compensators in place, the difference was reduced to 0~4.3% Therefore, it can be concluded that the compensator system constructed by isoheihnt technique can produce good dose distribution with acceptable inhomogeneity, and such compensator system can be electively applied to clinical radiotherapy.
Axis, Cervical Vertebra ; Compensation and Redress ; Film Dosimetry ; Radiotherapy ; Reading

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A Study on Rebuildup of 6MV X-ray by the Cavity.

Moon June CHO ; Eun Kyung CHOI ; Woong Ki CHUNG ; Wee Saing KANG ; Charn Il PARK

Journal of the Korean Society for Therapeutic Radiology.1989;7(1):113-122.

The inclusion of air filled cavities in treatment fields creates a potential dosimetric problem due to the rebuildup phenomenon near the air-tissue interface using a simulated phantom, such as air gap, air cylinder, and air cavity, the amount of rebuldup along the various field sizes and air cavity dimensions was measured. The results are as follows. 1. As the field size becomes larger in comparison with the cavity size, or as the cavity size gets bigger when the field size is equal to the cavity size, rebuildup decreases. 2. When the distance between the phantom surface and the air cavity is less than 1.5 cm, there is prominent rebuildup. And when the distance is more than 1.5 cm, rebuildup is relatively constant. 3. The change according to the depth of the cavity is affected by the field size and the cavity size, rebuildup usually increases when the depth of the cavity increases. 4. It is suggested that tissue equivalent material should be applied on the skin to make tissue thickness over the air cavity more than 1.5 cm and that the field size should include the air cavity with at least 1 cm margin.
Skin

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Treatment Planning and Dosimetry of Small Radiation Fields for Stereotactic Radiosurgery.

Sung Sil CHU ; Chang Ok SUH ; John J K LOH ; Sang Sup CHUNG

Journal of the Korean Society for Therapeutic Radiology.1989;7(1):101-112.

The treatment planning and dosimetry of small fields for stereotactic radiosurgery with 10 MV x-ray isocentrically mounted linear accelerator is presented. Special consideration in this study was given to the variation of absorbed dose with field size, the central axis percent depth doses and the combined moving beam dose distributon. The collimator scatter correction factors of small fields (1x1~3x3 cm2) were measured with ion chamber at a target chamber distance of 300cm where the projected fields were larger than the polystyrene buildup caps and it was calibrated with the tissue equivalent solid state detectors of small size (TLD, PLD, ESR and semiconductors). The central axis percent depth doses for 1x1 and 3x3 cm2 fields could be derived with the same acuracy by interpolating between measured values for larger fields and calcu1ated zero area data, and it was also calibrated with semiconductor detectors. The agreement between experimental and calculated data was found to be under +/-2% within the fields. The three dimensional dose planning of stereotactic focusing irradiation on small size tumor regions was performed with dose planning computer system (Therac 2300) and was verified with film dosimetry. The more the number of strips and the wider the angle of arc rotation, the larger were the dose delivered on tumor and the less the dose to surrounding the normal tissues. The circular cone, we designed, improves the alignment, minimizes the penumbra of the beam and formats ball shape of treatment area without stellate patterns. These dosimetric techniques can provide adequate physics background for stereotactic radiosurgery with small radiation fields and 10 MV x-ray beam.
Axis, Cervical Vertebra ; Computer Systems ; Film Dosimetry ; Particle Accelerators ; Polystyrenes ; Radiosurgery* ; Semiconductors

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Comparison of Electron Beam Dosimetries by Means of Several Kinds of Dosimeters.

Wee Saing KANG

Journal of the Korean Society for Therapeutic Radiology.1989;7(1):93-100.

Several combinations of measuring devices and phantoms were studied to measure electron beams. Silicon PN junction diode was used to find the dependence of depth dose profile on field size on axis of electron beam Depths of 50, 80 and 90% doses increased with the field size for small fields. For some larger fields, they were nearly constant. The smallest of field sizes over which the parameters were constant was enlarged with increase of the energy of electron beams. Depth dose distributions on axis of electron beam of 10 x 10 cm2 field were studied with several combinations of measuring devices and phantoms. Cylindrical ion chamber could not be used for measurement of surface dose, and was not convenient for measurement of near surface region of 6 MeV electron. With some exceptions, parameters agreed well with those studied by different devices and phantoms. Surface dose in some energies showed 4% difference between maximum and minimum. For 18 MeV, depths of 80 and 90% doses were considerably shallower by film than by others. Parallel-plate ion chamber with polystyrene phamtom and silicon PN junction would be recommended for measurement of central axis depth dose of electron beams with considerably large field size. It is desirable not to use cylindrical ion chamber for the purpose of measurement of surface dose or near surface region for lower energy electron beam. It is questionable that film would be recommended for measurement of dose distribution of electron with high energy like as 18 MeV.
Axis, Cervical Vertebra ; Polystyrenes ; Silicones

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High Energy Electron Dosimetry by Alanine/ESR Spectroscopy.

Sung Sil CHU

Journal of the Korean Society for Therapeutic Radiology.1989;7(1):85-92.

Dosimetry based on electron spin resonance(ESR) analysis of radiation induced free radicals in amino acids is relevant to biological dosimetry applications. Alanine detectors are without walls and are tissue equivalent. Therefore, alanine ESR dosimetry looks promising for use in the therapy level. The dose range of the alanine/ESR dosimetry system can be extended down to l Gy. In a water phantom the absorbed dose of electrons generated by a medical linear accelerator of different initial energies (6~21 MeV) and therapeutic dose levels(1~60 Gy) was measured. Furthermore, depth dose measurements carried out with alanine dosimeters were compared with ionization chamber measurements. As the results, the measured absorbed doses for shallow depth of initial electron energies above 15 MeV were higher by 2~ 5% than those calculated by nominal energy CE factors. This seems to be caused by low energy scattered beams generated from the scattering foil and electron cones of beam projecting device in medical linear accelerator.
Alanine ; Amino Acids ; Free Radicals ; Particle Accelerators ; Spectrum Analysis* ; Water

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Intracavitary Dosimetry: A Comparison of Doses at Point A and B to Curie-minutes in Cervical Cancer.

Seung Jee HUH

Journal of the Korean Society for Therapeutic Radiology.1989;7(1):81-84.

This study, involving thirty-two patients with carcinoma of uterine cervix treated by high dose rate intracavitary irradiation using a remotely controlled afterloading system, compares the doss at point A and B with the Curie-minutes prescription. A linear least-square regression analysis was used to compare the two sets of date. Correlation coefficients between doses at points A and B arid the Ci-min prescription are 0.92(p<0.001) and 0.90 (p<0.001), respectively, and linear relationship is observed between these two system. The limitation and significance of the comparison of the two approaches to intracavitary dosimetry is discussed.
Cervix Uteri ; Dioctyl Sulfosuccinic Acid ; Female ; Humans ; Prescriptions ; Uterine Cervical Neoplasms*

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Cevix Cancer Associated with Pregnancy: A Case Report and Review of the Literature.

Tae June LEE ; Hyung Cheol KWON

Journal of the Korean Society for Therapeutic Radiology.1989;7(1):77-80.

Invasive carcinoma of the cervix during the pregnancy is relatively uncommon , It must be considered fetal viability, tumor control as well. If the carcinoma is diagnosed in the first or second trimester, treatment should be undertaken immediately. At the third trimester, treatment should be undertaken until the fetus is viable.
Cervix Uteri ; Female ; Fetal Viability ; Fetus ; Humans ; Pregnancy Trimester, Second ; Pregnancy Trimester, Third ; Pregnancy* ; Uterine Cervical Neoplasms

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Radiation Treatment for Primary Adenocarcinoma of Bartholin's Gland: A Case Report and Review of Literature.

Won Yong OH ; In Soon WHANG

Journal of the Korean Society for Therapeutic Radiology.1989;7(1):71-76.

A patient with primary adenocarcinoma of Bartholin's gland is reported and the literatures relevant to this disease reviewed. Not only this disease is very rare but also primary carcinomas of Bartholin's gland are misdiagnosed as cysts or abscesses in half of the cases, leading to considerable delay in diagnosis. And so, It was wasted long time before definitive therapy. However, because of a different clinical behavior, cancer of the Bartholin's gland should be distinguished from other vulvar carcinomas. Histologically, squamous cell carcinoma and adenocarcinoma are the most common. Virtually all histologic types of Bartholin's gland carcinoma metastasize to lymph node, bone, lung and liver in distant sites. The authors data and a review of the literature support the concept that radical vulvectomy with or without bilateral inguina1-femoral lymphadenectomy is required. On the other hand, except primary radiation treatment for small or medium sized cancers, the results obtained by radiation therapy in carcinoma of the vulva including Bartholin's gland are generally discouraging. A role for postoperative adjuvant radiation therapy suggests because of high incidence of positive inguinal-femoral lymph nodes. In the near time, natural history and biological behavior of Bartholin's gland cancer must be disclosed in detail. And also optimal treatment modality and prognostic factors shall be determine.
Abscess ; Adenocarcinoma* ; Carcinoma, Squamous Cell ; Diagnosis ; Hand ; Humans ; Incidence ; Liver ; Lung ; Lymph Node Excision ; Lymph Nodes ; Natural History ; Vulva

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Early and Late Bowel Complication Following Irradiation of Cancer of the Uterine Cervix-Whole Pelvis Exlernal : Irradiation end High-Dose-Rate Inlracavitary Irradiation.

Myung Se KIM ; Kyung Ae KIM ; Sung Kyu KIM ; Sei One SHIN ; Sung Ho LEE ; Jae Chun CHANG

Journal of the Korean Society for Therapeutic Radiology.1989;7(1):59-70.

Cervix cancer is the most common female cancer in Korea. In spite of their relatively local invasive tendency, still 44% of patient will develop recurrent cancer This result suggests that more aggressive local treatment may increase the cure rate but increased complication risk also cannot be avoidable. Various institutions proposed different treatment regimen, but recommended dose were about 4500 cGy for whole pelvis and 8000 cGy at point A, even though they agreed that those doses may not be satisfactory for control of bulky disease. 96 cases of invasive cervical cancer, treated with postoperative or primary radiation therapy were analyzed to determine the complication rate and prognostic factor in our treatment regimen which is 500~1000 cGy higher than other institution. Mean follow up duration was 21 months. Symptomatic patients including mild but persistent abdominal discomfort was 46%, but only 1 patient (1%) had operative treatment because of incomplete obstruction of small bowel. Most symptoms appeared within 12 months and most common complaints were frequent bowel movement. Barium enema and sigmoidoscopy were performed for persistent symptomatic patients. Only one patient had abnormal finding in barium enema which showed inefficiency of this method for detecting bowel complication. Patient's age, total tumor dose, total TDF, rectal dose were not significant risk factors for complication, but boost dose, previous history of operation had some relationship with complication risk. Even though dose of point A and rectum is 500~1,000 cGy higher than other institution, such a low rate of severe complications may suggest that fear of complications should not be overestimated than cure rate and the possibility of more aggressive treatment for better local control should not be underestimated.
Barium ; Enema ; Female ; Follow-Up Studies ; Humans ; Korea ; Pelvis* ; Rectum ; Risk Factors ; Sigmoidoscopy ; Uterine Cervical Neoplasms

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