Trichostatin A, a Histone Deacetylase Inhibitor, Potentiated Cytotoxic Effect of Ionizing Radiation in Human Head and Neck Cancer Cell Lines / 대한방사선종양학회지

PURPOSE: We have previously reported that human glioblastoma cells are sensitized to radiation-induced death after their exposure to trichostatin A (TSA), a histone deacetylase inhibitor (HDAC-I), prior to the irradiation. We aimed to measure the magnitude of the radiosensitizing effect of TSA in human head and neck cancer cell lines. MATERIALS AND MEHTODS: Human head and neck cancer cell lines, HN-3 and HN-9, were exposed to 0, 50, 100, and 200 nM TSA for 18 hr prior to irradiation. Then, the TSA-treated cells were irradiated with 0, 2, 4, 6, and 8 Gy, and cell survival was measured by clonogenic assay. RESULTS: Pre-irradiation exposure to TSA was found to radiosensitize HN-3 and HN-9 cell lines. In HN-9 cells, the fraction surviving after 2 Gy (SF2) was significantly reduced by treatment of TSA at concentration as low as 50 nM. However, a treatment with 200 nM TSA was required to significantly decrease SF2 in the HN-3 cell line. SER of pre-irradiation treatment with 200 nM TSA was 1.84 in HN-3 and 7.24 in HN-9, respectively. CONCLUSIONS: Our results clearly showed that human head and neck cancer cell lines can be sensitized to ionizing radiation by pre-irradiation inhibition of histone deacetylase (HDAC) using TSA, and that this potentiation might well be a general phenomenon.

Radiation Dose Accuracy at the Isocenter: Standard Stereotactic Radiosurgery Technique Developed at Seoul National University Hospital / 대한방사선종양학회지

PURPOSE: To confirm the accuracy of the radiation dose at the isocenter by the standard linear accelerator-based stereotactic radiosurgery technique which was developed at Seoul National University Hospital. MATERIALS AND METHODS: Radiation dosimetry was undertaken during standard 5-arc radiosurgery using 6 MV X-ray beam from CL2100C linac. The treatment head was attached with circular tertiary collimators of 10 and 20 mm diameter. We measured the absorbed dose at the isocenter of a multi-purpose phantom using two kinds of detector : a 0.125 cc ionization chamber and a silicon diode detector. RESULTS: The dose differences at each arc plane between the planned dose and the measured dose at the isocenter raged from -0.73% to -2.69% with the 0.125 cc ion chamber, and from -1.29% to -2.91% with the diode detector during radiosurgery with the tertiary collimator of 20 mm diameter. Those with the 10-mm tertiary collimator ranged from -2.39% to -4.25% with the diode. CONCLUSION: The dose accuracy at the isocenter was +/-3%. Therefore, further efforts such as modification in processing of the archived image through DICOM3.0 format are required to lessen the dose difference.

Treatment Outcome of Brain Metastasis after the Cranial Radiotherapy Followed by Fractionated Stereotactic Radiotherapy and Its Prognostic Factors / Journal of the Korean Cancer Association, 대한암학회지

To evaluate the effectiveness of whole brain radiotherapy followed by stereotactic radiotherapy for newly diagnosed brain metastasis. MATERIALS AND METHODS: Thirty-three metastatic brain tumors received radiotherapy to the whole brain and stereotactic radiotherapy in 25 patients. Lung carcinomas were the most common (17/25) primary tumor. The radiation dose was 30 to 40 Gy for the whole brain, with a 12 to 40 Gy boost to the metastatic foci. Survival and local control rates were determined, and the prognostic factors for survival were evaluated. RESULTS: The overall median survival was 15 months and the actuarial survivals at 1- and 2-year were 67% and 31%, respectively. The local tumor control rate was 79%, with a median follow-up period of 9 months (2~36 months). The prognostic factors associated with survival were age, tumor size and the existence of active extracranial metastasis, with the performance status showing marginal significance. No acute or chronic complications were observed in the patients. CONCLUSION: From our data, cranial radiotherapy followed by stereotactic radiotherapy was useful in the local control of metastatic tumors, and in the survival of patients with tumor factors, such as small size or the absence of extracranial tumor activity, and host factors, such as young age or good performance status.

Confirmation of the Dose Distribution by Stereotactic Radiosurgery Technique with a Multi-purpose Phantom / 대한방사선종양학회지

PURPOSE: For the purpose of quality assurance of self-developed stereotactic radiosurgery system, a multi-purpose phantom was fabricated, and accuracy of radiation dose distribution during radiosurgery was measured using this phantom. MATERIALS AND METHODS: A farmer chamber, a 0.125 cc ion chamber and a diode detector were used for the dosimetry. Six MV x-ray from a linear accelerator (CL2100C, Varian) with stereotactic radiosurgery technique (Green Knife) was used, and multi-purpose phantom was attached to a stereotactic frame (Fisher type). Dosimetry was done by combinations of locations of the detectors in the phantom, fixed or arc beams, gantry angles (20 ~100 ), and size of the circular tertiary collimators (inner diameters of 10 degrees~40 degrees mm). RESULTS: The measurement error was less than 0.5% by Farmer chamber, 0.5% for 0.125 cc ion chamber, and less than 2% for diode detector for the fixed beam, single arc beam, and 5-arc beam setup. CONCLUSION: We confirmed the accuracy of dose distribution with the radiosurgery system developed in our institute and the data from this study would be able to be effectively used for the improvement of quality assurance of stereotactic radiosurgery or fractionated stereotactic radiotherapy system.

In vivo and in vitro Confirmation of Dose Homogeneity in Total Body Irradiation with Thermoluminescent Dosimeter / 대한방사선종양학회지

PURPOSE: Total body irradiation (TBI) or whole body irradiation is used to acquire immune suppression, to treat malignant lymphoma and leukemia, and as an conditioning regimen for bone marrow transplantation. For these purposes, many methods were developed to obtain homogenous dose distribution. The objective of this study was to analyze and confirm the accuracy and the homogeneity of the treatment setup, the parallel opposed lateral technique, currently used in Seoul National University Hospital. MATERIALS AND METHODS: Surface dose data, measured with a thermoluminescent dosimeter, of 8 patients among 10 patients, who were given total body irradiation with the parallel opposed lateral technique between September 1996 to August 1998, at Seoul National University Hospital were analyzed. Surface doses were measured at the head, neck, axilla, thigh, and ankle level. Surface and midline doses were measured with similar set-up and technique in the Humanoid phantom. RESULTS: Measured surface doses relative to prescribed dose for the head, neck, axilla, thigh, and ankle level were 91.3+/-7.8, 98.3+/-7.5, 95.1+/-6.3, 98.3+/-5.5, and 95.3+/-6.3%, respectively. The midline doses of the head, neck, axilla, thigh, and ankle level estimated from the surface-to-midline ratios in the Humanoid phantom were 103.4+/-9.0, 107.8+/-10.5, 91.1+/-6.1, 93.8+/-4.5, and 104.5+/-9.3%, respectively. Measured surface doses and estimated midline doses ranged from -8.9% to + 7.8%. Midline doses at the neck and the axilla level deviated more than 5% from the prescribed doses. The difference of the estimated midline doses at the neck and the axilla level and the actual doses were attributed to the thickness differences between the Humanoid phantom and the patients. CONCLUSION: Distribution of the midline doses as well as the surface doses were measured to be within -8.7 - +7.8% range. Actual dose distribution in the patient is expected to be better than the measured dose range mainly attributed to thickness difference between the patient and the Humanoid phantom.

Intracranial beta-hCG Secreting Germinoma: Clinical Significance and Radiotherapy Results / 대한암학회지

No abstract available.

Extracranial Doses with LIINAC Stereotactic Radiosurgery / 대한치료방사선과학회지

No astract is available

Radiation Exposure of Operator during Various Interventional Procedures

PURPOSE: To investigate the levels of radiation exposure of an operator which may be influenced by the wearing an apron, type of procedure, duration of fluoroscopy and operator's skill during various interventional procedures MATERIALS AND METHODS: Radiation doses were measured both inside and outside the apron(0.5mm lead equivalent) of the operator by a film badge monitoring method and the duration of fluoroscopy was measured in 96 procedures prospectively. The procedures were 30 transcatheter arterial embolizations (TAE), 25 percutaneous transhepatic biliary drainages (PTBD), 16 stone removals (SR), 15 percutaneous needle aspirations (PCNA) and 10 percutaneous nephrostomies(PCN). To assess the difference of exposure by the operator's skill, the procedures of TAE and PTBD were done separately by groups of staffs and residents. RESULTS: Average protective effect of the apron was 72.8%. Average radiation exposure(unit:micro Sv/procedure) was 23.3 in PTBD by residents, 10.0 in PTBD by staffs, 10.0 in SR, 8.7 in TAE by residents, 7.3 in TAE by staffs, 9.0 in PCN and 6.0 in PCNA. Average radiation exposure of residents were 1.9 times greater than those of staffs. CONCLUSION: Radiation exposure was not proportionally related to the duration of fiuoroscopy, but influenced by wearing an apron, various types o[procedure and operator's skills.

The Dosimetric Data of 10 MV Linear Accelerator Photon Beam for Total Body Irradiation / 대한치료방사선과학회지

PURPOSE: This study was to obtain the basic dosimetric data using the 10 MV X-ray for the total body irradiation. MATERIALS AND METHODS: A linear accelerator photon beam is planned to be used as a radiation source for total body irradiation (TBI) in Chonnam University Hospital. The planned distance from the target to the midplane of a patient is 360cm and the maximum geometric field size is 144cm' 144cm. Polystyrene phantom sized 30 30 30.2cm3 and consisted of several sheets with various thickness, and a parallel plate ionization chamber were used to measure surface dose and percent depth dose (PDD) at 345cm SSD, and dose profiles. To evaluate whether a beam modifier is necessary for TBI, dosimetry in build up region was made first with no modifier and next with an 1cm thick acryl plate 20cm far from the polystyrene phantom surface. For a fixed source-chamber distance, output factors were measured for various depth. RESULTS: As any beam modifier was not on the way of radiation of 10MV X-ray the dmax and surface dose was 1.8cm and 61%, respectively, for 345cm SSD. When an 1cm thick acryl plate was put 20cm far from polystyrene phantom for the SSD, the dmax and surface dose were 0.8cm and 94%, respectively. With acryl as a beam spoiler, the PDD at 10cm depth was 78.4% and exit dose was a little higher than expected dose at interface of exit surface. For two-opposing fields for a 30cm phantom thick phantom, the surface dose and maximum dose relative to mid-depth dose in our experiments were 102.5% and 106.3%, respectively. The off-axis distance of that point of 95% of beam axis dose were 70cm on principal axis and 80cm on diagonal axis. CONCLUSION: 1. To increase surface dose for TBI by 10MV X-ray at 360cm SAD, 1cm thick acrylic spoiler was sufficient when distance from phantom surface to spoiler was 20 cm. 2. At 345cm SSD, 10MV X-ray beam of full field produced a satisfiable dose uniformity for TBI within 7% in the phantom of 30cm thickness by two-opposing irradiation technique. 3. The uniform dose distribution region was 67cm on principal axis of the bean and 80cm on diagonal axis from beam axis. 4. The output factors at mid-point of various thickness revealed linear relation with depth, and it could be applicable to practical TBI.

Dose Distributions for LINAC Radiosurgery with Dynamically Shaping Fields / 대한치료방사선과학회지

An important problem in radiosurgery is the utilization of the proper beam parameters, to which dose shape is sensitive. Streotactic radiosurgery techniques for a linear accelerator typically, use circular radiation fields with multiple arcs to produce an spherical radiation distribution. Target volumes are irregular in shape for a certain case, and spherical distributions can irradiate normal tissues to high dose as well as the target region. The current improvement to dose distribution utilizes treating multiple isocenters or weighting various arcs to change treatment volume shape. In this paper another premising study relies upon dynamically shaping the treatment beam to fit the beam's eye view of the target. This conformal irradiation technique was evaluated by means of visual three dimensional dose distribution, dose volume histograms to the target volume and surrounding normal brain. It is shown that using even less arcs than multiple isocenter irradiation technique, the conformal therapy yields comparable dose gradients and superior homogeneity of dose within the target volume.

The Physical Penumbra of the 6MV X-ray / 대한치료방사선과학회지

High energy photon beam margin due to a less side scatter and the other things. But there still remains a penumbra where the dose changes rapidly in the region near the edge of a radiation beam, although it is short in width. It is suggested that the width of the penumbra depends on the source size, distance from source to diaphragm, source to skin distance, and depth in tissue. However, it is also supposed that the other factors influence the penumbra width. In this paper, we investigate changes of the physical penumbra widths according to various field sizes and depths, by using the three dimensional dosimetry system. As a result, we found that as field size and depth increase, the physical penumbra width also increases.

A Computerized Database and Statistical Analysis System for Radiotherapy / 대한치료방사선과학회지

A computerized system for database of radiotherapy patient and for its application was developed in 1987 and has been utilized till now. A radiotherapy planning computer (Eclipse S-14O) operated under AOS (Advanced Operating System) is the main processing unit of the system which was programmed with Fortran-5. Records of 30,000 patients can be separately registered and data of 5 courses of radiotherapy delivered to one patient can be separately registered but structurally linked together. The same environment is allowed for 60 follow-up data. Our system's utility is very convenient to use and provides simple or conditional list of records or items, periodic statistics concerning many parameters and survival or complication analysis of stored database or data manually put in. Structure, operation and several retrieval formats by data processings are reported.

A Study on Dose Distribution around Fletcher-Suit Colpostat Containing Cs-137 Source by a Computer / 대한치료방사선과학회지

Fletcher-Suit colpostat has an internal structure to reduce dose to bladder and rectum. Some programs were developed to calculate dose at any point in water in three dimension around the colpostat containing Cs-137 tube, to find the shielding effect to dose by the internal structure, and to draw isodose cuties and iso-shielding effect cuties. Computer was an IBM compatible AT with EGA card and language was MS-Basic V6.0. Material, shape and geometry of the structure, tube and colpostat were considered in algorithm for calculation of dose. Dose rates per unit mg. Ra. eq. in water calculated by a program were stored in auxiliary memory devices and retrieved in another programs. Isodose curves on medial side shrieked. Dose distribution was not symmetric about a transverse axis bisecting the colpostat. Reduction of dose was more excessive on top side than on bottom. Iso-shielding effect cutie showed that the shielding effect was higher on top side than on bottom, and that there was shielding effect over almost all area of medial side. Such results were related to both shifted position of tribe in the colpostat and asymmetric distribution of active source in the tube. Maximum of shielding effect was 49% on top side and 44% on bottom side. The direction of iso-shielding effect curve was generally radial from the center of active source. In treatment planning using Fletcher-Suit colpostat, the internal structure should be considered to find precise doses to bladder and rectum, etc.

Comparison of Electron Beam Dosimetries by Means of Several Kinds of Dosimeters / 대한치료방사선과학회지

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.

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

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.

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

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.

A Study on Dose Distribution around Fletcher-Suit Colpostat Containing 137Cs Source / 대한치료방사선과학회지

This paper presents dose distributions in water around Fletcher-Suit colpostat containing 137Cs tube, and shielding effect of internal lead shield. Using ready packed film, author measured dose distribution in water around the colpostat containing cesium source. Nine sheets of films on one side of the colpostat are packed with acryl frames cut out so as to fill water, and irradiated in water by cesium source in the colpostat. Dose distributions on transverse plane and upper plane 0.5 cm from upper surface of the colpostat were measured. Shielding effect was greater in upper medial direction than in lower medial direction. And that was the greatest around 30degree from the axis of the colpostat on upper side and around 50degree on lower side. In the region 7 cm from the center of the colpostat, shielding efficiency was 0.23 to 0.35 on the lower 50degree and 0.26 to 0.42 on the upper 30degree, and decreased with increase of distance.

The RBE of Fractionated Fast Neutron on Walker 256 Carcinosarcoma with KCCH-Cyclotron / 대한치료방사선과학회지

For evaluation of biological effect of p+(50.5 MeV) Be neutron beam produced by Korea Cancer Center Hospital(KCCH) cyclotron the RBE had been measured in experimental tumor Walker 256 carcinosarcoma as well as normal tissue, mouse intestine and bone marrow, in single and fractionated irradiation. As pilot study, the RBE had been measured for the mouse jejunal crypt cells in single whole body irradiation of which the result was 2.8. The obtained RBE values of TCD 50 of Walker 256 tumor, bone marrow and intestine in single irraiation were 1.9, 1.9 and 1.5 respectively. In fractionated irradiation, the RBE value of tumor Walker 256 was decreased as increasing of fraction number and increased as increaing of fraction size.

A Study on the Effect of Field Shaping on Dose Distribution of Electron Beams / 대한치료방사선과학회지

In electron therapy, lead cutout or low-melting alloy block is used for shaping the field. Material for shaping electron field affects the output factor as well as the collimation system. The authors measured the output factors of electron beams for shaped fields from Clinac-18 using ionization chamber of Farmer type on polystyrene phantom. They analyzed the incident energy, collimation system and size of shaped field. For shaped field the variation of output factor for the field (A/P) has appearance of a smooth curve for all energy and all applicator collimator combination. The output factors for open field deviate from the curves for shaped fields. An output factor for a given field can be calculated by equivalent field method such as A/P method, if a combination of applicator and collimator is fixed.

Treatment Planning Software for High Dose Rate Remote Afterloading Brachytherapy of Uterine Cervical Cancer / 대한치료방사선과학회지

In brachytherapy of uterine cervical cancer using the high dose rate remote afterloading system, it is of prime importance to determine the position of the radiation sources and to estimate the irradiation time. However, calculation with manual method is so time consuming and laborious, that authors designed a software as an aid to intracavitary radiotherapy planning using the personal computer to obtain the precision of treatment without being too complicated for routine use. Optimal source arrangement in combination with dose rate at each specific points and irradiation time can be easily determined using this software in several minutes.