• Radiation Oncology Journal
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• v.27 no.4
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• pp.240-248
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• 2009

Purpose: To provide a simple research tool that may be used to analyze a dose volume histogram from different radiation therapy planning systems for NTCP (Normal Tissue Complication Probability), OED (Organ Equivalent Dose) and so on. Materials and Metohds: A high-level computing language was chosen to implement Niemierko's EUD, Lyman-Kutcher-Burman model's NTCP, and OED. The requirements for treatment planning analysis were defined and the procedure, using a developed GUI based program, was described with figures. The calculated data, including volume at a dose, dose at a volume, EUD, and NTCP were evaluated by a commercial radiation therapy planning system, Pinnacle (Philips, Madison, WI, USA) for comparison. Results: The volume at a special dose and a dose absorbed in a volume on a dose volume histogram were successfully extracted using DVH data of several radiation planning systems. EUD, NTCP and OED were successfully calculated using DVH data and some required parameters in the literature. Conclusion: A simple DVH analyzer program was developed and has proven to be a useful research tool for radiation therapy.

• Proceedings of the Korean Society of Medical Physics Conference
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• 2006.08a
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• pp.121-121
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• 2006

• Progress in Medical Physics
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• v.23 no.4
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• pp.269-278
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• 2012

Aquaplast Thermoplastic (AT) is a tissue-equivalent oral compensator that has been developed to improve dose uniformity at the common boundary and around the treated area during radiotherapy in patients with head and neck cancer. In order to assess the usefulness of AT, the degree of improvement in dose distribution and physical properties were compared to those of oral compensators made using paraffin, alginate, and putty, which are materials conventionally used in dental imprinting. To assess the physical properties, strength evaluations (compression and drop evaluations) and natural deformation evaluations (volume change over time) were performed; a Gafchromic EBT2 film and a glass dosimeter inserted into a developed phantom for dose verification were used to measure the common boundary dose and the beam profile to assess the dose delivery. When the natural deformation of the oral compensators was assessed over a two-month period, alginate exhibited a maximum of 80% change in volume from moisture evaporation, while the remaining tissue-equivalent properties, including those of AT, showed a change in volume that was less than 3%. In a free-fall test at a height of 1.5 m (repeated 5 times as a strength evaluation), paraffin was easily damaged by the impact, but AT exhibited no damage from the fall. In compressive strength testing, AT was not destroyed even at 8 times the force needed for paraffin. In dose verification using a glass dosimeter, the results showed that in a single test, the tissue-equivalent (about 80 Hounsfield Units [HU]) AT delivered about 4.9% lower surface dose in terms of delivery of an output coefficient (monitor unit), which was 4% lower than putty and exhibited a value of about 1,000 HU or higher during a dose delivery of the same formulation. In addition, when the incident direction of the beam was used as a reference, the uniformity of the dose, as assessed from the beam profile at the boundary after passing through the oral compensators, was 11.41, 3.98, and 4.30 for air, AT, and putty, respectively. The AT oral compensator had a higher strength and lower probability of material transformation than the oral compensators conventionally used as a tissue-equivalent material, and a uniform dose distribution was successfully formed at the boundary and surrounding area including the mouth. It was also possible to deliver a uniformly formulated dose and reduce the skin dose delivery.

• Progress in Medical Physics
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• v.29 no.4
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• pp.143-149
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• 2018

To verify the correlations between the clinical outcomes and physical factors of short-course chemoradiotherapy (SCRT) and long-course chemoradiotherapy (LCRT) with delayed surgery in patients with rectal cancer. Seventy-two patients with rectal cancer were enrolled in this study. Nineteen patients were treated with SCRT (25 Gy, 5 fractions) by intensity-modulated radiation therapy (IMRT), and 53 patients were treated with LCRT (50.4 Gy, 28 fractions) by three-dimensional conformal radiation therapy (3DCRT). Various physical factors for the target and organs at risk (OARs) were calculated to compare the clinical outcomes. The organ equivalent dose (OED) and lifetime attributable risk (LAR) of bowels and bladders were similar between the SCRT and LCRT groups, whereas the values of femurs were higher in the LCRT group. The equivalent uniform dose and normal tissue complication probability were higher in the LCRT than the SCRT group for most organs. Treatment complications, including anastomotic leakage, bowel adhesion, and hematologic toxicity, were not significantly different between SCRT and LCRT groups. CIs were $0.84{\pm}0.2$ and $0.61{\pm}0.1$ for SCRT and LCRT, respectively. The CVIs were $1.07{\pm}0.0$ and $1.10{\pm}0.1$, and the HIs were $0.09{\pm}0.0$ and $0.11{\pm}0.1$ for SCRT and LCRT, respectively. The sphincter-saving rates were 89.5% and 94.3% for SCRT and LCRT, respectively. The complete pathologic remission rates were 21.1% and 13.2%, and the down-staging rates were 47.4% and 26.4% for SCRT and LCRT, respectively. SCRT with IMRT is comparable to conventional LCRT in both physical indexes and clinical outcome. The preoperative SCRT, compensated by IMRT, is an effective and safe modality.

• Progress in Medical Physics
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• v.22 no.4
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• pp.178-183
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• 2011

The applicability and feasibility of TomoTherapy in the lung radiation surgery was analyzed by comparison of the calculated dose distribution in TomoTherapy planning with the results of conventional IMRS (intensity modulated radiation surgery) using LINAC (linear accelerator). The acquired CT (computed tomograph) images of total 10 patients whose tumors' motion were less than 5 mm were used in the radiation surgery planning and the same prescribed dose and the same dose constraints were used between TomoTherapy and LINAC. The results of TomoTherapy planning fulfilled the dose requirement in GTV (gross tumor volume) and OAR (organ at risk) in the same with the conventional IMRS using LINAC. TomoTherapy was superior in the view point of low dose in the normal lung tissue and conventional LINAC was superior in the dose homogeneity in GTV. The calculated time for treatment beam delivery was long more than two times in TomoTherapy compared with the conventional LINAC. Based on the results in this study, TomoTherapy can be evaluated as an effective way of lung radiation surgery for the patients whose tumor motion is little when the optimal planning is produced considering patient's condition and suitability of dose distribution.

• The Journal of Korean Society for Radiation Therapy
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• v.26 no.2
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• pp.225-232
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• 2014

Purpose : The purpose of this study was to evaluate the surface and superficial dose for patients requiring postmastectomy radiation therapy(PMRT) with different treatment techniques. Materials and Methods : Computed tomography images were acquired for the phantom(I'mRT, IBA) consisting of tissue equivalent material. Hypothetical chestwall and lung were outlined and modified. Five treatment techniques(Wedged Tangential; WT, 4-field IMRT, 7-field IMRT, TOMO DIRECT, TOMO HELICAL) were evaluated using only 6MV photon beam. GafChromic EBT3 film was used for dose measurements at the surface and superficial dose. Surface dose profiles around the phantom were obtained for each treatment technique. For superficial dose measurements, film were used inside the phantom and analyzed superficial region for depth from 1-6mm. Results : TOMO DIRECT showed the highest surface dose by 47~70% of prescribed dose, while 7-field IMRT showed the lowest by 35~46% of prescribed dose. For the WT, 4-field IMRT and 7-field IMRT, superficial dose were measured over 60%, 70%, and 80% for 1mm, 2mm, and 5mm depth, respectively. In case of TOMO DIRECT and TOMO HELICAL, over 75%, 80%, and 90% of prescribed dose was measured, respectively. Surface and superficial dose range were uniform in overall chestwall for the 7-field IMRT and TOMO HELICAL. In contrast, Because of the dose enhancement effect with oblique incidence, The dose was gradually increased toward the obliquely tangential angle for the WT and TOMO DIRECT. Conclusion : For PMRT, TOMO DIRECT and TOMO HELICAL deliver the higher surface and superficial doses than treatment techniques based linear accelerator. It showed adequate dose(over 75% of prescribed dose) at 1mm depth in skin region.

• Journal of radiological science and technology
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• v.30 no.1
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• pp.13-23
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• 2007

In recent years, mammography system is changed rapidly from conventional screen-film system to digital system for application to screening and diagnosis. Digital mammography system provides several advantages over screen-film mammography system. According to the information provided by the manufacturer, digital mammography system offers radiation dose reduction in comparison with screen-film mammography system, because of digital detector, particularly direct digital detector has higher x-ray absorption efficiency than screen-film combination or imaging plate(IP). We measured average glandular doses(AGD) in screen-film mammography(SFM) system with slow screen-film combination, computed mammography(CM) system, indirect digital mammography(IDM) system and direct digital mammography(DDM) system using brest tissue-equivalent phantom(glandularity 30%, 50% and 70%). The results were shown as follows : AGD values for DDM system were highest than those for other systems. Although automatic exposure control(AEC) mode was selected, the curve of the AGD values against thickness or glandularity increased significantly for the SFM system with the uniform target/filter(Mo/Mo) combination. Therefore, the AGD values for the high energy examinations were highest in the SFM system, and those for the low energy examinations were highest in the DDM system. But the curve of the AGD values against thickness and glandularity increased gently for CM system with the automatic selection of the target/filter combination (from Mo/Mo to Mo/Rh or from Mo/Rh to Rh/Rh), and the AGD values were lowest. Consequently, the parameters in mammography for each exposure besides detection efficiency play an important role in oder to estimate a patient radiation dose.

• Progress in Medical Physics
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• v.19 no.2
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• pp.89-94
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• 2008

TomoTherapy has a merit to treat cancer with Intensity modulated radiation and combines precise 3-D imaging from computerized tomography (CT scanning) with highly targeted radiation beams and rotating beamlets. In this paper, we comparing the dose distribution between TomoTherapy and linear accelerator based intensity modulated radiotherapy (IMRT) for 10 Head & Neck patients using TomoTherapy which is newly installed and operated at National Cancer Center since Sept. 2006. Furthermore, we estimate how the homogeneity and Normal Tissue Complication Probability (NTCP) are changed by motion of target. Inverse planning was carried out using CadPlan planning system (CadPlan R.6.4.7, Varian Medical System Inc. 3100 Hansen Way, Palo Alto, CA 94304-1129, USA). For each patient, an inverse IMRT plan was also made using TomoTherapy Hi-Art System (Hi-Art2_2_4 2.2.4.15, TomoTherapy Incorporated, 1240 Deming Way, Madson, WI 53717-1954, USA) and using the same targets and optimization goals. All TomoTherapy plans compared favorably with the IMRT plans regarding sparing of the organs at risk and keeping an equivalent target dose homogeneity. Our results suggest that TomoTherapy is able to reduce the normal tissue complication probability (NTCP) further, keeping a similar target dose homogeneity.