Young-nam Kang

Radiation-induced brain injury: retrospective analysis of twelve pathologically proven cases.

Purpose This study was designed to determine the influencing factors and clinical course of pathologically proven cases of radiation-induced brain injury (RIBI). Materials and Methods The pathologic records of twelve patients were reviewed; these patients underwent surgery following radiotherapy due to disease progression found by follow-up imaging. However, they were finally diagnosed with RIBI. All patients had been treated with 3-dimensional conventional fractionated radiotherapy and/or radiosurgery for primary or metastatic brain tumors with or without chemotherapy. The histological distribution was as follows: two falx meningioma, six glioblastoma multiform (GBM), two anaplastic oligodendroglioma, one low grade oligodendroglioma, and one small cell lung cancer with brain metastasis. Results Radiation necrosis was noted in eight patients and the remaining four were diagnosed with radiation change. Gender (p = 0.061) and biologically equivalent dose (BED)3 (p = 0.084) were the only marginally influencing factors of radiation necrosis. Median time to RIBI was 7.3 months (range, 0.5 to 61 months). Three prolonged survivors with GBM were observed. In the subgroup analysis of high grade gliomas, RIBI that developed <6 months after radiotherapy was associated with inferior overall survival rates compared to cases of RIBI that occurred ≥6 months (p = 0.085). Conclusion Our study demonstrated that RIBI could occur in early periods after conventional fractionated brain radiotherapy within normal tolerable dose ranges. Studies with a larger number of patients are required to identify the strong influencing factors for RIBI development.

Helical tomotherapy with concurrent capecitabine for the treatment of inoperable pancreatic cancer

BackgroundHelical tomotherapy, an advanced intensity-modulated radiation therapy with integrated CT imaging, permits highly conformal irradiation with sparing of normal tissue. Capecitabine, a pro-drug of 5-FU that induces thymidine phosphorylase can achieve higher levels of intracellular 5-FU when administered concurrently with radiation. We evaluated the feasibility as well as the clinical outcome of concurrent administration of capecitabine with tomotherapy in patients with advanced pancreatic cancer.MethodsNineteen patients with advanced pancreatic cancer including primarily unresectable disease and recurrence after curative surgery were included in the study. Two planning target volumes (PTV) were entered: PTV1 is gross tumor volume; and PTV2, the volume of the draining lymph nodes. The total doses to target 1 and target 2 were 55 and 50 Gy, respectively. Capecitabine at 1600 mg/m2/day was administered on each day of irradiation.ResultsTwenty six measurable lesions were evaluated. Overall in-field response rate was 42.3%; partial responses were achieved in 53.3% of the pancreatic masses, 28.6% of distant metastatic lesions and 25.0% of regional lymph nodes. The median duration of follow-up after tomotherapy was 6.5 months. None of the lesions showed in-field progression. Treatment was well tolerated with only minor toxicities such as grade 1 nausea (one patient), grade 1 hand-foot syndrome (one patient) and grade 1/2 fatigue (three patients).ConclusionsHelical tomotherapy with concurrent capecitabine is a feasible option without significant toxicities in patients with advanced pancreatic cancer. We achieved excellent conformal distribution of radiation doses and minimal treatment-related toxicities with promising target volume responses.

Development of deformable moving lung phantom to simulate respiratory motion in radiotherapy.

Radiation treatment requires high accuracy to protect healthy organs and destroy the tumor. However, tumors located near the diaphragm constantly move during treatment. Respiration-gated radiotherapy has significant potential for the improvement of the irradiation of tumor sites affected by respiratory motion, such as lung and liver tumors. To measure and minimize the effects of respiratory motion, a realistic deformable phantom is required for use as a gold standard. The purpose of this study was to develop and study the characteristics of a deformable moving lung (DML) phantom, such as simulation, tissue equivalence, and rate of deformation. The rate of change of the lung volume, target deformation, and respiratory signals were measured in this study; they were accurately measured using a realistic deformable phantom. The measured volume difference was 31%, which closely corresponds to the average difference in human respiration, and the target movement was - 30 to + 32mm. The measured signals accurately described human respiratory signals. This DML phantom would be useful for the estimation of deformable image registration and in respiration-gated radiotherapy. This study shows that the developed DML phantom can exactly simulate the patient׳s respiratory signal and it acts as a deformable 4-dimensional simulation of a patient׳s lung with sufficient volume change.

Comparison of spinal Stereotactic Body Radiotherapy (SBRT) planning techniques: intensity-modulated radiation therapy, modulated arc therapy, and helical tomotherapy

Stereotactic body radiotherapy (SBRT) delivers a highly conformal, hypofractionated radiation dose to a small target with minimal radiation applied to the surrounding areas. Therefore, using the proper treatment planning techniques for SBRT is important. Intensity modulation techniques, such as static intensity-modulated radiation therapy (IMRT), modulated arc therapy (mARC), and helical tomotherapy (HT), are useful for spinal SBRT because of a rapid dose fall-off and spinal cord avoidance. This study compared the planning characteristics for hypofractionated spinal SBRT administered using 3 treatment techniques. The factors evaluated for spinal SBRT planning were dose coverage, cord avoidance, target conformity, homogeneity, and dose spillage. Target coverage was 82.74% ± 3.35%, 80.92% ± 0.81%, and 85.01% ± 7.27% for IMRT, mARC, and HT, respectively. HT was therefore a powerful technique with respect to target coverage. The spinal cord dose for HT (mean, 1763.96 cGy; standard deviation [SD], 164.48) was significantly different from those for mARC (mean, 1991.75 cGy; SD, 248.00) and IMRT (mean, 2053.24 cGy; SD, 164.48). In addition, the partial spinal cord volume at 2000 cGy for HT (mean, 0.12 cc, SD, 0.01) was significantly different from those for IMRT and mARC (0.50 ± 0.10 cc and 0.56 ± 0.25 cc, respectively). The conformity index was 1.30 ± 0.12, 1.08 ± 0.05, and 1.36 ± 0.23 for IMRT, mARC, and HT planning, respectively. mARC showed the highest conformity (p = 0.000). HT used a narrow field fan beam and exhibited remarkable improvement of target coverage and cord dose, offering an important benefit to spinal SBRT. mARC had the highest target conformity and better high- and intermediate-dose spillage than HT and IMRT did, respectively. These planning techniques have different advantages. In the case of spine SBRT, HT should be used for cord avoidance. In some cases, such as for a short treatment duration when the patient is considered to be in a poor general condition, mARC can be used.

Curative Radiotherapy in Metastatic Disease: How to Develop the Role of Radiotherapy from Local to Metastases

© 2013 Kay and Kang, licensee InTech. This is an open access chapter distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Curative Radiotherapy in Metastatic Disease: How to Develop the Role of Radiotherapy from Local to Metastases

Dosimetric comparison between modulated arc therapy and static intensity modulated radiotherapy in thoracic esophageal cancer: a single institutional experience

Purpose The objective of this study was to compare dosimetric characteristics of three-dimensional conformal radiotherapy (3D-CRT) and two types of intensity-modulated radiotherapy (IMRT) which are step-and-shoot intensity modulated radiotherapy (s-IMRT) and modulated arc therapy (mARC) for thoracic esophageal cancer and analyze whether IMRT could reduce organ-at-risk (OAR) dose. Materials and Methods We performed 3D-CRT, s-IMRT, and mARC planning for ten patients with thoracic esophageal cancer. The dose-volume histogram for each plan was extracted and the mean dose and clinically significant parameters were analyzed. Results Analysis of target coverage showed that the conformity index (CI) and conformation number (CN) in mARC were superior to the other two plans (CI, p = 0.050; CN, p = 0.042). For the comparison of OAR, lung V5 was lowest in s-IMRT, followed by 3D-CRT, and mARC (p = 0.033). s-IMRT and mARC had lower values than 3D-CRT for heart V30 (p = 0.039), V40 (p = 0.040), and V50 (p = 0.032). Conclusion Effective conservation of the lung and heart in thoracic esophageal cancer could be expected when using s-IMRT. The mARC was lower in lung V10, V20, and V30 than in 3D-CRT, but could not be proven superior in lung V5. In conclusion, low-dose exposure to the lung and heart were expected to be lower in s-IMRT, reducing complications such as radiation pneumonitis or heart-related toxicities.

Image similarity evaluation of the bulk-density-assigned synthetic CT derived from MRI of intracranial regions for radiation treatment

Objective Various methods for radiation-dose calculation have been investigated over previous decades, focusing on the use of magnetic resonance imaging (MRI) only. The bulk-density-assignment method based on manual segmentation has exhibited promising results compared to dose-calculation with computed tomography (CT). However, this method cannot be easily implemented in clinical practice due to its time-consuming nature. Therefore, we investigated an automatic anatomy segmentation method with the intention of providing the proper methodology to evaluate synthetic CT images for a radiation-dose calculation based on MR images. Methods CT images of 20 brain cancer patients were selected, and their MR images including T1-weighted, T2-weighted, and PETRA were retrospectively collected. Eight anatomies of the patients, such as the body, air, eyeball, lens, cavity, ventricle, brainstem, and bone, were segmented for bulk-density-assigned CT image (BCT) generation. In addition, water-equivalent CT images (WCT) with only two anatomies—body and air—were generated for a comparison with BCT. Histogram comparison and gamma analysis were performed by comparison with the original CT images, after the evaluation of automatic segmentation performance with the dice similarity coefficient (DSC), false negative dice (FND) coefficient, and false positive dice (FPD) coefficient. Results The highest DSC value was 99.34 for air segmentation, and the lowest DSC value was 73.50 for bone segmentation. For lens segmentation, relatively high FND and FPD values were measured. The cavity and bone were measured as over-segmented anatomies having higher FPD values than FND. The measured histogram comparison results of BCT were better than those of WCT in all cases. In gamma analysis, the averaged improvement of BCT compared to WCT was measured. All the measured results of BCT were better than those of WCT. Therefore, the results of this study show that the introduced methods, such as histogram comparison and gamma analysis, are valid for the evaluation of the synthetic CT generation from MR images. Conclusions The image similarity results showed that BCT has superior results compared to WCT for all measurements performed in this study. Consequently, more accurate radiation treatment for the intracranial regions can be expected when the proper image similarity evaluation introduced in this study is performed.

Compared Evaluation for Direct Aperture Optimization (DAO) PROWESS in Intensity Modulation Radiotherapy (IMRT) Pinnacle 8.0 treatment planning

Intensity Modulated Radiation Therapy (IMRT) is a means of delivering radiation therapy where the intensity of the beam is varied within the treatment field. One of the main problems of IMRT, which becomes even more apparent as the complexity of the IMRT plan increases, is the amazing increase in the number of Monitor Units (MU) required to deliver a fractionated treatment. The difficulty with this increase in MU is its association with increased treatment times and a greater leakage of radiation from the MLCs increasing the total body dose and the risk of secondary cancers in patients. Many approaches have been taken to reduce the complexity. In this study, we used a direct aperture optimization (DAO) IMRT plan Direct aperture optimization IMRT is an IMRT method in which the aperture shapes and aperture weights are optimized simultaneously, and the MLC constraints and the number of segments are directly included in the optimization process. In DAO-IMRT planning, the planner specifies the planning objectives on the basis of the dose volume criteria for the target and critical structures as well as the number of beam segments to be delivered. The optimization only considers aperture shapes that satisfy the conditions set by the MLC. As a result, high-quality DAO-IMRT treatment plans can be generated using fewer segments (apertures) per beam. We investigated the dosimetric and technical differences in using DAO-IMRT. We also compared DAO-IMRT plans with standard beamlet-IMRT plans on phantom in terms of dosimetry, number of segments, and monitor units. In this study, we found that DAO-IMRT can achieve equal or better plans than standard beamlet-IMRT in dose optimization, secondary scattering dose and treatment time. The DAO-IMRT planning is proficient, and the plans can be delivered efficiently because small numbers of segments and monitor units are used.

Comparison of beam data using diode and ion chamber in small field of CyberKnife

Ion chamber, diode detector and film are used for measuring small field of SRS. The diode detector is recommended to measure the beam from CyberKnife recently. In this study, various detectors had been used to measure the beam data and compared that for each CyberKnife of domestic and foreign departments.

BANG-3® polymer gel dosimetry in Cyberknife

In this study, we performed BANG-3® polymer gel dosimetry to propose an experimental technique for relative output factor and 3D dose distribution measurements of small radiosurgical fields.We were irradiated 2 collimators (5 and 30 mm diameter) with 6 MV radiosurgery beam. And, MR scanned with the same slice thickness and three different in plane resolutions. In these experiments, output factor measurements with the Pin Point ion chamber and diode, EBT films are compared with BANG-3® polymer gel. We used a spherical phantom filled with BANG-3® polymer gel to measure 3D dose distributions. The irradiated phantom was scanned with an MRI scanner. Dose distributions were obtained by calibrating the polymer gel for a relationship between the absorbed dose and the spin-spin relaxation rate of the magnetic resistance signal.