PURPOSE: Firstly, to analyze factors in terms of radiation treatment that might potentially cause subfrontal relapse in two patients who had been treated by craniospinal irradiation (CSI) for medulloblastoma. Secondly, to explore an effective salvage treatment for these relapses. MATERIALS AND METHODS: Two patients who had high-risk disease (T3bM1, T3bM3) were treated with combined chemoradiotherapy. CT-simulation based radiation-treatment planning (RTP) was performed. One patient who experienced relapse at 16 months after CSI was treated with salvage surgery followed by a 30.6 Gy IMRT (intensity modulated radiotherapy). The other patient whose tumor relapsed at 12 months after CSI was treated by surgery alone for the recurrence. To investigate factors that might potentially cause subfrontal relapse, we evaluated thoroughly the charts and treatment planning process including portal films, and tried to find out a method to give help for placing blocks appropriately between subfrotal-cribrifrom plate region and both eyes. To salvage subfrontal relapse in a patient, re-irradiation was planned after subtotal tumor removal. We have decided to treat this patient with IMRT because of the proximity of critical normal tissues and large burden of re-irradiation. With seven beam directions, the prescribed mean dose to PTV was 30.6 Gy (1.8 Gy fraction) and the doses to the optic nerves and eyes were limited to 25 Gy and 10 Gy, respectively. RESULTS: Review of radiotherapy portals clearly indicated that the subfrontal-cribriform plate region was excluded from the therapy beam by eye blocks in both cases, resulting in cold spot within the target volume. When the whole brain was rendered in 3-D after organ drawing in each slice, it was easier to judge appropriateness of the blocks in port film. IMRT planning showed excellent dose distributions (Mean doses to PTV, right and left optic nerves, right and left eyes: 31.1 Gy, 14.7 Gy, 13.9 Gy, 6.9 Gy, and 5.5 Gy, respectively. Maximum dose to PTV: 36 Gy). The patient who received IMRT is still alive with no evidence of recurrence and any neurologic complications for 1 year. CONCLUSION: To prevent recurrence of medulloblastoma in subfrontal-cribriform plate region, we need to pay close attention to the placement of eye blocks during the treatment. Once subfrontal recurrence has happened, IMRT may be a good choice for re-irradiation as a salvage treatment to maximize the differences of dose distributions between the normal tissues and target volume.
Brain ; Chemoradiotherapy ; Craniospinal Irradiation ; Humans ; Medulloblastoma* ; Optic Nerve ; Radiotherapy ; Recurrence*

Cone-beam digital tomosynthesis (CBDT) has greatly been paid attention in the image-guided radiation therapy because of its attractive advantages such as low patient dose and less motion artifact. Image quality of tomograms is, however, dependent on the imaging conditions such as the scan angle (beta(scan)) and the number of projection views. In this paper, we describe the principle of CBDT based on filtered-backprojection technique and investigate the optimization of imaging conditions. As a system performance, we have defined the figure-of-merit with a combination of signal difference-to-noise ratio, artifact spread function and floating-point operations which determine the computational load of image reconstruction procedures. From the measurements of disc phantom, which mimics an impulse signal and thus their analyses, it is concluded that the image quality of tomograms obtained from CBDT is improved as the scan angle is wider than 60 degrees with a larger step scan angle (Delta beta). As a rule of thumb, the system performance is dependent on . If the exact weighting factors could be assigned to each image-quality metric, we would find the better quantitative imaging conditions.
Artifacts ; Humans ; Image Processing, Computer-Assisted ; Radiotherapy, Image-Guided ; Thumb

The aim of the present study was to evaluate the efficacy and toxicity of stereotactic body radiation therapy (SBRT) for low- to intermediate-risk prostate adenocarcinoma. Thirty-nine patients were retrospectively reviewed. The SBRT was delivered using the CyberKnife with the fiducial tracking method combined with In-tempo imaging. The gross target volume, which included the prostate only, was delineated on the fused CT/MRI scans. The prescription dose was delivered every other day as 5 fractions of 7.5 Gy. Venous blood was obtained before and after SBRT to assess the prostate-specific antigen (PSA) level. Toxicity was evaluated using the CTCAE, v4.03. The median follow-up time was 30.0 months. The median initial PSA level was 7.7 ng/mL. PSA levels decreased in all patients treated with SBRT, and after 5 months, the median PSA was less than 2 ng/mL. The rate of overall 3-yr actuarial biochemical failure free survival was 93.9%. Acute side effects were generally comparable with those of previous studies. The PSA change and toxicity after SBRT for low- to intermediate-risk prostate adenocarcinoma indicates favorable biochemical responses and tolerable levels of toxicity. Additionally short course treatment may produce cost benefit and convenience to patients.
Adenocarcinoma/*diagnosis/*surgery ; Aged ; Aged, 80 and over ; Humans ; Male ; Middle Aged ; Prostatic Neoplasms/*diagnosis/*surgery ; Radiosurgery/*methods ; Radiotherapy Dosage ; Radiotherapy Planning, Computer-Assisted ; Radiotherapy, Image-Guided/*methods ; Risk Assessment ; Treatment Outcome

Intracranial germ cell tumors (ICGCT) occur in 2-11% of children with brain tumors between 0-19 years of age. For treatment of germinoma, relatively low radiation doses with or without chemotherapy show excellent 10 year survival rate of 80-100%. Past studies showed that neoadjuvant chemotherapy combined with focal radiotherapy resulted in unacceptably high rates of periventricular tumor recurrence. The use of generous radiation volume which covers the whole ventricular space with later boost treatment to primary site is considered as standard treatment of intracranial germinomas. For non-germinomatous germ cell tumors (NGGCT), 10-year overall survival rate is still much inferior than that of intracranial germinoma despite intensive chemotherapy and high-dose radiotherapy. Craniospinal radiotherapy combined with cisplatin-based chemotherapy provides the best treatment outcome for NGGCT; 60-70% of overall survival rate. There is a debate on the surgical role whether surgery can contribute to improved treatment outcome of NGGCT when added to combined chemoradiotherapy. Because higher dose of radiotherapy is required for treatment of NGGCT than for germinoma, it is tested whether whole ventricular irradiation can replace craniospinal irradiation in intermediate risk group of NGGCT to minimize radiation-related late toxicity in the recent studies. To minimize the treatment-related neural deficit and late sequelae while maintaining long-term survival rate of ICGCT patients, optimized administration of chemotherapy and radiotherapy should be selected. Use of technically upgraded radiotherapy modalities such as intensity-modulated radiotherapy or proton beam therapy is expected to bring an improved neurocognitive outcome with longitudinal assessment of the patients.
Biology ; Brain Neoplasms ; Chemoradiotherapy ; Child ; Craniospinal Irradiation ; Drug Therapy ; Germinoma ; Humans ; Neoplasms, Germ Cell and Embryonal ; Proton Therapy ; Radiotherapy ; Radiotherapy, Intensity-Modulated ; Recurrence ; Survival Rate ; Treatment Outcome

OBJECTIVES: With the increased use of computed tomography (CT) in clinics, dose reduction is the most important feature people seek when considering new CT techniques or applications. We developed an intensity-weighted region-of-interest (IWROI) imaging method in an exact half-fan geometry to reduce the imaging radiation dose to patients in cone-beam CT (CBCT) for image-guided radiation therapy (IGRT). While dose reduction is highly desirable, preserving the high-quality images of the ROI is also important for target localization in IGRT. METHODS: An intensity-weighting (IW) filter made of copper was mounted in place of a bowtie filter on the X-ray tube unit of an on-board imager (OBI) system such that the filter can substantially reduce radiation exposure to the outer ROI. In addition to mounting the IW filter, the lead-blade collimation of the OBI was adjusted to produce an exact half-fan scanning geometry for a further reduction of the radiation dose. The chord-based rebinned backprojection-filtration (BPF) algorithm in circular CBCT was implemented for image reconstruction, and a humanoid pelvis phantom was used for the IWROI imaging experiment. RESULTS: The IWROI image of the phantom was successfully reconstructed after beam-quality correction, and it was registered to the reference image within an acceptable level of tolerance. Dosimetric measurements revealed that the dose is reduced by approximately 61% in the inner ROI and by 73% in the outer ROI compared to the conventional bowtie filter-based half-fan scan. CONCLUSIONS: The IWROI method substantially reduces the imaging radiation dose and provides reconstructed images with an acceptable level of quality for patient setup and target localization. The proposed half-fan-based IWROI imaging technique can add a valuable option to CBCT in IGRT applications.
Cone-Beam Computed Tomography* ; Copper ; Humans ; Image Processing, Computer-Assisted ; Methods ; Pelvis ; Radiation Exposure ; Radiotherapy, Image-Guided*

PURPOSE: This study was performed to evaluate the effectiveness and tolerance of craniospinal irradiation for patients with medulloblastoma and to define the optimal radiotherapeutic regimen. MATERIALS AND METHODS: We retrospectively analyzed the records of 43 patients with medulloblastoma who were treated with external beam craniospinal radiotherapy at our institution between May, 1984 and April, 1998. Median follow up period was 47 months with range of 18 to 86 months. Twenty seven patients were male and sixteen patients were female, a male to female ratio of 1.7 : 1. Surgery consisted of biopsy alone in 5 patients, subtotal excision in 24 patients, and gross total excision in 14 patients. All of the patients were treated with craniospinal irradiation. All of the patients except four received at least 5,000 cGy to the posterior fossa and forty patients received more than 3,000 cGy to the spinal cord. RESULTS: The overall survival rates at 5 and 7 years for entire group of patients were 67% and 56%, respectively. Corresponding disease free survival rates were 60% and 51%, respectively. The rates of disease control in the posterior fossa were 77% and 67% at 5 and 7 years. Gross total excision and subtotal excision resulted in 5 year overall survival rates of 76% and 66%, respectively. In contrast, those patients who had biopsy alone had a 5 year survival rate of only 40%. Posterior fossa was a component of failure in 11 of the 18 recurrences. Seven recurrences were isolated to the posterior fossa. Four patients had neuraxis recurrences, three had distant metastasis alone and four had multiple sites of failure, all involving the primary site. CONCLUSION: Craniospinal irradiation for patients with medulloblastoma is an effective adjuvant treatment without significant treatment related toxicities. There is room for improvement in terms of posterior fossa control, especially in biopsy alone patients. The advances in radiotherapy including hyperfractionation, stereotactic radiosurgery and 3D conformal radiotherapy would be evolved to improve the tumor control rate at primary site.
Biopsy ; Craniospinal Irradiation ; Disease-Free Survival ; Female ; Follow-Up Studies ; Humans ; Male ; Medulloblastoma* ; Neoplasm Metastasis ; Radiosurgery ; Radiotherapy* ; Radiotherapy, Conformal ; Recurrence ; Retrospective Studies ; Spinal Cord ; Survival Rate

From October 1989 to March 1992, ten patients diagnosed as primary central nervous system(CNS) lymphoma were treated with radiation therapy at Asan Medical Center. To obtain pathologic diagnosis, five patients had stereotactic biopsy and the others underwent craniotomy & tumor removal. According to the classification by International Working Formulation, seven of 10 patients showed diffuse large cell types and the remaining 3 had diffuse mixed cell types. Computed tomographic scans of the brain disclosed solitary (6 cases) or multiple (4 cases) intracranial lesions. All patients received 4000cGy/20 fx to the whole brain followed by an additional 2000cGy/10 fx boost to the primary lesion. Six patients with initial cerebrospinal fluid (CSF) involvement were treated with whole brain irradiation and intrathecal Methotrexate(IT-MTX) chemotherapy. One of them received an additional spinal irradiation after 3 cycles of IT-MTX chemotherapy because of MTX induced arachnoiditis. One patient received 3 cycles of systemic chemotherapy prior to rodiation therapy and one received 5 cycles of salvage chemotherapy for recurrence. With a median follow up time of 8 months, all patients were followed from 7 to 26 months. Radiologically seven patients showed complete remission and the remaining three showed partial remission at one month after radiotherapy. The 1 and 2 year survival rate was 86% and 69% respectively. Until now, two patients expired at 7 and 14 months. These patients developed extensive CSF seeding followed by local failure. Considering initial good response to radiation therapy and low incidence of extraneural dissemination in primary CNS lymphoma, we propose to increase total tumor dose to the primary lesion by hyperfractionated radiotherapy or stereotactic radiosurgery. For the patients with CSF involvement at diagnosis, we propose craniospinal irradiation with IT MTX chemotherapy.
Arachnoid ; Arachnoiditis ; Biopsy ; Brain ; Cerebrospinal Fluid ; Chungcheongnam-do ; Classification ; Craniospinal Irradiation ; Craniotomy ; Diagnosis ; Drug Therapy ; Follow-Up Studies ; Humans ; Incidence ; Lymphoma ; Radiosurgery ; Radiotherapy ; Recurrence ; Survival Rate

PURPOSE: The purpose of this study is to investigate the dosimetric and clinical influence of computed tomography-based (3-dimensional [3D]) simulation versus conventional 2-dimensional (2D)-based simulation in postoperative chemoradiotherapy (CRT) for patients with advanced gastric cancer in terms of parallel opposed anteroposterior-posteroanterior field arrangement. MATERIALS AND METHODS: A retrospective stage-matched cohort study was conducted in 158 patients treated with adjuvant CRT following curative surgery and D2 dissection from 2006 to 2008 at Samsung Medical Center: 98 patients in the 3D group; and 60 patients in the 2D group. For comparison of the dosimetric parameters between 3D plan and 2D plan, second sets of radiation treatment plans were generated according to the same target delineation method used in the 2D group for each patient in the 3D group (V2D). Acute toxicity, recurrence, and survival were analyzed. The median follow-up period was 28 months (range, 5 to 51 months). RESULTS: The 3D group showed better dose-volume histogram (DVH) profiles than the V2D group for all dosimetric parameters, including the kidneys, liver, spinal cord, duodenum, pancreas, and bowel. However, no difference in acute gastrointestinal toxicity and survival outcomes was observed between the 3D group and the 2D group. CONCLUSION: The 3D plan enabled precise delineation of the target volume and organs at risk by visualization of geometric changes in the internal organs after surgery. The DVH of normal tissues in the 3D plan was superior to that of the V2D plan, but similar clinical features were observed between the 3D group and the 2D group.
Chemoradiotherapy ; Cohort Studies ; Duodenum ; Follow-Up Studies ; Humans ; Kidney ; Liver ; Organs at Risk ; Pancreas ; Radiotherapy ; Radiotherapy Planning, Computer-Assisted ; Recurrence ; Retrospective Studies ; Spinal Cord ; Stomach Neoplasms*

PURPOSE: The purpose of this study is to investigate the dosimetric and clinical influence of computed tomography-based (3-dimensional [3D]) simulation versus conventional 2-dimensional (2D)-based simulation in postoperative chemoradiotherapy (CRT) for patients with advanced gastric cancer in terms of parallel opposed anteroposterior-posteroanterior field arrangement. MATERIALS AND METHODS: A retrospective stage-matched cohort study was conducted in 158 patients treated with adjuvant CRT following curative surgery and D2 dissection from 2006 to 2008 at Samsung Medical Center: 98 patients in the 3D group; and 60 patients in the 2D group. For comparison of the dosimetric parameters between 3D plan and 2D plan, second sets of radiation treatment plans were generated according to the same target delineation method used in the 2D group for each patient in the 3D group (V2D). Acute toxicity, recurrence, and survival were analyzed. The median follow-up period was 28 months (range, 5 to 51 months). RESULTS: The 3D group showed better dose-volume histogram (DVH) profiles than the V2D group for all dosimetric parameters, including the kidneys, liver, spinal cord, duodenum, pancreas, and bowel. However, no difference in acute gastrointestinal toxicity and survival outcomes was observed between the 3D group and the 2D group. CONCLUSION: The 3D plan enabled precise delineation of the target volume and organs at risk by visualization of geometric changes in the internal organs after surgery. The DVH of normal tissues in the 3D plan was superior to that of the V2D plan, but similar clinical features were observed between the 3D group and the 2D group.
Chemoradiotherapy ; Cohort Studies ; Duodenum ; Follow-Up Studies ; Humans ; Kidney ; Liver ; Organs at Risk ; Pancreas ; Radiotherapy ; Radiotherapy Planning, Computer-Assisted ; Recurrence ; Retrospective Studies ; Spinal Cord ; Stomach Neoplasms*

High precision radiotherapy has been a hot issue to radiation oncologists for the last 100 years. Introduction of mega volt machine with linear accelerators changed the paradigm of radiotherapy, and development of computers and three-dimensional treatment opened the new era of high tech radiotherapy. However, the change and development in high tech radiotherapy for the last 10 years was much bigger than those of previous century, and it seems that we are very close to the finish line of high precision radiotherapy. Linear accelerator has been a firm base for such an evolution to high tech radiotherapy. It is the machine which is used most frequently for stereotactic radiosurgery, image-guided and respiratory gated radiotherapy and this review will introduce the basic concepts of this linac-based high precision radiotherapy.
Particle Accelerators ; Radiosurgery ; Radiotherapy, Image-Guided