A Correction Method of Dose to Attenuation Rate of Transmitting Photon Beam Through Couch Top for Radiosurgery Using Novalis / 의학물리

This study has its own goal to deliver the accurate dose on the target volume by calculating and modifying the attenuation rate of photon beam transmitting the couch top with geometric model. The experiment was that the transmission rate and attenuation rate of photon beam transmitting the couch top was predicted by the geometric model, then compared and analyzed with what was measured experimentally based on that. The result showed that the predicted value by the geometric model accorded closely with the experimental value. In addition, in order to judge whether the practical clinical application is available, the point dose, measured after modifying the attenuation rate modelinged according to the treatment plan of a patient of spine radiosurgery, was compared with the one done nothing. The result was that the former showed decreased error range with treatment planned one than the latter. This papers calculated the transmission and attenuation rate with the geometric model transmitting the couch top and verified it experimentally. This method is expected to be very useful in not only the radiosurgery using Novalis but also the general radiation therapy.

Development of Novalis Quality Assurance Protocol for Radiosurgery / 의학물리

In Republic of Korea, there are many Quality Assurance protocol for general radiation treatment machine such as linac. However, Quality Assurance protocol for radiosurgery treatment system is not ready perfectly. One of the radiation treatment machine for radiosurgery, novalis system needs to suitable Quality Assurance protocol for using it right way during radiation treatment and maintaining suitable accuracy for daily, weekly, monthly and annually periods. Therefore, in this article, we develop Quality Assurance protocol for novalis system. We collected and analysed domestic and foreign novalis Quality Assurance protocol. After that, we selected essential QA items and each tolerance range for developing proper QA protocol, and we made anatomical phantom for execution of selected QA items and evaluation of overall state of QA, and then, we use this measured value as a reference. Quality Assurance items are consisted of Mechanical accuracy QA part and Radiation delivery QA part. Mechanical accuracy QA part is comprised of radiation generation machine part, assistive devices part and multi-leaf collimator part. Radiation delivery QA part is divided into radiation isocenter accuracy and dosimetric evaluation. After that, developed novalis QA tables are made by using these QA items. These novalis QA tables would be used to good standard in order to maintain apt accuracy for radiosurgery in daily, weekly, monthly and annually periods.

Clinical Analysis of Novalis Stereotactic Radiosurgery for Brain Metastases

OBJECTIVE: The authors analyzed the effectiveness and therapeutic response of Novalis shaped beam radiosurgery for metastatic brain tumors, and the prognostic factors which influenced the outcome. METHODS: We performed a retrospective analysis of 106 patients who underwent 159 treatments for 640 metastatic brain lesions between January 2000 and April 2008. The pathologies of the primary tumor were mainly lung (45.3%), breast (18.2%) and GI tract (13.2%). We classified the patients using Radiation Therapy Oncology Group Recursive Partitioning Analysis (RPA) and then analyzed the survival and prognostic factors according to the Kaplan Meier method and univariate analysis. RESULTS: The overall median actuarial survival rate was 7.3 months from the time of first radiosurgery treatment while 1 and 2 year actuarial survival estimates were 31% and 14.4%, respectively. Median actuarial survival rates for RPA classes I, II, and III were 31.3 months, 7.5 months and 1.7 months, respectively. Patients' life spans, higher Karnofsky performance scores and age correlated closely with RPA classes. However, sex and the number of lesions were not found to be significantly associated with length of survival. CONCLUSION: This result suggests that Novalis radiosurgery can be a good treatment option for treatment of the patients with brain metastases.

Radiosurgery for Spinal Lesions

Spinal Stereotactic Radiosurgery (SRS) has become an important treatment modality for a broad range of spinal tumors and spinal vascular lesions. Recent clinical acceptance and awareness of the usefulness of spinal radiosurgery has escalated with the development of modern radiosurgical technology. Image-guided navigation systems incorporating non-invasive fiducial tracking and virtual simulation planning systems have made spinal radiosurgery increasingly effective and expanded the range of clinical applications for which it can be effectively used. Additional improvements such as Intensity Modulation and Micro-Multileaf Collimation that allow the accurate modulating and shaping of the radiation beam have also contributed greatly to the ability of clinicians to treat irregular and critically located lesions with greatly reduced collateral risk. Spinal Radiosurgery for spinal tumors can achieve similar clinical results to cranial stereotactic radiosurgery for brain tumors in terms of achieving local tumor control and improving quality of life and survival rates. Stereotactic radiosurgery, which has long been used for the treatment of intracranial lesions, is now recognized to be a viable option for treating spinal tumors and spinal vascular lesions.

Novalis Radiosurgery of Primary Central Nervous System Lymphoma in Elderly Patients: Preliminary Results

OBJECTIVE: Primary central nervous system lymphoma(PCNSL) is a non-Hodgkin's lymphoma arising in the central nervous system. Combined chemotherapy and radiation therapy is the standard treatment for PCNSL. However, treatment induced neurotoxicity is a major problem especially in elderly patients. METHODS: From May 2001 to April 2004, elderly five patients with PCNSL confirmed via pathological examination were underwent Novalis radiosurgery in authors' institution, who were investigated retrospectively. Of these patients, 2 were male and 3 were female, with a mean age 68 years old (range 65~73). The number of lesions was 1 in 2 patients, 2 in 2, and 3 in 1. The mean follow up period was 12.6 months (range 8~16). RESULTS: Clinical symptoms and signs in all patients markedly improved within 1 weeks after Novalis radiosurgery. The Karnofsky performance status score was also improved from a pre-radiosurgery average of 68 to a post-radiosurgery one of 82. All of treated lesions showed a partial or complete regression of the original mass. There have been no complication following Novalis radiosurgery. CONCLUSION: The preliminary results of our experience indicate that radiosurgery with Novalis provides a safe and effective therapeutic alternative treatment of PCNSL in elderly patients.