Dosimetry of CT-guided volumetric IR-192 brain implant

Journal Article · Sat Mar 01 04:00:00 EST 1986 · Int. J. Radiat. Oncol., Biol. Phys.; (United States)

DOI:https://doi.org/10.1016/0360-3016(86)90351-2· OSTI ID:5618055

Abrath, F G; Henderson, S D; Simpson, J R; Moran, C J; Marchosky, J A

Over the past 2 years, an afterloading technique has been developed and refined to implant radioactive Ir-192 sources into brain tumors. The implantation procedure integrates a stereotaxic system with computerized tomography (CT), which provides tumor position, volume, and guides the placement of catheters. A radiolucent ring-frame immobilizes the head as holes are made at 1 cm intervals with the aid of a template. Catheters containing dummy sources 1 cm apart are then inserted to the desired depth, and their position verified in three dimensions to insure complete coverage of visible tumor volume as defined by contrast enhancement. Once catheters are secured, the anesthetized patient is moved to the intensive care unit where the dummy sources are replaced by ribbons of Ir-192 seeds (specific activity 0.6-1.0 mg Ra eq). CT scans with the dummy sources in place are used to designate spatial coordinates of the active sources. A computer program converts position data and source strength into isodose contours in any plane. The implant duration (70-100 hours) for the desired dose to the tumor periphery (60-120 Gy) is then calculated. Dose rate contours are superimposed on preimplant CT scans. Maximum and minimum doses are determined in each of the various planes. Verification dosimetry has been carried out with thermoluminescent dosimeters placed in a catheter located in a plane along the tumor periphery. In vivo isodose values compared to idealized plans agree within +/-5%-10%.

• Research Organization: Washington Univ. School of Medicine, St. Louis, MO
• OSTI ID: 5618055
• Journal Information: Int. J. Radiat. Oncol., Biol. Phys.; (United States), Journal Name: Int. J. Radiat. Oncol., Biol. Phys.; (United States) Vol. 3; ISSN IOBPD
• Country of Publication: United States
• Language: English

Related Subjects

550604* -- Medicine-- Unsealed Radionuclides in Therapy-- (1980-)
62 RADIOLOGY AND NUCLEAR MEDICINE
AFTERLOADING
BETA DECAY RADIOISOTOPES
BETA-MINUS DECAY RADIOISOTOPES
BETA-PLUS DECAY RADIOISOTOPES
BODY
BRAIN
CENTRAL NERVOUS SYSTEM
COMPUTERIZED TOMOGRAPHY
DAYS LIVING RADIOISOTOPES
DIAGNOSTIC TECHNIQUES
DISEASES
DOSIMETRY
ELECTRON CAPTURE RADIOISOTOPES
HEAVY NUCLEI
IMPLANTS
INTERNAL CONVERSION RADIOISOTOPES
IRIDIUM 192
IRIDIUM ISOTOPES
ISOMERIC TRANSITION ISOTOPES
ISOTOPES
MEDICINE
MINUTES LIVING RADIOISOTOPES
NEOPLASMS
NERVOUS SYSTEM
NUCLEAR MEDICINE
NUCLEI
ODD-ODD NUCLEI
ORGANS
PATIENTS
POSITIONING
RADIATION SOURCE IMPLANTS
RADIATION SOURCES
RADIOISOTOPES
RADIOLOGY
RADIOTHERAPY
THERAPY
TOMOGRAPHY
YEARS LIVING RADIOISOTOPES