ABSTRACT
Stereotactic localization using PET and SPECT has been used together with the Leksell stereotactic frame and the other imaging tools routinely provided to Gamma Knife radiosurgery sites. The accuracy of the measurements has been confirmed with CT and MR using a Radiation Analog Dosimetry phantom. The activity of the radionuclide solution placed in the tubes of Elekta Radiosurgery's MR imaging box is somewhat critical because the window levels chosen for the scan will affect the apparent size of the lesion. A technique is presented to resolve areas of activity more than about 12-14 mm apart, and it may prove useful in targeting epileptogenic sites in patients with medically intractable epilepsy.
Subject(s)
Radiosurgery , Tomography, Emission-Computed, Single-Photon , Tomography, Emission-Computed , Humans , Tomography, X-Ray ComputedABSTRACT
Two phantoms, constructed from plastic and water and appropriately proportioned to simulate the female pelvis, were used in the evaluation of the dose delivered to a conceptus from two widely used computed tomographic (CT) scanners. Doses were measured along the central axis and surface of each phantom while scanning 25 contiguous 1-cm sections. Ionization chambers were used for data acquisition. Methods for correcting for partial volume effects inside the chambers are examined. Formulas for calculating the dose to the conceptus in a wide variety of possible situations are presented. These data may be used to guide management of pregnant patients who require or have had CT examinations.
