| Popis: |
The performance and dosimetric characteristics of the first U.S.-installed hybrid head scanner developed commercially by CGR Medical Corporation have been evaluated. Using a translate-rotate motion with a xenon gas detector array, the scanner produces excellent low contrast resolution at low dose levels (single slice surface dose of 1 rad). Console selection of scanning parameters, viz.: scan time, kV, mA, beam filtration, slice width, and pixel size permits optimization of image quality for various exams. For optimizing either spatial or low contrast resolution, a push-button choice of reconstruction algorithms is available. Using the American Association of Physicists in Medicine (AAPM) computed tomography (CT) phantom, spatial resolution and line spread functions for both algorithms were determined from the graphical display of CT numbers. Low contrast resolution was measured at various contrast levels as a function of kV, dose, beam width, pixel size, and algorithm. Values for noise (a) were also recorded for these scanning parameters. Patient dose distributions for various operator-selectable beam widths (3, 6, 9 mm) were obtained using film and TLDs. CT number linearity and contrast scale were determined using different plastic rods. |
