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AJNR - American Journal of Neuroradiology

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Effect of CT Acquisition Parameters in the Detection of Subtle Hypoattenuation in Acute Cerebral Infarction: A Phantom Study

C. Tanaka^a, T. Ueguchi^a,b, E. Shimosegawa^e, N. Sasaki^e, T. Johkoh^b,c, H. Nakamura^c and J. Hatazawa^a,d

^a Department of Radiology, Osaka University Hospital, Osaka University Graduate School of Medicine, Osaka, Japan
^b Department of Medical Physics, Osaka University Graduate School of Medicine, Osaka, Japan
^c Department of Radiology, Osaka University Graduate School of Medicine, Osaka, Japan
^d Department of Nuclear Medicine and Tracer Kinetics, Osaka University Graduate School of Medicine, Osaka, Japan
^e Department of Radiology and Nuclear Medicine, Akita Research Institute of Brain and Blood Vessels, Akita, Japan

View larger version (47K): [in a new window]   Fig 1. Low-contrast phantom. Phantom overview before CT scanning (A) and representative phantom image (window width, 100 HU; window level, 35 HU) (B). Two sets of 3-, 2-, and 1-cm-diameter acrylic resin spheres were embedded in an 18-cm-diameter cylindrical phantom. The attenuation was adjusted to 32 HU in one set of spheres (arrowheads), corresponding to complete cerebral infarction, and 34 HU in the other set of spheres (arrows), corresponding to early ischemic brain damage. The attenuation of the cylindrical phantom was 36 HU, corresponding to normal gray matter.

View larger version (20K): [in a new window]   Fig 2. Reproducibility of the HU values. The HU values obtained in 14 examinations performed on different days were plotted against various tube currents. The tube voltages were (A) 135 kVp, (B) 120 kVp, (C) 100 kVp, and (D) 80 kVp. The section thickness was fixed at 5 mm for all the measurements.

View larger version (43K): [in a new window]   Fig 3. Effect of tube voltage, tube current, and section thickness on the contrast-to-noise ratio (CNR). The section thicknesses were (A) 5 mm, (B) 10 mm, and (C) 20 mm, respectively. The CNRs obtained at different tube voltages were plotted against the tube current.

View larger version (14K): [in a new window]   Fig 4. Effect of tube current on the CNR in the 34-HU and 32-HU spheres. The CNRs for the 32-HU and the 34-HU spheres were separately plotted against the tube current. The tube voltage and section thickness were fixed at 120 kVp and 5 mm, respectively.