TY - GEN
T1 - Tradeoffs in helical CT
T2 - Medical Imaging 1996: Physics of Medical Imaging
AU - McNitt-Gray, Michael F.
AU - Cagnon, Chris
AU - Solberg, Tim
PY - 1996/1/1
Y1 - 1996/1/1
N2 - To investigate the tradeoffs that occur in helical CT scanning due to the different combinations of pitch and collimation available. These tradeoffs affect patient dose, image noise and slice sensitivity profiles. For both a single and dual detector helical CT scanners, different combinations of pitch and collimation were investigated. For each combination, patient dose was estimated using calculations from TLD measurements made with a standard CTDI phantom. Noise was measured using a homogeneous water phantom. Slice sensitivity profiles were measured using phantoms approximating impulse functions. For each scanner, the effects on noise, slice thickness and radiation dose of variations in pitch and collimation were reported. In addition, the tradeoffs between combinations of pitch and collimation that utilize the same table speed were examined. As an example, the single helical scanner can obtain a table speed of 10 mm/s using either: (1) a collimation of 10 mm and a pitch of 1, or by (2) collimating to 5 mm and using a pitch of 2. Assuming a constant mA, the radiation dose decreases from 1.2 rad at the center to .71 rad at the center, when going from the first to the second technique. The image noise increases from a standard deviation of 4.1 to 5.7; and the slice sensitivity profile decreases from 10.46 mm to 6.55 mm. Results for other pitch and collimation combinations are reported as well as the results for the dual helical scanner. For a fixed table movement speed, thinner slices with higher pitches give better z-axis resolution and lower patient dose while increasing image noise.
AB - To investigate the tradeoffs that occur in helical CT scanning due to the different combinations of pitch and collimation available. These tradeoffs affect patient dose, image noise and slice sensitivity profiles. For both a single and dual detector helical CT scanners, different combinations of pitch and collimation were investigated. For each combination, patient dose was estimated using calculations from TLD measurements made with a standard CTDI phantom. Noise was measured using a homogeneous water phantom. Slice sensitivity profiles were measured using phantoms approximating impulse functions. For each scanner, the effects on noise, slice thickness and radiation dose of variations in pitch and collimation were reported. In addition, the tradeoffs between combinations of pitch and collimation that utilize the same table speed were examined. As an example, the single helical scanner can obtain a table speed of 10 mm/s using either: (1) a collimation of 10 mm and a pitch of 1, or by (2) collimating to 5 mm and using a pitch of 2. Assuming a constant mA, the radiation dose decreases from 1.2 rad at the center to .71 rad at the center, when going from the first to the second technique. The image noise increases from a standard deviation of 4.1 to 5.7; and the slice sensitivity profile decreases from 10.46 mm to 6.55 mm. Results for other pitch and collimation combinations are reported as well as the results for the dual helical scanner. For a fixed table movement speed, thinner slices with higher pitches give better z-axis resolution and lower patient dose while increasing image noise.
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M3 - Conference contribution
AN - SCOPUS:0029711452
SN - 0819420832
SN - 9780819420831
T3 - Proceedings of SPIE - The International Society for Optical Engineering
SP - 427
EP - 437
BT - Proceedings of SPIE - The International Society for Optical Engineering
A2 - Van Metter, Richard L.
A2 - Beutel, Jacob
Y2 - 11 February 1996 through 13 February 1996
ER -