Abstract
A finite focal spot size is one of the sources to degrade the resolution performance in a fan beam CT system. In this work, we investigated the effect of the finite focal spot size on signal detectability. For the evaluation, five spherical objects with diameters of 1 mm, 2 mm, 3 mm, 4 mm, and 5 mm were used. The optical focal spot size viewed at the iso-center was a 1 mm (height) × 1 mm (width) with a target angle of 7 degrees, corresponding to an 8.21 mm (i.e., 1 mm / sin (7°)) focal spot length. Simulated projection data were acquired using 8 × 8 source lets, and reconstructed by Hanning weighted filtered backprojection. For each spherical object, the detectability was calculated at (0 mm, 0 mm) and (0 mm, 200 mm) using two image quality metrics: pixel signal to noise ratio (SNR) and detection SNR. For all signal sizes, the pixel SNR is higher at the iso-center since the noise variance at the off-center is much higher than that at the iso-center due to the backprojection weightings used in direct fan beam reconstruction. In contrast, detection SNR shows similar values for different spherical objects except 1 mm and 2 mm diameter spherical objects. Overall, the results indicate the resolution loss caused by the finite focal spot size degrades the detection performance, especially for small objects with less than 2 mm diameter.
| Original language | English |
|---|---|
| Title of host publication | Medical Imaging 2017 |
| Subtitle of host publication | Physics of Medical Imaging |
| Publisher | SPIE |
| Volume | 10132 |
| ISBN (Electronic) | 9781510607095 |
| DOIs | |
| Publication status | Published - 2017 Jan 1 |
| Event | Medical Imaging 2017: Physics of Medical Imaging - Orlando, United States Duration: 2017 Feb 13 → 2017 Feb 16 |
Other
| Other | Medical Imaging 2017: Physics of Medical Imaging |
|---|---|
| Country | United States |
| City | Orlando |
| Period | 17/2/13 → 17/2/16 |
Fingerprint
All Science Journal Classification (ASJC) codes
- Atomic and Molecular Physics, and Optics
- Electronic, Optical and Magnetic Materials
- Biomaterials
- Radiology Nuclear Medicine and imaging
Cite this
}
The effect of a finite focal spot size on location dependent detectability in a fan beam CT system. / Kim, Byeongjoon; Baek, Jongduk.
Medical Imaging 2017: Physics of Medical Imaging. Vol. 10132 SPIE, 2017. 1013254.Research output: Chapter in Book/Report/Conference proceeding › Conference contribution
TY - GEN
T1 - The effect of a finite focal spot size on location dependent detectability in a fan beam CT system
AU - Kim, Byeongjoon
AU - Baek, Jongduk
PY - 2017/1/1
Y1 - 2017/1/1
N2 - A finite focal spot size is one of the sources to degrade the resolution performance in a fan beam CT system. In this work, we investigated the effect of the finite focal spot size on signal detectability. For the evaluation, five spherical objects with diameters of 1 mm, 2 mm, 3 mm, 4 mm, and 5 mm were used. The optical focal spot size viewed at the iso-center was a 1 mm (height) × 1 mm (width) with a target angle of 7 degrees, corresponding to an 8.21 mm (i.e., 1 mm / sin (7°)) focal spot length. Simulated projection data were acquired using 8 × 8 source lets, and reconstructed by Hanning weighted filtered backprojection. For each spherical object, the detectability was calculated at (0 mm, 0 mm) and (0 mm, 200 mm) using two image quality metrics: pixel signal to noise ratio (SNR) and detection SNR. For all signal sizes, the pixel SNR is higher at the iso-center since the noise variance at the off-center is much higher than that at the iso-center due to the backprojection weightings used in direct fan beam reconstruction. In contrast, detection SNR shows similar values for different spherical objects except 1 mm and 2 mm diameter spherical objects. Overall, the results indicate the resolution loss caused by the finite focal spot size degrades the detection performance, especially for small objects with less than 2 mm diameter.
AB - A finite focal spot size is one of the sources to degrade the resolution performance in a fan beam CT system. In this work, we investigated the effect of the finite focal spot size on signal detectability. For the evaluation, five spherical objects with diameters of 1 mm, 2 mm, 3 mm, 4 mm, and 5 mm were used. The optical focal spot size viewed at the iso-center was a 1 mm (height) × 1 mm (width) with a target angle of 7 degrees, corresponding to an 8.21 mm (i.e., 1 mm / sin (7°)) focal spot length. Simulated projection data were acquired using 8 × 8 source lets, and reconstructed by Hanning weighted filtered backprojection. For each spherical object, the detectability was calculated at (0 mm, 0 mm) and (0 mm, 200 mm) using two image quality metrics: pixel signal to noise ratio (SNR) and detection SNR. For all signal sizes, the pixel SNR is higher at the iso-center since the noise variance at the off-center is much higher than that at the iso-center due to the backprojection weightings used in direct fan beam reconstruction. In contrast, detection SNR shows similar values for different spherical objects except 1 mm and 2 mm diameter spherical objects. Overall, the results indicate the resolution loss caused by the finite focal spot size degrades the detection performance, especially for small objects with less than 2 mm diameter.
UR - http://www.scopus.com/inward/record.url?scp=85020395705&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=85020395705&partnerID=8YFLogxK
U2 - 10.1117/12.2253981
DO - 10.1117/12.2253981
M3 - Conference contribution
AN - SCOPUS:85020395705
VL - 10132
BT - Medical Imaging 2017
PB - SPIE
ER -