The effect of a finite focal spot size on location dependent detectability in a fan beam CT system

Byeongjoon Kim; Jongduk Baek

doi:10.1117/12.2253981

The effect of a finite focal spot size on location dependent detectability in a fan beam CT system

Byeongjoon Kim, Jongduk Baek

School of Integrated Technology

Research output: Chapter in Book/Report/Conference proceeding › Conference contribution

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
Editors	Taly Gilat Schmidt, Joseph Y. Lo, Thomas G. Flohr
Publisher	SPIE
ISBN (Electronic)	9781510607095
DOIs	https://doi.org/10.1117/12.2253981
Publication status	Published - 2017
Event	Medical Imaging 2017: Physics of Medical Imaging - Orlando, United States Duration: 2017 Feb 13 → 2017 Feb 16

Publication series

Name	Progress in Biomedical Optics and Imaging - Proceedings of SPIE
Volume	10132
ISSN (Print)	1605-7422

Other

Other	Medical Imaging 2017: Physics of Medical Imaging
Country	United States
City	Orlando
Period	17/2/13 → 17/2/16

All Science Journal Classification (ASJC) codes

Electronic, Optical and Magnetic Materials
Biomaterials
Atomic and Molecular Physics, and Optics
Radiology Nuclear Medicine and imaging

Access to Document

10.1117/12.2253981

Fingerprint Dive into the research topics of 'The effect of a finite focal spot size on location dependent detectability in a fan beam CT system'. Together they form a unique fingerprint.

Cite this

Kim, B., & Baek, J. (2017). The effect of a finite focal spot size on location dependent detectability in a fan beam CT system. In T. G. Schmidt, J. Y. Lo, & T. G. Flohr (Eds.), Medical Imaging 2017: Physics of Medical Imaging [1013254] (Progress in Biomedical Optics and Imaging - Proceedings of SPIE; Vol. 10132). SPIE. https://doi.org/10.1117/12.2253981

@inproceedings{8e21914b3b6b430eb9b80976f4ffca9e,

title = "The effect of a finite focal spot size on location dependent detectability in a fan beam CT system",

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.",

author = "Byeongjoon Kim and Jongduk Baek",

year = "2017",

doi = "10.1117/12.2253981",

language = "English",

series = "Progress in Biomedical Optics and Imaging - Proceedings of SPIE",

publisher = "SPIE",

editor = "Schmidt, {Taly Gilat} and Lo, {Joseph Y.} and Flohr, {Thomas G.}",

booktitle = "Medical Imaging 2017",

address = "United States",

note = "Medical Imaging 2017: Physics of Medical Imaging ; Conference date: 13-02-2017 Through 16-02-2017",

}

Kim, B & Baek, J 2017, The effect of a finite focal spot size on location dependent detectability in a fan beam CT system. in TG Schmidt, JY Lo & TG Flohr (eds), Medical Imaging 2017: Physics of Medical Imaging., 1013254, Progress in Biomedical Optics and Imaging - Proceedings of SPIE, vol. 10132, SPIE, Medical Imaging 2017: Physics of Medical Imaging, Orlando, United States, 17/2/13. https://doi.org/10.1117/12.2253981

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. ed. / Taly Gilat Schmidt; Joseph Y. Lo; Thomas G. Flohr. SPIE, 2017. 1013254 (Progress in Biomedical Optics and Imaging - Proceedings of SPIE; Vol. 10132).

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

Y1 - 2017

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

T3 - Progress in Biomedical Optics and Imaging - Proceedings of SPIE

BT - Medical Imaging 2017

A2 - Schmidt, Taly Gilat

A2 - Lo, Joseph Y.

A2 - Flohr, Thomas G.

PB - SPIE

T2 - Medical Imaging 2017: Physics of Medical Imaging

Y2 - 13 February 2017 through 16 February 2017

ER -