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

Byeongjoon Kim, Jongduk Baek

Research output: Chapter in Book/Report/Conference proceedingConference 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 languageEnglish
Title of host publicationMedical Imaging 2017
Subtitle of host publicationPhysics of Medical Imaging
PublisherSPIE
Volume10132
ISBN (Electronic)9781510607095
DOIs
Publication statusPublished - 2017 Jan 1
EventMedical Imaging 2017: Physics of Medical Imaging - Orlando, United States
Duration: 2017 Feb 132017 Feb 16

Other

OtherMedical Imaging 2017: Physics of Medical Imaging
CountryUnited States
CityOrlando
Period17/2/1317/2/16

Fingerprint

Signal-To-Noise Ratio
fans
Fans
Signal to noise ratio
signal to noise ratios
Pixels
pixels
Image quality
Noise
projection
evaluation

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

Kim, B., & Baek, J. (2017). The effect of a finite focal spot size on location dependent detectability in a fan beam CT system. In Medical Imaging 2017: Physics of Medical Imaging (Vol. 10132). [1013254] SPIE. https://doi.org/10.1117/12.2253981
Kim, Byeongjoon ; Baek, Jongduk. / The effect of a finite focal spot size on location dependent detectability in a fan beam CT system. Medical Imaging 2017: Physics of Medical Imaging. Vol. 10132 SPIE, 2017.
@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",
month = "1",
day = "1",
doi = "10.1117/12.2253981",
language = "English",
volume = "10132",
booktitle = "Medical Imaging 2017",
publisher = "SPIE",
address = "United States",

}

Kim, B & Baek, J 2017, The effect of a finite focal spot size on location dependent detectability in a fan beam CT system. in Medical Imaging 2017: Physics of Medical Imaging. vol. 10132, 1013254, 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. Vol. 10132 SPIE, 2017. 1013254.

Research output: Chapter in Book/Report/Conference proceedingConference 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

VL - 10132

BT - Medical Imaging 2017

PB - SPIE

ER -

Kim B, Baek J. The effect of a finite focal spot size on location dependent detectability in a fan beam CT system. In Medical Imaging 2017: Physics of Medical Imaging. Vol. 10132. SPIE. 2017. 1013254 https://doi.org/10.1117/12.2253981