Said Mohd Shaffiq Said Rahmat1, Muhammad Khalis Abdul Karim2, Iza Nurzawani Che Isa3, Mohd Amiruddin Abd Rahman4, Noramaliza Mohd Noor5, Ng Kwan Hoong6. 1. Department of Radiology, National Cancer Institute, 4, Jalan P7, Presint 7, 62250, Putrajaya, Wilayah Persekutuan Putrajaya, Malaysia. 2. Department of Physics, Faculty of Science, Universiti Putra Malaysia, 43400, Serdang, Selangor, Malaysia. Electronic address: mkhalis@upm.edu.my. 3. Diagnostic Imaging and Radiotherapy Programme, Faculty of Health Sciences, Universiti Kebangsaan Malaysia, 50300, Kuala Lumpur, Wilayah Persekutuan Kuala Lumpur, Malaysia. 4. Department of Physics, Faculty of Science, Universiti Putra Malaysia, 43400, Serdang, Selangor, Malaysia. 5. Department of Radiology, Faculty of Medicine, Universiti Putra Malaysia, 43400, Serdang, Selangor, Malaysia. 6. Department of Biomedical Imaging, Universiti of Malaya Medical Centre, 50603, Kuala Lumpur, Malaysia.
Abstract
BACKGROUND: Unoptimized protocols, including a miscentered position, might affect the outcome of diagnostic in CT examinations. In this study, we investigate the effects of miscentering position during CT head examination on the signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR). METHOD: We simulate the CT head examination using a water phantom with a standard protocol (120 kVp/180 mAs) and a low dose protocol (100 kVp/142 mAs). The table height was adjusted to simulate miscentering by 5 cm from the isocenter, where the height was miscentered superiorly (MCS) at 109, 114, 119, and 124 cm, and miscentered inferiorly (MCI) at 99, 94, 89, and 84 cm. Seven circular regions of interest were used, with one drawn at the center, four at the peripheral area of the phantom, and two at the background area of the image. RESULTS: For the standard protocol, the mean CNR decreased uniformly as table height increased and significantly differed (p < 0.05) at +20 cm for MCS (435.70 ± 9.39) and -20 cm for MCI (438.91 ± 10.94) from the isocenter. Similarly, significant reductions (p < 0.05) were also noted for SNR for MCS (at +20 cm) and MCI (at -20 cm). For the low dose protocol, both CNR and SNR were significantly reduced (p < 0.05) at table heights of +20 and -20 cm from the isocenter. CONCLUSION: Miscentering is proven to significantly affect the image quality in both low and standard dose protocols for head CT procedure. This study implies that accurate patient centering is one of the approaches that can improve CT optimization practice.
BACKGROUND: Unoptimized protocols, including a miscentered position, might affect the outcome of diagnostic in CT examinations. In this study, we investigate the effects of miscentering position during CT head examination on the signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR). METHOD: We simulate the CT head examination using a water phantom with a standard protocol (120 kVp/180 mAs) and a low dose protocol (100 kVp/142 mAs). The table height was adjusted to simulate miscentering by 5 cm from the isocenter, where the height was miscentered superiorly (MCS) at 109, 114, 119, and 124 cm, and miscentered inferiorly (MCI) at 99, 94, 89, and 84 cm. Seven circular regions of interest were used, with one drawn at the center, four at the peripheral area of the phantom, and two at the background area of the image. RESULTS: For the standard protocol, the mean CNR decreased uniformly as table height increased and significantly differed (p < 0.05) at +20 cm for MCS (435.70 ± 9.39) and -20 cm for MCI (438.91 ± 10.94) from the isocenter. Similarly, significant reductions (p < 0.05) were also noted for SNR for MCS (at +20 cm) and MCI (at -20 cm). For the low dose protocol, both CNR and SNR were significantly reduced (p < 0.05) at table heights of +20 and -20 cm from the isocenter. CONCLUSION: Miscentering is proven to significantly affect the image quality in both low and standard dose protocols for head CT procedure. This study implies that accurate patient centering is one of the approaches that can improve CT optimization practice.
Authors: Pedro Augusto Gondim Teixeira; Nicolas Villani; Malik Ait Idir; Edouard Germain; Charles Lombard; Romain Gillet; Alain Blum Journal: Quant Imaging Med Surg Date: 2021-10
Authors: Mardhiyati Mohd Yunus; Ahmad Khairuddin Mohamed Yusof; Muhd Zaidi Ab Rahman; Xue Jing Koh; Akmal Sabarudin; Puteri N E Nohuddin; Kwan Hoong Ng; Mohd Mustafa Awang Kechik; Muhammad Khalis Abdul Karim Journal: Diagnostics (Basel) Date: 2022-07-08