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Influence of vertical position of the table from the isocenter on radiation dose in CT imaging
Marko Krpan
; Klinički zavod za radiologiju, Sveučilišna klinička bolnica Mostar, Mostar, Bosna i Hercegovina
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Bruno Rajič
; Klinički zavod za radiologiju, Sveučilišna klinička bolnica Mostar, Mostar, Bosna i Hercegovina
Marin Brajković
; Klinički zavod za radiologiju, Sveučilišna klinička bolnica Mostar, Mostar, Bosna i Hercegovina
Vedran Markotić
; Klinički zavod za radiologiju, Sveučilišna klinička bolnica Mostar, Mostar, Bosna i Hercegovina
Ivan Lasić
; Odjel za medicinsku fiziku i zaštitu od zračenja, Sveučilišna klinička bolnica Mostar, Mostar, Bosna i Hercegovina
Ante Bošnjak
; Klinički odjel za kardiokirurgiju, Sveučilišna klinička bolnica Mostar, Mostar, Bosna i Hercegovina
* Dopisni autor.
Sažetak
Precise positioning of the patient at the CT scanner isocenter is essential for achieving optimal image quality and minimizing radiation dose. Vertical deviations from the isocenter can alter projection geometry on the scout image, affecting the performance of the automatic exposure control (AEC) system and leading to unintended dose variations. Despite its importance, incorrect patient centering remains common in routine clinical practice.
The aim of this study was to quantify the effect of vertical table height deviation relative to the isocenter on CTDIvol and DLP during CT imaging of thoracic and pelvic phantoms. Measurements were performed on two CT scanners, GE Revolution Maxima 128 and GE Revolution ES 256. The table height was adjusted from –10 cm to +10 cm in 2 cm increments relative to the isocenter. Imaging was conducted using a thoracic phantom and an anthropomorphic pelvic phantom with standardized and optimized protocols specific to each scanner. Two scans were performed at each table position to ensure measurement reliability, and dose metrics were extracted from the dose reports.
Results showed that raising the table above the isocenter caused a substantial increase in radiation dose on both scanners. On the GE Revolution Maxima, a +10 cm deviation led to dose increases of 71% for thoracic imaging and 106% for pelvic imaging, whereas lowering the table reduced the dose by up to 30%. On the GE Revolution ES, the maximum dose increase was 53%, with dose reductions of up to 20% when the table was lowered. Dose variations were more pronounced in pelvic protocols, likely due to greater phantom thickness and increased AEC sensitivity.
In conclusion, vertical miscentering has a significant and clinically relevant impact on CT radiation dose. Accurate patient positioning at the isocenter is a simple yet critical dose optimization measure in CT practice.
Ključne riječi
CT; isocenter; CTDIvol; automatic exposure control (AEC); dose optimization
Hrčak ID:
347487
URI
Datum izdavanja:
5.5.2026.
Posjeta: 0 *