Implementation of patient-tailored contrast volumes based on body surface area and heart rate harmonizes contrast enhancement and reduces contrast load in small patients in portal venous phase abdominal CT.

PURPOSE: The aim of this study was to evaluate the impact of a patient-tailored contrast volume protocol on portal venous phase abdominal CT-images compared to a fixed volume protocol in daily radiological practice. METHOD: Data of 77 patients who underwent two contrast-enhanced CT-examinations were collected. The first examination was performed with a fixed contrast volume (95 ml), the follow-up examination was performed with a patient-tailored contrast volume based on patient's BSA and heart rate. The patient-tailored volume was calculated by a software application integrated in the interface of the injection pump. Two independent radiologists assessed subjective and objective image quality. Differences in enhancement and contrast volumes between both protocols were analysed. RESULTS: Despite a significant contrast volume reduction in women and in patients with low to normal BMI, enhancement was more consistent over different BMI-categories in the patient-tailored contrast volume protocol and there was no significant difference in subjective image quality between both injection protocols. CONCLUSIONS: A patient-tailored contrast volume protocol based on BSA and heart rate can be considered in daily radiological practice to decrease contrast volumes in women and in low to normal BMI patients and to achieve more consistent contrast enhancement across different BMI-categories in venous phase abdominal CT.

Comparing different methods for estimating radiation dose to the conceptus.

PURPOSE: To compare different methods available in the literature for estimating radiation dose to the conceptus (Dconceptus) against a patient-specific Monte Carlo (MC) simulation and a commercial software package (CSP). METHOD: Eight voxel models from abdominopelvic CT exams of pregnant patients were generated. Dconceptus was calculated with an MC framework including patient-specific longitudinal tube current modulation (TCM). For the same patients, dose to the uterus, Duterus, was calculated as an alternative for Dconceptus, with a CSP that uses a standard-size, non-pregnant phantom and a generic TCM curve. The percentage error between Duterus and Dconceptus was studied. Dose to the conceptus and percent error with respect to Dconceptus was also estimated for three methods in the literature. RESULTS: The percentage error ranged from -15.9% to 40.0% when comparing MC to CSP. When comparing the TCM profiles with the generic TCM profile from the CSP, differences were observed due to patient habitus and conceptus position. For the other methods, the percentage error ranged from -30.1% to 13.5% but applicability was limited. CONCLUSIONS: Estimating an accurate Dconceptus requires a patient-specific approach that the CSP investigated cannot provide. Available methods in the literature can provide a better estimation if applicable to patient-specific cases. KEY POINTS: • A patient's internal anatomy affects the dose to the conceptus. • Conceptus position has an influence on its dose estimation. • Patient anatomy and specific TCM must be considered for accurate conceptus dosimetry. • D uterus to a standard-size phantom should not be used as D conceptus .