Do we need 3D tube current modulation information for accurate organ dosimetry in chest CT? Protocols dose comparisons

Abstract

• The z-TCM information is sufficient for accurate dosimetry for standard protocols. • The z-TCM information is sufficient for accurate dosimetry for fast-speed scanning protocols. • For organ-based TCM schemes, the 3D-TCM information is necessary for accurate dosimetry. • At identical CTDI , the fast-speed scanning protocol delivered the highest doses. • Lung dose was higher in XCare than standard protocol at identical CTDI .

A comparison of breast and lung doses from chest CT scans using organ‐based tube current modulation (OBTCM) vs. Automatic tube current modulation (ATCM)

“…Franck et al, for example, noted an average 11% increase in lung dose with OBTCM relative to conventional ATCM in female, oncologic patients with MC simulations from ImpactMC 15 . Similarly, Lopez‐Rendon et al, observed an average 7.8% increase in lung dose when comparing OBTCM to conventional ATCM in female and male cadavers 17 . Additionally, the MC studies conducted by Fu et al using the female XCAT phantoms showed small decrease in lung dose when using a 180° of fluence reduction 16,18 .…”

“…15 Similarly, Lopez-Rendon et al, observed an average 7.8% increase in lung dose when comparing OBTCM to conventional ATCM in female and male cadavers. 17 Additionally, the MC studies conducted by Fu et al using the female XCAT phantoms showed small decrease in lung dose when using a 180°of fluence reduction. 16,18 This can be confounding when considering both breast and lung tissues are equally radiosensitive per ICRP 103 tissue weighting recommendations.…”

“…Lopez-Rendon et al was able to more directly compare OBTCM and conventional ATCM due to the use of cadavers but was limited in terms of the number of patients. 17 Both studies of Fu et al utilized computational patients and theoretical expressions of OBTCM and ATCM that may not take into account limitations of clinical systems and thus used modulation functions that might not be realized in the clinical setting. 16,18 In addition, the use of only female models presents the same issue of not considering the clinical relevance of dose penalties or savings for males as mentioned above.…”

“…Finally, their study did not consider the effects of patient size. Lopez‐Rendon et al was able to more directly compare OBTCM and conventional ATCM due to the use of cadavers but was limited in terms of the number of patients 17 . Both studies of Fu et al utilized computational patients and theoretical expressions of OBTCM and ATCM that may not take into account limitations of clinical systems and thus used modulation functions that might not be realized in the clinical setting 16,18 .…”

The impact of vertical off-centering on image noise and breast dose in chest CT with organ-based tube current modulation: A phantom study

“…Moreover, Siemens approach compensates anteriorly reduced tube current by increasing the current during the posterior projections, whereas GE and Canon approaches do not [6,15,[36][37][38]. In chest CT, the overall dose-reduction percentages yielded by the OBTCM methods for the breasts have been reported to be between 5% and 48% compared to chest CT scan protocols utilizing normal TCM [6,15,[36][37][38][39][40][41][42][43]. However, it has also been warned that the dose may increase in some parts of the breast tissue outside the reduced dose zone [12,37,38,40,41].…”