Abstract
Abstract
This study aimed to establish dose reference level (NDRL
S
S
D
E
) based on size-specific dose estimate (SSDE) derived using effective diameter (
D
e
f
f
) for adult chest and abdomen computed tomography (CT) procedures and to explore the feasibility of driving
D
e
f
f
using the product of tube current and time (mAs). In this retrospective study, dose data, scan parameters and patient body dimensions at the mid-slice level from 14 CT units (out of 63 total) were extracted. Additionally, the mAs values of the axial slice at the same z-location where the diameter measurements were made (mAs
z
) were recorded. Pearson’s correlation (r) analysis was used to determine the relationship of
D
e
f
f
with patient BMI, weight, and mAs
z
. The NDRL
S
S
D
E
for the chest and abdomen were 9.72 mGy and 13.4 mGy, respectively. The BMI and body weight were less correlated (r = 0.24 and r = 0.33, respectively) with
D
e
f
f
. The correlation between mAs
z
and
D
e
f
f
was considerably strong (r = 0.78) and can be used to predict
D
e
f
f
accurately. The absolute dose differences between SSDEs calculated using the AAPM–204 method and mAs
z
was less than 1.1 mGy (15%). Therefore, mAs
z
is an efficient parameter to derive
D
e
f
f
. Further, the direct conversion factors to estimate SSDEs at different locations along the z-direction in the scan region from corresponding mAs and CTDI
v
o
l
were calculated. The NDRL
S
S
D
E
suggested in the present study can be used as a reference for size-dependent dose optimisation in Sri Lanka, and existing NDRL based on CTDI
v
o
l
underestimate the average adult CT dose by 36.0% and 39.7% for chest and abdomen regions respectively. The results show that using mAs
z
to determine SSDE is a simple and practical approach with an accuracy of 95% and 85% for abdomen and chest scans, respectively. However, the obtained linear relationship between
D
e
f
f
and mAs is highly dependent on the ATCM technique and the user-determined noise levels of the scanning protocol. Finally, the phantom study resulted in the strongest correlation (r = 0.99) between the D
w
z
and mAs
z
, and the prediction of patient size would be more precise than
D
e
f
f
method.
Subject
Public Health, Environmental and Occupational Health,Waste Management and Disposal,General Medicine
Cited by
6 articles.
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