1. Title:
PET/CT Radiation Burden: Entire Body vs. Skull Base to Mid-Thigh Scanning
Objectives
PET/CT systems utilize a low level CT prior to performing PET scans. This exposes patients to
radiation proportional to the length of scanned area, also known as dose length product (DLP).
Entire body scans (top of head through toes) deliver a larger DLP compared to skull base to mid-
thigh scans. The goals of this research were to observe correlation between body mass index
(BMI) and DLP and to determine if all patients can safely receive an entire body scan regardless
of diagnosis.
Methods
A G.E. PET/CT (Discovery D710) system with smart mA was utilized. The DLP for entire body
scanned patients and their projected skull base to mid-thigh DLP were recorded. Patient height
and weight were also recorded and used to calculate BMI. The study consisted of 55 adult
patients, with varying BMI. Patient BMI was compared to their DLP, along with the difference
between entire body and skull base to mid-thigh DLP.
Results
Patient BMI in the study ranged from 18.7 kg/m2 to 48.7 kg/m2. The data showed that as patient
BMI increased, DLP also increased. The patient with the largest BMI (48.7 kg/m2) received the
highest radiation burden in both entire body and skull base to mid-thigh scans. The patient with
the smallest BMI (18.7 kg/m2) received the lowest radiation burden in both scans. A percent
decrease of DLP was calculated between the entire body and skull base to mid-thigh scans and
generated an average decrease of 17% ± 6.2%. A t-test was performed between the two scans
and a p-value = 0.046 was obtained.
Conclusions
The data shows that height and weight contribute to DLP amount. A larger BMI implies an
increase in x-rays attenuated by the patient resulting in a higher DLP. The t-test performed shows
that entire body scanning statistically gives a slightly significant increase of radiation to patients
(0.046 < 0.050). Due to this result, entire body scanning should be performed at a minimum and
not on all patients. Circumstances where entire body scans are required, such as specific cancers
or patients presenting with symptoms in the lower extremity, should continue to be performed