English abstract
The purpose of this study was to develop effective local dose reference levels (DRL) for
SPECT/CT and PET/CT imaging in order to monitor and audit locally scanning protocols
for the most frequent SPECT/CT and PET/CT imaging examinations performed at Sultan
Qaboos University Hospital (SQUH).
Thousand one hundred and thirty-four adult patients, who have undergone SPECT/CT and
PET/CT scanning over a period of 4 years (2018-2021), were included in this study. The
scans consisted of 401 PET/CT scans (whole body, brain and cardiac) and 733 SPECT/CT
scans (bone, myocardial perfusion imaging (MPI), thyroid uptake, thyroid post ablation,
and parathyroid). Low-dose CT scans were used for attenuation correction and
localization. The PET administered activity was based on the patient's body-mass-index
(BMI). The CT dosimetry data (CT dose index (CTDIvol), dose length product (DLP))
and the administered activities were collected. The third quartile was calculated for
CTDIvol, DLP and administrated activity for each SPECT/CT and PET/CT examination.
The PET/CT and SPECT/CT total effective doses (ED) were also derived.
The estimated LDRLs are given as follows (third quartile CTDIvol (mGy):third quartile
DLP (mGy.cm):third quartile administrated activity (MBq)): whole body PET/CT:
2.37:219.5:298; brain PET/CT: 12.86:301.7:270; cardiac PET/CT: 1.79:42.5:383; bone
SPECT/CT: 3.18:135.3:814; MPI SPECT/CT (stress-rest): 1.77:60:821-809; parathyroid
SPECT/CT: 3.52:140: 815; thyroid uptake (with I-131) SPECT: 4.36:189.5:207; thyroid
post ablation 4.7:3.1. The estimated total ED (mSv) was: 7.5:7.8, 7.9:7.9, 6.9 :7.2 , 5.2:5.2,
7.4:7.8-7.3:7.7, 7.6:7.9, 4555:4555, 1.5:1.9 for (males: Females) whole body PET/CT,
Cardiac PET/CT, Brain PET/CT, bone SPECT/CT, MPI SPECT/CT (stress-rest),
parathyroid SPECT/CT, thyroid-uptake (with I-131) SPECT/CT, and thyroid post ablation
SPECT/CT, respectively.
The derived local DRLs has facilitated careful monitoring of doses delivered to patients
and could act as a trigger to investigate doses that systematically exceeds the local DRLs
set. Regular auditing of doses is expected to impact positively the department quality
management program.
