Whole-Body PET/CT Scanning: Estimation of Radiation Dose and Cancer
Risk1
Bingsheng Huang, Martin Wai-Ming
Law and Pek-Lan Khong
Address correspondence to P.L.K.
(e-mail: plkhong@hkucc.hku.hk).
1From the Departments of Diagnostic Radiology (B.H.,
P.L.K.) and Clinical Oncology (M.W.M.L.), University of Hong Kong,
Queen Mary Hospital, 102 Pokfulam Rd, Room 406, Block K, Hong Kong.
Received July 30, 2008; revision requested August 18; revision
received September 10; accepted October 3; final version accepted
October 26.
Vol. 251: Issue. 1:
Pages. 166-174
(Issue publication date: April 2009)
DOI: 10.1148/radiol.2511081300
Purpose: To estimate the radiation dose
from whole-body fluorine 18 (18F)-fluorodeoxyglucose
(FDG) positron emission tomographic (PET)/computed tomographic (CT)
studies and to evaluate the induced cancer risk to U.S. and Hong
Kong populations.
Materials and Methods: Fluorine 18–FDG
PET/CT studies obtained by using a 64-detector CT unit and one of
three CT protocols were evaluated. CT protocol A consisted of 120
kV; rotation time, 0.5 second; pitch, 0.984; 100–300 mA; and noise
level, 20. CT protocol B was the same as A, except for a fixed tube
current of 250 mA. CT protocol C consisted of 140 kV; rotation
time, 0.5 second; pitch, 0.984; 150–350 mA; and noise level, 3.5.
CT doses were measured in a humanoid phantom equipped with
thermoluminescent dosimeters. Doses
from 18F-FDG PET scanning were
estimated by multiplying the 18F-FDG
radioactivity (370 MBq) with dose coefficients. Effective doses
were calculated according to International Commission on
Radiological Protection publication 103. Lifetime attributable risk
(LAR) of cancer incidence was estimated according to the National
Academies' Biological Effects of Ionizing Radiation VII Report.
Results: Effective doses with protocols
A, B, and C, respectively, were 13.45, 24.79, and 31.91 mSv for
female patients and 13.65, 24.80, and 32.18 mSv for male patients.
The LAR of cancer incidence associated with the dose was higher in
the Hong Kong population than in the U.S. population. For
20-year-old U.S. women, LARs of cancer incidence were between
0.231% and 0.514%, and for 20-year-old U.S. men, LARs of cancer
incidence were between 0.163% and 0.323%; LARs were 5.5%–20.9%
higher for the Hong Kong population. The induced cancer risks
decreased when age at exposure increased.
Conclusion: Whole-body PET/CT scanning
is accompanied by substantial radiation dose and cancer risk. Thus,
examinations should be clinically justified, and measures should be
taken to reduce the dose.
Supplemental material: http://radiology.rsnajnls.org/cgi/content/full/2511081300/DC1
© RSNA, 2009
Keywords: BEIR = Biological Effects of Ionizing
Radiation; FDG =
fluorodeoxyglucose; ICRP
= International Commission on Radiological
Protection; LAR =
lifetime attributable risk; TLD = thermoluminescent dosimeter
Figure
a:(a–c) Graphs show excess
cancer incidence risks estimated to be associated with radiation
from a single whole-body 18F-FDG PET/CT
examination at a given age. PET/CT was performed with three CT
protocols (A, B, and C), as shown
in (a), (b),
and (c), respectively.
Figure
b:(a–c) Graphs show excess
cancer incidence risks estimated to be associated with radiation
from a single whole-body 18F-FDG PET/CT
examination at a given age. PET/CT was performed with three CT
protocols (A, B, and C), as shown
in (a), (b),
and (c), respectively.
Figure
c:(a–c) Graphs show excess
cancer incidence risks estimated to be associated with radiation
from a single whole-body 18F-FDG PET/CT
examination at a given age. PET/CT was performed with three CT
protocols (A, B, and C), as shown
in (a), (b),
and (c), respectively.
Table
1. TLD Distribution
Table
2. Parameters of the Three CT
Protocols
Table
3. CT Dose for Male and Female
Patients with Protocols A, B, and C
Table
5. LARs of Cancer Incidence for U.S.
and Hong Kong Populations
Table
6. Top Five Cancer Sites in U.S. and
Hong Kong Populations
Author contributions: Guarantors of
integrity of entire study, all authors; study concepts/study design
or data acquisition or data analysis/interpretation, all authors;
manuscript drafting or manuscript revision for important
intellectual content, all authors; manuscript final version
approval, all authors; literature research, all authors;
experimental studies, B.H., M.W.M.L.; statistical analysis, B.H.,
M.W.M.L.; and manuscript editing, all authors
Authors stated no financial relationship to disclose.
We thank Ms. Li Sau-Ching for her assistance in TLD processing
and all staff members at the PET/CT Unit of the University of Hong
Kong for their technical help.
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