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Table 3 Comparison of key protocol settings contributing to dose differences between maximum and minimum DLP75kg systems

From: A Nordic survey of CT doses in hybrid PET/CT and SPECT/CT examinations

Examination

Clinical purpose of CT

Max/min DLP75kg

Max or min DLP75kg protocol

Scan length (cm)

Summary of main protocol differences contributing to variation in DLP75kg

PET/CT brain

Localisation/characterisation

16.8

Max

18

Exceptionally high effective mAs for localisation/characterisation (images originally intended for diagnostic use)

Min

23

 

PET/CT and SPECT/CT cardiac

AC only

19.6

Max

29

High effective mAs for AC only; long scan length

Min

16

Attempted to optimise for AC only with low effective mAs (low mA, high pitch) and low kV; use of IR

SPECT/CT lung

AC only

27.4

Max

32

High kV; high effective mAs for AC only

Min

36

Attempted to optimise for AC only with low effective mAs (low mA, high pitch); use of IR

Localisation/characterisation

4.2

Max

32

Higher kV and effective mAs than minimum DLP75kg protocol

Min

33

Low kV and effective mAs

SPECT/CT bone

Localisation/characterisation

10.0

Max

106

Three times greater scan length, higher kV and effective mAs than minimum DLP75kg protocol

Min

37

Use of IR

SPECT/CT parathyroid

Localisation/characterisation

7.8

Max

28

Much higher effective mAs (but lower kV) than minimum DLP75kg protocol

Min

24