DOS Kongressen 2014 ·
173
Micro dose acquisition in Leg length Discrepancy
using the EOS imaging system
Janni Jensen, Bo Mussmann, Niels Wisbech, Zaid Al-Aubaidi, Trine Torfing
Department of Radiology, Odense University Hospital; Department of
Orthopedic Surgery, Odense University Hospital
Background:
Leg Length Discrepancy (LLD) is often diagnosed in young pa-
tients who undergo repeated x-ray examinations quantifying the length discrep-
ancy and monitoring progression. In our department LLD images are currently
acquired using a low dose bi-plane system named EOS. Prior to the acquisition
of diagnostic images a scout image is acquired at extremely low dose for plan-
ning purposes, i.e. approximately 1% of the dose required for diagnostic images.
Dose reduction is important because children and adolescents are more sensi-
tive to radiation than adults and they may undergo several LLD examinations.
Purpose / Aim of Study:
The purpose of the study was to investigate the
accuracy and reliability of LLD measurements performed on scout images com-
pared to diagnostic images.
Materials and Methods:
A retrospective pilot study including 30 consecutive
patients (age 6-15 years) was performed. Two senior musculoskeletal radiolo-
gists measured the length of the femur, tibia and the total leg length on both
legs on scout and diagnostic images. The measurements on scout and diagnos-
tic images were performed in two separate sessions and the radiologists were
blinded to the identity of the patients.
Findings / Results:
No significant differences between scouts and diagnos-
tic images were found. The mean femoral length difference for the observers
was 0.11 cm (p=0.09) and 0.07 cm (p=0.24) respectively, mean tibial length
difference was 0.02 cm (p=0.77) and 0.01 cm (p=0.84). The mean total leg
length difference was 0.01 cm (p= 0.92) and 0.03 cm (p=0.73). ICC was >0.99
indicating excellent inter rater reliability.
Conclusions:
The results suggest that there is no significant difference in LLD
measurements performed on scouts and diagnostic images. Thus, scout based
LLD measurements can be accurately and reliably performed in EOS.
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