Detecting small anatomical change with 3D serial MR subtraction images
Proc Society of Photo-Optical Instrument Engineers (SPIE), Bellingham,
WA, vol 3661, pp 44-55, (February, 1999)
E. R. E. Denton,
J. M. Jarosz,
T. C. S. Cox,
D. J. Hawkes
D. L. G. Hill
Radiological Sciences, GKT, Guy's Hospital,
London, SE1 9RT, UK.
Spoiled gradient echo volume MR scans were obtained from 5
growth hormone (GH) patients and 6 normal controls.
The patients were scanned before treatment and after 3 and
6 months of GH therapy.
The controls were scanned at similar intervals.
A calibration phantom was scanned on the same day as each subject.
The phantom images were registered with a 9 degree of
freedom algorithm to measure scaling errors due to changes in scanner
The second and third images were each registered with a 6 degree of
freedom algorithm to the first (baseline) image by maximising normalised
mutual information, and transformed, with and without scaling error
correction, using sinc interpolation.
Each registered and transformed image had the baseline image subtracted to
generate a difference image.
Two neuro-radiologists were trained to detect structural change with
difference images containing synthetic misregistration and scale changes.
They carried out a blinded assessment of anatomical
change for the unregistered; aligned and subtracted; and
scale corrected, aligned and subtracted images.
The results show a significant improvement in the detection of
structural change and inter-observer agreement
when aligned and subtracted images were used instead of unregistered
The structural change corresponded to an increase in brain:CSF ratio.
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