Diffusion-weighted perinatal postmortem magnetic resonance imaging as a marker of postmortem interval
Owen J. Arthurs
0
1
Gemma C. Price
0
1
David W. Carmichael
0
1
Rod Jones
0
1
Wendy Norman
0
1
Andrew M. Taylor
0
1
Neil J. Sebire
0
1
0
N. J. Sebire Histopathology, UCL Institute of Child Health
,
London
,
UK
1
N. J. Sebire Department of Histopathology, Great Ormond Street Hospital for Children NHS Foundation Trust
,
London
,
UK
Objective To evaluate perinatal body organ apparent diffusion coefficient (ADC) values at postmortem magnetic resonance imaging (PMMR) in order to evaluate postmortem changes. Methods Postmortem diffusion-weighted imaging (DWI) of the thorax and abdomen were performed with diffusion gradient values b= 0, 500, and 1000 s/mm2 on 15 foetal and childhood cases (mean 33.37.8 weeks gestation) compared to 44 live infants (mean age 75.5 53.4 days). Mean ADC values were calculated from regions of interest (ROIs) for the lungs, liver, spleen and renal cortex, compared to normative live infantile body ADC values of similar gestational age. Results Mean ADC values were significantly lower in postmortem cases than in normal controls for liver (0.88 10-3 mm / 2 s SD 0.39 vs. 1.130.13; p<0.05) and renal cortex (0.85 0.26 vs. 1.190.13; p<0.05) but not spleen or muscle. Mean lung ADC values were significantly higher than normal controls (1.06 0.18 vs. 0 0; p < 0.001), and there was a significant correlation between postmortem interval and lung ADC (R2=0.55). Conclusion Lung PMMR ADC values are related to postmortem interval, making them a potential marker of time since death. Further research is needed to understand the organspecific changes which occur in the postmortem period. Key Points Liver and spleen PM ADC values were lower than controls. Lung ADC changes correlate with PM interval. These findings may be useful in medicolegal cases.
-
Abbreviations
ADC Apparent diffusion coefficient
DTI Diffusion tensor (magnetic resonance) imaging
DWI Diffusion weighted (magnetic resonance)
imaging
(PM)MR (postmortem) magnetic resonance imaging
Postmortem imaging now plays a significant role in the
paediatric and perinatal minimally invasive autopsy, largely due
to a decline in parental acceptance of traditional autopsy
techniques fuelling a drive to develop a novel less invasive
postmortem approach [1, 2]. Several different imaging
modalities are being employed in this regard, including
postmortem (PM) skeletal radiographs, typically used to diagnose
skeletal dysplasias and assess bone gestational changes [3],
and cross-sectional imaging techniques including PM
computerized tomography (CT) and PM magnetic resonance
imaging (PMMR), which have been reviewed extensively
elsewhere [4]. Postmortem CT is rapidly available, and readily
gives vascular and bone detail, it has not been shown to be
diagnostically accurate for soft tissue abnormalities in fetuses
and children. PMMR has been shown to have high diagnostic
accuracy for perinatal abnormalities, in both small preliminary
(e.g., Breeze et al. [5]) and large blinded studies [6], and
PMMR is widely believed to likely become the mainstay of
a less invasive perinatal imaging service [4].
However, there remain areas of potential diagnostic
improvement, with true ischaemia and necrosis difficult to
evaluate with conventional magnetic resonance (MR) techniques
[7]. Diffusion-weighted imaging (DWI) is a structural MR
imaging technique which measures the diffusivity of water
molecules. It can be measured quantitatively and expressed as
an apparent diffusion coefficient (ADC) value, such that a
lower ADC value represents a tissue with more restricted
water diffusivity. ADC measures of body organs have been
used to evaluate tumour characteristics in paediatric tumours,
such as Wilms tumours and neuroblastoma [810].
Following death, there are several changes in tissues due to
tissue breakdown (autolysis) and decomposition. In the initial
hours following death, tissue ischaemia will occur, followed
by a period of cell lysis, membrane breakdown, fluid
redistribution and gas formation/putrefaction [11]. We hypothesise
that PMMR DWI changes in individual organs will
correspond to these changes, with an initial decrease in ADC values
secondary to ischaemia (such as in stroke), followed by a
possible increase in ADC values following cell breakdown
and autolysis. Human PM specimens have recently been used
to confirm DWI tractography [12], and several animal studies
have suggested an effect of PM interval on DWI changes in
the brain [1317].
This study was therefore designed to establish whether (a)
DWI changes are detectable by PMMR in fetuses and
stillbirths, (b) PMMR DWI changes increase following death,
possibly due to cellular barriers breaking down and increasing
water movement, and (c) PMMR DWI changes correlate with
PM interval, and could be possible surrogate markers for
autolysis.
Live infants We retrospectively searched our hospital
database for all cases of thoraco-abdominal MRI in infants under
the age of 6 months of age over a 5-year period (April 2008 to (...truncated)