Application of contrast media in post-mortem imaging Experimental Study and Review of the Literature

Introduction Contrast medium (or contrast agent) is a substance used to enhance the contrast of structures or fluids within the body in medical imaging. Since the dawn of medical imaging the use of contrast medium spreaded rapidly allowing the development of many imaging applications in medicine. Only more recently have been applied to forensic investigations supporting the forensic pathologist in establishing cause and the manner of death. Aim of the research project The aims of the present study are: to perform a review on the use of contrast medium in post-mortem imaging, and to perform experimental studies directed to develop new contrast medium solutions and to test them for post-mortal CT and MRI examination of coronary arteries and of stab wounds. Materials and methods The literature review on applications of contrast medium on post-mortem imaging was performed searching different databases with the identification of 220 sources. From these sources, 69 papers more significant for the topic were taken into account. In the experimental studies different contrast media were developed and tested on human heart samples to assess the coronaric circulation and on stab wounds produced on human calves to study their morphometric features, focusing on the depth of the wound. All the samples were analysed by CT and MRI coupled to an imaging analysis software. Results Reviewing the literature, the selected papers were classified and discussed considering the way in which contrast medium was injected: into the major vessels to enhance whole body’s vasculature; through selective angiography of in situ or ex-situ organs; into in situ or ex-situ body structures different from the vessels. Moreover, other applications in the forensic field were also considered. For the experimental studies on stab wounds a mixture of 1,5 mL of Omnipaque®, 1 mL of saline and 7,5 mL of ultrasound gel was identified as the optimal contrast solution for both CT and MRI analyses of human hearts. For the experimental studies on stab wounds a mixture of 1cc of Omnipaque® and 9 cc of ultrasound gel (i.e. 1:9 dilution) was employed for both CT and MRI analyses for stab wounds. The injection of such contrast medium allows a reliable and accurate MSCT analysis of the coronary tree both before and after formalin fixation. Moreover, contrast medium enhanced MRI demonstrated to be less sensitive than MSCT to parietal calcifications, but provided a better morphologic representation of the myocardial walls. The same contrast medium solution demonstrated to be suitable for both MSCT and MRI analyses of the internal features of stab wounds. On this point the developed protocol demonstrated a high level of agreement between radiological and anatomical measurements (i.e. wound dissection) with a similar systematic underestimation for both MSCT and MRI analyses. Conclusions This study demonstrates that contrast media enhancement of body structures is rising in forensic imaging during the last years. A number of contrast media also consisting of formulations not suitable for living subjects may be injected into different body structures and have been employed also in forensic applications which lie outside the boundaries of investigations on a human corpse. As demonstrated from the herein described experimental studies many new contrast medium solutions may be developed and tested on different substrates aiming to solve a nearly boundless number of forensic issues.