Date Published: April 23, 2019
Publisher: Public Library of Science
Author(s): Olga Szaluś-Jordanow, Joanna Bonecka, Filip Pankowski, Karolina Barszcz, Sylwia Tarka, Magdalena Kwiatkowska, Michał Polguj, Marcin Mickiewicz, Agata Moroz, Michał Czopowicz, Tadeusz Frymus, Jarosław Kaba, Carlos Zaragoza.
Evaluation of the usefulness of air as a negative contrast medium of blood vessels in goats in post mortem computed tomography (PMCT) and establishing the protocol with appropriate doses and timing of the contrast medium administration.
Thirty three goats were euthanized 10 to 300 min before the study. First, in 3 goats air was administered into the left or right common carotid artery at dose of 60, 100 and 120 ml/kg, and after each dose PMCT was performed in lateral recumbency. As the latter dose proved to visualize blood vessels best, following 30 goats were examined in the same manner but only with the use of air dose of 120 ml/kg. The quality of CT scans was evaluated independently by two board-certified radiologists.
In all studied animals the vascular system filled with air was clearly visualized on CT scans. In most of goats this amount of air revealed vessels smaller than 4 mm in diameter.
PMCT with air as a negative contrast agent may be an alternative technique used in post-mortem angiography.
Post mortem computed tomography (PMCT) is commonly used in both human and veterinary forensic medicine[1–10]. Plain CT examination, without intravenous contrast agent, provides much less information about the vascular system compared to contrast-enhanced examination.
Initially, in 3 goats 60 ml/kg of air was administered and CT scans were performed. After administration of this amount of air only main vessels became visible (Fig 9) so an additional dose of 40 ml/kg of air was added. The volume of 100 ml/kg was still found as too little. After administration of further 20 ml/kg of air (a total dose of 120 ml/kg) all blood vessels in the entire body including head were filled and this dose was used in next 30 goats.
Post mortem CT has many advantages, however high costs and limited availability of the equipment render it a rarely employed diagnostic procedure. Oily contrast is expensive as is also a special pump which produces circulation. The use of air as a contrast medium significantly improves imaging quality and reduces costs. On the other hand owners are reluctant to give their consent to the post mortem examination because of a strong emotional connection with their animal. The proposal of the post-mortem examination involves a great deal of sadness, which is often the reason for the refusal. Similar situation is observed in case of humans, when the family finds the idea of their loved ones being dissected after death upsetting. PMCTis an alternative to anatomopathological examination which may allow to establish definitive diagnosis in many situations. PMCT can reveal some causes of death, like massive bleeding, cardiac tamponade, massive pleural effusions and large pneumothorax. Compared to autopsy, PMCT can be reviewed easily and repeatedly by many professionals, since CT scans exported to DICOM files can be shared immediately all over the world. The whole PMCT procedure including preparations is short, takes less than 20 minutes including CT scanning. The necessary equipment is very inexpensive (the cost is about 1 euro and can be used repeatedly). In addition, some protocols require three full exams so that the scans obtained are of sufficiently high quality. This method allows to visualize the vascular system of the head, thorax, abdomen and limbs. It is important to emphasize that CT scans of the living animals vary from these obtained post mortem due to rigor mortis which changes the shape of organs. Moreover, the longer time elapses from death to CT examination, the more changes related to the body decay such as gas accumulation due to bacteria growth or migration of body fluids are visible. On the other hand, the main advantage of PMCT versus ante mortem examination is the lack of motion-related artefacts resulting from heartbeat and breathing.