MIA procedure in general
In our hospital, consent for MIA from the next-of-kin is asked by the treating physician. Written and signed informed consent forms are then sent to the mortuary (Pathology Department), together with an autopsy request form including clinical information. The bodies are not embalmed prior to the MIA procedure and are stored in a standard refrigerated environment. The body is prepared for scanning at the mortuary (e.g. closure of open wounds, removal of metals from the body) and placed in an MRI-compatible body bag. After regular working hours, following the daily scan program, the body is transported to the Radiology Department by a dedicated team. The MIA consists of an MRI of head and trunk, followed by a total-body CT - with coronary CT-angiography on indication – followed by CT-guided biopsies of internal organs and suspected lesions. If consent is obtained, brain biopsies are performed when the body has been returned to the mortuary. A schematic overview of the MIA procedure is shown in Figure 1 and a flow-chart of the MIA procedure is shown in Figure 2. 

MIA procedure

MRI protocol

Our MRI protocol is performed on a 1.5T scanner (Signa CV/i, GE Medical systems, Milwaukee, Wisconsin USA) and consists of T1-weighted and T2 weighted scans acquired with the body coil from the cranium to the pelvis and high resolution thoracic and cardiac T2-weighted scans and T1-weighted fat suppressed scans with a cardiac coil. The total MRI scan time is approximately 1 hour.

CT protocol

Our CT protocol is performed on a dual-source CT scanner (SOMATOM Definition Flash, Siemens Forchheim, Germany) and  consists of scans from head to toe reconstructed in axial, coronal and sagittal planes with sharp and smooth kernels. The total CT scan time is approximately 3 minutes and additional time needed for image reconstruction is 15-30 minutes. 

Our current total body CT protocol consists of:

1. Total-body scans: containing 8 recon jobs (axial, coronal, sagittal) with bone/lung and soft tissue kernel + appropriate window width/level.

2. Head-neck scans: containing 7 recon jobs (axial, coronal, sagittal) with bone and head/neck kernel + appropriate WW/WL.

To optimize image quality, we scan the head-neck separately; head kernels contain beam-hardening correction and use different bowtie filtering in the x-ray tube. 

Detailed MRI and CT scan protocols are shown in Figure 3 and 4. In Figure 5 an example of a post-mortem MRI is shown. In Figures 6 and 7 technical issues with positioning and common artefacts are shown. 

The scans are directly interpreted by a radiologist with expertise in post-mortem imaging. A coronary CT angiography (Figure 8) is performed if there is clinical suspicion of a cardiac cause of death, or if there is no plausible cause of death identified after CT and MRI scanning. Subsequently, standardized CT guided biopsies (11 gauge) are taken from the lungs, heart, liver, spleen and kidneys. If additional lesions or regions of interest are identified, these are biopsied as well. The biopsies are immediately put in formalin for routine H and E slides and additional stains if necessary. Other procedures, such as freezing the tissue, can be readily applied. The body is returned to the mortuary when the biopsies are finished. If consent is obtained, brain biopsies are taken in the autopsy facility under stereotactic guidance by our neurosurgeons (Figure 9), using the post-mortem CT scan of the head. 

Limitations and advantages

Logistics

A MIA procedure takes about 3 to 5 hours, depending of the number of biopsies taken. The MIA is performed in the evening hours, so as not to interfere with the daily workflow, and to avoid uninvolved people to be exposed to the body. The preferred situation would be to have scan facilities in the autopsy room, close to the mortuary. Due to our study design, bodies are scanned from Sunday to Thursday. Sufficient reimbursement of a MIA procedure is necessary to offer a 24/7 post-mortem service.

Data storage 
In our pilot study, bodies were scanned on a 16-slice CT scanner (Somatom Sensation 16, Siemens, Forchheim, Germany). The CT protocol consisted of three separate CT scans of head-neck (7 recon jobs), thorax-abdomen (8 recon jobs) and legs (8 recon jobs). (9) Because of the high number of reconstructions and thus large data storage, we revised to a more sophisticated total-body protocol using a dual-source CT scanner and consequently reduced recon jobs. 

Biopsy technique

A potential problem is biopsy sampling error. A possible solution is the application of 3D-stereotactic guided needle biopsies. With this technique the biopsy gun is guided to the correct position using a stereotactic infrared camera. This technique is less operator dependent and allows for more precise targeting of small lesions. 

Tissue quality

As compared to tissue procured at autopsy, the tissue of the MIA biopsies is of slightly better quality with less autolytic changes in the microscopic slides, and less degradation of RNA, thus suitable for expression studies. (12) 

MIA interpretation and reporting 

Interpretation and reporting of a MIA is a joint effort of the radiologist and the pathologist, both dedicated to the MIA. The radiologist should be familiar with post-mortem changes in CT and MRI images (see Wagensveld et al. ECR 2016 poster #2482). The pathologist has to be able to integrate the “gross” findings from the radiological images with the microscopic findings in the biopsies, similar to the integration of macroscopy and microscopy at autopsy. The MIA offers an unprecedented platform of comparing CT- and MR images to histo-pathology, and thereby is a great learning experience.