The virtual autopsy which is also popularly known as ‘Virtopsy’ is an emerging technique in forensic medicine.

It not only minimizes the need for conventional autopsy but also provides useful clues about various skeletal injuries and haemorrhages which occur even in those regions which are often missed out during conventional autopsy.

A virtual autopsy can also serve as important evidence in the court of law in many cases where the kin of the deceased plead for exemption.

In many cases, there is not a fair acceptance due to fear of disfigurement of the body, religious beliefs etc. In such cases, it comes to the rescue.

It uses various imaging modalities which use 2D images to reconstruct a 3D model of the body. There are various advantages associated with this technique, like time-saving, better acceptance, storage of digital data for future reference, cost-saving, reduced need for human resources, etc.

Various Imaging Modalities Employed in Virtual Autopsy

• Optical Surface scanner
  
• Postmortem Computed Tomography (PMCT)
  
• Postmortem Magnetic Resonance Imaging (PMMR)

Surface Scanner

Surface scanning is a non-invasive method to capture the shape, texture and volume information of a 3-dimensional object.

The surface scanner generates virtual specimens of the external surface of the body which can be stored, shared, re-measured and addressed with a new set of measurements(1). 

They also depict the exact position and size of various external injuries and their relative positions to various anatomical landmarks with precision by using digital close range photogrammetry.

It employs the use of multiple rotating cameras mounted on a framework at various angles to get a full coverage of the external surface of the body.

Postmortem Computed Tomography (PMCT)

PMCT is similar to any Computed Tomography which takes multiple sections of the body in all the three planes to give very thin slices so that even the smallest pathology does not remain missed out.

PMCT captures a series of 2D planar X-ray images and reconstruct the data into 2D cross-sectional slices which can then even be reconstructed into 3-dimensional models. 

Micro-CT, also known as Micro-Computed Tomography does imaging on a small scale but with greatly increased resolution. Samples can be imaged with pixel sizes as small as 100 nm and objects as large as 200 mm can be scanned.

PMCT is of great help in diagnosing cortical skeletal fractures which are most likely to be missed out in Conventional autopsy. They are also used to detect various intracranial haemorrhages and even measure their volume with precision. 

• They can also be useful in computing various anthropometric measures especially for identification purposes.

• They can also detect various small pathology in the organs which are not found macroscopically on gross dissection.

• They can be used to detect the exact location of thromboemboli without dislodging them by conventional dissection. 

• They can also detect the air-fluid levels in cases of effusion. 

• They can show fading away of bronchovascular markings in cases of pulmonary oedema as in a case of drowning. 

• They can also detect the depth of the injuries in cases of 3-dimensional wounds such as stab wounds. 

• They can also find out fractures in the vertebra and other small bones, which are least examined.

Postmortem Magnetic Resonance Imaging (PMMR)

PMMR also serves the same purpose as the MRI used in clinical practice. PMMR can be useful to detect soft tissue lesions better than CT. T1 and T2 weighted images generated by MRI can be useful to deduce brain pathologies with accuracy. 

They can also be used for the estimation of weight and volumes of various organs. Short Tau Inversion – Recovery (STIR) images enable investigators to screen for pathological fluid accumulation, commonly referred to as the ‘forensic sentinel sign’.

PMMR offers excellent anatomical detail and is especially useful in visualizing pathologies in the heart, brain and abdominal organs. PMMR is also useful in documenting skeletal injuries.

PMMR can detect the earliest stages of ischaemic injury to the cardiovascular system which is not possible by the conventional autopsy and routine histological examination.

Multiplanar Reconstruction (MPR)

The 2-D planar X-ray images generated can be used to reconstruct 3-D images thus able to visualize any structure in all the 3 planes namely axial, coronal and sagittal.

The MPR helps to pin point the exact site of a lesion as it enables one to visualise a spatial configuration by projecting the same site in all 3 possible planes and thus improving the quality of interpretation. 

It also enables one to adjust window parameters so as to enhance the organ being viewed at the greatest contrast. It also has a feature that has made it possible to know the tissue attenuation coefficient of any tissue at a particular point and thus giving the Hounsfield Unit (HU) at that point.

This can be used in comparison with the surrounding healthy tissue to know the pathophysiology behind the observed lesion such as calcification, consolidation, atelectasis etc.

3-D Reconstruction

This is made possible by means of various software that enables one to visualise the 3-D reconstructed image and virtually dissect the body at various planes to look for various abnormalities.

The virtual scalpel and the clip plane inversion help in dissecting the body at a particular plane and viewing the dissected portion from any angle. 

• This is mainly useful in skeletal injuries to know the exact course of the fracture line or even fractures in the skull base which would not be visible on traditional dissection. 

• It also makes it possible to visualise fracture of the bones in the upper and lower limbs which are not dissected at all as per the conventional autopsy procedures. 

• They can be very useful to know the type of the weapon as sharp or blunt based on the nature of the injury produced.

• They can be used to know the direction of force in an impact as seen by the bevelling on the bone.

• Also helpful in case of comminuted fractures as in Road Traffic Accidents where there tend to be multiple bone fragments.

• To know the degree of fusion of skull sutures so as to estimate the age in cases of unidentified bodies.

• If there are isolated fractures of the inner table of the skull or if there are any cortical defects of the bone.

• To differentiate the manner of death as in hanging and strangulation where each presents with fracture of the hyoid at different sites.

• To know about pelvic bone fractures which are usually skipped in conventional autopsy and also fractures of neck of femur etc.

• To differentiate between the entry and exit wounds in firearm injuries and also to study the tract of the firearm within the body.

• The various organ filters available enhances the particular system to be visualized with the maximum contrast.

3-D Trauma

This is an upgrade to the 3-D reconstruction which is of paramount help in cases of comminuted fractures.

It enables the investigator to assemble the comminuted bone pieces in their respective places as in case of a jigsaw puzzle.

This also finds importance in routine clinical practice especially for maxillofacial reconstructive surgeries.

This can help to put back the bone pieces to establish the identity in case of severe mutilation as in mass disasters.

Postmortem Angiography

This employs the use of suitable contrast agents preferably dispersed in an oily medium so as to avoid extravasation into the surrounding tissue and employing CT to visualize the cardiovascular system.

Additionally, Polyethylene Glycol (PEG) is used to reduce tissue edema and also to flush out postmortem clots. 

Then the exact location of thromboemboli can be found out and may lead to concluding the exact cause of death in many a cases. It also helps to know the exact source and site of bleed as in case of intracranial haemorrhages.

Fly Through

This technique can described in simple terms as virtual endoscopy.

This is very useful in cases where there is an obstructive pathology in the respiratory or the alimentary tract.

The outcome of this procedure is a videograph which gives us the tracing from one orifice to the exiting orifice provided there is no obstructive pathology intruding in between. 

The videograph either starts from the nasal opening or the oral cavity and continues till the alveoli or anal opening respectively. There is a fluorescent virtual guide which helps us follow the path in which the endoscopy is proceeding.

Virtobot

This makes use of an industrial six-axis robot with additional extensions such a multi-slice CT scanner with angiography and also a biopsy end effector for automatic needle placement.

The Virtobot is capable of performing surface documentation with the help of the optical surface scanning system and also helps in tissue sampling, liquid sampling or placement of guide wires for various procedures with an accuracy of 1.4 mm as recorded by various studies when performed in biopsy phantoms. 

It is an essential tool for a scalpel free dissection which purely employs imaging techniques and the Virtobot can be the future in Virtual autopsy with its efficiency in programmed and algorithmic biopsy sampling.

Conclusion

Virtual autopsy as a screening tool before performing conventional autopsy in my institution is a routine practice.

Extensive research is being carried out to prove virtopsy is equally efficient as conventional autopsy and it can be adapted as a routine practice in those cases in which the cause of death can be ascertained just using virtopsy.

Efforts have been constantly made to convince the court regarding this, and I am sure it is going to turn into reality in the near future. Comment on various modalities in virtopsy has been made out of my own experience with few of them.

References

1. Schweitzer W, Röhrich E, Schaepman M, Thali MJ, Ebert L. Aspects of 3D surface scanner performance for post-mortem skin documentation in forensic medicine using rigid benchmark objects. J Forensic Radiol Imaging. 2013 Oct 1;1(4):167–75. 

2. Offiah CE, Dean J. Post-mortem CT and MRI: appropriate post-mortem imaging appearances and changes related to cardiopulmonary resuscitation. Br J Radiol. 2016 Feb;89(1058):20150851. 

3. Grabherr S, Djonov V, Yen K, Thali MJ, Dirnhofer R. Postmortem Angiography: Review of Former and Current Methods. Am J Roentgenol. 2007 Mar;188(3):832–8. 

4. Virtual Endoscopy: A Promising New Technology | AAFP [Internet]. [cited 2023 Mar 21].

Available from: https://www.aafp.org/pubs/afp/issues/2002/0701/p107.html

5. Ebert LC, Ptacek W, Breitbeck R, Fürst M, Kronreif G, Martinez RM, et al. Virtobot 2.0: the future of automated surface documentation and CT-guided needle placement in forensic medicine. Forensic Sci Med Pathol. 2014 Jun;10(2):179–86. 

Written by: Dr. Aishwarya M