Virtopsy

Death is an inevitable part of life and at few occasions scientific examination of bodies after death becomes mandatory. The contribution of Forensic science in achieving this is noteworthy. Forensic pathology is a discipline of Forensic science which deals with pathologic and physiologic changes of a body before and after death wherein autopsy plays a significant role. Conventional Autopsy involves Invasive body opening – the traditional means of postmortem investigation in Humans. Contrary to it is Virtopsy, a minimally invasive emerging technology in the field of Forensic medicine which incorporates Imaging technology that relies on certain fundamental pillars which include – Three-dimensional surface scanning 3D/CAD photogrammetry, MSCT- multi slice computed tomography, MRI- magnetic resonance imaging and Magnetic resonance imaging spectroscopy.

1. VIRTOPSY Virtual Autopsy BY LOKESHWARI.V(15MCA14) ASHA.V(15MCA03 )

2. Introduction Virtopsy is a term that came from virtual autopsy. It was developed by Richard Dirnhofer , former director of Forensic Medicine, Berne, Switzerland. Originated in mid 1990’s. It is a scalpel free procedure to carry out autopsy using medical imaging techniques.

3. Autopsy v/s virtopsy Autopsy Thorough examination of corpse through dissection. Types of autopsy: Medico-legal Autopsy Clinical Autopsy Anatomical Autopsy Second opinion is not possible as it would have damaged some of the parts. virtopsy Alternate method for much safer procedure as it is a blood less procedure. Techniques used are: Robot guided 3D surface scanning Multi-Slice Computed Tomography(MSCT) Post mortem Angiography The findings of virtopsy are in digital format. Second opinion of any expert is possible even if the body is cremated

4. Techniques in virtopsy 3D Surface Scan photogrammetry Multi-Slice Computed Tomography [MSCT] Magnetic Resonance Imaging [MRI] Radiography Angiography

5. 3D Surface Scan A 3D surface scan takes pictures of the patient to provide a visual record of the condition. The images are taken in a booth that includes several cameras. These cameras are positioned to obtain photographs from multiple angles of the anatomy under consideration. This may involve the face,the entire head ,the torso or the whole body. The images are then combined to create a photorealistic 3-D static image of the patient.

6. photogrammetry The photographic projection in a camera can be described mathematically as central projection of the object onto the plane. Every single object is mapped in an image point ,which is the intersection point of the projection beam and the image plane.

7. Multi-Slice Computed Tomography [MSCT] The full-body multislice computed tomography (MSCT) was performed for study of bone lesions and cause of death. MSCT was superior to autopsy in diagnosis of traumatic bone lesions and also revealed dental anomalies and signs of drowning.

8. Magnetic Resonance Imaging [MRI] Magnetic resonance imaging (MRI) is another non-ionising technique available for forensic analysis. It is much less extensive compared to ionising approaches. It is more frequently applied in cases involving living individuals.  It is primarily used in relation to the estimation of skeletal age, and for the specific purpose of the determination of legal culpability.

9. Radiography Radiography is an imaging technique using X-rays to view the internal structure of an object. To create the image, a beam of X-rays, a form of electromagnetic radiation, is produced by an X-ray generator and is projected toward the object. The X-rays that pass through the object are captured behind the object by a detector (either photographic film or a digital detector). A certain amount of X-ray is absorbed by the object, dependent on its density and composition.

10. Angiography Angiography is the use of fluoroscopy to view the cardiovascular system. An iodine-based contrast is injected into the bloodstream and watched as it travels around. Since liquid blood and the vessels are not very dense, a contrast with high density (like the large iodine atoms) is used to view the vessels under X-ray. Angiography is used to find aneurysms, leaks, blockages (thromboses), new vessel growth, and placement of catheters and stents. Angiogram showing a   transverse projection of the  vertebro  basilar and posterior cerebral circulation.

11. Procedure of virtopsy It uses combination of techniques like 3D surface scan, Photogrammetry & MRI scan. It uses a robotic machine called “VIRTIBOT”. Small disks along the exterior of the body is placed. Using Virtibot 3D color model of the corpse is created. The robot moves over the body creating 3D image for about 10s. Then the body is placed inside a blue bag which prevents from contamination and helps x-rays to pass easily is scanned using MRI, CT MRS equipment. The body undergoes CT scan that finishes in 20s and acquires up to 25,000 images. Each image is cut through or slice of the body. Within 10 minutes the detailed image of tissue, bone are reconstructed using powerful desktop computers. With the click of mouse, the pathologist can peel through the layers of virtual skin and muscle.

12. IMPLEMENTATION The reconstruction of 2-D images can be performed with a Filtered Back-Projection (FBP) type reconstruction and an iterative Ordered S ubset Convex (OSC) maximum-likelihood method A special software is used to simulate transmission tomography scans with different signal-to-noise ratios (SNR ) The noise and modulation transfer function is calculated for FBP and OSC reconstruction at several positions, distributed over the field-of-view (FOV) The OSC method achieves a lower level of noise compared with FBP at the same resolution The reconstruction with OSC can save a factor of up to nine of x-ray dose compared with FBP in the investigated range of noise levels The OSC algorithm was modified so it calculates the normalization term before the iterative process to save computational cost. The modified version requires only one back projection per iteration as compared to two required for the original OSC

13. The OSC algorithm updates all estimates of the attenuation coefficients µ n s+1 (k) Y i represents the measured transmission counts in bin i d i represents the blank scan counts in bin i l ij is the length of projection line i through voxel j S(s) contains the projections in subset s

14. Transmission images were reconstructed with the OSC algorithm using 50, 125 and 250 subsets They were compared with images reconstructed with the standard convex algorithm serving as the ‘gold standard ’ The N subsets were chosen such that the angles θ between the n projections in each subset were equal (θ = 2π/n) The order in which the subsets were used during each iteration of OSC was- Δθ ∈ {0, 1.2π/ N.n , 2.2π/ N.n , . . . , (N − 1).2π/ N.n } between s+1 & s A ngular difference Δθ was as close as possible to the centre of the largest angular gap of projection angles that had not yet been processed in the current OSC iteration ( Δθ as close as possible to π/n )

15. Uses of virtopsy Time of death. Identification of individuals. Determination of age and sex of individual. Death due to burns. Manual strangulation or hanging. Road traffic accidents.

16. conclusion Autopsy has its merits but virtopsy has futuristic advancements that provide privacy to deceased family. At the present virtopsy cannot replace conventional autopsy since it is a new development in the field of investigation of death.

17. REFERENCES http://www.sciencedirect.com/science/article/pii/S2090536X16300211 http://medind.nic.in/jal/t14/i2/jalt14i2p195.pdf https://www.wired.com/2012/10/virtual-autopsy-2/ http://journal.opus12.org/o12-ojs/ojs-2.1.1/index.php/o12sci/article/viewFile/249/75 https://link.springer.com/chapter/10.1007%2F978-90-481-8990-8_9

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