Recent Advances in Medical and Forensic Imaging

A one day meeting organized jointly by the Imaging Science Group and the Medical Group, co-sponsored by The Institute of Physics and Engineering in Medicine.

This meeting was sponsored by FLIR Infrared Sysytems, Photometrix, and Calumet. Abstracts of most of the presentations are included below.

Monday 14 February 2011,
The Kohn Centre, The Royal Society, 6 Carlton House Terrace, London, SW1Y 5AG

Convenors: E F J Ring & R L Tapper

Programme:

Registration 9.15 to 10am

10.00 Welcome by Sir Ralph Kohn FRS

10.10 Has Digital Technology Subverted the Truth in Photographic Evidence?
Hoosain Ibrahim, University of Limpopo, South Africa

Photographic truth is being entirely challenged by the emerging technology of digital image manipulation and synthesis. Photographs can be altered in ways that are virtually undetectable and photorealistic synthesized images are becoming increasingly difficult to distinguish from actual photographs.

Image-processing software can rearrange and otherwise transform the elements of a scene. The same software can combine fragments of different images into a new image. Digital images make photographic falsehoods quicker and easier – and often more difficult to trace. The question of how to distinguish visual fact from fiction is becoming increasingly important as we witness the explosive proliferation of digital imaging technology. The fact that an image presents a seamless surface no longer provides evidence for concluding that it has not been manipulated. We must look for other clues such as internal consistency, documentable provenance and consistency with existing beliefs. In general, the more information there is in an image, the more difficult it is to change without introducing detectable inconsistencies.

The provenance of a conventional photograph is often easy to trace whereas digital imaging technology eliminates negatives, it can replicate files in seconds, digital images can be transmitted rapidly and invisibly through computer and telephone networks.

The subtlest challenge is posed by images that show no detectable signs of tampering and no obvious internal inconsistencies and yet contradict our established beliefs.

Digital imaging technology can provide openings for principled resistance to established social and cultural practices, and at the same time it can create possibilities for cynical subversion of those practices. Digital images have less standardized production processes than photographs. These processes are less subject to institutional policing of uniformity, offer more opportunities for human intervention, and are for more complex and varied in their range of possible representational commitments.

10.40 3D Imaging in Forensic Odontology
Samuel Evans, Illustration Unit, School of Dentistry, Cardiff University

This work describes the investigation of a new 3D capture method for acquiring and subsequent forensic analysis of bite mark injuries on human skin. When documenting bite marks with standard 2D cameras errors in photographic technique can occur if best practice is not followed. Subsequent forensic analysis of the mark is problematic when a 3D structure is recorded into a 2D space. Although strict guidelines (BAFO) exist, these are time consuming to follow and due to their complexity may produce errors. A 3D image capture and processing system might avoid the problems resulting from the 2D reduction process, simplifying the guidelines and reducing errors.

A series of experiments are described in this work to demonstrate that the potential of a 3D system might produce suitable results. The experiments tested precision and accuracy of the traditional 2D and 3D methods.

A first set of experiments tested and demonstrated which method of forensic analysis creates the least amount of intra-operator error. A second set tested and demonstrated which method of image capture creates the least amount of inter-operator error and visual distortion. In a third set the effect of angular distortion on 2D and 3D methods of image capture were evaluated.

The results of the experiment are consistent with what was expected from the known limitations and abilities of both the 2D and 3D methods.

The results of the experiments demonstrate that distortion and errors created by 2D image capture can hinder the digital measurement process.

A 3D image capture device minimises the amount of angular distortion, therefore such a system has the potential to create more robust forensic evidence for use in courts.

11.00 – 11.30 Coffee break

11.30 The Imaging and Mechanisms of Non-accidental Injuries in Infants
Prof. N.Ebrahim, Dpt of Radiography, University of Limpopo, S.Africa

Injuries associated with child abuse may involve any anatomic focus and organ system. Although many, if not most of the injuries associated with physical abuse cannot serve as definitive evidence of maltreatment, awareness of patterns of injuries in abused infants may serve to identify potential victims of abuse and stimulate more thorough clinical and radiological investigation

The purpose of the study was to investigate the mechanism of injury and the imaging modalities that would best demonstrate the resultant skeletal and soft tissue injuries

A collection of case studies was obtained from the Red Cross War Memorial Hospital in Cape Town. A literature review was undertaken to compile the common mechanisms of injuries that would match the radiological findings. The mechanisms of injury were simulated and recorded photographically.

OUTCOMES

  • The lecture is incorporated into the MBCHB and radiography syllabus
  • A Proposed Code of Practice for Radiographers regarding the imaging and management of NAI in children was formulated and published in the SA Radiology in 2002
  • A Portfolio of Evidence was submitted as partial fulfilment of an MSc (Diagnostic Radiography) degree at the Anglia Polytechnic University (now known as the Ruskin University), Cambridge, United Kingdom
  • An article was published in the SA Fam Pract Journal 2008;(50(3):5-13

12.00 An Integrated Multi-Modal Imaging Method for Skin Condition Inspection
Jiuai Sun, Machine Vision Lab. University of The West of England, Bristol

The complex nature of the optical reflection properties of human skin makes the task of accurately and robustly monitoring its surface (and sub-surface) characteristics a surprisingly demanding and difficult task. Traditional medical or forensic photography can only provide a single spectral mapping or three channel colour texture description of skin surface. With the new development of optical sensor techniques, we exploited and developed the synergy of a multi-modal approach combining multi-spectral and (photometric) stereo imaging technology for the analysis of skin reflection and geometrical dimension. The new approach enables the reconstruction and visualization of registered skin topographic surface and enhanced subsurface biological chromophore mappings.  This portable and affordable imaging means may find extensive applications in comprehensively documenting skin surface for reference, assessment and judgement purposes.

12.30 Microwave Breast Tumour Imaging, The Challenge of Resolution vs. Speed
Prof. A.W Preece et al. University of Bristol

A number of studies have examined the feasibility of using radiofrequency to image the human breast. It has the advantages of a non-ionising characteristic, does not require breast compression or skilled operators and is inherently 3D.

We use an ultra wide band waveform up to 10GHz to measure multiple paths across the breast in an attempt to visualize dielectric anomalies caused by cellular growth (tumours) or fluid (cysts). The signal is emitted by antennae in contact with the breast, each antenna in turn transmitting and every other antenna in turn receives the signal in a wide aperture radar technique. This has required complex switching arrangements into an automatic vector network analyzer (VNA) and off-line image processing. Clinical experiments to date have used a 16 element array arranged around a 6.5cm radius, near hemispherical, acrylic cup in close contact with the breast, followed by a 31 element array around a set of different size nested ceramic cups. These provided 120 and 465 imaging paths respectively, taking about 30 seconds and 90 seconds to complete a single scan. Two scans rotated by 10 degrees are required per breast so that the huge skin reflection can be subtracted. The clinical results have been very pleasing compared with mammography in dense tissue, but mixed – “when it worked, it worked well” giving overall about 50 – 70 % agreement with ultrasound or mammographic images. Investigation of scans with time showed in some patients a drift in the recorded microwave signal over several minutes thereby degrading performance. This may be sufficient to explain the inconsistent performance so effort has been put into dramatically improving scan times without losing resolution.

The latest scanner, just about to be put into use, has 60 antennae of new compact design giving1770 paths (which improve resolution) and a multiport VNA. With increased computer speed, and new data collection, the scan time even with the increased path number is down to 8 – 10 seconds which we hope will get around the patient changes and movement – it would even be feasible for the subject to hold their breath for this time.

Lunch

2.00 Recent Advances in Security Screening
Dr E.Morton Rapiscan Systems, Guildford

Over the past decade, there has been a considerable advance in the state-of-the-art in security screening. This talk shall focus on the latest developments in the field, exploring screening of persons, baggage, vehicles and cargo using both ionising and non-ionising radiation probes. Following a review of underlying physics, a couple of case studies shall be presented to show how the latest security screening systems are both designed and optimised. This discussion shall include a review of radiation protection measures used in such systems with some real-world examples of their application. One of the Case Studies shall focus on the design of an X-ray system to scan containerised cargo on trains using a Linear Accelerator X-ray source. X-ray images produced by such systems (see figure) provide inspection of all regions of the cargo including dense regions as well as visualisation of quite small thicknesses of low-Z materials. The Case Study shall analyse the radiation protection and control system safety measures that are intrinsic to the design of these systems.

2.30 Tomographic Imaging with Cosmic Ray Muons for Security Screening
C.Steer. S.Quillin, L.Cox. AWE, Reading Berks.

Muons are highly penetrating charged particles that form the dominant component of cosmic radiation at sea-level, with an energy-integrated flux of approximately 10,000 muons per square metre per minute. It has been demonstrated that this naturally occurring source of muons can be used to detect and image concealed and contraband nuclear materials in cluttered backgrounds and other objects that might be opaque to x-ray
imaging or passive radiation detectors. Muon Scattering Tomography works by inferring material distribution from measurements of the scattering of muons as they traverse an object. After an initial review of the technique, the progress towards a demonstrable system is reported. Particular attention is paid to the development of tomographic reconstruction methods and the processing required in order to obtain the threedimensional material information. Finally, we discuss recent results of Monte-Carlo modelling, in which high-fidelity simulations have been reconstructed, and how these results have informed our design considerations.

3.00 Latent Fingerprint Detection with Novel Fluorescent Dyes
Dr Jari Louhelainen, Dpt Biochemistry, and Molecular Biology, University of Helsinki, Finland

3.30 Investigation of Infrared Fluorescence of Fingerprint Dyes through Imaging
Rebecca Smith, John Smith, Stephen Bleay, University of Westminster and Home Office Development Branch, London

Fingerprint identification has proved to be a vital tool in the fight against crime for many years. Fingerprints are deposited on a wide range of surfaces and an equally wide range of techniques has been developed to enhance prints on different surfaces. Once developed many prints may be enhanced further utilising imaging techniques in both the visible and non visble regions of the electromagnetic specturm. This investigation looks primarily into the use of imaging in the visualisation of infra-red dyes used to enhance fingerprints developed from the Superglue development teachnique.

This study uses the near infra-red (700-1100nm) region of the spectrum using a scientific grade digital camera without an integral infra-red blocking filter. A number of samples were prepared on different materials, the samples were handled and then processed according to standard Superglue development techniques. After standard development the samples were submersed into a solution of the following dyes IR 676, IR 768, IR793, IR 820, all dissolved in ethanol.

Each sample was imaged using the IRIS system (KODAK KAF-4202 Series Camera) and lighting set up firstly using the following luminations – visual, and filtered arc lamp (Quaser 40) emitting light at 600nm, 650nm, 700nm, 750nm and 800nm central wavelengths and 50nm bandwidths. Each was then used in combination with the following Schott glass long-pass filters RG665, RG695, RG715, RG780, RG830, RG850, RG1000.
To obtain quantitative data each combination image was reviewed and graded between zero and five. In addition to visual observations, the grading scores were reviewed to show a graphical representation of the ideal illumination and filter combination for each dye.

Subsidiary investigations looked into the infra-red imaging properties of other common fingerprint development techniques. These include Physical Developer, Magnetic Powder, Superglue and the standard Basic Yellow 40 dye was also used as a control.

4.00 Examination of Drugs Transfer using TOF-SIMS
Prof M.I. Szynkowska, A. Parczewski Institute of Chemistry, Technical Univ. Lodz Poland

Surface imaging and the possibility of identification of substances on the surface make ToF-SIMS a very attractive method of solving some important problems of forensic science. It opens new perspectives for the examination of fingerprints, especially in visualization of fingermarks in various ions.

The results of our preliminary examination of fingerprints have demonstrated that the ToF-SIMS technique can be a powerful tool in chemical investigations of fingerprints left on a glass or metal surface and detection of traces of exogenic substances which do not exist in natural excretion, and have been found at the crime scene, for example gunpowder residues or arsenic. It suggests the possibility of relating the fingerprint residues revealed in ToF-SIMS analysis to other evidence found at the crime scene.

In the present work, special attention is paid to the application of ToF-SIMS in chemical investigations of fingerprints and detection of traces of drugs (e.g. amphetamine – AF, methamphetamine – MA, methylenedioxymethamphetamine – MDMA; ecstasy). This domain of study is very important and can lead to new developments in dactyloscopy, especially if dermatoglyphics can be identified simultaneously with detection of traces of exogenic chemical substances left on fingerprints which are important from the point of view of the investigation process.

TOF-SIMS mass spectra and images of ions were obtained on secondary ion mass spectrometer TOF-SIMS IV, (ION-TOF GmbH, Germany). The analysis was carried out using gallium and bismuth cluster gun working at 25 keV. In the case of insulators, flood gun was used to compensate the surface charging.

Experimental work was carried out using different kinds of bases (aluminium, stainless steel, brass, copper, glass, paper) on which fingerprints were imprinted. The results indicate that even if crime residues have been thoroughly removed from one’s hands, some pollutants still remain on one’s fingers and they are noticeable for ToF-SIMS analysis.

ToF-SIMS imaging is also expected to be very useful in solving other problems of forensic science, e.g. fingermark deposits transfer, fingermark aging processes, gunshot residues or fibers examination.

4.30 New Developments in Infrared Thermal Imaging Systems
Prof. Roderick Thomas, Swansea Metropolitan University, Swansea and TWI (Wales), Port Talbot

5.00 Close