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Low-dose X-ray Imaging

Principal Investigator: Tania Douglas

Collaborator: Lodox Systems, Funding: NRF/THRIP, Lodox Systems

The MRC/UCT Medical Imaging Research Unit has assisted with the development, testing and commissioning of a low-dose diagnostic x-ray imaging system for trauma applications, an adaptation of a device originally developed by De Beers. We are investigating further medical applications of this system (Statscan, Lodox Systems), which has been installed at Groote Schuur Hospital, Red Cross Children’s Hospital, at MIRU and at several other locations in South Africa and abroad. Current research includes: (1) investigating the advantages of Statscan in paediatric imaging; (2) detecting tuberculosis in Statscan images of the chest; (3) exploring the use of Statscan in forensics; (4) reducing radiation dose while maintaining image quality. Research assistantships for MSc and PhD degrees, as well as postdoctoral fellowships, are available.

Filtration to Reduce Paediatric Dose

We have developed a software tool to model the effects of changing imaging parameters on patient dose. This tool has enabled us to develop a new filtration technique for paediatric imaging on the Lodox Statscan, which reduces effective radiation dose for paediatric patients by 27% on average, while maintaining image quality. The lowered dose is especially significant for children, as the risks associated with ionizing radiation are higher in paediatric than in adult radiology. The filtration method will be implemented in future Lodox scanners, and the modelling software may be used to optimise imaging parameters for a range of applications.

3D Reconstruction of Landmarks for Orthopaedic Measurement

The aim is to determine true patient dimensions from planar X-ray images. It is not possible to measure true distances in 3D objects that are imaged in 2D unless the distance to be measured is co-planar with the detector. In addition, the shape of the X-ray beam may distort the X-ray image. It is possible to reconstruct true geometry from two images of the same object, taken from different vantage points, using stereo-photogrammetry and image disparity. A method has been implemented to measure femoral neck anteversion for orthopaedic surgery planning; the software developed will be adapted for other applications requiring bone measurement.

Optimising Imaging Parameters for Forensic Applications

The Lodox Statscan is increasingly being installed in forensic pathology laboratories, which necessitates an adaptation of the scanning parameters, for example for decomposing bodies and individual organs. We are using modeling software and predict the optimal parameters to ensure high image quality, and validating the parameters through by scanning cadavers and organs.

Simulation of a Slot Scanning System

We are developing a novel way of simulating slot scanning X-ray systems using the general-purpose Monte Carlo simulation package PENELOPE and penEasy Imaging. Different phantoms can be defined with the help of the PENGEOM package, which defines bodies as combinations of volumes limited by quadric surfaces. The simulator may be used to design new imaging systems or modifications of existing ones.

Computer Aided Diagnosis for Tuberculosis Detection

We have explored methods to classify chest X-ray images of children with suspected TB as normal or containing pathology. Two approaches have been taken: statistical shape analysis, to detect changes in airway shape and size that may be indicative of TB; and identification of diseased lung tissue using pattern recognition techniques. We have shown that texture-based pattern analysis of airways could successfully be used to classify lung pathology in chest X-ray images from the Lodox Statscan. Shape-based classification algorithms were however unable to distinguish between suspected TB-infected and healthy airways, although visual inspection suggested that suspected TB-infected airways were more irregular in shape than healthy ones. We are exploring further research directions in collaboration with University College London, in particular the use of 3D airway shape models derived from computed tomography to define the range of normal shapes whose projections can be used for comparison with chest X-ray images of suspected TB cases.

Journal Publications

  • Beningfield SJ, Potgieter JH, Bautz P, Shackleton M, Hering E, de Jager G et al. “Evaluation of a new type of direct digital radiography machine”, South African Medical Journal 89:1182-88, 1999.
  • Beningfield SJ, Potgieter H, Nicol A, van As S, Bowie G, Hering E. “Report on a new type of trauma fullbody digital x-ray machine”, Emergency Radiology 10:29, 2003.
  • Douglas TS, Vaughan CL, Wynne SM. “Three-dimensional point localisation in low-dose x-ray images using stereo-photogrammetry”, Medical & Biological Engineering & Computing, 42(1):37-43, 2004.
  • Marchal JP. “Extension of x-ray imaging linear systems analysis to detectors with energy discrimination capability” Medical Physics 32(8):2717-2728 2005.
  • Marchal J, Hussein K, John LR, Vaughan CL. “Photon counting threshold optimization in mammography” Nuclear Instruments & Methods in Physics Research Section A – Accelerators Spectrometers Detectors and Associated Equipment 563(1):137-141 2006.
  • van As AB, Douglas TS, Kilborn T, Pitcher R, Rode H. “Multiple injuries diagnosed by full body digital x-ray”. Journal of Pediatric Surgery, 41(7):e25-e28, 2006.
  • Koning L, Douglas TS, Pitcher R, van As AB. “Short emergency department length of stay attributed to full body digital radiography: a review of 3 paediatric cases”. South African Medical Journal, 96(7): 613-614, 2006.
  • Vaughan CL. “Digital X-rays come of age”. South African Medical Journal, 96(7): 610-612, 2006.
  • Douglas TS, Sanders V, Machers S, Pitcher R, van As AB. “Digital radiographic measurement of the atlantodental interval in children”. Journal of Pediatric Orthopaedics, 27(1):23-26, 2007.
  • Maree GJ, Irving BJ, Hering ER. “Pediatric dose measurement in a full body digital X-ray machine”, Pediatric Radiology, 37(10):990-7, 2007.
  • Pitcher RD, van As AB, Sanders V, Douglas TS, Wieselthaler N, Vlok A, Paverd S, Kilborn T, Rode H, Potgieter H, Beningfield S. “A Pilot Study Evaluating the Statscan Digital X-ray Machine in Paediatric Polytrauma”, Emergency Radiology, 15(1):35-42, 2008.
  • Douglas TS, Sanders V, Pitcher R, van As AB. “Early detection of fractures with low-dose digital x-ray images in a pediatric trauma unit”, Journal of Trauma Injury, Infection, and Critical Care, 65(1):E4-7, 2008.
  • Irving BJ, Maree GJ, Hering ER, Douglas TS.  “Radiation dose from a linear slit scanning X-ray machine with full body imaging capabilities”, Radiation Protection Dosimetry, 130(4):482-489, 130(4):482-489, 2008.
  • Pitcher RD, Wilde JCH, Douglas TS, van As AB. “The use of the STATSCAN digital X-ray unit in paediatric polytrauma – a review”, Pediatric Radiology, 39(5):433-437, 2009.
  • Hussein K, Vaughan CL, Douglas TS. “Modeling, validation and application of a mathematical tissue-equivalent breast phantom for digital mammography”, Physics in Medicine and Biology, 54, 1533-1553, 2009.
  • Sanders VM, Pitcher RD, Douglas TS, Kibel MA, van As AB. “Digital radiographic measurement of the pediatric main bronchi – a pilot study”, Annals of Tropical Paediatrics, 29:209-216, 2009.
  • Daya RB, Kibel MA, Pitcher RD, Workman L, Sanders V, Douglas TS. “A pilot study evaluating the STATSCAN® digital x-ray machine in paediatric chest radiography”. South African Journal of Radiology, 13(4):80-85, 2009.
  • Douglas TS, Pitcher RD, van As AB. Full-body digital radiographic imaging of the injured child. Continuing Medical Education Theme issue: “What’s new in Paediatric Trauma?” 28(3):108-112, 2010.
  • Mouton A, Douglas TS. Computer-aided diagnosis in chest radiography. Continuing Medical Education Theme issue: “Biomedical Engineering and Medical Imaging”, 29(3): 127-128, 2011.
  • Douglas TS, Gresak LK, Koen N, Fenton-Muir M, van As AB, Pitcher RD. Measurement of prevertebral cervical soft tissue in lateral digital radiographs. Journal of Pediatric Orthopaedics, 32(3):249:252, 2012.
  • Douglas TS, Fenton-Muir N, Kewana K, Ngema Y, Liebenberg L. Radiological findings in cases of sudden unexpected death in infants at the Salt River Forensic Pathology Laboratory. South African Journal of Radiology, February:4-6, 2012.
  • Whiley SP, Mantokoudis G, Ott D, Zimmerman H, Exadaktylos AK. A Review of Full-Body Radiography in Nontraumatic Emergency Medicine. Emergency Medicine International, Article ID 108129, 2012.
  • Stull KE, L’Abbé EN, Steiner S. Measuring Distortion of Skeletal Elements in Lodox Scatscan-Generated Images. Clinical Anatomy, 26(6):780:786, 2013.
  • Dendere R, Whiley SP, Douglas TS. Computed Digital Absorptiometry for Measurement of Phalangeal Bone Mineral Mass on a Slot-scanning Digital Radiography System, Osteoporosis International, 2014 doi:10.1007/s00198-014-2792-4 [full-text]
  • Chimhundu C, Smit J, Sivarasu S, Douglas TS. 2014. Inter-landmark measurements from Lodox Statscan images. Journal of Medical Devices-Transactions of the ASME, doi: 10.1115/1.4027102 [full-text]
  • Perks TD, Dendere, R, Irving B, Hartley T, Lawson A, Scholtz, P, Trauernicht C, Steiner S, Douglas TS. Filtration to reduce paediatric dose for a linear slot scanning digital X-ray machine. Radiation Protection Dosimetry, DOI:10.1093/rpd/ncu339.
  • Chimhundu C, Smit J, Sivarasu S, Douglas, TS. Femoral neck anteversion measurement using x-ray stereophotogrammetry. Medical Engineering & Physics 2016 DOI:10.1016/j.medengphy.2015.11.017.
  • Kulkarni M, Dendere R, Nicolls F, Steiner S, Douglas TS. Monte-Carlo simulation of a slot-scanning X-ray imaging system. Physica Medica 2016 DOI:10.1016/j.ejmp.2015.12.003.

Conference proceedings

  • Lease A, Vaughan CL, Beningfield SJ, Potgieter JH, Booysen A  “Feasibility of using Lodox technology for mammography”, Proc. SPIE 4682:656-664, Medical Imaging: Physics of Medical Imaging; LE Antonuk & MJ Yaffe; Ed. 2002.
  • Scheelke M, Potgieter JH, de Villiers M “System characterization of the STATSCAN full body slit scanning radiography machine: theory and experiment”, Proc. SPIE 5745:1179-1190, Medical Imaging 2005: Physics of Medical Imaging; Michael J. Flynn; Ed. 2005.
  • Potgieter JH, de Villiers M, Scheelke M, de Jager G. “An explanation for the extremely low, but variable, radiation dosages measured in a linear slit scanning radiography system”, Proc. SPIE 5745: 1138-1145, Medical Imaging 2005: Physics of Medical Imaging; Michael J. Flynn; Ed. 2005.
  • Long M, Mouton A, Douglas TS. Landmark location in x-ray images using active appearance models. Proceedings of the IFMBE World Congress on Medical Physics and Biomedical Engineering 25/IV, Munich, pp. 1764–1767, September 2009.
  • Mouton A, Pitcher RD, Douglas TS. Computer-aided detection of pulmonary pathology in pediatric chest radiographs. Proceedings, Medical Image Computing and Computer-Assisted Intervention, T. Jiang et al. (Eds.): MICCAI 2010, Part III, LNCS 6363, pp. 620–626. Springer, Heidelberg, 2010.
  • Tezoo T, Douglas TS. Interactive Segmentation of Airways from Chest X-ray Images using Active Shape Models. Proceedings of the 32nd Annual International Conference of the IEEE Engineering in Medicine and Biology Society, San Diego, pp. 1498-1501, August 2012.
  • Perks TD, Trauernicht C, Hartley T, Hobson C, Lawson A, Scholtz P, Dendere R, Steiner S, and Douglas TS. Effect of aluminium filtration on dose and image quality in paediatric slot-scanning radiography. Proceedings of the 33rd Annual International Conference of the IEEE Engineering in Medicine and Biology Society, Osaka 2013.
  • Dendere R, Kabelitz G, Douglas TS. Model-based segmentation of the middle phalanx in digital radiographic images of the hand. Proceedings of the 33rd Annual International Conference of the IEEE Engineering in Medicine and Biology Society, Osaka 2013.
  • Irving B, Douglas T, Taylor P. 2D X-ray airway tree segmentation by 3D deformable model projection and registration. 5th International Workshop on Pulmonary Image Analysis, Nagoya 2013.

Completed student projects

  • Flash G. Feasibility of using an industrial robot with the LODOX technology, MSc 2002
  • Lease A. Feasibility of using LODOX technology for mammography, MPhil 2003
  • van den Berg M. Use of LODOX for digital subtraction angiography, MSc 2003
  • Scheelke M. System characterization of a full body slit scanning radiography machine: theory and experiment, MSc 2006
  • Wynne S. Localising discrete points in 3D space using stereo pairs of digital slot-scanning x-rays, MSc 2007
  • Irving B. Radiation dose measurement and prediction for linear slit scanning radiography, MSc 2008
  • Long M. Segmentation of body regions and airways in full-body digital paediatric x-ray images, MSc 2008
  • Hussein K. Computer models for the design and optimization of a linear slot scanning mammography system, PhD 2009
  • Mouton A. Computer-aided diagnosis of tuberculosis in paediatric chest x-rays using local textural analysis, MSc 2009
  • Bolton F. Automated 3D reconstruction of Lodox Statscan images for forensic application, MSc 2011
  • Kulkarni R. Locating regions of interest prior to X-ray imaging using stereo-photogrammetry, MSc 2011
  • Dixon T-L. Implementation and evaluation of a bony structure suppression software tool for chest X-ray imaging, MSc 2012
  • Tezoo T. Airway delineation in slot-scanning chest radiographs, MSc 2013
  • Esmail M. Towards improving the Statscan X-ray image quality through sliding mode control of the C-arm, MSc 2013
  • Chimhundu C. Interlandmark measurements from Lodox Statscan images with application to femoral neck anteversion assessment, MSc 2014
  • Perks, T. Reducing Radiation Dose for a Linear Slot Scanning Digital X-ray Machine using a Filtration Technique, MSc 2014