The establishment of a 3D breast photography service in medical illustration.

This paper aims to describe the development of a 3D breast photography service managed by the Medical Illustration Department, in the Belfast Health and Social Care Trust, Northern Ireland. Dedicated 3D breast photography equipment was installed in Medical Illustration for 18 months. Women were referred for a variety of indications including pre- and post-surgical assessment. A dedicated 3D breast photography protocol was developed locally and this requires further refinement to allow reproducibility in other centres. There are image/data artefacts associated with this technology and special techniques are required to reduce these. Specialist software is necessary for clinicians and scientists to use 3D breast photography data in surgical planning and measurement of surgical outcome.

Variation in radiographic protocols in paediatric interventional cardiology.

The aim of this work is to determine current radiographic protocols in paediatric interventional cardiology (IC) in the UK and Ireland. To do this we investigated which imaging parameters/protocols are commonly used in IC in different hospitals, to identify if a standard technique is used and illustrate any variation in practice. A questionnaire was sent to all hospitals in the UK and Ireland which perform paediatric IC to obtain information on techniques used in each clinical department and on the range of clinical examinations performed. Ethical and research governance approval was sought from the Office for Research Ethics Committees Northern Ireland and the individual trusts. A response rate of 79% was achieved, and a wide variation in technique was found between hospitals. The main differences in technique involved variations in the use of an anti-scatter grid and the use of additional filtration to the radiation beam, frame rates for digital acquisition and pre-programmed projections/paediatric specific programming in the equipment. We conclude that there is no standard protocol for carrying out paediatric IC in the UK or Ireland. Each hospital carries out the IC procedure according to its own local protocols resulting in a wide variation in radiation dose.

Validation of a passive stereophotogrammetry system for imaging of the breast: a geometric analysis.

The overall aim of this study was to assess the accuracy, reproducibility and stability of a high resolution passive stereophotogrammetry system to image a female mannequin torso, to validate measurements made on the textured virtual surface compared with those obtained using manual techniques and to develop an approach to make objective measurements of the female breast. 3D surface imaging was carried out on a textured female torso and measurements made in accordance with the system of mammometrics. Linear errors in measurements were less than 0.5mm, system calibration produced errors of less than 1.0mm over 94% over the surface and intra-rater reliability measured by ICC=0.999. The mean difference between manual and digital curved surface distances was 1.36 mm with maximum and minimum differences of 3.15 mm and 0.02 mm, respectively. The stereophotogrammetry system has been demonstrated to perform accurately and reliably with specific reference to breast assessment.

Temperature elevation during simulated polymethylmethacrylate (PMMA) cranioplasty in a cadaver model.

The aims of this study were to: (i) obtain temperature measurements during in vitro polymerisation of polymethylmethacrylate (PMMA) disks of a range of thicknesses; and (ii) obtain tissue temperature measurements at various locations within a skull defect during a simulated PMMA cranioplasty procedure using a cadaver. In vitro, higher temperatures were recorded with increasing PMMA thickness. During the simulated cranioplasty, the maximum temperature was observed inside the PMMA sample, with nearby tissues being exposed to temperatures of greater than 50 degrees C over prolonged periods. There is conflicting information in the literature concerning the sensitivity of brain tissue and bone to elevated temperatures. Preoperatively fabricated PMMA cranioplasty prostheses are recommended.

Algorithms for digital image processing in diabetic retinopathy.

This work examined recent literature on digital image processing in the field of diabetic retinopathy. Algorithms were categorized into 5 steps (preprocessing; localization and segmentation of the optic disk; segmentation of the retinal vasculature; localization of the macula and fovea; localization and segmentation of retinopathy). The variety of outcome measures, use of a gold standard or ground truth, data sample sizes and the use of image databases is discussed. It is intended that our classification of algorithms into a small number of categories, definition of terms and discussion of evolving techniques will provide guidance to algorithm designers for diabetic retinopathy.

Technical validation of the Di3D stereophotogrammetry surface imaging system.

The purpose of this work was to assess the technical performance of a three-dimensional surface imaging system for geometric accuracy and maximum field of view. The system was designed for stereophotogrammetry capture of digital images from three-dimensional surfaces of the head, face, and neck. A mannequin head was prepared for imaging by adding texture in the form of red paint, and facial landmarks as black ink dots. The mannequin was imaged at the manufacturer's recommended settings for human studies. Colour-coded surface difference images among repeated exposures were computed. We compared measurements of physical linear distance with digital measurements. The three-dimensional stereophotogrammetry system had a mean error in the three-dimensional surfaces of 0.057mm, a repeatability error (variance) of 0.0016mm, a mean error of 0.6mm in linear measurements compared with manual measurements, and a field of view of 170 degrees horizontally and 102 degrees vertically.

Patient dose from 3D rotational neurovascular studies.

The use of image-guided interventional radiological techniques is increasing in prevalence and complexity. Imaging system developments have helped improve the information available to interventionalists to plan and guide procedures. Information on doses to patients resulting from alternative imaging techniques or protocols is useful for both the process of justifying particular procedures and in optimizing the resultant exposures. Such information is not always available, especially for new or developing imaging techniques. We have undertaken a study of doses to patients associated with two alternative imaging methods for pre-intervention assessment of intracranial aneurysms. In the first technique the aneurysm is assessed from a series of digital subtraction angiography (DSA) runs taken at different imaging projections. The second technique involved acquiring images from one single image run while the imaging system rotated 180 degrees around the patient's head. In this technique, the aneurysm was then evaluated from a 3D reconstruction of the projection images. Effective doses were calculated using a computer model to simulate the exposure geometry and parameters. The mean dose from the DSA protocol used at our centre was 3.4 mSv and from the 3D rotational angiography (RA) technique was 0.20 mSv.

3D surface accuracy of CAD generated skull defect contour.

The creation of a satisfactory cosmetic outcome in the repair of cranial defects relies on manual skill. However, computer aided design is gaining acceptance in the creation of custom cranial implants. The purpose of this work is to demonstrate the accuracy of a CAD generated skull defect contours using 3D difference maps. 3D multi-slice CT scanning was carried out on a life size plastic skull. Surface models were generated of the original skull and of temporofrontal and parietal defects. Surface contours were interpolated towards the centre of the defect from the edges where it was blended. The CAD contour deviation ranged from 0.0 mm to 2.0 mm with 80% of the total defect area less than 0.66 mm as measured by difference maps. CAD techniques can be used to produce contours for the repair of cranial defects with minimum deviation from the original skull contour. This enables accurate design and production of cranial implants.

"Virtual unwrapping" of a mummified hand.

The purpose of this work is to demonstrate the feasibility of medical virtual reality technologies in the investigation of a mummified hand. The Ulster Museum obtained the mummy hand, which originated from Thebes, without any identifying information. The mummified hand was investigated using conventional X-ray and 3D multi-slice Computed Tomography (CT). Imaging revealed a range of fractures of the wrist, metacarpals and phalanges whilst 3D CT demonstrated internal structures using volume rendering. The absence of any features of bone healing at the fracture sites would imply that they occurred just prior to death or in the mummified state possibly during excavation. Conventional X-ray imaging indicated that the hand, although small, was likely to have originated from an adult. Medical imaging and virtual reality display will enable us to produce a rapid prototyped model using fused deposition technology. Therefore, further paleopathological research can be performed on the replica without the need to handle the original specimen.

CT virtual intravascular endoscopy of abdominal aortic aneurysms treated with suprarenal endovascular stent grafting.

BACKGROUND: We investigated the clinical applications of virtual intravascular endoscopy (VIE) in patients with abdominal aortic aneurysms (AAA) treated by endovascular stent grafting with a suprarenal component. METHODS: Thirty-four patients with AAA undergoing endovascular stent grafting were included in the study (28 male, six female; mean age = 76 years). Helical computed tomography (CT) scanning was performed within 1 week after stent graft implantation. All patients received a Zenith/AAA endovascular graft with uncovered suprarenal struts 2.5 cm long placed around the level of the renal arteries. VIE images were created for each patient. The follow-up periods ranged from 3 to 18 months (mean = 8.3 +/- 3.7 months). RESULTS: Three of 34 celiac arteries, 22 of 34 superior mesenteric arteries, 32 of 34 right renal arteries, and 30 of 35 left renal arteries were affected by the suprarenal stent struts (wires) to different extents. VIE was able to demonstrate the struts, arterial ostia, and the strut/ostia configuration. Follow-up CT showed that all of these aortic branches were patent. CONCLUSION: Our preliminary experience has demonstrated that VIE is a novel imaging technique to visualize the three-dimensional intralumenal relationship of the aortic stent struts to the arterial ostia in patients with AAA after suprarenal stent graft placement.

Abdominal aortic aneurysm and stent graft phantom manufactured by medical rapid prototyping.

A novel human aorta phantom built by medical rapid prototypingfor use in computed tomography (CT) scanning is described. The phantom contained a stent graft that was deployed internally to mimic a repaired aortic aneurysm. The phantom was produced to allow assessment of the CT appearance of a stent graft inside an aorta using the new virtual intravascular endoscopy image presentation technique. The stent graft utilized contained suprarenal components (metalfixation struts), and these were placed with these struts covering the renal artery ostia. The phantom was filled with iodinated contrast medium at a concentration that produced a density similar to that found in normal CT angiographic scanning. The model was scanned at a variety of slice thicknesses, pitch and image reconstruction intervals. Visualization of the stent suprarenal components in relation to the renal artery ostia is shown and the overestimation of stent wire strut diameter demonstrated.

Assessment of distortion in a three-dimensional rotational angiography system.

The purpose of this project was to determine the degree of geometrical distortion in a three-dimensional (3D) image volume generated by a digital fluorography system with rotational image acquisition capabilities. 3D imaging is a valuable adjunct in neuroangiography for visualization and measurement of cerebral aneurysms and for determination of the optimum projection for intervention. To enable spatially accurate 3D reconstruction the system must correct for geometrical distortion in the image intensifier television system as well as for deviations in gantry motion. 3D volumes were reconstructed from 100 X-ray projections acquired over a 180 degrees arc over a period of 8 s. A phantom was constructed to assess geometrical distortion in the three dimensions. The phantom consisted of 1 mm diameter ball bearings embedded in Perspex in a cubic lattice configuration. The ball bearings were placed at 20 mm intervals over a 140 mm cubic volume. Distortion was assessed by taking measurements between points of known separation and using a differential distortion measurement. The maximum error in the 3D location of objects was found to be 1.4 mm, while the differential distortion was found to range from -1.0% to +2.3%. The 3D images were found to have negligible visual distortion, enabling subjective assessments to be made with confidence to aid intervention.