Wendy Tindale

Correlation of left ventricular count rate with patient weight in Tc-99m myocardial perfusion imaging.

ObjectivesThe aim of this retrospective investigation wasto devise a protocol for obtaining consistent myocardial counts for patients attending myocardial perfusion imaging. MethodsA total of 229 patients were included in the study sample. For each rest single-photon emission computed tomography data set, a three-dimensional ellipse was manually defined to isolate the left ventricle. The count rate per voxel was measured from a threshold region of interest covering the normally perfused myocardium (70–100% ofmaximum counts). Data were normalized for net administered activity and plotted against patient weight. The correlation between the variables was used to derive aprotocol for adjusting injected activity or scan time to obtain consistent counts from patient to patient. ResultsThere was a significant correlation between counts per second per voxel per MBq and patient weight. The best fit was achieved with an inverse model. A correlation equation was derived for patients weighing more than 60 kg (combined R=0.79): [CPS/voxel/MBq=(0.0163/weight(kg)]−3.68×10−5+A in which A, a sex-dependent constant, was 0 for men and −2.920×10−5 for women. ConclusionThere was a significant inverse correlation between patient weight and CPS per voxel per MBq.

Using a registration-based motion correction algorithm to correct for respiratory motion during myocardial perfusion imaging.

Objective The aim of the study was to develop and evaluate a registration-based motion correction algorithm as a method of reducing respiratory motion artefacts in myocardial perfusion imaging. Materials and methods The NCAT software was used to build nine male and nine female computer simulations of myocardial perfusion imaging data, with different respiratory motions and left ventricular ejection fractions. Imaging data were generated at various time points throughout each cardiac cycle. The data were summed over each cardiac cycle, forward projected, normalized, noise added and reconstructed with and without motion correction. Motion correction was performed using an algorithm that aligns images within a projection using nonlinear registrations. A standard simulation with no respiratory motion was also generated for comparison. The algorithm was applied to the standard to determine its effect on images with no respiratory motion. Results The median difference in mean segmental counts compared with the standard was calculated for each simulation. The mean (range) of these values was 3% (1–6%), 14% (12–16%) and 28% (28–29%) for displacements of 1, 2 and 3 cm, respectively. The largest changes occurred inferiorly and anteriorly. Motion correction reduced these differences to 2% (0–4%), 5% (2–7%) and 7% (7–7%), respectively. The process of correcting for motion reduced the mean counts in all segments by 3% (1–5%). Conclusion Artefacts resulting from respiratory motion are improved using our algorithm when motion is 2 cm or greater.

99mTc white-cell imaging in inflammatory bowel disease: a comparison of planar versus SPECT.

Objective 99mTc-labelled white-cell scintigraphy is sensitive and specific for detecting inflammatory bowel disease (IBD). A retrospective analysis was carried out on 99 consecutive studies to compare results from planar imaging and single photon emission computed tomography (SPECT). Materials and methodsTwo observers blindly and independently reported all planar images followed by the SPECTs. Both sets of scans were reported in random order. All possible abnormalities were assigned a confidence rating and specific, preagreed bowel location and their extent measured. ResultsThe observers disagreed on whether studies were normal in 17 of 99 planar scans (&kgr;=0.56) but only eight of 99 SPECTs (&kgr;=0.83). Consensus reporting, where there was disagreement between observers, yielded the following results: planar and SPECT normal in 56 of 99 cases; planar and SPECT positive in 29 of 99 cases; planar normal but SPECT positive in 13 of 99 cases; planar positive but SPECT normal in one of 99 cases. In the 14 of 99 cases where there was discordance between planar and SPECT, confirmation of active IBD was sought from other investigations (e.g. histology). Relevant other investigations were available in eight of these discordant cases and showed agreement with the SPECT result in seven of eight patients.Where the same abnormalities were identified in both planar and SPECT, there was a significant increase (P<0.001 mean: 57mm) in the extent of abnormalities as measured from SPECT compared with planar. ConclusionReporting from SPECT improves inter-operator variability and appears to improve sensitivity for detecting IBD. Planar imaging also appears to underestimate the extent of active disease

Unmet needs: relevance to medical technology innovation?

Abstract This paper describes and discusses the role of unmet needs in the innovation of new medical technologies using the National Institute for Health Research Devices for Dignity (D4D) Healthcare Technology Co-operative as a case study. It defines an unmet need, providing a spectrum of classification and discusses the benefits and the challenges of identifying unmet need and its influence on the innovation process. The process by which D4D has captured and utilized unmet needs to drive technology innovation is discussed and examples given. It concludes by arguing that, despite the challenges, defining and reviewing unmet need is a fundamental factor in the success of medical technology innovation.

Healthcare technology co-operatives: Innovative about innovation

Abstract The paper provides an introduction to the National Institute for Health Research Devices for Dignity Healthcare Technology Co-operative. Embedded within the NHS, Devices for Dignity identifies areas of unmet clinical need and translates these into research and development projects to develop new medical technologies. It addresses the needs of people living with long-term conditions, helping them to live more dignified and independent lives. Through partnerships with patients, universities, the NHS and industry, Devices for Dignity has developed an innovation methodology for successful medical technology innovation.

Implications of the UK NHS consent policy for nuclear medicine practice

To comply with government policy on consent, the Sheffield Teaching Hospitals (STH) National Health Service (NHS) Trust introduced a new consent policy in February 2002. Verbal or written consent (depending on the level of risk) must be obtained prior to each study. The patient must be fully informed and given time to reach a decision. Consideration needs to be given to the following: to whom, when and how to provide such information and obtain consent. Each study type and patient circumstance needs to be classified according to risk. Consideration of the risks resulted in a local policy in which written consent is required for the following: therapeutic procedures, studies on pregnant women, studies in which pregnancy needs to be avoided, research procedures, cardiac stress for myocardial perfusion scintigraphy and intrathecal administration. Patient information leaflets have been updated with new information about the study and any risks. Information is now available for both patients and hospital staff. Compliance with the consent policy in a service department provides logistic challenges, but it is possible to fully inform patients in advance about their treatment, allowing them to give informed consent.

26 Correction for respiratory motion in myocardial perfusion images using a registration based correction algorithm (RBCA)

Aim To model respiratory motion during myocardial perfusion imaging and evaluate a RBCA. Method The NCATsoftware phantom was used to build 6 models, each with different degrees of diaphragmatic and thoracic motion. These were gated into 20 bins, each representing one cardiac cycle. At each acquisition angle, motion correction was performed by registering the 20 projection images to a summed image. Reconstructed images of the heart, with and without motion correction, were divided into 17 segments. For each segment the percentage difference in the maximum and mean counts from a baseline image without respiratory motion were calculated. Results Artefacts were not visible for diaphragmatic displacements of 1 cm but were visible for 2 cm and 3 cm displacements. The most obvious artefact occurred in the inferior-basal wall. For images with motion, the differences in maximum counts from the baseline were: median (range), 5% ( – 3–16%), 17% (0–39%), 29% (8–48%), for diaphragmatic displacements of 1 cm, 2 cm and 3 cm respectively. Motion correction visibly improved artefacts and reduced the difference in counts to 3% (– 8–10%), 5% ( – 1–15%), 10% (2–16%) respectively. Conclusion Inferior-basal artefacts are introduced when the diaphragmatic displacement is Z 2 cm. These artefacts can be reduced using a RBCA.