Fit for purpose? A cross-sectional study to evaluate the acceptability and usability of HeadUp, a novel neck support collar for neurological neck weakness

The HeadUp collar (previously known as the Sheffield Support Snood) provides support for neck weakness caused by amyotrophic lateral sclerosis (ALS) and has shown to be superior to alternative options in a small cohort of patients from one single center. Here we report the assessment of the HeadUp collar in a larger cohort of patients, exploring the use in other neurological conditions and expanding to other centers across the UK and Ireland. An interventional cross-sectional study design was implemented to investigate the usability and acceptability of the HeadUp collar. A total of 139 patients were recruited for the study, 117 patients had a diagnosis of ALS and 22 patients presented with neck weakness due to other neurological conditions. Participants were assessed at baseline, fitted a HeadUp collar and followed-up one month later. The performance of the HeadUp collar was rated favorably compared to previously worn collars in terms of the ability to eat, drink and swallow. Findings suggest that the collar also permitted a more acceptable range of head movements whilst maintaining a good level of support. We conclude that the HeadUp collar is a suitable option for patients with neck weakness due to ALS and other neurological conditions.

A study to quantify the effect of patient motion and develop methods to detect and correct for motion during myocardial perfusion imaging on a CZT solid-state dedicated cardiac camera

BACKGROUND

Due to differences in the design and acquisition parameters on the solid-state CZT cardiac camera the effect of patient motion may vary compared to Anger cameras. This study evaluates the effect of motion, two new methods of three-dimensional (3D) motion detection and a method of motion correction.

METHOD

Phantom acquisitions were offset in the X, Y, and Z directions and combined to simulate different types of motion. Motion artifacts were identified using the total perfusion defect and blinded visual interpretation. Motion was detected by registering planar and reconstructed 30 second images, and corrected by summing the aligned reconstructed images. Validation was performed on phantom data. These techniques were then applied to 40 patient studies.

RESULTS

Motion ≥10 mm and ≥60 seconds in duration introduced significant artifacts. There was no significant difference (P = .258) between the two methods of motion detection. Motion correction removed artifacts from 9/10 phantom simulations. Superior-inferior motion ≥8 mm was measured on 10% of patient studies, and 5% were affected by motion. Motion in the lateral and anterior-posterior directions was <8 mm.

CONCLUSION

Superior-inferior patient motion artifacts have been identified on myocardial perfusion images acquired on a CZT camera. Routine QC to identify studies with significant motion is recommended.

Healthcare technology co-operatives: Innovative about innovation

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.

Development of two electronic bladder diaries: a patient and healthcare professionals pilot study

AIMS

Assess patients' preferences in a pilot crossover study of two different electronic voiding diaries against a standard paper diary. Assess urological health professional (HP) opinions on the electronic bladder diary reporting system.

METHODS

Two different electronic diaries were developed: (1) electronically read diary-a card with predefined slots read by a card reader and (2) e-diary-a handheld touch screen device. Data uploaded from either electronic diary produced an electronic report. We recruited 22 patients split into two cohorts for each electronic diary, 11 completed each type of electronic diary for 3 days either preceded or followed by a standard paper diary for 3 days. Both diaries were completed on the 7th day. Patients' perceptions of both diaries were recorded using a standardized questionnaire. A HP study recruited 22 urologists who were given the paper diary and the electronic reports. Time taken for analysis was recorded along with accuracy and HP preferences.

RESULTS

The majority of patients (82%) preferred the e-diary and only 1/11 found it difficult to use. Patients had the same preference for the electronically read diary as the paper diary. The paper diary took 66% longer to analyze than the electronic report (P < 0.001) and was analyzed with an accuracy of 58% compared to 100%. Slightly more HP (9%) preferred the electronic report to the paper diary.

CONCLUSIONS

This proposed e-diary with its intuitive interface has overcome previous deficiencies in electronic diaries with most patients finding the format user-friendly. Electronic reports make analysis and interpretation by HP quicker and more accurate.

PET scan in clinically suspected paraneoplastic neurological syndromes: a 6-year prospective study in a regional neuroscience unit

BACKGROUND

The role of PET in the diagnosis of paraneoplastic neurological syndromes (PNS) has previously been reported in retrospective studies, from specialized neuro-oncology units, often selecting patients with positive paraneoplastic antibodies.

OBJECTIVES

To prospectively assess the usefulness of PET in detecting malignancy in patients clinically suspected of having PNS.

METHODS

PET was performed in patients suspected of PNS within 4 weeks of the normal CT body scan. All patients were followed up.

RESULTS

Eighty patients suspected of having PNS underwent PET. 18/80 (23%) were abnormal and suspicious of malignancy. The total number of definite and probable PNS with abnormal PET was 11/18 (61%). The total number of definite and probable PNS with a normal PET was 3/62 (5%). Only 50% of patients with biopsy-proven malignancy were positive for paraneoplastic antibodies. The prevalence of abnormal PET in patients presenting with classical PNS was 41% as opposed to 21% in patients with non-classical PNS. The sensitivity and specificity of PET in diagnosing PNS was 75% and 87% respectively.

CONCLUSIONS

PET is a valuable tool in clinically suspected PNS. Its use should not be restricted to specialized neuro-oncology units or in patients with positive paraneoplastic antibodies. Positive yield is the highest amongst patients with classical PNS.

Nonrigid image registration for head and neck cancer radiotherapy treatment planning with PET/CT

Purpose: Head and neck radiotherapy planning with positron emission tomography/computed tomography (PET/CT) requires the images to be reliably registered with treatment planning CT. Acquiring PET/CT in treatment position is problematic, and in practice for some patients it may be beneficial to use diagnostic PET/CT for radiotherapy planning. Therefore, the aim of this study was first to quantify the image registration accuracy of PET/CT to radiotherapy CT and, second, to assess whether PET/CT acquired in diagnostic position can be registered to planning CT.

Methods and Materials: Positron emission tomography/CT acquired in diagnostic and treatment position for five patients with head and neck cancer was registered to radiotherapy planning CT using both rigid and nonrigid image registration. The root mean squared error for each method was calculated from a set of anatomic landmarks marked by four independent observers.

Results: Nonrigid and rigid registration errors for treatment position PET/CT to planning CT were 2.77 ± 0.80 mm and 4.96 ± 2.38 mm, respectively, p = 0.001. Applying the nonrigid registration to diagnostic position PET/CT produced a more accurate match to the planning CT than rigid registration of treatment position PET/CT (3.20 ± 1.22 mm and 4.96 ± 2.38 mm, respectively, p = 0.012).

Conclusions: Nonrigid registration provides a more accurate registration of head and neck PET/CT to treatment planning CT than rigid registration. In addition, nonrigid registration of PET/CT acquired with patients in a standardized, diagnostic position can provide images registered to planning CT with greater accuracy than a rigid registration of PET/CT images acquired in treatment position. This may allow greater flexibility in the timing of PET/CT for head and neck cancer patients due to undergo radiotherapy.

Training of staff for the delivery of PET/CT services in the UK

Evidence for the cost effectiveness of PET/CT imaging is now driving the widespread introduction of PET/CT services throughout the UK. The provision of PET/CT facilities will require a workforce of medical, scientific, technical and engineering staff who are adequately trained and fit for purpose. Suitably trained staff in this speciality are scarce. The development and accreditation of training courses and other educational resources for training programmes in all disciplines will therefore be required at a national and regional level. The implementation of PET/CT training can be achieved more cost-effectively by developing multi-professional learning resources whenever possible. It is intended that the recommendations would be implemented by close co-operation of both public and private healthcare providers together with educational establishments.

The clinical impact of a combined gamma camera/CT imaging system on somatostatin receptor imaging of neuroendocrine tumours

AIM

With a combined gamma camera/CT imaging system, CT images are obtained which are inherently registered to the emission images and can be used for the attenuation correction of SPECT and for mapping the functional information from these nuclear medicine tomograms onto anatomy. The aim of this study was to evaluate the clinical impact of SPECT/CT using such a system for somatostatin receptor imaging (SRI) of neuroendocrine tumours.

MATERIALS AND METHODS

SPECT/CT imaging with (111)In-Pentetreotide was performed on 29 consecutive patients, the majority of whom had carcinoid disease. All SPECT images were first reported in isolation and then re-reported with the addition of the CT images for functional anatomical mapping (FAM).

RESULTS

Fifteen of the 29 SPECT images were reported as abnormal, and in 11 of these abnormal images (73%) FAM was found to either establish a previously unknown location (7/11) or change the location (4/11) of at least one lesion. The revised location could be independently confirmed in 64% of these cases. Confirmation of location was not possible in the other patients due to either a lack of other relevant investigations, or the fact that lesions seen in the SPECT images were not apparent in the other investigations. FAM affected patient management in 64% of the cases where the additional anatomical information caused a change in the reported location of lesions.

CONCLUSION

These results imply that FAM can improve the reporting accuracy for SPECT SRI with significant impact on patient management.

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.

Introduction, audit and review of guidelines for delegated authorization of nuclear medicine investigations in compliance with the Ionising Radiation (Medical Exposure) Regulations 2000

The introduction of the Ionising Radiation (Medical Exposure) Regulations 2000 in Great Britain required every nuclear medicine investigation to be justified by a practitioner holding an appropriate Administration of Radioactive Substances Committee (ARSAC) certificate. The task of authorizing the radiation exposure may be performed by the practitioner (direct authorization) or delegated to an appropriately trained operator working to written guidelines approved by the practitioner (delegated authorization). In this study, we look at the process of implementation, audit and review of a set of Delegated Authorization Guidelines (DAG). The process of drafting the DAG is outlined. Following the introduction of the DAG, an audit of nuclear medicine referrals was performed at two sites for a period of 3 months. Each referral was compared with the DAG to determine whether it matched the criteria set out. If it did not match, it was further categorized as being due to: (1) insufficient referral information; or (2) clinical indication not included in the DAG. All non-matching requests were reviewed by the practitioner. Four hundred and thirty-seven of 632 (69%) referrals fitted the DAG, 12% (n=75) required clarification from the referrer before fitting with the criteria and 19% (n=120) were directly authorized by the practitioner. From those referrals that were directly authorized, some additional indications were identified and the DAG were subsequently revised. In conclusion, a delegated authorization procedure for nuclear medicine investigations can be implemented successfully. Regular audit is essential. This study identified the need to improve the format of the request card and to obtain additional referral information from the referrer.

A survey of the role of the UK physicist in nuclear medicine: a report of a joint working group of the British Institute of Radiology, British Nuclear Medicine Society, and the Institute of Physics and Engineering in Medicine

Guidelines for the provision of physics support to nuclear medicine were published in 1999 by a joint working group of the British Institute of Radiology, the British Nuclear Medicine Society, and the Institute of Physics and Engineering in Medicine. Following publication of the guidelines, a survey was conducted by the working group to gather data on the actual level of physicist support in UK hospitals of different types and on the activities undertaken by physicists. The data were collected in the 12 months following the publication of guidelines and cover different hospital models and seven UK regions. The results provide evidence that many of the smaller units - small teaching hospitals and, particularly, small district general hospitals - have insufficient physics support. Although, on average, there is good agreement between the guidelines and the survey data for medium and large district general hospitals, there is wide variation in the level of physics provision between hospitals delivering apparently similar services. This emphasizes the need for national guidelines, against which institutions may be bench-marked and which may be used as a recommendation for the staffing levels necessary to ensure services are delivered safely and standards are not compromised. The complexity and variety of workload is an important factor in determining the level of physics support. As services develop, it is vital that this aspect is recognized to ensure that appropriate resources are available for the required physics input, even if any new service represents only a modest clinical throughput in terms of patient numbers.

Subcortical hypoperfusion following surgery for aneurysmal subarachnoid haemorrhage: implications for cognitive performance?

The incidence and severity of cognitive deficits after surgery for aneurysmal subarachnoid haemorrhage and their relationship to aneurysm site remains controversial. The aim of this study was to investigate the pattern of regional cerebral blood flow which exists in patients one year post-surgery and to identify whether different patterns exist which may be related to the type of cognitive deficit or the location of the aneurysm. 62 patients underwent cognitive assessment and HMPAO SPECT imaging at a mean time of 12 months following surgery. Results were compared to those from healthy control subjects (n = 55 for neuropsychological testing; n = 14 for SPECT imaging). In the patient group, significant stable cognitive deficits occurred in all cognitive domains but no cognitive measure differentiated aneurysm site. On SPECT images, statistical parametric mapping identified a large common area of subcortical hypoperfusion in the patient group as a whole. The findings of this study suggest a possible link between reduced subcortical function and the extent and severity of cognitive deficits.

Gastric emptying and intestinal transit of pancreatic enzyme supplements in cystic fibrosis

OBJECTIVE

To investigate gastric emptying and intestinal transit of pelleted pancreatin in relation to food boluses.

METHODS

Dual isotope scintigraphy combined with breath hydrogen sampling was used to track the concurrent gastric emptying and intestinal transit of 111indium labelled microspheres and a 99mtechnetium labelled tin colloid test meal. Twelve pancreatic insufficient cystic fibrosis patients aged 5 to 38 years performed the study.

RESULTS

50% gastric emptying times showed patient to patient variation. The mean discrepancy in 50% gastric emptying times between the two labels was > 67 minutes. Mean small bowel transit time for the food bolus was prolonged at 3.6 minutes. A significant correlation was seen between weight standard deviation score and 50% emptying time for pancreatin (r = +0.73).

CONCLUSION

Gastric mixing of food and pancreatin may be limited by rapid emptying of microspheres. Patients with high dosage requirements could benefit from changing the pattern of their pancreatin supplementation.

Dose rate measurements from radiopharmaceuticals: implications for nuclear medicine staff and for children with radioactive parents

Following the introduction of a number of radiopharmaceuticals, we assessed the dose received by staff working in the nuclear medicine department and also by children who may be in close contact with a radioactive parent. We measured departure dose rates (microSv.h-1) at distances of 0.1, 0.5 and 1.0 m from the skin surface at the level of the thyroid, chest and bladder of patients undergoing the following nuclear medicine procedures: MUGA scans using 99Tcm-labelled red blood cells, myocardial perfusion scans using 99Tcm-labelled radiopharmaceuticals, lymphoscintigraphy using colloidal 99Tcm (Re) sulphide, bone scans using 99Tcm-labelled oxidronate, 111In-octreotide scans, 111In-labelled leukocyte studies and cardiac reinjection studies using 201Tl. The maximum dose rates at 0.1 m were those from MUGA studies (167.3 microSv.h-1) and myocardial perfusion studies (one-day protocol = 391.7 microSv.h-1, two-day protocol = 121.8 microSv.h-1). The implications of these dose rates on both technical and nursing staff are assessed. Also, the dose received by an infant in close contact with a parent following a nuclear medicine investigation was estimated.

The use of image registration in the analysis of bone scans for the assessment of temporomandibular joint uptake

Bone scanning is a commonly used technique in the assessment of patients with facial asymmetry. Uptake in the temporomandibular joints can be assessed quantitatively, either as a right-to-left ratio or as the uptake in the joint relative to some other bony structure. We used image registration techniques in the development of an automatic method of quantitative analysis and compared this with a manual region of interest method. Both image warping and region warping were studied. Normal ranges were established in a series of 25 subjects with no evidence of temporomandibular disorder. The results of this study indicate that, by using image registration and standard regions of interest, the results from normal subjects show a smaller standard deviation and improved correlation between observers when compared with manual analysis.

The use of dual-isotope imaging to compare the gastrointestinal transit of food and pancreatic enzyme pellets in cystic fibrosis patients

Cystic fibrosis patients require pancreatic enzyme supplements to aid food digestion. It is suspected that incorrect delivery of this enzyme may result in both significant malabsorption and the development of strictures in the proximal colon caused by the high-dose supplement reaching this region before the food. Investigations into the drug's delivery were performed using dual-isotope imaging; a method was developed to directly label the enteric-coated enzyme pellets with 111In, re-applying the enteric coating afterwards, and this was then ingested with a pancake meal labelled with 99Tcm-tin colloid. Consecutive image data, acquired over a period of > or = 4 h using a dual-headed gamma camera, were analysed to assess intestinal transit. In-vitro stability checks on these labelling techniques were encouraging, showing < 2% 99Tcm and < 7% 111In elution over 90 min in hydrochloric acid. In 5 of the 12 patients studied to date, the pellets were seen to pass through significantly faster than the food, with a mean difference in 50% gastric emptying time of greater than 93 min. The mean absolute difference in emptying time for all 12 patients was > 67 min. Thus, a technique has been developed to effectively radiolabel pancreatic enzyme pellets, and analysis of dual-isotope images using this preparation, together with radiolabelled solid food, has demonstrated significant differences in the transit of these two substances through the gastrointestinal tract of some cystic fibrosis patients.

Modelling dual isotope parathyroid scans: objective decision making for tumour detection

Parathyroid subtraction imaging using the radioisotopes thallium-201 and technetium-99m was first described in 1983. Since then it has become a routine method for the pre-operative localization of parathyroid tumours. Despite its widespread use, the interpretation of the subtraction images remains very subjective. This paper describes and evaluates an automatic objective method for the analysis of parathyroid scans. The method is based on the calculation of a likelihood ratio (the probability of obtaining a count in a given pixel if a tumour is present divided by the probability of obtaining that same count if a tumour is not present). The likelihood ratio is calculated for each pixel in a subtraction image. The calculated value is compared with a threshold. Pixels with likelihood ratios greater than the threshold are classified as belonging to tumour sites. Pixels with likelihood ratios less than, or equal to, the threshold are classified as belonging to 'no tumour' sites. The probability density functions required were obtained from computer simulated images. The likelihood ratio technique has a similar sensitivity and specificity to that of experienced human observers analysing computer simulated images. Furthermore, it is a completely automatic method which can provide the basis of a decision support system.

Value of technetium-99m HMPAO-labelled leucocyte scintigraphy as an initial screening test in patients suspected of having inflammatory bowel disease

OBJECTIVE

This study was designed to evaluate the role of technetium-99m (99mTc) hexamethyl propylene amine oxime (HMPAO)-labelled leucocyte imaging as an initial screening test in patients suspected of having inflammatory bowel disease (IBD).

PATIENTS AND METHODS

Thirty-one patients in whom a final diagnosis of irritable bowel syndrome (IBS) was made (group 1) and another 33 patients with established Crohn's disease (group 2) were studied. All patients had 99mTc HMPAO-labelled leucocyte scan with imaging at 40 and 120 min. Scans with abnormal bowel uptake were considered positive and this uptake was quantified by visual grading and computer-based methods (scan score). Group 1 patients with positive 99mTc HMPAO scan underwent an indium-111 (111In)-labelled leucocyte scan (imaging at 180 min) followed by endoscopy and barium radiology as deemed necessary in order to verify the 99m Tc HMPAO result.

RESULTS

Three scan patterns were seen: well localized and unequivocally positive scans at both 40 min and 2 h were obtained from 28 patients. All but one had established Crohn's disease. Diffuse bowel uptake was seen in 14 scans. Ten of these (false positive) were obtained from symptomatic patients with IBS and four (false negative) from patients with asymptomatic Crohn's disease. No bowel uptake at 40 min and 2 h was seen in 22 scans. All but two of these (who had quiescent Crohn's disease) were obtained from patients with IBS. Active Crohn's disease is associated with significantly higher scan score (mean +/- SEM, 82.1 +/- 13.6) than the false positive scans (12.5 +/- 3.1, P > or = 0.001). Patients with false positive 99mTc HMPAO scans had negative 111In scans, endoscopy and barium radiology.

CONCLUSION

Bowel scanning using either 111In or 99mTc HMPAO is useful in excluding active IBD. Because of radiation dose, image quality and availability 99mTc may be preferred to 111In.

A survey of close contact regimes between patients undergoing diagnostic radioisotope procedures and children

When following diagnostic radioisotope procedures, UK legislation requires that we advise patients to avoid close contact with children [1, 2]. How does this advice affect the average nuclear medicine patient? Over a 4 month period, 90 patients in contact with children were asked about their home circumstances, how they coped with avoidance of close contact and the problems caused. On average, the patients were in contact with two children with a mean age of 7 years. Thirty-nine per cent of patients spent < 5 h per day and 30% between 5 and 10 h per day in close contact. However, 13% spent 20-24 h in close contact with children. For most patients (55%), it is easy to avoid close contact, but 25% found it difficult or very difficult. The average in-patient received one visit a day from children of 0.5-1 h duration and 65% of children sat on the patient's bed. Restriction of visits was a problem for 14% of patients. Initially, over one-third of the out-patients felt a medium level of anxiety or higher regarding close contact with children. Given more detailed written information and the opportunity to discuss any queries with a member of staff (70% wished to do so), the proportion fell to less than one-tenth. We found it important to question patients carefully, because home circumstances and levels of close contact cannot be deduced from the age of the child or the relationship between the child and the patient.

The virtual gamma camera room

The installation of a gamma camera is time-consuming and costly and, once installed, the camera position is unlikely to be altered during its working life. Poor choice of camera position therefore has long-term consequences. Additional equipment such as collimators and carts, the operator's workstation and wall-mounted display monitors must also be situated to maximize access and ease of use. The layout of a gamma camera room can be optimized prior to installation by creating a virtual environment. Super-Scape VRT software running on an upgraded 486 PC microprocessor was used to create a 'virtual camera room'. The simulation included an operator's viewpoint and a controlled tour of the room. Equipment could be repositioned as required, allowing potential problems to be identified at the design stage. Access for bed-ridden patients, operator ergonomics, operator and patient visibility were addressed. The display can also be used for patient education. Creation of a virtual environment is a valuable tool which allows different camera systems to be compared interactively in terms of dimensions, extent of movement and use of a defined space. Such a system also has applications in radiopharmacy design and simulation.

Computer aided test selection (CATS) for nuclear medicine--a prototype system for renal investigations

An expert system for renal test selection in nuclear medicine has been developed as the first stage of a collaborative project on test selection in nuclear medicine. The stages of knowledge elicitation and knowledge representation were addressed by means of a questionnaire which was completed by five experts in the field of renal nuclear medicine. A flow chart was developed from the responses and implemented using a commercially available expert system shell (Crystal 4.5). A menu specifying clinical problems, for which renal nuclear medicine is useful, is displayed to the user who is prompted for a choice. Specific aspects of the chosen problem are then shown and again a choice is requested. Selected tests, in order of expert preference, are displayed and further information on any of these is available, if required, on selection from a menu subdivided into categories such as patient preparation, preliminary investigations, etc. The system provides cross-referencing to other areas of investigation and is currently being evaluated using a structured approach commonly employed in the assessment of user interfaces.

Quantitative assessment of overall inflammatory bowel disease activity using labelled leucocytes: a direct comparison between indium-111 and technetium-99m HMPAO methods

The ideal imaging method in inflammatory bowel disease would reliably detect inflammation, identify the correct intestinal location, and assess the severity of the disease. The aim of this study was to compare scintigraphic methods of quantifying overall disease activity using both indium-111 (111In) and technetium-99M (99mTc) HMPAO labelled leucocyte scans. The four day faecal excretion of 111In was measured after 111In scintigraphy in 24 patients known to have inflammatory bowel disease. The same patients also underwent 99mTc HMPAO scanning. The scans were performed 10 days or less apart with no changes in treatment between scans. Bowel activity on the 99mTc HMPAO scans was assessed using a computer based method (scan score) and a visual grading method in a further 54 99mTc HMPAO. The results showed a close correlation between inflammatory activity defined by faecal 111In excretion and the scan score generated from the computer analysis of the 99mTc HMPAO image (Spearman rank correlation: rs = 0.78; p < 0.001). Accurate information to localise inflammatory activity could be obtained by simple visual assessment of both types of scan images, although image quality was superior with 99mTc HMPAO. Qualification of disease activity from 99mTc HMPAO images by visual grading was associated with a large variability, only 69% of scans had similar scores when graded by three observers. Computer generated image analysis was more reproducible. In conclusion, in inflammatory bowel disease 99mTc HMPAO scintigraphy and faecal 111In excretion correlated well. Either method can quantify and localise the inflammation. As 99mTc HMPAO scanning provides a quicker result, with a lower radiation dose, and avoids faecal collection, it may be the preferred method.

Air contamination following aerosol ventilation in the gamma camera room

Air contamination levels arising from lung aerosol ventilation studies have previously been monitored [1]. Residence time in the room used for ventilation was perceived to be an important factor in dose received. This study was designed to assess air contamination levels when ventilation and imaging are carried out in the same room. Air samples were taken before, during and after aerosol administration, over 24 studies where a mouthpiece was used. The mean airborne contamination during administration was 4.39 kBq m-3, implying an effective dose equivalent (EDE) to the operator from inhaled activity of 0.004 microSv. Measurements made during studies on three patients where a mask was used gave a mean EDE of 0.065 microSv (the highest EDE was 0.08 microSv). Ten minutes after nebulizing had stopped, the contamination had reduced to background levels in all but two cases; in these cases, the levels were less than 1.1 kBq m-3. Aerosol ventilation in the gamma camera room does not constitute a significant radiation hazard to staff. Patient compliance is an important factor in minimizing doses. Clear instructions and practice are a vital part of the procedure.

Specifying dual-detector gamma cameras and associated computer systems

Increasingly, dual-detector gamma cameras are being purchased as replacements for single-headed cameras. The improvement in sensitivity offered by a dual-detector device can be used in several ways: to shorten acquisition times, to improve signal-to-noise ratios, or to reduce administered doses. This paper focuses on the practical aspects of dual-headed devices and aims to provide some guidance for potential purchasers in the drawing up of an equipment specification.

Automatic registration of SPECT images as an alternative to immobilization in neuroactivation studies

Subtraction of the two components (baseline and stimulation) of a neuroactivation study using 99Tcm HMPAO SPECT requires accurate registration of the two images. Immobilization of the subject during and between the two components of the study can prove difficult and degrades signal to noise ratio. The use of an automated image registration technique for registering the two components of the test can, even in the case where the subject is removed from the scanner, produce significantly better registration than immobilization.

Background subtraction in 99Tcm-DTPA renography using multiple background regions: a comparison of methods

In order to obtain quantitative information from a 99Tcm-diethylenetriaminepentaacetate (DTPA) renogram it is first necessary to correct for the presence of background activity in the kidney time-activity curve. Three different methods of background subtraction which have been previously described are compared. Method 1 is a linear regression technique which uses separate tissue and heart time-activity curves to represent the background. Method 2 also uses multiple background regions and involves multiple regression. Method 3 uses a single heart region to represent the background. The three techniques are assessed using both simulation studies and patient data. The results show that method 3, which does not correct for extravascular activity, overestimates renal function particularly in poorly functioning kidneys. Method 1 gives the most accurate and reproducible results for both the simulation studies and patient data.

Background subtraction: a new approach to the assessment of disease activity in Crohn's disease using 99mTc-HMPAO-labelled leucocytes

A computer-based technique for the quantification of abnormal bowel uptake in Crohn's disease has been developed and compared with pre-existing clinical, laboratory and scintigraphic methods of assessment. The standard technique for labelling leucocytes with 99mTc-HMPAO is applied. Images were obtained at 40, 120 and 240 min after the injection of radiolabelled leucocytes. The count in the bowel area after subtracting background activity corrected to the injected dose and image acquisition times is the 'scan score', an objective measure of disease activity. The scan score is significantly higher in patients with clinically active disease (mean 82.1 +/- SEM 13.6) than in those with quiescent disease (24.7 +/- 7.0) (p < or = 0.005). Optimum separation between active and quiescent disease is achieved with a threshold scan score of 20. The scan score was comparable in small bowel disease (73.3 +/- 16.2), large bowel (94.4 +/- 33) and disease at both locations (94.1 +/- 19.2). The scan score correlated favourably with Crohn's Disease Activity Index (rs = 52, p < or = 0.0001), Harvey & Bradshow Simple Index (rs = 0.4, p < or = 0.001), serum C-reactive protein (rs = 0.72, p < or = 0.001), serum alpha acid glycoprotein (rs 0.67, p < or = 0.001), haemoglobin (rs = 0.66, p < or = 0.001), platelet count (rs = 0.47, p < or = 0.006), albumin (rs = 0.61, p < or = 0.0001) and faecal 111Indium excretion (rs = 0.78, p < or = 0.001), but not with the ESR (rs = 0.22, p < or = 0.4).(ABSTRACT TRUNCATED AT 250 WORDS)

Quantification of disease activity in Crohn's disease by computer analysis of Tc-99m hexamethyl propylene amine oxime (HMPAO) labelled leucocyte images

The reliability and clinical applications of computerised image analysis measurement of bowel uptake of Tc-99m HMPAO labelled leucocytes has been examined as a measure of disease activity in Crohn's disease. In 54 studies carried out on 33 patients with established Crohn's disease, the mean 'scan score', a quantitative assessment of image intensity, was 82.1 SEM (13.6), in patients with clinically active disease compared to 24.7 (7.0) in those with quiescent disease, p < or = 0.0005. A significant correlation was found between the scan score and Crohn's Disease Activity Index (rs = 0.52, p < 0.0001), and Harvey and Bradshaw Simple Index (rs = 0.4, p < 0.004). A low scan score correctly identified seven patients whose raised Crohn's Disease Activity Index incorrectly indicated active disease because symptoms used in calculation of the index were not caused by active inflammation. Of the laboratory measurements, the scan score correlated with the haemoglobin (rs = 0.66, p < 0.0001), albumin level (rs = -0.6, p < 0.0001), C-reactive protein (rs = 0.7, p < 0.0001), alpha-acid glycoprotein (rs = 0.57, p < 0.001), and platelet count (rs = 0.47, p < or = 0.006), but not with the erythrocyte sedimentation rate (rs = 0.2, p < or = 0.25). The scan score was raised in all patients who had clinically active disease but normal laboratory tests. The results of this study indicate that the scan score provides an objective indicator of disease activity in Crohn's disease which may be superior to clinical indices, and also to laboratory tests which although objective are often normal in the presence of active disease.

Determination of the arterial flow fraction in normal and diseased livers using constrained deconvolution

There is some evidence that the ratio of the blood flow to the liver through the hepatic artery to the total flow to the liver through the hepatic artery and portal vein (the hepatic arterial flow fraction, AFF) is altered in the presence of cirrhosis. Several methods have been published that seek to provide an index of this ratio. These indices are dependent on factors other than the AFF and cannot provide a true measure of it. The impulse retention function of the liver has two components and these may be derived using a model-driven deconvolution of the arterial tracer concentration curve and the curve of tracer concentration in the liver. The AFF may then be obtained from the relative heights of these two components. Simulation studies show that the AFF calculated using this method is reasonably accurate and a small clinical series shows that it is capable of appropriate clinical classification of patients into cirrhotic and non-cirrhotic groups.

Liver blood flow: non-invasive estimation using a gamma camera

A non-invasive radioisotope technique for the measurement of total liver blood flow (TBF) is described. The method requires the use of two intravenously administered tracers, 99mTc (technetium 99m) human serum albumin (HSA) and 99mTc colloid. Computer analysis of first-pass time activity curves for HSA for liver and lung tissues yields values for the arterial and portal contributions to liver blood flow, from which TBF can be determined. These values are then corrected for attenuation using the images of the colloid distribution. The use of the method is illustrated in 17 subjects. Assumptions, limitations and possible applications of the technique are discussed.

99Tcm HMPAO-labelled leucocyte imaging in Crohn's disease: a subtraction technique for the quantification of disease activity

A new technique for the quantitative analysis of labelled leucocyte images from patients with inflammatory bowel disease is described. The method involves the computer generation of a 'background' image which, after appropriate registration, is subtracted from the patient's image to leave a residue which represents abnormal uptake in the bowel. Quantification of the residual activity yields a scan score which can be related to the level of disease activity in patients with Crohn's disease. In 54 investigations on 33 patients the scan scores correctly agreed with a clinical assessment of disease activity in 16 of 20 cases with inactive disease and 32 out of 34 cases with active disease. Most of the discrepancies reflected inaccuracies in the clinical assessment of activity rather than shortcomings of the imaging technique.

The effect of forced expiration on the uniformity of 99Tcm-DTPA aerosol ventilation images in patients with excess sputum production

This study examines the use of the forced expiratory technique (FET) as a means of improving the uniformity of radionuclide aerosol ventilation images in patients with excess sputum production. Ventilation images are objectively classified by two computer derived indices to characterize the degree of radioaerosol clumping and overall uniformity. In a series of twenty five patients with a long-standing history of daily sputum production, images acquired before and after forced expiration and again after a second ventilation immediately following FET showed no significant change in either index. The results obtained do not provide evidence to support the routine use of FET in conjunction with radioaerosol scintigraphy. The method of image classification correlates well with a visual assessment of image uniformity and has general application.

The effect of methodology and tracer identity on a non-invasive index of liver blood flow

There are a number of clinical conditions in which quantification of the relative flow in the arterial and portal vessels supplying the liver may be of diagnostic use. The hepatic perfusion index has been proposed as a non-invasive indicator of relative blood flows. The technique involves analysis of first-pass time-activity curves over the liver and kidney with the calculations of an index which is derived from the slopes of the hepatic curve before and after the renal peak. In previously published studies, the methodology adopted has been variable, both in the analysis and in tracer identity. This study examines the effect of both physical and physiological variables on the index. The results indicate that in addition to relative arterial and portal flows, the index is dependent on bolus quality, the length of time over which the slopes are averaged, transit times through the liver and splenic and mesenteric circulations, and the degree of tracer extraction. Furthermore, the data suggest that values in the currently considered abnormal range may be poor indicators of relative arterial and portal venous flows.

Modification of the Gorlin equation for use with heart valve substitutes

The Gorlin equation, which was used to assess the obstruction to flow by a stenosed heart valve, is based on steady flow (time independent) criteria derived from hydraulics. Recently, this equation has been used to obtain an effective orifice area for heart valve substitutes both in vitro and in vivo. In this study, a modification of the original Gorlin equation for use with heart valve substitutes considers both the pulsatility of the valvar flow and possible variations in volumetric flow waveforms induced by differences in myocardial performance. The modified equation also allows for the possibility of regurgitant flows. Its use is illustrated in a study of the hydrodynamic performance of a series of heart valve substitutes and recommendations are made concerning its application to cardiac catheterisation procedures.

The physics of red cell sedimentation

Blood was withdrawn from the ante-cubital vein of five normal volunteers and the erythrocytes were washed and resuspended in isotonic saline. The rate of descent of the erythrocyte-saline boundary was measured every hour for a period of at least 4 h for different suspended cell concentrations. The velocity of this boundary remained constant during the period of observation for a specific concentration. There was, however, an experimental variation of sedimentation rate with red cell concentration. Extrapolation to zero concentration allowed the 'Svedberg constant' for normal red cells to be evaluated. A continuum physics theory was used to explain the observations. The sedimentation rate was also measured in anticoagulated whole blood. The rates of descent in whole blood and the red cell-saline suspension were significantly different. Furthermore, the erythrocyte boundary in whole blood displayed both acceleration and deceleration during the period of observation. These experiments support the concept, proposed in an earlier theoretical study, of an internal energy dissipative mechanism which occurs in heterogeneous fluids (such as blood) but not in homogeneous fluids (such as water).

In vitro evaluation of prosthetic heart valves: anomalies and limitations

The in vitro evaluation of fifteen commercially available prosthetic heart valves is described. The group comprised both mechanical and bioprosthetic valves. The experimental studies were carried out in a steady flow circuit which included a flexible valve test section, the geometry of which was modelled on the aortic anatomy. The fluidic performance of the valves was examined over a range of flows and in particular, the phenomenon of "pressure recovery" distal to the valve was studied in depth. A number of theoretical parameters which might be used to define valve performance were evaluated but none was found to be ideal. The conclusions of the study emphasise the limitations of such in vitro testing and the danger of extrapolating such experimental data to the possible valve performance in vivo.