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P H Jarritt

Publications and source records attributed to P H Jarritt.

At least 19 recordsLinked to original sources
PubMed1997

Effect of attenuation correction on myocardial thallium-201 distribution in patients with a low likelihood of coronary artery disease.

Regional variation of tracer distribution is seen in uncorrected thallium-201 images of normal hearts. This study evaluates the effect of attenuation correction on myocardial 201T1 distribution in patients with low risk of coronary artery disease. An L-shaped dual-detector single-photon emission tomographic system equipped with a pair gadolinium-153 scanning line sources was used for sequential emission/transmission imaging in 36 patients (14 men and 22 women) with less than 5% risk for coronary artery disease. Uncorrected emission images were reconstructed using filtered back-projection (FBP) whereas the attenuation corrected (AC) images were iteratively reconstructed using the attenuation map computed from the transmission data. Both sets of images were reorientated into short axis, vertical long axis and horizontal long axis images. For quantification data were reconstructed into polar plots and count density estimated in 17 myocardial segments. The population % standard deviation for each segment of AC data was significantly smaller than that for FBP data, indicating improved homogeneity of tracer distribution. In men the anterior-basal inferior activity ratio improved from 1.20 for FBP to 0.96 for AC (stress) and from 1.23 for FBP to 0.98 for AC (delay) (P < 0.0001). In women the anterior-basal inferior activity ratio changed from 1.08 for FBP to 0.94 for AC (stress) and from 1.08 for FBP to 0.93 for AC (delay) (P < 0.001). These ratios reflect appropriate compensation for basal attenuation but a lack of scatter correction. The lateral-septal activity ratio in men changed from 1.05 for FBP to 0.99 for AC (stress) and from 1.02 for FBP to 0.96 for AC (delay), while in women it changed from 1.05 for FBP to 0.98 for AC (stress) and from 1.04 for FBP to 0.98 for AC (delay) (P < 0.005 in all cases). The apex of AC images showed a decrease in activity consistent with wall thining at this site. It is concluded that the use of attenuation correction yields improved homogeneity of myocardial tracer distribution in patients with low risk of coronary artery disease. The diagnostic benefits of attenuation correction are yet to be fully assessed.

Adenosine↗
PubMed1997

Transmission scanning for attenuation correction of myocardial 201Tl images in obese patients.

For attenuation correction (AC) of 201Tl myocardial perfusion images, an accurate attenuation map is required. This study assessed whether prolonged transmission scanning is required in obese compared to normal-sized patients. Twenty-nine obese patients (mean body mass index 33 kg m-2) underwent sequential emission/transmission imaging for AC using an L-shaped, dual-headed gamma camera fitted with two 153Gd scanning line sources. Transmission data were acquired for 5 s per view (scan time for normal-sized patients) and for 10 s per view and used to reconstruct individual attenuation maps. Emission data were reconstructed using each attenuation map in turn to produce attenuation-corrected images (AC5 and AC10). Tracer distribution in the AC5 and AC10 images was compared by two observers blinded to study type. For each data set, count density was measured in 17 segments of a polar plot and segmental uptake expressed relative to study maximum. Although myocardial count density was low on the 5 s per view transmission images (0.5-13.0 and 3.0-14.0 counts per pixel in the anteroposterior and lateral projections respectively), no significant differences in tracer distribution were seen between the AC5 and AC10 images and these were reported identically. In addition, the mean segmental relative uptake values were similar (P > 0.05) for corresponding segments of the AC5 and AC10 images. We conclude that prolonged transmission scanning is not required in obese compared to normal-sized patients. The transmission scanning protocol used in normal-sized patients is applicable across a wide patient weight range.

Aged↗
PubMed1996

PET imaging using gamma camera systems: a review.

Optimized positron emission tomographs have begun to demonstrate an ever widening range of clinical applications for positron labelled pharmaceuticals. This potential has led to a renewed interest in the use of the more widely available Anger gamma camera detectors for imaging the 511 keV photons from the positron decay process. Two forms of detection can be considered: either the detection of the 511 keV photons as single events or the detection of coincidence events from the opposed pair annihilation photons. The widespread availability of dual, opposed-pair, large field-of-view detectors has promoted the development of coincidence detection without collimation. With detector rotation, positron emission tomography (PET) can be performed. An alternative and lower cost option has been the universal development of ultra high-energy collimators to perform single photon emission tomography (SPET) with 511 keV photons. This review outlines the currently available performance characteristics of these two approaches and compares them with those from two- and three-dimensional PET optimized systems. The limitations on the development of these systems is discussed through the analysis of the principles underlying both single photon and coincidence detection. Preliminary clinical experience indicates that limitations in the performance characteristics of these systems has implications for their potential role, although applications in cardiology and oncology are being pursued.

Gamma Cameras↗
PubMed1995

High-resolution renal SPECT in eight minutes using a multi-detector gamma camera.

Planar renal scintigraphy with Tc-99m DMSA has become established as a standard diagnostic test to determine if a kidney has been scarred by infection. It has been suggested that high resolution SPECT may improve the sensitivity of detection of renal scars. To determine if it is possible to produce good quality renal SPECT with a short acquisition time, 10 adults were examined with a new multi-detector gamma camera using 8 minute, 16 minute, and 32 minute acquisitions. The number of defects seen (N = 16) with an 8 minute acquisition was not significantly different from the defects (N = 15) seen using a 16 minute and a 32 minute acquisition. In adults when imaging with a multi-detector gamma camera there was no clinical advantage in using an acquisition of longer than 8 minutes.

Adolescent↗
PubMed1995

Combined rest thallium-201/stress technetium-99m-tetrofosmin SPECT: feasibility and diagnostic accuracy of a 90-minute protocol.

UNLABELLED: Technetium-99m tetrofosmin is a recently developed compound that clears from background organs rapidly. Tetrofosmin has a good correlation with 201Tl. This study assesses the feasibility and diagnostic accuracy of a combined protocol involving rest 201Tl SPECT and stress imaging with 99mTc-tetrofosmin. METHODS: Twenty-five patients (23 men, 2 women; aged 36-73 yr) with known coronary artery disease underwent the combined protocol. Twenty minutes after the resting injection of 201Tl, resting SPECT data were acquired using low-energy, high-resolution collimators. A stress test using adenosine infusion combined with low-level dynamic exercise was performed. The stress data were collected 20 min later. The reconstructed vertical long-axis, horizontal long-axis and short-axis slices were analyzed qualitatively. Analysis was carried out using nine segments of the left ventricle. The segments were reported either as fixed or reversible. The results were compared to coronary angiography results. RESULTS: The sensitivity and specificity for the detection of diseased coronary vessels were 85% and 70% for the left anterior descending territory, respectively, 78% and 71% for the right coronary artery, and 69% and 70% for the left circumflex. Overall, the sensitivity was 80% and the specificity 70%. CONCLUSION: Combined rest 201Tl/stress 99mTc-tetrofosmin SPECT provides a protocol of short duration which displays similar diagnostic accuracy to a protocol using tetrofosmin as a single agent.

Adult↗
PubMed1994

201Tl myocardial perfusion SPET: adenosine alone or combined with dynamic exercise.

201Tl myocardial perfusion single photon emission tomography (SPET) with pharmacological coronary vasodilatation using adenosine is now often used in the investigation of a patient with ischaemic heart disease (IHD). In this study, we present data from two groups of patients. Group A (n = 40) experienced 201Tl SPET with adenosine only as the pharmacological stress test, using an infusion rate of 140 micrograms kg-1 min-1. Group B patients (n = 50) had the same test combined with low-level dynamic exercise. The side effects were noted for both groups and 201Tl SPET studies were acquired for stress and redistribution images. There was a lesser degree of non-cardiac side effects in patients of group B. There was a significant difference in the haemodynamic parameters between the two groups. There was no significant difference in overall sensitivity (87% versus 90%) and specificity (84% versus 88%) in the detection of IHD between the two groups. In conclusion, addition of low-level dynamic exercise with adenosine is to be preferred to adenosine infusion alone, as this protocol is better tolerated and may enhance the detection of right coronary artery disease (sensitivity = 82% versus 90%, n.s.).

Adenosine↗
PubMed1994

Clinical experience with a multidetector SPET system (Toshiba GCA-9300A).

The clinical experience with the Toshiba GCA-9300A single photon emission tomography (SPET) system is discussed along with typical acquisition protocols for various SPET studies. The system was used to perform SPET studies in normals and in a variety of brain and body disorders. Its three Anger-type gamma cameras forming a triangular aperture offer a substantial increase in sensitivity compared to a single rotating gamma camera. This has allowed the routine use of lead fanbeam super high-resolution collimators (SHR FB) for 99Tcm-hexamethylpropyleneamine oxime (HMPAO) brain SPET studies and high-resolution parallel-hole collimators (HR PH) for cardiac and other body studies. The resulting improvement in spatial resolution coupled with the ease of patient positioning and the greater patient throughput compared to a conventional tomographic gamma camera, will enhance the role of brain and body SPET for both routine and research purposes.

Bone and Bones↗
PubMed1993

Clinical high resolution skeletal single photon emission tomography using a triple-headed gamma camera.

Planar skeletal scintigraphy has become established as a standard diagnostic test performed within the nuclear medicine department. Since the 1970s good quality images have been produced using an Anger gamma camera and 99Tcm-labelled diphosphonates. Single photon emission tomography (SPET) has improved the sensitivity of detection and the ability to localize bony pathology, particularly benign bone disease in the spine. Recently multi-detector gamma cameras dedicated to SPET have become available. One such system, the Toshiba GCA-9300A, has been used to perform routine clinical skeletal SPET in 81 patients. Good quality images have been obtained using an 8 min acquisition in the axial skeleton and a 16 min acquisition protocol in the peripheral skeleton. Multiple sites can be tomographed in the same patient during the same examination using two or more 8 min acquisitions. Such a multi-detector gamma camera offers advantages over the standard single-headed rotating camera for skeletal SPET in terms of both imaging time and image quality. A cost analysis was performed which demonstrated that the additional cost of purchasing such a multidector gamma camera was less than 30.00 pounds per SPET study.

Bone Neoplasms↗
PubMed1993

Physical performance evaluation of the Toshiba GCA-9300A triple-headed system.

The physical performance of the Toshiba GCA-9300A triple-headed SPECT system has been assessed. Using a water-filled cylinder containing 99mTc, the tomographic volume sensitivity was 33.8 and 34.8 kcps/(MBq/ml)/cm for the high-resolution, parallel-hole (HR-PH) collimator and the super high-resolution, lead fanbeam (SHR-FB) collimator, respectively, excluding the rotation time(s) during scanning when data are not acquired. The tomographic spatial resolution at the center, in air, with 132 mm radius of rotation was 10.2 and 7.8 mm FWHM with the HR-PH and SHR-FB collimators, respectively; in water it was 11.0 and 7.8 mm. Reconstructed relative activity concentrations were accurate for both collimator sets if attenuation correction was used. With the SHR-FB collimators, the average peak-to-valley ratio of five-line sources in water improved significantly when an asymmetric energy window was used. Using the three-dimensional Hoffman brain phantom which simulates a 4:1 grey matter-to-white matter ratio and the usual choice of acquisition and processing parameters for brain studies, the reconstructed grey matter-to-white matter ratio was only about 1.7 for total counts typically acquired in a 99mTc-HMPAO study (4.0 M counts) and only 2.3 for 40 M counts. There was a qualitative improvement with an asymmetric energy window.

Brain↗
PubMed1992

Physical assessment of the GE/CGR Neurocam and comparison with a single rotating gamma-camera.

The GE/CGR Neurocam is a triple-headed single photon emission tomography (SPET) system dedicated to multi-slice brain tomography. We have assessed its physical performance in terms of sensitivity and resolution, and its clinical efficacy in comparison with a modern, single rotating gamma-camera (GE 400XCT). Using a water-filled cylinder containing technetium-99m, the tomographic volume sensitivity of the Neurocam was 30.0 and 50.7 kcps/MBq.ml.cm for the high-resolution (HR) and general-purpose (GP) collimators, respectively; the corresponding values for the single rotating camera were 7.6 and 12.8 kcps/(MBq/ml)/cm. Tomographic resolution was measured in air and in water. In air, the Neurocam resolution at the cente of the field-of-view (FOV) is 9.0 and 10.7 mm full width at half-maximum (FWHM) with the HR and GP collimators, respectively, and is isotropic in the three orthogonal planes; the resolution of the GE 400XCT with 13 cm radius of rotation is 10.3 and 11.7 mm, respectively. For the Neurocam with the HR collimator, the transaxial FWHM values in water were 9.7 mm at the centre and 9.5 mm radial (6.6 mm tangential) at 8 cm from the centre. The physical characteristics of the Neurocam enable the routine acquisition of brain perfusion data with technetium-99m hexamethyl-propylene amine oxime (99mTc-HMPAO) in about 14 min, yielding better image quality than with a single rotating camera in 40 min.

Brain↗
PubMed1992

Assessment of myocardial viability with 201Tl SPET and reinjection technique: a quantitative approach.

The definition of viable myocardium after an acute myocardial infarction (MI) is important as it will determine which therapeutic option will be best for the patient. In 201Tl scintigraphy it has been shown that late redistribution (8-24 h) or reinjection may help to identify viable myocardium which does not appear to reperfuse on the 4 h redistribution image. In a prospective study 20 patients with a persistent defect seen on both stress and redistribution images were imaged after reinjection of 201Tl. On visual analysis a total of 180 segments were studied, 85 were normal, 18 reperfused at redistribution and a further nine (in six patients) after reinjection. Bull's-eye analysis at stress demonstrated a mean defect size of 279 pixels, S.D. +/- 74. After redistribution, there was no significant change in mean defect size (227 +/- 96 pixels). At reinjection, there was a significant reduction in mean defect size (189 +/- 107 pixels) (P < 0.05, paired 't'-test). Quantification shows a significant reduction in defect size between stress and reinjection. The use of the 201Tl reinjection technique in patients with a fixed perfusion deficit on stress and redistribution images improves the detection of viable myocardium and is to be preferred to a method of redistribution analysis alone.

Adult↗
PubMed1991

The APE nebuliser--a new delivery system for the alveolar targeting of particulate technetium 99m diethylene triamine penta-acetic acid.

We report the validation of a new delivery system--aerosol production equipment (known by the acronym APE), which generates a particulate aerosol of technetium 99m diethylene triamine penta-acetic acid (DTPA) with a mass-median aerodynamic diameter of 0.35 microns and a geometric standard deviation of 1.8 Twenty subjects were studied; in group 1 were 12 healthy men with normal spirometry; in group 2 were 8 men with AIDS who had mildly abnormal lung function following an episode of pneumocystis pneumonia-spirometry FEV1 3.08 (0.73) L, FVC 4.83 (0.82) L [mean (SD)]. The APE nebulizer was used to form a particulate aerosol with 200 MBq of 99mTc DTPA, which was collected in a 35 1 reservoir of air, which was subsequently inhaled. The mean (SD) inhalation time was 4.7 (0.44) min. The output of the nebulizer (% of activity inhaled) was 82%. Using planar imaging, the penetration index (right lung) in group 1 was 0.93 (0.18), mean (SD), and in group 2 it was 0.91 (0.12). There was virtually no tracheal deposition and extrapulmonary deposition (oropharynx and stomach) was less than 5% of the aerosol delivered. Single-photon emission tomography (SPET) studies carried out in five patients from group 1 confirmed homogeneous intrapulmonary deposition of 99mTc-DTPA. In view of the excellent intrapulmonary deposition of 99mTc-DTPA produced by the APE nebulizer, it may provide an alternative to conventional ventilation studies using radioactive gases.

Acquired Immunodeficiency Syndrome↗
PubMed1990

The investigation of osteoradionecrosis of the mandible by 99mTc-methylene diphosphonate radionuclide bone scans.

The need for a reliable non-invasive investigation in osteoradionecrosis (ORN) of the mandible is discussed. The results of 99mTc-methylene diphosphonate bone scans using single photon emission tomography, and measuring dynamic uptake in 13 patients are presented. These suggest that sites of osteoradionecrosis may be defined by a paradoxically increased uptake of 99mTc-methylene diphosphonate.

Gamma Cameras↗
PubMed1989

Intracellular localization of 99Tcm-d,l-HMPAO and 201Tl-DDC in rat brain.

The intracellular localization and relative distribution of 99Tcm-hexamethylpropyleneamine-oxime (99Tcm-d, l-HMPAO) and 201Tl-diethyldithiocarbamate (201Tl-DDC), which have been used to assess regional cerebral blood flow (rCBF) in man, were investigated in rat brain. 99Tcm-d, l-HMPAO was found attached mainly to cell organelles whilst 201Tl-DDC was localized mainly in free state in the cytosolic fraction. Isolation of neuronal and glial nuclei showed that there is higher uptake of 99Tcm-d, l-HMPAO in neuronal nuclei than in glial nuclei for all the different regions of the rat brain investigated. These data demonstrate a different subcellular localization of the two lipophilic agents studied. In view of their proposed clinical utility, this difference merits further investigation.

Animals↗
PubMed1987

Functional imaging of the brain.

The radionuclide tracer method is unique amongst all other imaging methodologies in its ability to trace organ or tissue function and metabolism. It derives this advantage from the nature of the signal used for image generation, and its single interaction with the organ or system under examination. Physical processes such as electron or proton density assessment or resonance, edge identification, electrical or ultrasonic impedence, do not pertain to the image generation process in nuclear medicine, and if so, only in a rather secondary manner. The nuclear medicine imaging study is primarily a study of the chemical nature, distribution and interaction of the tracer/radiopharmaceutical utilised with the cellular system which requires investigation: the thyroid cells with sodium iodide, the recticular endothelial cells with colloidal particles, the adrenal medulla cells with metaiodobenzylguanidine, and so on. In the two most recent areas of nuclear medicine expansion, oncology (with labelled monoclonal antibodies) and neurology and psychiatry (with a whole new series of lipid soluble radiopharmaceuticals), specific cell systems can also be targeted and hence imaged and investigated. The study of structure as masterly performed by Virchow and all his successors over more than a century, is now definitely the prerogative of such imaging systems which excel with spatial and contrast resolution (x-ray computed transmission tomography, nuclear magnetic resonance imaging, diagnostic ultrasound). However the investigation of function and metabolism (as performed by Claude Bernard, Georg von Hevesy, and so many others), has clearly passed from the laboratory animal protocol and experiment to the direct investigation in man, this being the achievement of the radionuclide tracer methodology. In this article, we review present interest and developments in that part of nuclear medicine activity which is aimed at the study of the neurological or psychiatric patient.

Amines↗
PubMed1987

Relative and absolute 99Tcm-DMSA uptake measurements in normal and obstructed kidneys.

Relative and absolute 99Tcm-DMSA uptake measurements were carried out on 25 adult patients among whom there were 23 normal and 25 malfunctioning kidneys. Data were collected at 3 and 6 h post intravenous tracer injection. Four methods of calculating absolute uptake were investigated and evaluated. These were based on: (1) posterior view and measured kidney depth; (2) posterior view and Raynauld's depth; (3) geometric mean assuming kidney thickness is small enough not to introduce self attenuation of counts in the kidney itself; (4) geometric mean taking kidney thickness into account. Whilst (1) and (2) were found to overestimate and underestimate renal uptake by up to 5 and 14%, respectively, (3) and (4) were found to be more accurate and comparable. The measurement of relative DMSA uptake (right to left) showed no change between the 1 and 6 h measurements for both obstructed and non-obstructed kidneys. Based on the results from method 4, the absolute renal DMSA uptake had a mean value of 25.4%, S.D. 8.9% and 30.0%, S.D. 9.2% at 3 and 6 h, respectively, for normal/non obstructed kidneys. For obstructed kidneys (responding to frusemide), the mean uptake was 23.0%, S.D. 7.2 and 25.6%, S.D. 6.7% at 3 and 6 h, respectively. For obstructed kidneys not responding to frusemide, the mean uptake was 16.8%, S.D. 3.9 and 20.6%, S.D. 4.8% at 3 and 6 h, respectively. No correlation was found between absolute DMSA uptake and degree of renal obstruction.

Adult↗
PubMed1986

The in vivo distribution of 99Tcm-HM-PAO in normal man.

The distribution of 99Tcm-HM-PAO is described in normal man. Since our initial report on the clinical potential of this new radiopharmaceutical in 1984, a number of clinical trials are in progress worldwide. As the tracer has been designed to enable the in vivo assessment of the distribution of cerebral blood flow in man, significant interest in this new 99Tcm-labelled compound can be detected not only in the nuclear medicine practice in general, but in the more specialist areas of medicine such as neurology and psychiatry. In this paper we report findings which should aid in the evaluation of this compound in normal individuals.

Adult↗