P. E. Blackshaw

Effect of a test meal on the intragastric distribution of urea in the 13C-urea breath test for Helicobacter pylori.

Test meals are invariably used in the 13C-urea breath test (UBT) but their effect on the intragastric distribution and gastric residence time of urea given in the test is unknown. The site of Helicobacter pylori urease measured in the test is unknown and whether the test measures total or regional gastric urease is uncertain. This study reports the results of paired UBTs with simultaneous gastric distribution studies, one with and one without a fatty test meal, two weeks apart on seven H pylori infected subjects. The test meal did not affect UBT results at 10 minutes, but increased values at 30 minutes and thereafter. The amount of scintigraphic label in the antrum at 10 minutes was also unaffected by the meal but increased at 30 minutes and thereafter, whereas the amount in the body/fundus was greatly increased both at 10 minutes and throughout the test. There was considerable variation in intragastric distribution of urea between subjects, both with and without the test meal. This study shows that a test meal profoundly affects intragastric distribution of urea solution in the UBT, and increases UBT values at 30 minutes and later. Variability between subjects, however, means that accurate measurement of total or regional gastric urease is probably unrealistic.

Impaired oesophageal transit of capsule versus tablet formulations in the elderly.

Drug induced oesophageal injury is an important and preventable cause of iatrogenic injury. In most cases the injury is considered to be due to mucosal contact from formulations lodged in the oesophagus. A scintigraphic study was performed comparing the oesophageal transit of enteric coated tablets with similar sized and shaped gelatin capsules, using a population of elderly healthy volunteers similar in age (50-79 years) to the population most likely to be receiving regular treatment. Twenty three volunteers injected the radiolabelled tablet or capsule with 50 ml of water while sitting on two separate occasions according to a randomisation schedule. Oesophageal transit was assessed by gamma scintigraphy. Gastric residence was also assessed in 11 of 23 subjects. While the tablet was readily cleared from the oesophagus, mean transit time 4.3 seconds (range 1.0-14.0), the capsule often showed a comparatively prolonged holdup, mean transit time 20.9 seconds (range 1.5-174.5). Ten of 11 tablets emptied from the stomach intact, while all 11 capsules broke up in the stomach. Gelatin capsules showed a clear tendency to remain within the oesophagus of healthy elderly volunteers, while similar sized enteric coated tablets did not. These studies show the importance of assessing oesophageal transit when designing the formulation of drugs with a potential for oesophageal injury.

Novel MRI tests of orocecal transit time and whole gut transit time: studies in normal subjects.

Colonic transit tests are used to manage patients with Functional Gastrointestinal Disorders. Some tests used expose patients to ionizing radiation. The aim of this study was to compare novel magnetic resonance imaging (MRI) tests for measuring orocecal transit time (OCTT) and whole gut transit time (WGT), which also provide data on colonic volumes.

Measurement of gastric meal and secretion volumes using magnetic resonance imaging

MRI can assess multiple gastric functions without ionizing radiation. However, time consuming image acquisition and analysis of gastric volume data, plus confounding of gastric emptying measurements by gastric secretions mixed with the test meal have limited its use to research centres. This study presents an MRI acquisition protocol and analysis algorithm suitable for the clinical measurement of gastric volume and secretion volume. Reproducibility of gastric volume measurements was assessed using data from 10 healthy volunteers following a liquid test meal with rapid MRI acquisition within one breath-hold and semi-automated analysis. Dilution of the ingested meal with gastric secretion was estimated using a respiratory-triggered T1 mapping protocol. Accuracy of the secretion volume measurements was assessed using data from 24 healthy volunteers following a mixed (liquid/solid) test meal with MRI meal volumes compared to data acquired using gamma scintigraphy (GS) on the same subjects studied on a separate study day. The mean ± SD coefficient of variance between 3 observers for both total gastric contents (including meal, secretions and air) and just the gastric contents (meal and secretion only) was 3  ±  2% at large gastric volumes (>200 ml). Mean ± SD secretion volumes post meal ingestion were 64  ±  51 ml and 110  ±  40 ml at 15 and 75 min, respectively. Comparison with GS meal volumes, showed that MRI meal only volume (after correction for secretion volume) were similar to GS, with a linear regression gradient ± std err of 1.06  ±  0.10 and intercept -11  ±  24 ml. In conclusion, (i) rapid volume acquisition and respiratory triggered T₁ mapping removed the requirement to image during prolonged breath-holds (ii) semi-automatic analysis greatly reduced the time required to derive measurements and (iii) correction for secretion volumes provided accurate assessment of gastric meal volumes and emptying. Together these features provide the scientific basis of a protocol which would be suitable in clinical practice.

Reproducibility of gastric emptying of a pancake and milkshake meal in normal subjects.

Comparisons of gastric emptying between different centres are difficult because of wide variations in methods. Reproducibility of a method is very important before it is used to compare different subjects or to assess the effect of treatment. The aim of this study was to measure the reproducibility of gastric emptying of a solid and liquid meal in normal subjects. Ten males were studied on two occasions. After an overnight fast, the subjects ate a radiolabelled solid and liquid meal. There were no significant differences in T50 on the 2 days (136.6 ± 23.2 vs 121.3 ± 26.7 min for solid and 30.7 ± 12.6 vs 32.6 ± 18.7 min for liquid; mean ± SD). Intra-subject variability was between 7 and 21% for the solid component and 1.5 and 63% for the liquid component. The mean difference in T50, between the 2 days was 15.3 ± 21.9 min for the solid component and −5.1 ± 19.7 min for the liquid component. Only one difference between the T50 results was not in the 95% confidence interval for the liquid component. Thus despite some inter- and intra-subject variability, the method showed good reproducibility.

A high resolution Small Field Of View (SFOV) gamma camera: a columnar scintillator coated CCD imager for medical applications

We describe a high resolution, small field of view (SFOV), Charge Coupled Device (CCD) based camera for imaging small volumes of radionuclide uptake in tissues. The Mini Gamma Ray Camera (MGRC) is a collimated, scintillator-coated, low cost, high performance imager using low noise CCDs. The prototype MGRC has a 600 μm thick layer of columnar CsI(Tl) and operates in photon counting mode using a thermoelectric cooler to achieve an operating temperature of - 10°C. Collimation was performed using a pin hole collimator. We have measured the spatial resolution, energy resolution and efficiency using a number of radioisotope sources including 140 keV gamma-rays from 99mTc in a specially designed phantom. We also describe our first imaging of a volunteer patient.

Small bowel transit of a bran meal residue in humans: sieving of solids from liquids and response to feeding

Background—Ileal motor patterns are adapted to the propulsion of viscous meal residue, such as bran, which accumulates in the distal ileum postprandially. Aims—To examine the effects of a second liquid/solid meal on ileal emptying. Subjects and methods—Eleven healthy fasting subjects consumed a 1.47 MJ pancake containing 15 g bran and 5 MBq Technetium-99m labelled amberlite resin (meal A). Gastric emptying and transit through the left upper quadrant (proximal) and right lower quadrant (distal) small bowel regions and colon were assessed scintigraphically. Transit was compared with and without a second Indium-111 liquid/solid DTPA labelled 2.28 MJ meal (B) given three hours after the first meal. Results—Gastric emptying of meal A was slower than meal B (the time for 50% of the activity to leave the stomach (T50) being 113 (11) minutes versus 48 (3) minutes respectively, p<0.01, n=11). Both meals passed rapidly through the proximal small bowel (T50 meal A = 57 (14) minutes versus T50 meal B = 42 (11) minutes). Transit of meal A through the distal small bowel was much slower (T50 more than 390 minutes versus 176 (29) minutes for meal B, p<0.01), resulting in meal B overtaking meal A and entering the colon earlier. Ingestion of the second meal (B) resulted in significantly less meal A marker entering the colon (5 (3)%) at 11 hours than when meal A was taken alone (18 (4)%) (p<0.05, n=8). Conclusions—The distal small bowel selectively retains bran, allowing liquid phase markers through to the colon. Consuming a second liquid/solid meal does not stimulate ileal transit of bran which seems to be propelled quicker by fasting motor patterns.

Design and use of mini-phantoms for high resolution planar gamma cameras.

There is now wide spread interest in the application of small field of view gamma cameras for clinical use in operating theatres, intensive care units and bedside imaging. The development of these imaging systems some of which have improved spatial resolution has necessitated a reappraisal of the suitability of conventional phantoms intended for use with gamma cameras. The testing of imagers having increased system resolution requires phantoms and test objects of smaller dimensions. We have investigated the use of high resolution mini-phantoms for the evaluation of planar imaging devices with spatial resolution of the order of 1 mm. We present images of a number of phantoms that show their suitability for evaluating high resolution planar gamma cameras. It is also apparent that there are a number of practical difficulties that have not been previously reported when using liquid filled phantoms with hole sizes between 1 and 4 mm. In particular problems of filling small diameter holes and liquid surface tension effects can limit the utility of these phantoms. Initial observations when imaging mini-phantoms with a high resolution CCD based gamma camera are presented.

A Hybrid Camera for simultaneous imaging of gamma and optical photons

We present a new concept for a medical imaging system, the Hybrid Mini Gamma Camera (HMGC). This combines an optical and a gamma-ray camera in a co-aligned configuration that offers high spatial resolution multi-modality imaging for superimposition of a scintigraphic image on an optical image. This configuration provides visual identification of the sites of localisation of radioactivity that would be especially suited to medical imaging. An extension of the new concept using two hybrid cameras (The StereoScope) offers the potential for stereoscopic imaging with depth estimation for a gamma emitting source.

A hybrid camera for locating sources of gamma radiation in the environment

We present a new concept for a portable environmental imaging system, the Compact Hybrid Gamma Camera (CHGC). This combines an optical and a gamma-photon camera in a co-aligned configuration that offers high spatial resolution multi-modality imaging for superposition of gamma ray and optical images. We report on its potential use for surveying, monitoring and clean-up of radioactive sources in the environment.