Noninvasive measurement of gastric accommodation by means of pertechnetate SPECT: limiting radiation dose without losing image quality.
The gastric accommodation response to a meal is impaired in conditions such as functional dyspepsia. At present, a barostat study is the gold standard to assess fundic relaxation in response to a meal. However, this method is invasive and possibly induces artifacts as a result of positive intraluminal balloon pressure. A noninvasive scintigraphic test has been developed to measure gastric accommodation in humans. The aim of this study was to refine this method, increasing the imaging time span and limiting the radiation dose applied without losing image quality, so that repeated measurements within 1 subject are possible without increasing radiation risk.


METHODS
Thirteen healthy volunteers without gastrointestinal symptoms were recruited from a student population. Each volunteer had previously undergone a barostat study. After an overnight fast, volunteers were scanned twice on separate days after intravenous injection of 200 MBq (99m)Tc-pertechnetate. On 1 occasion, volunteers were pretreated with a proton pump inhibitor. Thirty minutes after injection, sequential, 7-min SPECT scans (72 views, 10 s/view, 128 matrix) were acquired on a dual-head gamma-camera system before and up to 2 h after ingestion of a test meal. After reconstruction (filtered backprojection, ramp-Butterworth filter; order, 10; cutoff, 0.45 Nyquist), fundus volume was calculated semiautomatically by means of a threshold voxel volume tool.


RESULTS
Limiting injection dose from 370-740 MBq to 200 MBq (99m)Tc-pertechnetate resulted in good-quality images, with high target-to-background ratio up to 150 min after injection. This represents a significant dose reduction, from 4.6-9.3 to 2.5 mSv. There was no significant difference between SPECT fundic volumes or accommodation response with or without proton pump inhibitor pretreatment. Volume kinetics were similar to those with barostat studies, but gastric volumes were inferior.


CONCLUSIONS
Refining the methodology yields an improved noninvasive test for the assessment of gastric accommodation without unnecessarily increasing radiation burden. This technique enables repeated and serial measurement of gastric accommodation to a test meal, a process that is potentially useful for characterization and follow-up of dyspeptic patients with and without drug intervention.
Bennink
Roelof J
RJ
Department of Nuclear Medicine, Academic Medical Center, Amsterdam, The Netherlands. r.bennink@amc.uva.nl
van den Elzen
Bram D
BD
Kuiken
Sjoerd D
SD
Boeckxstaens
Guy E
GE
D000222:Adaptation, Physiological / Q000502:physiology*; D000328:Adult; D005260:Female; D005502:Food; D005746:Gastric Emptying / Q000502:physiology*; D005753:Gastric Mucosa / Q000378:metabolism; D006801:Humans; D008297:Male; D008657:Metabolic Clearance Rate; D019047:Phantoms, Imaging; D010865:Pilot Projects; D011829:Radiation Dosage; D011832:Radiation Injuries / Q000517:prevention & control; D011835:Radiation Protection / Q000379:methods*; D019275:Radiopharmaceuticals / Q000493:pharmacokinetics; D013670:Sodium Pertechnetate Tc 99m / Q000493:pharmacokinetics; D013270:Stomach / Q000000981:diagnostic imaging* / Q000502:physiology*; D015899:Tomography, Emission-Computed, Single-Photon / Q000379:methods*
D019275:Radiopharmaceuticals; D013670:Sodium Pertechnetate Tc 99m