Abstract
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.
Highlights
magnetic resonance imaging (MRI) is a very useful tool for studying both the structure and function of the stomach (Curcic et al, 2010, Marciani, 2011) as well as the mechanisms by which food is digested in and emptied from the stomach (Marciani et al, 2012, Marciani et al, 2013, Marciani et al, 2007, Kwiatek et al, 2009) A key advantage of MRI is that this techniques can acquire near simultaneous measurements of multiple parameters of gastric function in a single scanning session without ionizing radiation
This paper reports the development and validation of a method for the rapid and reliable assessment of gastric meal and secretion volumes from magnetic resonance imaging (MRI)
The findings demonstrate rapid secretion after consumption of this nutrient liquid test meal that continues throughout the emptying process such that secretion contributes more than half the volume of the gastric contents 75 minutes after ingestion of this meal
Summary
MRI is a very useful tool for studying both the structure and function of the stomach (Curcic et al, 2010, Marciani, 2011) as well as the mechanisms by which food is digested in and emptied from the stomach (Marciani et al, 2012, Marciani et al, 2013, Marciani et al, 2007, Kwiatek et al, 2009) A key advantage of MRI is that this techniques can acquire near simultaneous measurements of multiple parameters of gastric function in a single scanning session without ionizing radiation. Gastric emptying can be measured by the reduction in the volume of gastric contents over time on anatomical MRI scans (Fruehauf et al, 2009, Marciani et al, 2001b, Marciani et al, 2000, Schwizer et al, 1992, Steingoetter et al, 2006), gastric motility can be assessed using cine imaging (Borovicka et al, 1999, Kwiatek et al, 2006, Marciani et al, 2005, Marciani et al, 2001c) and gastric secretion can be estimated by monitoring the dilution of the meal (Sauter et al, 2012, Treier et al, 2008, Goetze et al, 2009) Based on these findings, gastric MRI has been proposed as a clinical investigation for the diagnosis of gastroesophageal reflux (Curcic et al, 2014a), gastroparesis (Ajaj et al, 2004) and functional dyspepsia (Tucker et al, 2012), as well as to determine residual volumes in preoperative sedation ahead of surgery (Lobo et al, 2009, Schmitz et al, 2012, Schmitz et al, 2011).
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