Stijn Dirix

Abnormal Regional Brain Activity During Rest and (Anticipated) Gastric Distension in Functional Dyspepsia and the Role of Anxiety: A H 2 15 O-PET Study

OBJECTIVES:During gastric distension in hypersensitive functional dyspepsia (FD), activation was found in somatosensory cortex (SI/SII) and ventrolateral prefrontal cortex (vlPFC) but, contrary to controls, not in pregenual anterior cingulate (pACC). The aims of this article were to study (i) cortical activations and deactivations during distension and sham compared with baseline in FD, regardless of sensitivity status; (ii) differences in brain activity between health and FD during “no distension” conditions; and (iii) the relationship between anxiety and brain activity in FD.METHODS:Brain H215O-PET was performed in 25 FD patients (13 hypersensitive) during three conditions: baseline, distension at discomfort threshold, and sham. Brain activity was compared against healthy controls using SPM2.RESULTS:Discomfort threshold was lower; sensation scores in all conditions were higher in patients than controls. (i) Activations were similar to controls, except for a lack of pACC activation during distension in FD. Patients showed no dorsal pons and amygdala deactivation during distension and sham, respectively. (ii) Comparing baseline or sham activity showed the following differences: higher activity in SII/SI, insula, midcingulate (MCC), dorsolateral and ventrolateral PFC in controls; and higher activity in occipital cortex in FD. Differences in left lateral PFC were specific to sham. (iii) Anxiety correlated negatively with pACC and MCC and positively with dorsal pons activity.CONCLUSIONS:FD patients failed to activate pACC, to deactivate dorsal pons during distension, and to deactivate amygdala during sham; this may represent arousal–anxiety-driven failure of pain modulation. During baseline and sham, differences between patients and controls were found in sensory as well as affective–cognitive areas.

Regional Brain Activity in Functional Dyspepsia: A H215O-PET Study on the Role of Gastric Sensitivity and Abuse History

BACKGROUND & AIMS Differences in brain activity between health and functional dyspepsia (FD) have been reported; it is unclear whether this is influenced by gastric hypersensitivity or abuse history. Therefore, we aimed to determine the influence of gastric sensitivity and abuse history on gastric sensation scores and brain activity in homeostatic-afferent, emotional-arousal, and cortical-modulatory brain regions in FD. METHODS Abuse history was assessed using a validated self-report questionnaire. H(2)(15)O positron emission tomography was performed in 25 FD patients (13 hypersensitive and 8 abused) during 3 conditions, that is, no distension, gastric distension at discomfort threshold, and sham distension. Data were analyzed in SPM2. Region of interest analysis was used to confirm differences in prehypothesized regions. RESULTS No association between hypersensitivity and abuse history was found. Gastric hypersensitivity was associated with significantly higher gastric sensation scores during baseline and sham. A condition-independent difference in ventral posterior cingulate activity was found between groups, as well as distension and sham-specific differences in brainstem and cingulate areas. Abuse history was associated with higher gastric sensation scores in all conditions and with differences in insular, prefrontal, and hippocampus/amygdala activity. CONCLUSIONS Gastric sensitivity and abuse history independently influence gastric sensation as well as brain activity in FD.

Reduction of the Influence of Intravenous Contrast in PET/CT by Using a Threshold Conversion Method

In PET/CT an attenuation map for PET is derived from the CT image. However, when a full diagnostic CT with intravenous contrast is performed, the PET attenuation values are overestimated. This results in increased SUV values when compared with contrast-free studies. Although several groups have reported that the impact of contrast on the SUV values is small, the effect may not be negligible in treatment follow-up. Conventionally the hybrid scaling method is used for the conversion of CT attenuation values to PET attenuation. Here, we propose a new conversion method in an attempt to minimize the influence of the intravenous contrast on the SUV values. With the new method, CT attenuation values are converted from [0, 0.16] to [0, 0.091] (units in cm) and all the attenuation values greater than the threshold 0.16 are converted to 0.091. The threshold value of 0.16 was derived using 9 patient studies involving 14 ROIs and was further evaluated using 5 patient studies involving 13 ROIs. For the first 9 patient studies, the mean influence of the intravenous contrast on the SUV values is 5.53% (range [1.59-11.63]) with the conventional method and 2.04% (range [0.25-5.73]) with the new threshold method. Very similar results were obtained in the second group: 5.90% (range [1.29-9.59]) with the conventional method and 1.91% (range [0.04-4.59]) with the new threshold method.