Oral contrast medium in PET/CT: should you or shouldn't you?

PURPOSE: It has been suggested that the use of computed tomography (CT) positive contrast agents has led to attenuation-induced artefacts on 18F-fluorodeoxyglucose positron emission tomography (18F-FDG PET/CT) systems. Consequently, centres may withhold the use of such agents. Whilst there is theoretical evidence to support the aforementioned claim, the clinical relevance of the induced artefacts has not been widely established. Moreover, the potential benefits of bowel enhancement on PET/CT have yet to be formally evaluated. We therefore prospectively examined PET/CT studies to assess whether the use of oral contrast medium induces clinically relevant artefacts and whether the use of these agents is diagnostically helpful. METHODS: Over a 2-month period, 18F-FDG PET/CT images were prospectively reviewed from 200 patients following Gastrografin administration 2 h prior to examination. Both a radiologist and a nuclear medicine physician reviewed the images for contrast medium-mediated clinically relevant artefacts. Artefacts were sought on the CT attenuation-corrected images and were compared with the appearance on non-attenuated-corrected images. The number of examinations in which the oral contrast aided image interpretation was also noted. RESULTS: There were no oral contrast medium-induced clinically significant artefacts. In 38 of the 200 patients, oral contrast aided image interpretation (owing to differentiation of mass/node from bowel, discrimination of intestinal wall from lumen or definition of the anatomy of a relevant site). In 33 of these 38 patients, the anatomical site of interest was the abdomen/pelvis. CONCLUSION: The use of oral contrast medium in 18F-FDG PET studies should not be withheld as it improves image interpretation and does not produce clinically significant artefacts.

How often do patients undergo repeat PET or PET/CT examinations? Experience from a UK institution.

BACKGROUND AND AIM: According to the report of the Intercollegiate Standing Committee on Nuclear Medicine, the UK requires 40-60 positron emission tomography (PET) machines in the next decade (Intercollegiate Standing Committee on Nuclear Medicine). Positron Emission Tomography: a Strategy for Provision in the UK. London: Royal College of Physicians of London; 2003, pp. 1-9). This figure is based mainly on patients receiving only one examination and restricting the clinical indication to three primary diagnoses. The aim of this study was to assess the appropriateness of this figure and the assumptions made in the Intercollegiate report on UK PET provision. METHODS: We examined retrospectively our institution's entire PET and PET/computed tomography (CT) database, which spans 4 years and 9 months. We recorded the number of patients who received repeat examinations. RESULTS: Reports were available for 3354 PET/CT or PET-only studies; 418 of 2268 patients (18.4%) received at least one repeat PET/CT examination. The three main indications for PET examination in the Intercollegiate report only accounted for approximately 60% of the examinations undertaken. CONCLUSION: Our records suggest that basing the UK's future PET provision on a single examination and on three clinical indications only is no longer realistic.

Myocardial perfusion scintigraphy: patients' perception of benefit and risk.

BACKGROUND AND AIM: Myocardial perfusion scintigraphy is a useful and safe investigation, which has now received approval by the National Institute of Clinical Excellence (NICE). However, there are common unpleasant side-effects to the drugs used and there is a risk from radiation. This study was performed to assess patients' perceptions of the benefits and risks of myocardial perfusion scintigraphy, and to determine whether the cardiac stress component influenced these perceptions. METHODS: Ninety patients attending our institution for thallium-201 myocardial perfusion study over a period of 2 months were interviewed with regard to their perception of the benefits of the study. Patients were interviewed prior to and following the stress study. RESULTS: On average, patients thought they had a good (three in four) chance of benefiting from myocardial perfusion imaging. Sixty per cent of patients were unaware that they were going to be exposed to ionizing radiation and over 80% were unaware of the side-effects. Two-thirds of the patients said they would undergo the test even if there was only a one in ten chance of benefiting. The majority of patients were uninfluenced by the stress component of the study. CONCLUSIONS: Many patients lack a knowledge of the risks of myocardial perfusion scintigraphy. Most patients would undergo myocardial perfusion studies even if they had a poor chance of benefit.