Lionel S. Zuckier

Radionuclide Studies in the Determination of Brain Death : Criteria, Concepts, and Controversies

Forty years after the publication of a landmark paper by the Ad Hoc Committee of the Harvard Medical School, the general concept of brain death has achieved widespread acceptance. In the United States, irreversible dysfunction of the brain and brainstem are required for the diagnosis of brain death. Although primarily based on clinical evaluation, confirmatory examinations, including radionuclide blood flow studies, play an important role in augmenting the physical examination in special situations when some of its specific components cannot be performed or reliably evaluated. The 2 main radionuclidic techniques used in evaluation of brain death are radionuclide angiography with nonlipophilic radiopharmaceuticals and parenchymal imaging with lipophilic agents. Specific technical guidelines for determination of brain death have been promulgated by professional medical societies. In the vast majority of cases, blood flow examinations are useful in confirming brain death. Nonetheless, on occasion patients clinically diagnosed with brain death will exhibit persistent intracranial blood flow or electrical activity. Existence of these contradictory cases reveals underlying inconsistencies in the definitions of brain death. We hypothesize that the existence of these apparent contradictions is related to differences in sensitivity of the physical examination and the confirmatory examinations, differences in localization of the physical examination and confirmatory tests, and differences between blood flow and cerebral function as markers of brain death.

Selective role of nuclear medicine in evaluating the acute abdomen

The imaging evaluation of the acute abdomen has clearly evolved with the introduction of high-resolution imaging techniques, such as CT, US, and MR imaging, leaving scintigraphic examinations an important, though selective, role based on their noninvasive, physiologic, and functional nature. Proper use of these examinations among all the diagnostic methods requires a good understanding of their strengths and limitations.

Synthetic Positron Emission Tomography-Computed Tomography Images for Use in Perceptual Studies

To better understand fundamental issues, perception studies of the fusion display would best be performed with a panel of lesions of variable location, size, intensity, and background. There are compelling reasons to use synthetic images that contain artificial lesions for perception research. A consideration of how to obtain this panel of lesions is the nucleus of the present review. This article is a conjoint effort of 3 groups that have joined together to review results from work that they and others have performed. The techniques we review include (1) substitution of lesions into a preexisting image matrix (either using actual prior patient-derived lesions or mathematically modeled artificial lesions), (2) addition of images (either in the attenuation-corrected image space or at an earlier stage before image reconstruction), and (3) simulation of the entire patient image. A judicious combination of the techniques discussed in this review may represent the most efficient pathway of simulating statistically varied but realistic appearing lesions.

Re: Morris-Stiff G, Falk G, Kraynak L, et al.: The Cholecystokinin Provocation HIDA Test: Recreation of Symptoms Is Superior to Ejection Fraction in Predicting Medium-Term Outcomes. J Gastrointest Surg 2010

While it is important from time to time to visit and even revisit the validity and utility of diagnostic examinations, the recent paper “The cholecystokinin Provocation HIDA Test: Recreation of Symptoms Is Superior to Ejection Fraction in Predicting Medium-Term Outcomes” reports extraordinary findings which are not easily reconciled with published literature and clinical experience. First of all, 41 of the 42 patients with right upper quadrant pain and normal ultrasound examinations became persistently pain free following cholecystectomy, suggesting a nearly 100% prevalence of biliary dyskinesia in this population. Either the group studied was highly preselected and skewed to disease, or that the methods and criteria of evaluation (“gold standard”) were overly lax, which exaggerated the prevalence of disease in this cohort. Secondly, even if we accept that all 41 patients had biliary dyskinesia, it is equally remarkable that they all experienced “typical pain” following a 30-min Sincalide injection, reflecting a 100% sensitivity for this maneuver, which is in contradiction to a large body of prior clinical experience where infusion of Sincalide does not usually elicit pain, even in patients with documented disease. One has to wonder whether methodological issues are the cause of these anomalous findings. To wit, the paper is very short on details regarding the subjective measurement of pain. It is unclear when the patients were asked about the pain, as we are only told that they were interviewed in the outpatient clinic following the procedure. Was this done immediately following the procedure, or at the 2-week follow-up? Were any written instruments employed? Was there any attempt to grade the severity of the pain? It would seem that the most accurate assessment of symptoms during infusion of Sincalide would be made by directly observing and quizzing the patient during the actual infusion itself, and not by eliciting recollections at a follow-up interview. A similar lack of detail is noted with respect to the 2-week assessment and the subsequent final telephone follow-up. Finally, even were these extraordinary findings validated, elementary epidemiologic understanding dictates that it is impossible to evaluate a diagnostic study in a population where the prevalence of disease is nearly 100%. In this group, a diagnostic exam which calls every patient positive would be deemed to perform admirably, while the true ability to discriminate normal from abnormal would remain completely untested. Were this test to be ported to a population with a more normally distributed prevalence of disease, it is very possible that the specificity of this highly sensitive examination would be abysmal, leading to a large number of false positive normal patients. Since the study group only included a solitary patient without disease (who in fact experienced pain during Sincalide infusion), there is no way to evaluate specificity. It is an optimal time to revisit the validity and utility of the gallbladder ejection fraction as a marker of biliary dyskinesia in light of new standardized practice guidelines that have been recently promulgated by expert panels. A prospective clinical trial utilizing these newly codified best-