PubMed · 7449240
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D Front. 1981. Brain scintigraphy now.. https://doi.org/10.1097/00003072-198101000-00010
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PURPOSE: To investigate pharmacokinetic and physiologic factors that determine the time to peak intravenous contrast medium enhancement in computed tomographic (CT) and magnetic resonance (MR) angiography in the porcine mid-abdominal aorta. MATERIALS AND METHODS: Four pigs were imaged repeatedly in seven to eight sets: For each set, 20 dynamic CT scans were obtained at a fixed aortic level after intravenous injection of contrast medium. From a physiologically based compartment model, aortic contrast enhancement curves were generated by varying contrast medium injection duration from 1 to 40 seconds. Contrast enhancement curves and times to peak aortic enhancement from the experiment and model were compared. Time to peak aortic enhancement obtained from the injection with the shortest duration was considered the time to peak test bolus contrast enhancement. Mathematic and pharmacokinetic analyses were performed to investigate factors that determine peak enhancement. RESULTS: Empiric and compartmental model times to peak aortic enhancement were in good agreement. Time to peak aortic enhancement corresponded to the weighted sum of injection duration and time to peak test bolus enhancement. With increasing injection duration, the relative contribution of injection duration to peak aortic enhancement time increased. When injection duration was longer than time to peak test bolus enhancement, time to peak aortic enhancement increased linearly with injection duration and occurred shortly after completion of injection. However, when injection duration was shorter than time to peak test bolus enhancement, time to peak aortic enhancement was determined predominantly by time to peak test bolus enhancement and only gradually increased with injection duration. CONCLUSION: Time to peak aortic enhancement is determined by the relative contributions of injection duration and contrast medium traveling time and may well be explained by contrast medium volumetric inflow and recirculation physiology.
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BACKGROUND: We sought to identify whether transcutaneous oxygen tension (tcPo2) measurements could be used to noninvasively detect lesions in the arterial network supplying blood flow to the hypogastric circulation. METHODS AND RESULTS: A study was undertaken in vascular patients with suspected (PC, n=43) and not with suspected (NPC, n=34) proximal ischemia. TcPo2 was measured on both buttocks and with a chest reference electrode. Arteriography on the right or left side was positive for stenoses (> or =75%) or occlusion of one or more of the following arteries: the aorta, the common iliac arteries, or the internal iliac arteries. The arteriography was compared with the resting tcPo2 values (REST) and with the minimal value (MIN) and maximal change from rest normalized to eventual chest changes (DROP) recorded during or after a treadmill test. REST, MIN, and DROP were, respectively, as follows in positive versus negative arteriograms (mean+/-SD; in mm Hg): 80.2+/-10.9 versus 78.6+/-11.5 (P>0.05), 55.2+/-20.0 versus 69.9+/-15.8 (P<0.001), and -31.8+/-17.6 versus -9.5+/-6.4 (P<0.0001) in PC and 78.9+/-14.0 versus 80.5+/-14.3 (P>0.05), 64.4+/-21.0 versus 75.1+/-14.6 (P<0.02), and -24.1+/-13.5 versus -8.7+/-4.8 (P<0.0001) in NPC. In PC and NPC respectively, with a cutoff point of -16 and -15 mm Hg, DROP showed, respectively, 83%/82% and 79%/86% sensitivity/specificity in the diagnosis of positive arteriograms. CONCLUSIONS: Proximal ischemia is a frequent finding in vascular patients. TcPo2 measurement on the buttocks during exercise is a sensitive and specific indicator for lesions in the arterial tree toward the hypogastric circulation. Potentially it could objectively assess the response to endovascular or surgical approaches to iliac lesions.