Coronary Artery Lumen Segmentation Using Location–Adaptive Threshold in Coronary Computed Tomographic Angiography: A Proof-of-Concept

ObjectiveTo compare the lumen parameters measured by the location-adaptive threshold method (LATM), in which the inter- and intra-scan attenuation variabilities of coronary computed tomographic angiography (CCTA) were corrected, and the scan-adaptive threshold method (SATM), in which only the inter-scan variability was corrected, with the reference standard measurement by intravascular ultrasonography (IVUS).Materials and MethodsThe Hounsfield unit (HU) values of whole voxels and the centerline in each of the cross-sections of the 22 target coronary artery segments were obtained from 15 patients between March 2009 and June 2010, in addition to the corresponding voxel size. Lumen volume was calculated mathematically as the voxel volume multiplied by the number of voxels with HU within a given range, defined as the lumen for each method, and compared with the IVUS-derived reference standard. Subgroup analysis of the lumen area was performed to investigate the effect of lumen size on the studied methods. Bland-Altman plots were used to evaluate the agreement between the measurements.ResultsLumen volumes measured by SATM was significantly smaller than that measured by IVUS (mean difference, 14.6 mm³; 95% confidence interval [CI], 4.9–24.3 mm³); the lumen volumes measured by LATM and IVUS were not significantly different (mean difference, −0.7 mm³; 95% CI, −9.1–7.7 mm³). The lumen area measured by SATM was significantly smaller than that measured by LATM in the smaller lumen area group (mean of difference, 1.07 mm²; 95% CI, 0.89–1.25 mm²) but not in the larger lumen area group (mean of difference, −0.07 mm²; 95% CI, −0.22–0.08 mm²). In the smaller lumen group, the mean difference was lower in the Bland-Altman plot of IVUS and LATM (0.46 mm²; 95% CI, 0.27–0.65 mm²) than in that of IVUS and SATM (1.53 mm²; 95% CI, 1.27–1.79 mm²).ConclusionSATM underestimated the lumen parameters for computed lumen segmentation in CCTA, and this may be overcome by using LATM.     

Effect of marginal zinc deficiency on the lymphatic absorption of [14C]cholesterol

The effect of zinc deficiency on intestinal absorption of cholesterol was investigated in adult male rats fed 3.6 ppm of dietary zinc (ZD) and compared with pair-fed (PF) and ad-libitum (CT) controls fed 30.6 ppm of zinc for 10 to 12 wk. The intestinal absorption of cholesterol was measured by collecting the mesenteric lymph at hourly intervals for 8 h after infusing a dose of [14C]cholesterol in a lipid emulsion through an indwelling duodenal catheter. Data on the hourly lymphatic output of [14C]cholesterol showed that the absorption of [14C]cholesterol plateaued at 4 h postdosing in all groups. The rate of the appearance of [14C]cholesterol in the mesenteric lymph significantly decreased in ZD rats at 5 h and thereafter. The cumulative absorption of [14C]cholesterol by ZD rats for the 8-h period was 4.4 +/- 1.0% of the dose, compared with 11.8 +/- 1.1% by PF and 10.7 +/- 1.4% by CT rats. There were no differences in percent distribution of esterified [14C]cholesterol among the three groups. Also, no significant change in mucosal cholesterol esterase activity was observed due to zinc deficiency. The present data and previous findings taken together suggest that the primary mechanism responsible for the impaired absorption of cholesterol may be associated with defective formation of chylomicrons in the intestinal mucosa.     

Aluminum contamination of infant formulas

This study aims to determine the extent of aluminum (Al) contamination in whole milk, milk formulas, and other nutrient products commonly used for infants. Similar products from different manufacturers and different lots were measured for Al using electrothermal atomic absorption technique. Aluminum measurements were made directly from the samples or after reconstitution or dilution with Al-free water. Aluminum content was lowest (less than 50 micrograms/liter) in human milk, whole cow milk, and products that appear to require minimal manufacture processing and have few additives such as skim milk, cow milk with 2% fat, bottled glucose water, and sterile water. Highest Al levels (up to 2346 micrograms/liter) were found in highly processed and modified formulas including soy formula, preterm infant formula, and formulas for specific metabolic disorders. Aluminum content of humanized cow milk formula and bottled glucose-electrolyte solution were between the two ranges and usually less than 400 micrograms/liter. There were no significant differences in Al content of similar products from different manufacturers. Liquid formula stored in glass bottles has highest Al content compared to that stored in steel cans or powder preparation of the same product (p less than 0.05). Thus there are marked differences in Al loading depending on the type of formula, whether it is a powder or liquid preparation and the type of storage container. We speculate that raw materials such as soybean, additives such as calcium and phosphorus, manufacturing processes and storage containers are potential sources of contamination of infant formulas.     

Ischemic monomelic neuropathy: An under-recognized complication of hemodialysis access

During the past 3 years six episodes of ischemic monomelic neuropathy (IMN) have been identified in five patients as a complication of upper extremity dialysis grafts. All patients had long-standing insulin-dependent diabetes, peripheral neuropathy, and brachial artery graft origins, whereas 60% had peripheral vascular disease. Five episodes occurred immediately after graft placement, whereas one was due to a graft-related thromboembolus. Diagnostic delay was common with initial findings attributed to anesthesia, positioning, or surgical trauma. Electrophysiologic studies showed underlying diabetic neuropathy with severe multifocal neuropathy distal to the grafts. Digital pressure indices were reduced but there was no critical ischemia. In three cases ischemia was completely corrected with improvement in one. One patient had proximal balloon angioplasty with no improvement and of the two untreated patients, one improved slightly. Ischemic monomelic neuropathy is a rare but disabling complication of dialysis access in diabetic uremic patients. Its occurrence is unpredictable and diagnostic delay is common. Correction of ischemia is indicated but usually does not improve the neuropathy. Prevention requires further research to more accurately characterize the patients at risk.Presented at the Twelfth Annual Meeting of the Southern California Vascular Surgical Society, Coronado, Calif., September 17–19, 1993.