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- Wikström, Johan, et al.
(författare)
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Abdominal vessel enhancement with an ultrasmall, superparamagnetic iron oxide blood pool agent : evaluation of dose and echo time dependence at different field strengths
- 1999
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Ingår i: Academic Radiology. - 1076-6332 .- 1878-4046. ; 6:5, s. 292-298
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Tidskriftsartikel (refereegranskat)abstract
- RATIONALE AND OBJECTIVES: The purpose of the study was to determine the dose and echo time dependence of abdominal vessel enhancement at magnetic resonance (MR) imaging after injection of a blood pool contrast agent at two field strengths. MATERIALS AND METHODS: Sixteen healthy volunteers received NC100150 Injection at three dose levels (1.0 mg, 2.5 mg, and 4.0 mg of iron per kilogram of body weight). Images of the aorta and inferior vena cava (IVC) were obtained at 0.5 or 1.5 T. Four sequences with varying echo times were used with each subject. Signal intensities were recorded from the aorta, IVC, vessel vicinity, air, and a marker outside the patient. Contrast-to-noise ratios (CNRs) were calculated for the vessels. Aortic delineation was subjectively evaluated. RESULTS: Images with the highest mean vessel signal intensities, subjectively assessed as satisfactory for aortic delineation, were obtained with 2.5-4.0 mg of iron per kilogram of body weight at both field strengths. The highest CNR was found with 4.0 mg of iron per kilogram of body weight at 1.5 T. An increase in echo time caused larger signal intensity loss at larger dose levels. The signal intensity from the IVC was higher than that of the aorta at all dose levels, echo times, and field strengths. CONCLUSION: NC100150 Injection is an efficient T1-reducing agent at both 0.5 and 1.5 T. A positive dose response for CNR of the aorta and IVC was seen at 1.5 T.
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- Stenström, Mats, et al.
(författare)
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Methodologic aspects of computed microtomography to monitor the development of osteoporosis in gastrectomized rats
- 1995
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Ingår i: Academic Radiology. - 1076-6332. ; 2:9, s. 785-791
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Tidskriftsartikel (refereegranskat)abstract
- Rationale and Objectives We investigated the methodologic development of computed microtomography (CMT) for monitoring the development of osteoporosis in male Sprague-Dawley rats. Methods Eight rats were gastrectomized and eight rats were sham operated. Femurs, tibias, and tails were prepared, and CMT scans with spatial resolutions of 5–500 μm were made. Bone diameters, bone areas, and moments of inertia were determined from the CMT scans. Optimal slice position and the need for spatial resolution and energy optimization for future in vivo applications were investigated. Results Gastrectomy caused dramatic changes in the bone architecture of the tibia and the femur. The main features were vacuolization of the bone and reduced amounts of compact bone. Although the outer diameters of tubular bones (femur and tibia) were largely unaffected, their inner diameters were greatly increased following gastrectomy. Relative bone area and moment of inertia were greatly reduced. The optimal photon energy was 12 keV. Conclusion It is possible to monitor gastrectomy-evoked changes in bone morphology at various sites in rats using CMT scanning. The changes are suggestive of osteoporosis. By optimizing the energy spectrum and spatial resolution, as well as choosing the proper slice position, it should be possible to keep absorbed doses low enough to avoid acute radiation injury in repeated in vivo measurements.
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- Frennby, Bo, et al.
(författare)
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Clearance of iohexol, chromium-51-ethylenediaminetetraacetic acid, and creatinine for determining the glomerular filtration rate in pigs with normal renal function: comparison of different clearance techniques
- 1996
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Ingår i: Academic Radiology. - 1878-4046. ; 3:8, s. 651-659
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Tidskriftsartikel (refereegranskat)abstract
- RATIONALE AND OBJECTIVES: We wanted to improve determination of the glomerular filtration rate (GFR) with plasma clearance techniques because the alternative-renal clearance techniques-may involve inaccurate urine sampling or risk of urinary tract infection when bladder catheterization becomes necessary. Therefore, we compared the renal and plasma clearances of iohexol and chromium-51-ethylenediaminetetraacetic acid (51Cr-EDTA), as well as endogenous creatinine clearance, in 19 normal pigs using different techniques. METHODS: After an intravenous bolus injection of the GFR markers, 16 plasma samples were used to plot the marker concentrations versus time for 4.5 hr. Urine was collected during nine 30-min periods. Plasma clearance was calculated by dividing the dose of marker with the area under the plasma concentration curve (AUC) from the time of injection to infinity using one-compartment (ClAUC-slope) and three-compartment (ClAUC-3comp) models. The renal clearance was calculated by dividing the amount of marker excreted in the urine in a period with the AUC in the same period. This AUC was determined by integrating the total area in the period (Clren adv)--our reference method representing the "true" GFR--or by using the arithmetic mean of the plasma concentrations of the marker at the beginning and end of the urine collection period (Clren simple). Creatinine clearance was determined according to Clren simple. RESULTS: Renal clearances of iohexol and 51Cr-EDTA were significantly higher than creatinine clearance (P = .0002). There was no significant difference between the renal clearances of iohexol and 51Cr-EDTA or between their plasma clearances. The two mathematical methods of calculating the renal clearance of iohexol were highly correlated (rs = .99), as were the two methods of calculating its plasma clearance (rs = .95). Because of the extrarenal clearance of the markers, the plasma clearance methods for iohexol and 51Cr-EDTA always overestimated the true GFR. ClAUC-3comp was the method closest to the true GFR. For iohexol, the median overestimation of the GFR was higher with ClAUC-slope when early plasma samples (30-120 min) after injection of the marker were used (5.5 ml.min-1.10 kg-1) than when late samples (180-270 min) were used (4.0 ml.min-1.10 kg-1). After subtracting the median extrarenal clearances of iohexol and 51Cr-EDTA (previously determined in nephrectomized pigs) from their plasma clearances (ClAUC-3comp), the median overestimation of the true GFR was reduced from 2.0 to 1.1 ml.min-1.10 kg-1 with iohexol and from 2.1 to 1.3 ml.min-1.10 kg-1 with 51Cr-EDTA. CONCLUSION: GFR determination with plasma clearance techniques can be improved in three- and one-compartment models by taking late plasma samples and by subtracting the extrarenal plasma clearance of the species. One-compartment models can be improved by determining a correction formula in the species for the early parts of the decay curve of the plasma concentration of the marker
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- Frennby, Bo, et al.
(författare)
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Extrarenal plasma clearance of iohexol, chromium-51-ethylenediaminetetraacetic acid, and inulin in anephric pigs
- 1996
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Ingår i: Academic Radiology. - 1878-4046. ; 3:2, s. 145-153
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Tidskriftsartikel (refereegranskat)abstract
- RATIONALE AND OBJECTIVES: To improve the measurement of the glomerular filtration rate (GFR), we determined the extrarenal plasma clearance of the GFR markers iohexol, chromium-51-ethylenediaminetetraacetic acid (51Cr-EDTA), and inulin using 11 anephric pigs. METHODS: After an intravenous (i.v.) bolus injection of the markers, the decay curves of their plasma concentrations were monitored for 29 hr by 16 plasma samples. The area under the curve (AUC; concentration of marker versus time) was calculated according to one- and three-compartment kinetics. The extrarenal clearance was calculated by dividing the dose of marker by the AUC. RESULTS: In the three-compartment model, the median of the extrarenal clearances of iohexol, 51Cr-EDTA, and inulin were 0.87 ml.min-1.10 kg-1 (range = 0.62-1.26 ml.min-1.10 kg-1), 0.79 ml.min-1.10 kg-1 (range = 0.61-1.04 ml.min-1.10 kg-1), and 0.83 ml.min-1.10 kg-1 (range = 0.65-1.17 ml.min-1.10 kg-1). The extrarenal clearance of 51Cr-EDTA was slightly lower than that of iohexol and inulin when measured with the three-compartment model (p = .015). There was no statistically significant difference between the two models of kinetics in calculating clearance of the same marker. CONCLUSION: Our results indicate that subtracting the median values of the extrarenal clearance of the markers from the total plasma clearance will provide GFR values closer to the "true" GFR. This technique might prove useful in GFR calculations in patients with a very low GFR (e.g., residual GFR in patients on dialysis)
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- Nilsson, Håkan, et al.
(författare)
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Assessment of respiration during video fluoroscopy of dysphagic patients
- 1997
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Ingår i: Academic Radiology. - 1878-4046. ; 4:7, s. 503-507
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Tidskriftsartikel (refereegranskat)abstract
- RATIONALE AND OBJECTIVES: The authors evaluated the coordination of swallowing and respiration in dysphagic patients. MATERIALS AND METHODS: Video fluoroscopy and respirometry were performed simultaneously during 98 swallows in 33 patients (18 women, 15 men) with a median age of 70 years (interquartile range, 52-78 years). Pharyngeal transit time, deglutition apnea, and the ratio between the two (swallowing safety index) were calculated. Presence of a misdirected swallow (aspiration or penetration) was indicated. RESULTS: Pharyngeal transit time was not associated with deglutition apnea. Misdirected swallow was associated with a slightly prolonged pharyngeal transit time, a slightly shorter deglutition apnea, and a significantly lower swallowing safety index (1.8 [1.0-4.2] vs 4.5 [2.4-6.7]; P < .001) compared with normally directed swallow. The association between misdirected swallow and lower swallowing safety index was independent of pharyngeal transit time. CONCLUSION: Assessment of respiration is important in the evaluation of dysphagia. Aspiration, especially in elderly dysphagic patients, may be a consequence of primarily disturbed respiration. A low swallowing safety index may indicate risk of misdirected swallow.
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- Olsson, Rolf, et al.
(författare)
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Combined videomanometric identification of abnormalities related to pharyngeal retention
- 1997
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Ingår i: Academic Radiology. - 1878-4046. ; 4:5, s. 349-354
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Tidskriftsartikel (refereegranskat)abstract
- RATIONALE AND OBJECTIVES: The authors determined the usefulness of performing videoradiography and pharyngeal solid-state manometry during barium swallow in dysphagic patients with pharyngeal retention. METHODS: Results were retrospectively analyzed of simultaneous videoradiography and manometry examinations in 14 patients with retention of barium in the pharynx. Twelve age-matched patients without retention served as a control group. RESULTS: Patients with retention regularly had less opening of the upper esophageal sphincter than patients without retention (7.6 vs 10.3 mm, respectively; P = .003). In patients with retention, the laryngeal elevation was lower (17.1 vs 23.8 mm, respectively; P = .001), and the resting pressure of the upper esophageal sphincter was significantly lower (42.4 vs 54.0 mm Hg, respectively; P = .04). The duration of upper esophageal sphincter relaxation was also shorter in patients with retention (374 vs 603 msec, respectively; P = .003). The peak pharyngeal contraction pressure was not significantly different. CONCLUSION: The constrictors play a minor role in the conveyance of the bolus through the pharynx. Pharyngeal shortening could be the most important mechanism in bolus transport.
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| 22. |
- Olsson, Rolf, et al.
(författare)
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Videomanometry of the pharynx in dysphagic patients with a posterior cricopharyngeal indentation
- 1995
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Ingår i: Academic Radiology. - 1878-4046. ; 2:7, s. 597-601
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Tidskriftsartikel (refereegranskat)abstract
- RATIONALE AND OBJECTIVES: Patients with a posterior indentation in the pharyngoesophageal segment (PES) are generally considered to have an abnormality of the cricopharyngeal muscle (CPM). In this study we determined the actual width of the PES and the pressure circumstances during swallowing within the pharynx and PES in such patients. METHODS: Simultaneous videofluoroscopy and solid state manometry, radiologic examination of the pharynx, PES, and cervical esophagus were performed in 16 dysphagic patients with a cricopharyngeal (CP) bar. In eight patients the indentation was 25-50%, and in eight it was more than 50% of the adjacent gullet. Sixteen dysphagic patients without a CP bar were used as control subjects. In each patient swallows of 10-ml barium bolus were recorded. RESULTS: Patients with CP bars had a significantly wider PES above (p = .0005) and below (p = .02) the CPM, whereas the diameter at the level of the CPM was smaller only in the patients with more than 50% indentation compared with the patients without a CP bar. The contraction pressure above the CP bar (i.e., at the level of the inferior pharyngeal constrictor) was significantly (p = .002) weaker in patients with a CP bar (131 +/- 16 mm Hg) than in those without a CP bar (222 +/- 20 mm Hg). CONCLUSION: Our findings in patients with a posterior CP bar suggest that the major abnormality is weak constrictors with outpouching of the gullet above and below. Only in patients with more than 50% indentation was there a slight narrowing at the level of the CP bar. The CPM showed no manometric abnormalities in terms of resting pressure, relaxation, and contraction pressure. Therefore, the CPM is likely to relax and distend normally during swallowing in patients with a CP bar.
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