| 1. |
- Bjerner, Tomas, et al.
(författare)
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High in-plane resolution T2-weighted magnetic resonance imaging of acute myocardial ischemia in pigs using the intravascular contrast agent NC100150 injection.
- 2004
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Ingår i: Investigative Radiology. - 0020-9996 .- 1536-0210. ; 39:8, s. 470-478
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Tidskriftsartikel (refereegranskat)abstract
- Rationale and Objectives: The intravascular contrast agent NC100150 injection was tested for its ability to demarcate nonperfused myocardium in a porcine model of coronary occlusion. Materials and Methods: A T2-weighted fast spin echo sequence was acquired ex vivo and in vivo during first pass and steady-state circulation of the contrast agent in 2 dosages (2 and 5 mg Fe/kg bw) or saline. Results: Ex vivo, in the high-dose group, the volume of nonperfused myocardium determined from T2-weighted images was 99% of that determined from photographs where perfused myocardium stained with fluorescein. A significantly higher contrast to noise ratio between perfused and nonperfused myocardium was found (both ex and in vivo in steady state) compared with the control group. During first pass, a significant reduction in signal intensity (74 ± 18%) was found in perfused myocardium after contrast injection. Conclusion: NC100150 injection, combined with T2-weighted turbo spin echo imaging, allowed detailed visualization of non-perfused myocardium in the steady state, which corresponded to the area at risk as determined by fluorescein.
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| 2. |
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| 3. |
- Briley-Saebo, Karen C., et al.
(författare)
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Clearance of iron oxide particles in rat liver : effect of hydrated particle size and coating material on liver metabolism
- 2006
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Ingår i: Investigative Radiology. - : Ovid Technologies (Wolters Kluwer Health). - 0020-9996 .- 1536-0210. ; 41:7, s. 560-571
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Tidskriftsartikel (refereegranskat)abstract
- OBJECTIVES: We sought to evaluate the effect of the particle size and coating material of various iron oxide preparations on the rate of rat liver clearance. MATERIALS AND METHODS: The following iron oxide formulations were used in this study: dextran-coated ferumoxide (size = 97 nm) and ferumoxtran-10 (size = 21 nm), carboxydextran-coated SHU555A (size = 69 nm) and fractionated SHU555A (size = 12 nm), and oxidized-starch coated materials either unformulated NC100150 (size = 15 nm) or formulated NC100150 injection (size = 12 nm). All formulations were administered to 165 rats at 2 dose levels. Quantitative liver R2* values were obtained during a 63-day time period. The concentration of iron oxide particles in the liver was determined by relaxometry, and these values were used to calculate the particle half-lives in the liver. RESULTS: After the administration of a high dose of iron oxide, the half-life of iron oxide particles in rat liver was 8 days for dextran-coated materials, 10 days for carboxydextran materials, 14 days for unformulated oxidized-starch, and 29 days for formulated oxidized-starch. CONCLUSIONS: The results of the study indicate that materials with similar coating but different sizes exhibited similar rates of liver clearance. It was, therefore, concluded that the coating material significantly influences the rate of iron oxide clearance in rat liver.
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| 4. |
- Hagiwara, Akifumi, et al.
(författare)
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SyMRI of the Brain : Rapid Quantification of Relaxation Rates and Proton Density, With Synthetic MRI, Automatic Brain Segmentation, and Myelin Measurement
- 2017
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Ingår i: Investigative Radiology. - : Lippincott Williams & Wilkins. - 0020-9996 .- 1536-0210. ; 52:10, s. 647-657
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Forskningsöversikt (refereegranskat)abstract
- Conventional magnetic resonance images are usually evaluated using the image signal contrast between tissues and not based on their absolute signal intensities. Quantification of tissue parameters, such as relaxation rates and proton density, would provide an absolute scale; however, these methods have mainly been performed in a research setting. The development of rapid quantification, with scan times in the order of 6 minutes for full head coverage, has provided the prerequisites for clinical use. The aim of this review article was to introduce a specific quantification method and synthesis of contrast-weighted images based on the acquired absolute values, and to present automatic segmentation of brain tissues and measurement of myelin based on the quantitative values, along with application of these techniques to various brain diseases. The entire technique is referred to as "SyMRI" in this review. SyMRI has shown promising results in previous studies when used for multiple sclerosis, brain metastases, Sturge-Weber syndrome, idiopathic normal pressure hydrocephalus, meningitis, and postmortem imaging.
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| 5. |
- Hahn, Gabriele, et al.
(författare)
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Pharmacokinetics and safety of gadobutrol-enhanced magnetic resonance imaging in pediatric patients
- 2009
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Ingår i: Investigative Radiology. - 0020-9996 .- 1536-0210. ; 44:12, s. 776-783
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Tidskriftsartikel (refereegranskat)abstract
- OBJECTIVES: This clinical study investigated the pharmacokinetics and safety of gadobutrol, a magnetic resonance (MR) imaging extracellular contrast agent, in pediatric patients aged 2 to 17 years. MATERIALS AND METHODS: In this open-label, multicenter study, patients scheduled for routine contrast-enhanced MR imaging of the brain, spine, liver or kidney, or MR angiography received a single intravenous injection of gadobutrol (0.1 mmol/kg/0.1 mL/kg). Patients were stratified by age groups (2-6, 7-11, and 12-17 years). Blood and urine samples were collected at prespecified time points and analyzed for gadolinium concentrations. Plasma data were evaluated by means of a nonlinear mixed effects model, and urine data were analyzed using descriptive statistics. In addition, the safety of gadobutrol was evaluated. RESULTS: A total of 130 patients (2-6 years, n = 45; 7-11 years, n = 39; 12-17 years, n = 46) were included in the final population pharmacokinetic analysis. Gadobutrol pharmacokinetics in children aged 2 to 17 years were adequately described by an open 2-compartment model with elimination from the central compartment. The median estimates (2.5th percentile, 97.5th percentile) of body weight-normalized total body clearance (L/h/kg) per age group were 0.10 (0.05, 0.17) for all ages, 0.13 (0.09, 0.17) in the 2 to 6 year age group, 0.10 (0.05, 0.17) in the 7 to 11 year age group and 0.09 (0.05, 0.10) in the 12 to 17 year age group. The body weight-normalized median estimates of total volume of distribution (L/kg) were 0.20 (0.12, 0.28) for all ages, 0.24 (0.20, 0.28) in the 2 to 6 year age group, 0.19 (0.14, 0.23) in the 7 to 11 year age group and 0.18 (0.092, 0.23) in the 12 to 17 year age group. Median gadolinium plasma concentrations at 20 minutes postinjection were simulated using the population pharmacokinetic model and ranged from 414 (13 kg subject) to 518 micromol/L (65 kg subject). Body weight was identified as the major covariate influencing the pharmacokinetic parameters of total body clearance and central volume of distribution. Age was not found to be an additional independent parameter. The median amount of renally excreted gadolinium was 77.0% of the administered dose within 6 hours postinjection, indicating that gadobutrol was renally excreted in this pediatric population aged 2 to 17 years. Gadobutrol was well tolerated, with drug-related adverse events of mild intensity reported for 8 (5.8%) of 138 patients. CONCLUSIONS: Observed differences in pharmacokinetics were attributed to body weight, with no additional independent effect of age. Thus, no dose adjustment from the standard dose of gadobutrol in adults based on body weight (0.1 mmol/kg) is necessary in pediatric patients aged 2 to 17 years. Gadobutrol was safe and well tolerated in the pediatric population in this study.
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| 6. |
- Nygren, A, et al.
(författare)
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Red-cell trapping in the rat renal microcirculation induced by low-osmolar contrast media and mannitol
- 1993
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Ingår i: Investigative Radiology. - 0020-9996 .- 1536-0210. ; 28:11, s. 1033-1038
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Tidskriftsartikel (refereegranskat)abstract
- RATIONALE AND OBJECTIVES: In acute renal failure after ischemia, intravascular obstruction by trapped red blood cells in the microvasculature of the renal outer medulla is a consistent finding. The influence of intravenously injected contrast media (CM) on such obstruction was investigated. METHODS: Anesthetized rats were subjected to 45 minutes of unilateral renal ischemia. Red-cell trapping in ischemically injured kidneys and in the contralateral uninjured kidneys was estimated from the intrarenal distribution of 51Cr-labelled erythrocytes after injection of ioxaglate or iopamidol in a dose of 1,600 mg I/kg body weight. As an osmolar control substance, mannitol (950 mOsm/kg) was given to a third group and isotonic Ringer's solution was administered to a fourth group. RESULTS: In the uninjured kidneys, treatment with ioxaglate or mannitol resulted in no red-cell trapping, while the iopamidol-treated group showed red-cell trapping in the inner stripe of the outer medulla in a dose-dependent manner. In the ischemically injured kidneys, both CM and mannitol enhanced the red-cell trapping in the inner stripe of the renal medulla. CONCLUSION: The results indicate that intravenously administered ioxaglate and iopamidol enhance the microvascular obstructions evoked by ischemic injury and that iopamidol may induce local impairment in renal medullary microcirculation in a normal kidney.
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| 7. |
- Sundín, Anders, et al.
(författare)
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Computed tomography of experimental liver metastases using an iodinated hepatocyte-specific lipid emulsion : a correlative study in the nude rat
- 1994
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Ingår i: Investigative Radiology. - 0020-9996 .- 1536-0210. ; 29:11, s. 963-969
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Tidskriftsartikel (refereegranskat)abstract
- RATIONALE AND OBJECTIVES: A hepatocyte-specific iodinated lipid emulsion, NRI 757, was used for detection of experimental hepatic metastases. MATERIALS AND METHODS: The study was performed in a correlative model of multiple hepatic metastases from a human colonic cancer implanted in the nude rat. RESULTS: After intravenous injection, normal liver parenchyma remained enhanced for several hours, whereas the uptake in hepatic metastases was negligible. A liver-to-lesion contrast of 45 Hounsfield units (HU) was obtained at a dose of 1 mL NRI 757/kg body weight (BW). In a lesion-by-lesion analysis of 177 metastases ranging in size from 1 to 32 mm, the mean +/- standard deviation overall detection rate for native scanning and contrast-enhanced scanning in vivo and post mortem, 20 +/- 0.4%, 53 +/- 5.2%, and 55 +/- 4.0%, respectively and 28%, 84%, and 82%, retrospectively. When metastatic size also was considered, for native scanning the maximum detection rate of 61% was reached for 8- to 10-mm lesions, whereas for contrast-enhanced computed tomography scanning, 100% of the 5- to 7-mm lesions and 42% of the 1- to 2-mm nodules were detected. CONCLUSION: The use of NRI 757 improved the diagnostic yield considerably.
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| 8. |
- Wikström, Johan, et al.
(författare)
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Gadobenate dimeglumine-enhanced magnetic resonance angiography of the pelvic arteries
- 2003
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Ingår i: Investigative Radiology. - : Ovid Technologies (Wolters Kluwer Health). - 0020-9996 .- 1536-0210. ; 38:8, s. 504-515
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Tidskriftsartikel (refereegranskat)abstract
- RATIONALE AND OBJECTIVES: To evaluate 4 doses of gadobenate dimeglumine (Gd-BOPTA) for contrast-enhanced magnetic resonance angiography (CE-MRA) of the pelvic arteries and to compare CE-MRA with unenhanced time-of-flight MRA (2D-TOF-MRA). METHODS: A multicenter Phase II dose-finding study was performed in 136 patients with Gd-BOPTA doses of 0.025, 0.05, 0.1, and 0.2 mmol/kg bodyweight. Evaluation of CE-MRA images and comparison with 2D-TOF-MRA images was performed onsite and by 2 blinded offsite reviewers in terms of subjective image quality, number of lesions detected, and confidence in lesion characterization. RESULTS: Significant (P < 0.05) improvements over unenhanced findings were observed for CE-MRA at all dose levels. For reviewer 1 and the onsite investigators, the overall image quality increased up to a dose of 0.1 mmol/kg and then plateaued. For reviewer 2, increased image quality was noted up to a dose of 0.2 mmol/kg. Significant (P < 0.005) increases in diagnostic confidence on CE-MRA versus unenhanced MRA was observed for all dose groups by reviewer 1 and the onsite investigators and for the 0.1 and 0.2 mmol/kg dose groups by reviewer 2. No serious adverse events were recorded that were attributable to the study drug and no trends in laboratory parameters, vital signs, or electrocardiogram recordings were observed. CONCLUSIONS: Gadobenate dimeglumine-enhanced MRA is safe and significantly more effective than unenhanced 2D-TOF-MRA for imaging the pelvic arteries. A dose of 0.1 mmol/kg appears the most appropriate dose for subsequent Phase III clinical evaluation.
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| 9. |
- Ahmad, Tashfeen, et al.
(författare)
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Peripheral quantitative computed tomography for the detection of diabetic osteopathy: a study in the Goto-Kakizaki rat.
- 2003
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Ingår i: Investigative radiology. - 0020-9996. ; 38:3, s. 171-6
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Tidskriftsartikel (refereegranskat)abstract
- RATIONALE AND OBJECTIVE: To assess the utility of dual energy x-ray absorptiometry (DEXA) and peripheral quantitative computed tomography (pQCT) in detecting trabecular and cortical bone changes in diabetes as a model of osteopenia. MATERIALS AND METHODS: The tibia from 10 type-2 diabetic Goto-Kakizaki (GK) rats and 10 control Wistar rats were analyzed by DEXA, pQCT, and ash weight determination. RESULTS: DEXA of GK rats showed a significant reduction in mineral content (32%) and density (24%) of the metaphysis, but not of the diaphysis. PQCT disclosed that the reduction of density predominantly pertained to the trabecular bone (reduced by 62%). Periosteal and endosteal circumferences of the diaphyses were increased and cortical thickness was unchanged leading to increased moment of inertia. CONCLUSIONS: This study suggests that in osteopathic conditions, cortical and trabecular bone should be separately examined within specific subregions to obtain relevant information. Loss of metaphyseal trabecular bone seems to be a predominant feature in diabetic rats. Moreover, there is increased moment of inertia in the diaphysis implying increased strength. These diagnostic features of diabetic osteopathy can only be assessed by pQCT. It may prove that similar changes occur in human type-2 diabetes, which could explain the susceptibility to periarticular fracture and Charcot arthropathy.
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| 10. |
- Aksit Ciris, P., et al.
(författare)
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Accelerated Segmented Diffusion-Weighted Prostate Imaging for Higher Resolution, Higher Geometric Fidelity, and Multi-b Perfusion Estimation
- 2019
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Ingår i: Investigative Radiology. - 0020-9996. ; 54:4, s. 238-246
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Tidskriftsartikel (refereegranskat)abstract
- Purpose The aim of this study was to improve the geometric fidelity and spatial resolution of multi-b diffusion-weighted magnetic resonance imaging of the prostate. Materials and Methods An accelerated segmented diffusion imaging sequence was developed and evaluated in 25 patients undergoing multiparametric magnetic resonance imaging examinations of the prostate. A reduced field of view was acquired using an endorectal coil. The number of sampled diffusion weightings, or b-factors, was increased to allow estimation of tissue perfusion based on the intravoxel incoherent motion (IVIM) model. Apparent diffusion coefficients measured with the proposed segmented method were compared with those obtained with conventional single-shot echo-planar imaging (EPI). Results Compared with single-shot EPI, the segmented method resulted in faster acquisition with 2-fold improvement in spatial resolution and a greater than 3-fold improvement in geometric fidelity. Apparent diffusion coefficient values measured with the novel sequence demonstrated excellent agreement with those obtained from the conventional scan (R 2 = 0.91 for b max = 500 s/mm 2 and R 2 = 0.89 for b max = 1400 s/mm 2 ). The IVIM perfusion fraction was 4.0% ± 2.7% for normal peripheral zone, 6.6% ± 3.6% for normal transition zone, and 4.4% ± 2.9% for suspected tumor lesions. Conclusions The proposed accelerated segmented prostate diffusion imaging sequence achieved improvements in both spatial resolution and geometric fidelity, along with concurrent quantification of IVIM perfusion. © 2019 Wolters Kluwer Health, Inc. All rights reserved.
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| 11. |
- Amundsen, T, et al.
(författare)
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A closed-chest pulmonary artery occlusion/reperfusion model in the pig: detection of experimental pulmonary embolism with MR angiography and perfusion MR imaging
- 2000
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Ingår i: Investigative Radiology. - 0020-9996. ; 35:5, s. 295-303
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Tidskriftsartikel (refereegranskat)abstract
- RATIONALE AND OBJECTIVES: To establish a pig model suitable for imitating pulmonary emboli to facilitate research in the diagnosis of pulmonary embolism. METHODS: Thirteen animals were anesthetized, mechanically ventilated, and subjected to pulmonary artery catheterization initiated from the right external jugular vein. With the use of a Swan-Ganz catheter, repetitive occlusion/reperfusion maneuvers were done at different locations of the pulmonary arterial tree. Conventional pulmonary angiography, MR angiography, and perfusion MR imaging were performed. RESULTS: The model remained hemodynamically stable throughout the 13 experiments, without any significant difference between the blood pressure measurements at the start and at the end of the right-heart and pulmonary artery catheterizations. In each of the nine animal experiments that investigated MR imaging, four of four using perfusion MR imaging (proximal and distal occlusions) and five of five using MR angiography (larger pulmonary artery occlusions), all repeated pulmonary artery occlusions were successfully performed (reproducibility of 100%). CONCLUSIONS: The closed-chest pulmonary artery occlusion/reperfusion model in the pig allowed repetitive, controlled imitations of pulmonary emboli at different levels of the pulmonary artery in the same experiment. MR angiography and perfusion MR imaging were adequate to detect the pulmonary artery occlusions and the nonperfused lung regions, respectively. The model may be a helpful tool for future research in this field.
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| 12. |
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| 13. |
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| 14. |
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| 15. |
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| 16. |
- Bååth, Lars, et al.
(författare)
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Effects of nonionic monomeric and dimeric contrast media on the twitching reaction of the rat. Importance of osmolality and electrolyte content
- 1994
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Ingår i: Investigative Radiology. - 0020-9996. ; 29:11, s. 985-989
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Tidskriftsartikel (refereegranskat)abstract
- RATIONALE AND OBJECTIVES. The authors established a rat model of the twitching reaction to contrast media in striated muscle and investigated the influence of nonionic contrast medium on the twitching reaction regarding the nonionic dimer iodixanol compared with the monomer iohexol and the dimer iotrolan. The authors also studied the influences from the electrolyte additions of iodixanol. METHODS. The interval from start of contrast medium injection to start of head movement was compared for iohexol (140 and 350 mg iodine/mL), iodixanol (150 and 320 mg iodine/mL), and iotrolan (300 mg iodine/mL). Comparison was made with mannitol and mannitol containing the same electrolyte concentrations as iodixanol (150 and 320 mg iodine/mL). RESULTS. No differences in latency period were found between iohexol 140 mg iodine/mL (isotonic) and 350 mg iodine/mL (880 mOsm/kg). Iodixanol caused a lesser effect on the twitching reaction than the iohexol solutions and iotrolan. When the electrolytes of iodixanol were added to mannitol (300 mOsm/kg), there was a later onset of the twitching reaction than with electrolyte-free mannitol. CONCLUSIONS. Differences in latency period caused by a change in osmolality were not found. The interval for a twitching reaction was longer with iodixanol than with iohexol, iotrolan, and iso-osmolar mannitol. The weak effect of the iodixanol solution was probably partially caused by the electrolyte content.
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| 17. |
- Bååth, Lars, et al.
(författare)
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Sodium-calcium balance in nonionic contrast media. Effects on the risk of ventricular fibrillation in the isolated rabbit heart
- 1993
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Ingår i: Investigative Radiology. - 0020-9996. ; 28:3, s. 223-227
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Tidskriftsartikel (refereegranskat)abstract
- RATIONALE AND OBJECTIVES. During coronary arteriography the blood is replaced for a short period of time with a contrast medium (CM) solution. The CM may cause a risk of arrhythmias and ventricular fibrillation (VF). Previous investigations have shown that the addition of small amounts of sodium (10-30 mmol/L) to nonionic CM may decrease the risk of VF from these media. Calcium addition to nonionic CM may reduce a negative inotropic effect. In the current investigation, the changed risk of VF from nonionic CM with 19 to 30 mmol/L NaCl was studied when the media also contained calcium or calcium and magnesium. METHODS. An isolated rabbit heart model was used. The risk of arrhythmias and VF from the nonionic monomer iohexol and the nonionic dimer iodixanol containing 19 to 30 mmol/L NaCl with 0 to 2.5 mmol/L calcium as CaCl2 was studied. In the series with iodixanol, 0 to 0.95 mmol/L MgCl2 also was added to the solutions with sodium and calcium, but the role of magnesium was not especially evaluated in the investigation. RESULTS. Nonionic CM with small amounts of NaCl (19-30 mmol/L), without calcium or with calcium at the level of 0.05 to 0.3 mmol/L, caused the lowest risk of VF. When relatively higher additions of calcium reached the physiologic concentration of 2.5 mmol/L, the CM caused a greater risk of arrhythmias and VF. CONCLUSIONS. When calcium is added to a nonionic CM, the concentration of calcium must be balanced against the NaCl concentration to minimize the risk of VF. Excessive calcium concentration will increase the risk of VF.
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| 18. |
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| 19. |
- Fahlvik, A K, et al.
(författare)
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Magnetic starch microspheres, efficacy and elimination. A new organ-specific contrast agent for magnetic resonance imaging
- 1990
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Ingår i: Investigative Radiology. - 0020-9996. ; 25:2, s. 113-120
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Tidskriftsartikel (refereegranskat)abstract
- A new particulate magnetic resonance (MR) contrast agent was prepared by controlled precipitation of iron oxide in an aqueous starch solution. The potential of the magnetic starch microspheres (MSM) as a hepatosplenic contrast enhancer was studied by MR spectroscopy and MR imaging. Intravascular administration of MSM to rodents showed an effective blood clearance and a tissue-specific localization of the substance. MSM doses in a range of 0.3-1.5 mg Fe/kg caused a 50% alteration in sensitive contrast parameters (ED50 doses) of liver and spleen. The contrast effect of MSM in liver and spleen was halved within 2 to 5 days. The approximated lethal MSM dose in mice was 150-200 mg Fe/kg. MSM is a tissue-specific MR contrast substance with high efficacy, rapid bioelimination, and low acute toxicity.
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| 20. |
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| 21. |
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| 22. |
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| 23. |
- Hellbach, Katharina, et al.
(författare)
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In Vivo Dark-Field Radiography for Early Diagnosis and Staging of Pulmonary Emphysema.
- 2015
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Ingår i: Investigative Radiology. - 0020-9996. ; 50:7, s. 430-435
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Tidskriftsartikel (refereegranskat)abstract
- The aim of this study was to evaluate the suitability of in vivo x-ray dark-field radiography for early-stage diagnosis of pulmonary emphysema in mice. Furthermore, we aimed to analyze how the dark-field signal correlates with morphological changes of lung architecture at distinct stages of emphysema.
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| 24. |
- Herrlin, K, et al.
(författare)
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Contrast-enhanced radiography by differential absorption, using a laser-produced X-ray source
- 1997
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Ingår i: Investigative Radiology. - 0020-9996. ; 32:5, s. 306-310
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Tidskriftsartikel (refereegranskat)abstract
- RATIONALE AND OBJECTIVES. The authors evaluate the feasibility of differential imaging of contrast media, with division of individual pixel values obtained from digital images generated by characteristic radiation from a laser-produced plasma, bridging the K-absorption edge of the contrast agent. METHODS. Laser pulses from an ultrashort-pulse terawatt laser system were focused onto gadolinium and tantalum targets, creating a plasma from which characteristic radiation and Bremsstrahlung was emitted. The elements of the target were selected so the characteristic emission lines of one of the elements were below the K edge of the contrast agent and the emission lines of the other element above. A phantom with gadolinium and other elements in various concentrations was examined. One radiographic exposure was made using a gadolinium target source and a subsequent exposure using a tantalum source. Both images were recorded digitally and the transmission ratios calculated by division of the individual pixel values. RESULTS. When viewed separately, the two images of the test phantom appeared similar. In the differential image, only the gadolinium solutions were bright, reflecting a difference in attenuation between the two exposures. CONCLUSIONS. Element-specific radiographs can be obtained by differential imaging. When fully explored, the technique may allow for contrast-enhanced radiography with increased sensitivity and decreased contrast dose.
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| 25. |
- Karstoft, J, et al.
(författare)
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Topographic representation of the pharyngoesophageal segment during swallowing
- 1990
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Ingår i: Investigative Radiology. - 0020-9996. ; 25:2, s. 184-188
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Tidskriftsartikel (refereegranskat)abstract
- Motility of the pharyngoesophageal segment (PES) was monitored by cineradiography (50 frames a second) during barium swallow and analyzed by a computerized topographic mapping of sagittal wall motion. Through measurement of wall displacement on 20 consecutive levels of the PES, distention, contraction, and peristalsis were studied. Topographic mapping of three patients with normal PES motility, delayed opening of the cricopharyngeus, and incomplete opening of the cricopharyngeus, was performed. These topographic mappings show that "narrowing" at the level of the cricopharyngeus reflects expansion of the hypopharynx and cervical esophagus around the cricopharyngeus, rather than a true narrowing. In addition, analysis of wall motion demonstrated that abnormality of the circopharyngeus is often associated with abnormality of wall motion in the adjoining hypopharynx and cervical esophagus. Thus, topographic mapping of the cricopharyngeus is of value because it enables detailed analysis of wall motion during various pathologic conditions.
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| 26. |
- Langbein, Björn J, et al.
(författare)
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A Pilot Study of Multidimensional Diffusion MRI for Assessment of Tissue Heterogeneity in Prostate Cancer
- 2021
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Ingår i: Investigative Radiology. - 0020-9996. ; 56:12, s. 845-853
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Tidskriftsartikel (refereegranskat)abstract
- OBJECTIVES: The objectives of this exploratory study were to investigate the feasibility of multidimensional diffusion magnetic resonance imaging (MddMRI) in assessing diffusion heterogeneity at both a macroscopic and microscopic level in prostate cancer (PCa).MATERIALS AND METHODS: Informed consent was obtained from 46 subjects who underwent 3.0-T prostate multiparametric MRI, complemented with a prototype spin echo-based MddMRI sequence in this institutional review board-approved study. Prostate cancer tumors and comparative normal tissue from each patient were contoured on both apparent diffusion coefficient and MddMRI-derived mean diffusivity (MD) maps (from which microscopic diffusion heterogeneity [MKi] and microscopic diffusion anisotropy were derived) using 3D Slicer. The discriminative ability of MddMRI-derived parameters to differentiate PCa from normal tissue was determined using the Friedman test. To determine if tumor diffusion heterogeneity is similar on macroscopic and microscopic scales, the linear association between SD of MD and mean MKi was estimated using robust regression (bisquare weighting). Hypothesis testing was 2 tailed; P values less than 0.05 were considered statistically significant.RESULTS: All MddMRI-derived parameters could distinguish tumor from normal tissue in the fixed-effects analysis (P < 0.0001). Tumor MKi was higher (P < 0.05) compared with normal tissue (median, 0.40; interquartile range, 0.29-0.52 vs 0.20-0.18; 0.25), as was tumor microscopic diffusion anisotropy (0.55; 0.36-0.81 vs 0.20-0.15; 0.28). The MKi could not be predicted (no significant association) by SD of MD. There was a significant correlation between tumor volume and SD of MD (R2 = 0.50, slope = 0.008 μm2/ms per millimeter, P < 0.001) but not between tumor volume and MKi.CONCLUSIONS: This explorative study demonstrates that MddMRI provides novel information on MKi and microscopic anisotropy, which differ from measures at the macroscopic level. MddMRI has the potential to characterize tumor tissue heterogeneity at different spatial scales.
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| 27. |
- Leander, Peter, et al.
(författare)
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A comparison between IEEC, a new biodegradable particulate contrast medium, and iohexol in a tumor model of computed tomography imaging of the liver
- 1993
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Ingår i: Investigative Radiology. - 0020-9996. ; 28:6, s. 513-519
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Tidskriftsartikel (refereegranskat)abstract
- RATIONALE AND OBJECTIVES. Higher contrast between normal and pathologic tissues in the liver may enable detection of smaller lesions in computed tomography (CT). This can be obtained using a liver-specific contrast medium. The authors evaluate a new agent, IEEC (1'-Ethyloxycarbonyloxy)-ethyl-5-acetylamino-3-(N-methyl-acetylami no)-2,4,6- triiodo-benzenecarboxylate), in an animal model, as a potential contrast agent for CT scanning of the liver. The IEEC particulate contrast medium used is based on a prodrug ester design of metrizoic acid and accumulates rapidly in the liver. The particles are quickly degraded into well-known metabolites and excreted from the body. METHODS. Two groups of rabbits were inoculated with VX2-carcinoma directly into the liver by laparotomy. Computed tomography imaging studies were carried out 9 and 11 days after the inoculation. The investigation was designed as a crossover study. The first group was imaged both as controls (without contrast medium) and with the particulate contrast medium on the 9th day and with iohexol on the 11th day. The second group was imaged with iohexol on the 9th day and as controls, and with the particulate contrast medium on the 11th day. The contrast medium was administered in a dose of 100 mgI/kg. Iohexol was administered in a dose of 570 mgI/kg according to a standard clinical scheme in use at a radiology department for dynamic CT. Changes in normal liver/lesion contrast and the conspicuity of tumors were assessed. On completion of imaging studies on day 11, all animals were killed. The liver was removed and evaluated for the presence of tumors. RESULTS. At macroscopic inspection, all rabbits were found to have tumors ranging from 2 to 14 mm in diameter. The size and location of the tumors corresponded well with the CT images. In the images where the particulate contrast medium was used, the attenuation in the normal liver parenchyma and the contrast between normal liver and lesion was significantly higher compared with the images where iohexol was used or the controls. For all tumor sizes, the lesion detection capability with the particulate contrast medium was significantly higher compared with iohexol (P < .005) and controls (P < .05). CONCLUSIONS. VX2-carcinoma in rabbit liver is a useful model for studying the efficacy of contrast media in CT imaging. The particulate contrast medium IEEC improved visualization of liver tumors.
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| 28. |
- Leander, Peter, et al.
(författare)
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Early effect of gadopentetate and iodinated contrast media on rabbit kidneys
- 1992
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Ingår i: Investigative Radiology. - 0020-9996. ; 27:11, s. 922-926
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Tidskriftsartikel (refereegranskat)abstract
- RATIONALE AND OBJECTIVES. The authors compared the physiologic and nephrotoxic effects of the magnetic resonance imaging contrast medium gadopentetate with two conventional radiographic contrast media. METHODS. Rabbits were injected intravenously with one of the following solutions: 1) gadopentetate (0.1 M); 2) iohexol (300 mg I/mL); 3) metrizoate (300 mg I/mL); and 4) NaCl (0.9%). Blood samples were taken before and 5, 15, 45, 90, and 180 minutes after injection of the solutions and were analyzed for creatinine, aldosterone, and contrast media levels. Urine was sampled before and 1, 2.5, and 5 hours after injection of the solutions, and creatinine, leucine amino peptidase (LAP), alkaline phosphatase (ALP), gamma glutaryl transferase (GGT), and N-acetyl beta-D-glucosaminidase (NAG) activities were quantified. RESULTS. Contrast media clearance was similar for gadopentetate, iohexol, and metrizoate. Plasma aldosterone was significantly higher in the two groups injected with iodinated contrast agents compared with the gadopentetate and saline groups in the 3-hour samples. During the 5 hours after injection, the excretion of brushborder enzymes LAP, ALP, and gamma GT was significantly higher for all contrast media compared with pre-contrast values and 0.9% NaCl controls. NAG, a lysosomal enzyme from tubular cells, showed a significant increase compared with pre-contrast values for all contrast media. CONCLUSIONS. Intravenous injection of gadopentetate in rabbits showed nephrotoxicity of the same order as that of conventional iodinated contrast media.
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| 29. |
- Leander, Peter, et al.
(författare)
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MRI contrast media for the liver. Efficacy in conditions of acute biliary obstruction
- 1990
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Ingår i: Investigative Radiology. - 0020-9996. ; 25:10, s. 1130-1134
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Tidskriftsartikel (refereegranskat)abstract
- The authors investigated in a rat model the efficacy of magnetic resonance imaging (MRI) contrast media for evaluating the liver in conditions of acute biliary obstruction. Two liver-specific MRI contrast media, Cr-DEHIDA and Mn-DPDP, and the nonspecific agent Gd-DTPA were studied in normal rats and in rats whose bile ducts had been ligated before administration of the contrast medium. Images were made using a 2.4 T animal MRI system, and intensity enhancement of liver after contrast medium injection was calculated. Metal analyses of serum and liver tissue and T1 and T2 measurements on liver samples in vitro were performed. The differences in image intensity enhancement of liver between normal rats and rats with ligated bile ducts were not significant for any of the three contrast media. Imaging with Mn-DPDP resulted in the highest intensity enhancement of the liver compared with Cr-DEHIDA and Gd-DTPA. Contrast media concentrations in liver tissue were not significantly different between normal rats and rats with ligated bile ducts; however, Cr-DEHIDA concentrations in serum were higher after bile duct ligation. In vitro measurements of liver tissue indicated unique relaxation properties for Mn-DPDP. This investigation indicates that the contrast media studied may be useful in situations where suspected liver pathology is complicated by acute biliary obstruction.
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| 30. |
- Leander, Peter, et al.
(författare)
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Orally Administered Manganese With and Without Ascorbic Acid as a Liver-Specific Contrast Agent and Bowel Marker for Magnetic Resonance Imaging: Phase I Clinical Trial Assessing Efficacy and Safety.
- 2010
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Ingår i: Investigative Radiology. - 0020-9996. ; 45:9, s. 559-564
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Tidskriftsartikel (refereegranskat)abstract
- OBJECTIVES:: The objectives of this clinical trial of orally administered manganese in magnetic resonance imaging (MRI) of the liver were to assess signal enhancements in the liver with and without the addition of an uptake promoter, ascorbic acid, and to evaluate acute safety. MATERIALS AND METHODS:: A total of 18 healthy adult males were enrolled in the present trial. Contrast medium: MnCl2, doses: 25, 50, and 100 mumoL/kg bw, respectively, and promoting agent: Ascorbic acid, doses: 50, 100, and 200 mumoL/kg bw, respectively, were used. All imaging was performed on a 1.5 T clinical MRI system. Three pulse-sequences in the abdomen were used: (1) T1-weighted axial gradient-echo (GRE), (2) T1-weighted coronal gradient-echo, and (3) T1-weighted axial spin-echo (SE). Time-points for imaging were precontrast, 1 hour, 2.5, 4, 6, 9, and 24 hours after MnCl2 intake. Safety parameters assessed were clinical examinations and vital signs, including heart rate and blood pressure. Hematology and clinical chemistry were assessed with standard laboratory procedures. RESULTS:: All pulse-sequences showed a clear dose-response in liver-enhancement. Temporally, high enhancements in the liver were seen between 2.5 and 6 hours after MnCl2 intake. At the manganese dose 50-mumoL/kg bw, with ascorbic acid and at the dose 100-mumoL/kg bw, both with and without ascorbic acid, the hepatic enhancements were higher than 100% with the GRE pulse-sequence. The promoting effect of ascorbic acid was significant at a manganese-dose of 100-mumoL/kg bw. The contrast media distributed well in the small intestine, delineating intra-abdominal organs well. No serious or unexpected adverse events were encountered. The drug was generally well tolerated, except for minor gastrointestinal adverse events. No significant alteration in hematology or clinical chemistry was seen. CONCLUSIONS:: Oral manganese is easy to use, and has few side effects. Besides the liver-specific effect, an additional benefit is the delineation of the intestine.
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| 33. |
- Olsson, R, et al.
(författare)
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An experimental manometric study simulating upper esophageal sphincter narrowing
- 1994
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Ingår i: Investigative Radiology. - 0020-9996. ; 29:6, s. 630-635
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Tidskriftsartikel (refereegranskat)abstract
- RATIONALE AND OBJECTIVES. Elevated intrabolus pressure above a pharyngeal narrowing has been postulated as an important finding in patients with cricopharyngeal bars. To elucidate the significance of intrabolus pressure around lumen narrowings in the pharynx, intraluminal pressure characteristics were evaluated in a laboratory model simulating upper esophageal sphincter narrowing. METHODS. Intraluminal solid-state manometry was performed in an experimental model in which variable narrowing was created in an expandable balloon simulating the pharyngeal walls. RESULTS. Intrabolus pressure was dependent on the position of the manometric sensor, degree of lumen narrowing, bolus volume, flow rate, and fluid viscosity. CONCLUSIONS. Elevated intrabolus pressure is an important finding. Intrabolus pressure is dependent on many parameters, and hence, is difficult to evaluate. If results found with this model hold true in patients, manometric sensor positioning is crucial, and concurrent fluoroscopy is highly recommended to achieve a standardized manometric technique in pharyngeal manometry.
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| 34. |
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