Biomedical subjects

F J Londy

Publications and source records attributed to F J Londy.

15 recordsLinked to original sources

PubMed2001

Gadolinium-enhanced MR angiography (Gd-MRA) of thoracic vasculature in an animal model using double-dose gadolinium and quiet breathing.

OBJECTIVE: To evaluate a gadolinium-enhanced MR angiography (Gd-MRA) imaging protocol for the assessment of thoracic vessels using double-dose gadolinium and quiet breathing. An animal model was used to simulate imaging in infants and young children. MATERIAL AND METHODS: Six baboons (Papio anubis), mean weight 5.7 kg, were sedated and intubated. After the injection of double-dose Gd-DTPA (0.2 mmol/kg) through a peripheral vein, a coronal spoiled 3D gradient-echo volume acquisition was obtained during quiet breathing. Two radiologists reviewed the images for visualization of aortic arch, brachiocephalic vessel origins, pulmonary arteries (central, upper lobe and descending branches), and pulmonary veins (upper and lower). RESULTS: Visualization was excellent for the aortic arch, brachiocephalic vessel origins, and pulmonary arteries, including the hilar branches. Visualization was excellent for the lower and right upper pulmonary veins and fair for the left upper pulmonary vein. There was excellent agreement between radiologists. CONCLUSION: Imaging of thoracic vessels with Gd-MRA using double gadolinium during quiet breathing was effective in our animal model. The advantages of this technique include a short imaging time and depiction of vascular segments--branches of pulmonary arteries and intraparenchymal segments of pulmonary veins--not optimally visualized with other non-invasive imaging techniques.

Animals↗

PubMed2001

Multiphase-multistep gadolinium-enhanced MR angiography of the abdominal aorta and runoff vessels.

RATIONALE AND OBJECTIVES: To optimize three-dimensional gadolinium magnetic resonance angiography (3D-Gd-MRA) of the aorta and runoff vessels by addressing fundamentally different requirements for temporal and spatial resolution in a single semiautomated examination. METHODS: The technique was designed to obtain pure arterial-phase 3D-Gd-MR angiograms with adequate spatial resolution for each station while avoiding incomplete enhancement due to delayed filling vessels as well as venous overlay. During gadolinium-chelate infusion, a breath-held multiphase 3D-Gd-MRA scan was initiated in the aorta by automatic triggering, followed by automatic table movement. The acquisition was tailored to the vessels of interest by tilting of the 3D volumes. A spatial resolution of 1.7 x 1.2 x 0.8 mm in the calves was achieved by use of elliptical-centric k-space reordering. Signal-to-noise ratio was maximized with a 12-element peripheral vascular coil. Twelve patients with peripheral vascular disease were studied. RESULTS: In cases of aortic occlusive disease (n = 2), dissections (n = 3), or aneurysms (n = 4), substantially delayed fill-in of reconstituted arteries, false lumens, or aneurysmal segments occurred, which was detected only on the later 3D-Gd-MRA phase. High-resolution arterial-phase scans in the calves were obtained, with only one case of substantial venous overlay. Correlation to digital subtraction angiography revealed excellent agreement of pathological findings. CONCLUSIONS: Multiphase-multistep 3D-Gd-MRA reduces the limitations of standard 3D-Gd-MRA techniques with respect to anatomic coverage, spatial resolution, and nonuniform arterial vessel enhancement.

Adult↗

PubMed2001

P-selectin antagonism causes dose-dependent venous thrombosis inhibition.

Inhibition of P-selectin by antibody or selectin antagonist decreases inflammation and thrombosis. This study evaluates the dose-response relationship using a selectin receptor antagonist. Eight male baboons (Papio anubis) underwent inferior vena caval thrombosis using a 6 h balloon occlusion model. Three animals received 500 microg/kg P-selectin antagonist (rPSGL-Ig) and five 1 mg/kg rPSGL-Ig with or without a non-anticoagulant dose of Dalteparin. These animals were compared to our published results in this model with 4 saline controls and 8 animals that received 4 mg/kg rPSGL-Ig. A statistically significant dose-response relationship existed between rPSGL-Ig dose and thrombosis (p < 0.01), and between rPSGL-Ig dose and spontaneous recanalization (p<0.05). Inflammatory assessment revealed decreased gadolinium enhancement in all rPSGL-Ig groups compared to previously reported control, despite no significant differences in inflammatory cell extravasation. No dose of rPSGL-Ig caused anticoagulation. Selectin antagonism results in a dose-dependent decrease in thrombosis and increase in spontaneous recanalization.

Animals↗

PubMed2000

Venous thrombosis prophylaxis by inflammatory inhibition without anticoagulation therapy.

OBJECTIVE: This study was performed to determine the effectiveness of recombinant P-selectin glycoprotein ligand Ig (rPSGL-Ig) pretreatment to decrease thrombosis and inflammation in experimental venous thrombosis. rPSGL-Ig, a unique mucin-like glycoprotein, has a high affinity for P-selectin. METHODS: Twelve juvenile baboons underwent inferior vena cava (IVC) thrombosis with temporary 6-hour IVC balloon occlusion. Before balloon placement, the animals received rPSGL-Ig (4 mg/kg; n = 8) or saline solution for control (n = 4). The animals underwent evaluation with duplex ultrasound scan imaging, magnetic resonance venography (MRV), phlebography, coagulation profile, and tissue analysis at death for cytokines and vein wall leukocyte morphometrics. With the MRV results, thrombus development, thrombus resolution, and inflammation (gadolinium; square millimeters of enhancement) were assessed. RESULTS: Each animal provided two time points for evaluation (days 2 and 6 after balloon occlusion). A significant decrease in IVC thrombosis between balloons was found in the rPSGL-Ig animals (1 of 16) versus the control animals (5 of 8; P <.01). The MRV results showed significantly less enhancement in the rPSGL-Ig animals at days 2 and 6 (P <.05). Spontaneous thrombus resolution (including balloon sites) was significantly greater from day 2 to day 6 in the rPSGL-Ig animals versus the control animals (23% vs 2%; P <.001), without pulmonary embolism. Lower interleukin-8, platelet factor IV, and monocyte chemotactic protein-1 levels were found in rPSGL-Ig vein walls without significant differences in vein wall leukocyte morphometrics. There were significantly lower D-dimer levels in the rPSGL-Ig-treated animals (P <.05), but there were no differences in measurements of coagulation. Adequate circulating rPSGL-Ig levels were documented. CONCLUSION: Pretreatment with rPSGL-Ig results in: (1) a significant inhibition of thrombosis and vein wall inflammation; (2) a decrease in vein wall cytokine expression; and (3) a promotion of thrombus resolution. Inflammatory inhibition by rPSGL-Ig without anticoagulation therapy provides effective venous thrombosis prophylaxis in experimental venous thrombosis.

Animals↗

PubMed2000

Subclavian MR arteriography: reduction of susceptibility artifact with short echo time and dilute gadopentetate dimeglumine.

At arterial phase gadolinium-enhanced magnetic resonance (MR) angiography, artifactual stenosis of the subclavian artery is sometimes seen adjacent to the subclavian vein on the side of the contrast material injection. Experiments in phantoms and in 19 patients showed increased artifact with longer echo time and higher concentration of injected contrast material. An effective method to substantially decrease this susceptibility artifact was threefold dilution of gadopentetate dimeglumine and use of a short echo time (1 msec).

Adolescent↗

PubMed1998

Renal anatomic changes on magnetic resonance imaging and gadolinium-enhanced magnetic resonance angiography after renal revascularization. Original investigation.

RATIONALE AND OBJECTIVES: The anatomic and hemodynamic renal changes after renal arterial revascularization (RAR) were investigated. METHODS: Thirty-seven kidneys and 40 renal arteries were evaluated in 20 patients by using magnetic resonance imaging/magnetic resonance angiography (MRI/MRA) to assess pre- and post-RAR renal length and mass, parenchymal thickness, renal enhancement, renal artery caliber, poststenotic dilation, and signal dephasing on 3D phase contrast (PC). The kidneys and renal arteries were segregated into three groups. Group 1 included 16 patients who benefited from RAR (defined as clinical improvement based on decreased serum creatinine or fewer number of antihypertensive medications) in whom 26 renal arteries in 25 kidneys were studied. Intervention included renal artery endarterectomy (n = 20); aortorenal bypass (n = 3); renal artery reimplantation (n = 3); and percutaneous transluminal angioplasty (PTA; n = 1). A total of 27 interventions was performed, as PTA failed for one patient who subsequently underwent aortorenal bypass before reimaging. Group 2 included four patients who did not clinically benefit. A total of eight revascularized arteries were studied in seven kidneys. In group 3, six renal arteries in five kidneys from groups 1 and 2 without RAS/RAR were analyzed as an internal control. RESULTS: Technical success (defined as increased vessel caliber after intervention) was achieved in 33 of the 34 revascularized arteries. A statistically significant increase in renal length occurred regardless of clinical outcome (pre-RAR, 9.5 cm; post-RAR, 10.5 cm; P < 0.0001). Parenchymal thickness and renal mass, however, improved only in patients who benefited clinically from RAR. Parenchymal enhancement was unchanged in any of the groups studied. No significant morphologic changes were detected in the control group. CONCLUSIONS: Magnetic resonance imaging and Gd-MRA detect anatomic and hemodynamic changes that occur with renal revascularization.

Adult↗

PubMed1998

Magnetic resonance angiography with gadomer-17. An animal study original investigation.

RATIONALE AND OBJECTIVES: Our purpose was to investigate a "blood pool" contrast agent for abdominal and thoracic MR angiography by comparison with standard ionic and nonionic gadolinium-based contrast agents, which redistribute into the extracellular fluid compartment. METHODS: Abdominal and thoracic MR angiography was performed in three adult dogs using a three-dimensional spoiled gradient echo pulse sequence before and after intravenous administration of one of three gadolinium-based contrast agents (gadopentetate dimeglumine, gadobutrol, and gadomer-17). Each compound was tested at five different doses in all three dogs. Quantitative analysis of signal-to-noise ratio (SNR) was performed in the aorta, inferior vena cava (IVC), liver, spleen, kidney (medulla and cortex), fat, and muscle. RESULTS: Gadomer-17 improved visualization of vascular anatomy at doses of 0.025, 0.05, 0.1, and 0.2 mmol/kg with three-fold greater aorta SNR during the arterial phase and more than four-fold greater aorta and IVC SNR during the equilibrium phase, in comparison with gadopentetate dimeglumine and gadobutrol at equal doses. CONCLUSIONS: Gadomer-17 is a promising contrast agent for both arterial phase and equilibrium phase MR angiography.

Adipose Tissue↗

PubMed1997

Anti-P-selectin antibody decreases inflammation and thrombus formation in venous thrombosis.

PURPOSE: Venous thrombosis and inflammation are interrelated. P-selectin contributes to activation of leukocyte-mediated inflammation. Therefore, we hypothesized that the neutralization of P-selectin would decrease vein wall inflammation and thrombosis. METHODS: Twelve baboons underwent infrarenal inferior vena caval balloon occlusion to induce thrombosis. Two groups of four baboons received neutralizing intravenous anti-P-selectin antibody (PSab) GA6 or CY1748 before occlusion and at days 2 and 4. Four baboons received saline control injections. One baboon per group was killed at days 2, 6, and 13, and at 2 months. Analysis included phlebography, ultrasound, gadolinium (Gd)-enhanced magnetic resonance venography (reflecting vein wall inflammation), and histologic, morphometric, and protein evaluation of the vein wall. Thrombus presence or absence was assessed. RESULTS: By day 2 in PSab baboons, vein wall Gd enhancement was decreased in the mid-inferior vena cava and the right iliac vein (p < 0.05; GA6 vs control baboons), normalizing by 2 months. The mid-inferior vena cava revealed fewer neutrophils and total leukocytes in PSab baboons; however, for GA6 in the right iliac vein these decreases were not present despite the absence of Gd enhancement; they were decreased with CY1748. PSab baboons demonstrated significantly less thrombus than control baboons (p < 0.01, GA6 and CY1748 vs control baboons). CONCLUSIONS: Anti-P-selectin antibody decreases vein wall inflammation and thrombus formation. Inhibition of P-selectin may be useful in venous thrombosis prophylaxis.

Acute Disease↗

PubMed1997

Contrast-enhanced abdominal MR angiography: optimization of imaging delay time by automating the detection of contrast material arrival in the aorta.

PURPOSE: To improve gadolinium-enhanced magnetic resonance (MR) angiogram quality by automatically synchronizing acquisition of central k-space image data with the arterial phase of contrast material bolus infusion. MATERIALS AND METHODS: A spin-echo pulse sequence with orthogonal 90 degrees and 180 degrees pulses was used to monitor signal in a single 4 x 4 x 12-cm voxel that encompassed a segment of aorta. An increase in signal that corresponded to the arrival of gadolinium was used to trigger three-dimensional, spoiled gradient-echo abdominal MR angiography in 50 adult patients. RESULTS: Arterial signal intensity increased 28-fold with automatic compared to 19-fold with manual triggering (P < .05) at an approximate dose of 0.3 mmol/kg. Automatic triggering with a lower dose (approximately 0.2 mmol/kg) resulted in 20-fold arterial enhancement, which is comparable with enhancement after manual triggering at the high dose. In addition, venous enhancement was less (1.5-fold) with automatic than with manual (3.5-fold) triggering at the same dose (P < .05). CONCLUSION: Automatic triggering results in improved arterial-tovenous contrast. It increases arterial enhancement or enables MR angiograms to be obtained with less contrast material. The authors now routinely use this technique for aortorenal imaging with a gadolinium-based contrast material dose of 20 mmol (40 mL) in patients who weigh more than 50 kg and 10 mmol (20 mL) in patients who weigh less than 50 kg.

Abdomen↗

PubMed1997

Hemodynamically significant atherosclerotic renal artery stenosis: MR angiographic features.

PURPOSE: To identify magnetic resonance (MR) angiographic features of hemodynamically significant renal artery stenosis. MATERIALS AND METHODS: Forty-seven patients underwent MR angiography of the renal arteries, including T1-weighted spin-echo and three-dimensional gadolinium-enhanced spoiled gradient-echo and three-dimensional phase-contrast pulse sequences, followed by renal revascularization. Thirty-five patients (52 arteries) were identified who benefited from renal revascularization, which indicated that they had hemodynamically significant renal artery stenoses. Kidney length, cortical thickness, parenchymal enhancement, and poststenotic dilatation were measured. Arteries were also examined for signal drop-out (dephasing) on phase-contrast angiograms; dephasing was considered severe if the stenotic artery appeared occluded on phase-contrast angiograms. RESULTS: Poststenotic dilatation of greater than 20% was present in 36 (59%) of 52 hemodynamically significant renal artery stenoses, and severe dephasing was present in 45 (87%) of 52. In patients with unilateral hemodynamically significant stenosis or occlusion, mean ischemic kidney length was reduced to 9.3 cm compared with 10.7 cm for the contralateral normal kidney (P = .009), mean parenchymal thickness was reduced (1.2 vs 1.7 cm; P < .001), and mean parenchymal enhancement was 15% less on the ischemic side (P = .05). Severe dephasing on phase-contrast angiograms was present in nine (75%) of 12 unilateral hemodynamically significant stenoses but in only one contralateral normal renal artery (P < .001). CONCLUSION: MR angiography depicts features of renal artery stenosis that are markers of hemodynamic significance.

Adult↗

PubMed1997

Effect of gadolinium on phase-contrast MR angiography of the renal arteries.

OBJECTIVE: Our aim was to evaluate the effect of gadolinium chelates on image quality in phase-contrast MR angiography of renal arteries in patients suspected of having renal artery stenosis. MATERIALS AND METHODS: In 24 patients, axial three-dimensional phase-contrast MR angiography of the renal arteries was obtained on a 1.5-T MR imaging system before and after administration of gadolinium contrast agent. The improvement in distal renal artery signal-to-noise ratio after enhancement was measured and correlated with patient age, serum creatinine level, clinical estimation of renal artery flow, and the imaging parameter flip angle. RESULTS: On average, the distal renal artery signal-to-noise ratio increased 2.2-fold after gadolinium administration (p < .001). The increase was greatest in patients more than 60 years old (3.1-fold; p < .001) and in patients with serum creatinine levels greater than 3.0 mg/dl (4.3-fold; p < .01). After enhancement, we found an apparent increase in renal artery diameter (3.5 +/- 1.1 mm before enhancement versus 4.8 +/- 1.4 mm after enhancement [mean +/- SD; p < .001]). We believe this increase reflects improved visualization of slow blood flow along the artery wall. Although the visualization of renal arteries was better in most patients after enhancement, two patients had poorer image quality after enhancement because of increased venous signal obscuring the arteries. CONCLUSION: Gadolinium administration significantly increases distal renal artery signal-to-noise ratio on three-dimensional phase-contrast MR angiography in most patients. The signal-to-noise ratio improvement is greatest in older patients and in patients with impaired renal function. However, in some cases, increased venous signal may obscure arteries.

Adult↗

PubMed1996

A simple MR-compatible infusion pump.

A simple, mechanical infusion pump that employs a constant force, nonferromagnetic spring to squeeze a syringe is described. The contrast infusion rate is determined by the spring force, gadolinium solution viscosity, and the resistance of either a user-selected needle or a precision oriffice according to Poiseuille's Law or the Bernoulli effect. Its use in dynamic, gadolinium-enhanced 3D MR angiography is described.

Contrast Media↗

PubMed1995

Dynamic three-dimensional imaging with partial k-space sampling: initial application for gadolinium-enhanced rate characterization of breast lesions.

PURPOSE: To evaluate a method to monitor gadolinium enhancement patterns at magnetic resonance (MR) imaging with high temporal resolution and full coverage through both breasts. MATERIALS AND METHODS: In 12 patients with 13 masses, including nine carcinoma, nonenhanced three-dimensional MR imaging was performed with full-matrix resolution. At dynamic imaging, 32 serial passes were made during bolus administration of contrast material, and temporal resolution was reduced to 12 seconds by collecting the central (low spatial frequency) 32 x 16 or 16 x 16 phase-encode views. Full-matrix dynamic images were reconstructed by complementing central phase-encode data with precontrast data from peripheral high-spatial-frequency views. RESULTS: Results at time-course analysis with a mono-exponential saturation model indicated malignant lesions tend to show rapid (< 60 seconds) contrast change relative to benign masses and normal tissues. One cancer displayed an exceptionally slow contrast change (260 seconds). CONCLUSION: The technical objectives of full tissue coverage, rapid temporal sampling, and quantification of enhancement curves are met with this method for certain lesions (> 5 mm in largest diameter).

Adult↗

PubMedDate not supplied

The effects of time varying intravascular signal intensity and k-space acquisition order on three-dimensional MR angiography image quality.

The optimum infusion timing and k-space ordering for obtaining gadolinium-enhanced three-dimensional MR angiograms was determined through computer modeling using temporal contrast characteristics obtained from patient gadolinium infusion data. The effects of bolus timing were evaluated by varying the relationship between peak intravascular gadolinium concentration and the time at which the center of k space was acquired (tck) for sequential and centric acquisition techniques. Flow phantom experiments were performed to validate the theoretical computations. Gadolinium concentration at the time of central k-space acquisition determines intravascular signal intensity. Artifacts, including vessel broadening and edge ringing, depend on the order in which k space is collected and on how rapidly the gadolinium concentration changes. Artifacts are greatest when the center of k space is acquired before the intravascular gadolinium peak. Application of the optimal infusion timing results in preferential arterial enhancement with a minimum of artifacts in patients undergoing MR angiography.

Algorithms↗

PubMedDate not supplied

Detection of perivenous inflammation in a rat model of venous thrombosis using MRV.

Venous thrombosis is associated with a significant inflammatory response in the vein wall, which can be imaged noninvasively with gadolinium (Gd)-enhanced magnetic resonance venography (MRV). Interleukin-10 (IL-10), a naturally occurring anti-inflammatory cytokine, has been found to decrease the inflammatory response at the proper dosage and timing of administration. The present study determines if MRV with Gd is useful in a rat model of stasis-induced venous thrombosis to document the anti-inflammatory effects of rIL-10. Rats underwent laparotomy and ligation of the inferior vena cava (IVC). Animals were infused with rIL-10 at 2.5 microg (n = 6), rIL-10 at 10 microg (n = 6), or rIL-10 at 40 microg (n = 6). Six animals without IVC ligation or drug infusion served as controls. Two days after thrombosis induction, the rats underwent MRV with both time-of-flight imaging and pre/post-Gd T1-weighted imaging. Inflammation was analyzed by measuring the area of Gd enhancement at the point of IVC thrombosis. Enhancement area was also measured in the distal IVC where flow persisted. All animals with IVC ligation developed thrombosis, and all control rats were free of thrombus. In areas where flow remained, the area of enhancement was 1.8 +/- 0.4 mm2, while controls demonstrated 3.8 +/- 1.0 mm2 enhancement. Enhancement was significantly greater in all groups at the level of thrombus compared to the area of distal IVC flow and control IVCs (p < .001). Animals receiving rIL-10 at 40 microg revealed the most enhancement, 32.7 +/- 6.2 mm2, while the least enhancement was noted with 2.5 microg, 14.7 +/- 1.5 mm2 (p < .05). In conclusion, Gd-enhanced MRV was found useful in this rat model of stasis-induced venous thrombosis to document inflammation noninvasively and to evaluate the effects of anti-inflammatory interventions during stasis-induced IVC venous thrombosis.

Animals↗