Journal of Computer Assisted Tomography, May 1, 1987
Sequential fast magnetic resonance (MR) images (repetition time = 33 ms, echo time = 7 ms, alpha ... more Sequential fast magnetic resonance (MR) images (repetition time = 33 ms, echo time = 7 ms, alpha = 22 degrees, one image every 12 s) were acquired using gadolinium-diethylenetriamine pentaacetic acid (Gd-DTPA) (10 or 100 mumol/kg) to study perfusion and concentrating ability in normal rabbit kidneys and in kidneys with HgCl2-induced acute tubular necrosis (ATN). In normal rabbits receiving 100 mumol Gd-DTPA/kg a concentric region of decreased MR signal was observed. In sequential images the dark ring pattern migrated centripetally through the kidney moving from the corticomedullary junction to the inner medulla. The decrease in MR signal intensity occurred as a consequence of T2 relaxation (magnetic susceptibility) due to high concentration of Gd-DTPA within the tubules. This suggests that the dark ring pattern may serve as a qualitative feature indicative of the ability of the kidneys to concentrate. With the onset of HgCl2-induced ATN the pattern of enhancement due to Gd-DTPA administration changed markedly. Although the kidneys with ATN did continue to be perfused, the concentric dark ring pattern seen in normal kidneys receiving 100 mumol Gd-DTPA/kg was not observed. These results suggest that Gd-DTPA and fast imaging MR may provide a method of assessing perfusion and concentrating ability within the healthy or diseased kidney.
The paramagnetic magnetic resonance (MR) imaging contrast agent gadolinium diethylenetriaminepent... more The paramagnetic magnetic resonance (MR) imaging contrast agent gadolinium diethylenetriaminepentaacetic acid (DTPA) is freely filtered at the glomerulus and is neither secreted nor reabsorbed by the renal tubules. Fast MR imaging techniques, either gradient-echo or spin-echo, can be used to document the passage of Gd-DTPA through the renal tubules, as reflected by alteration in the MR signal intensity within the different anatomic regions of the kidney. Gradient-echo (repetition time of 35 msec, echo time of 7 msec, flip angles of 10 degrees-100 degrees) and spin-echo (repetition time of 35 msec, echo time of 8 msec) pulse sequences were used to acquire 20 consecutive images, one every 12 seconds, of the rabbit kidney. Both pulse sequences depicted the time course of Gd-DTPA distribution through the kidney but with distinctly different patterns of MR signal change. These dynamic MR images provide an MR nephrogram that directly demonstrates renal morphology and indirectly reflects the functional status of the renal vasculature, renal perfusion, and tubular concentrating ability.
Even though the intrinsic soft tissue contrast sensitivity of magnetic resonance imaging (MRI) af... more Even though the intrinsic soft tissue contrast sensitivity of magnetic resonance imaging (MRI) affords excellent visualization of anatomic detail, certain pathologic processes may be diagnosed earlier with the administration of a contrast-enhancing agent. At present there is one agent, gadopentetate dimeglumine, GdDTPA, that has received FDA approval for use in the MR scanning of the brain and spine in human patients. This paramagnetic chelate distributes throughout the extracellular fluid space as dictated by capillary permeability so that abnormal vascularity and sites of blood-CNS barrier breakdown are highlighted. Primary neoplastic disease, metastases, meningeal extension, residual and recurrent tumor have been found to be better distinguished in MR images acquired after administration of GdDTPA. Routine administration of GdDTPA for cranial imaging has resulted in the discovery of otherwise occult lesions in approximately 3 of patients. Although the clinical utility and high therapeutic safety index of the first approved magnetic resonance contrast agent, GdDTPA, have been well established, other contrast agents, having different physical, chemical and biological properties, may offer improved sensitivity and bio-specificity. Agents currently being evaluated in vivo include: low osmolal paramagnetic chelates, superparamagnetic particles, metalloporphyrins, liposome encapsulated agents, perfluorocarbons, intravascular macromolecular chelate complexes and labeled monoclonal antibodies. Concurrent with advances in the development of new compounds, innovations in scanning hardware, pulse sequence design and image post-processing are helping to extend the efficacy of contrast media. Additional clinical experience will indicate which contrast agents and which MR techniques can best facilitate the early detection of specific neoplastic lesions.
Small, multiple foci of increased signal intensity (T2 weighted images) in the centrum semiovale ... more Small, multiple foci of increased signal intensity (T2 weighted images) in the centrum semiovale and basal ganglia are frequently-observed on magnetic resonance images of the brain. Often, these findings are of doubtful significance with respect to the patient’s clinical state. Several explanations for this phenomenon have been advanced and much controversy surrounds this issue. We correlated images of 5 fresh and fixed brains obtained at 1.5 T and 4.7 T and of 10 fixed brains obtained at 1.5 T with pathologic analysis of these brains and also with an evaluation of the perivascular spaces in fixed brain specimens from the Yakovlev collection of the Armed Forces Institute of Pathology (AFIP). These foci of hyperintensity in part correlated with the location of the deep penetrating arteries and probably represent extracellular water in the perivascular (Virchow-Robin) spaces. These spaces typically enlarge with aging and with various systemic disorders such as hypertension. We then retrospectively reviewed 100 MR scans of patients with various clinical/pathologic conditions and found that these hyperintense foci were frequent findings. It is our conclusion that many of the hyperintense foci in the centrum semiovale and basal ganglia represent extracellular water in the Virchow-Robin spaces.
The I n t e r a c t i o n s o f two p o s i t i o n a l 1somers and one ana logue o f m e s o t e... more The I n t e r a c t i o n s o f two p o s i t i o n a l 1somers and one ana logue o f m e s o t e t r a ( 4 N m e t h y l p v r i d v l ) p o r p h i n e , w i t h the s y n t h e t i c p o l y n u d e o t i d e s p o l y [ d ( A T ) ] p o l y C d U T ) ] and po l y [ d (G-C ) ] • p o l y [ d ( G C ) ] have been I n v e s t i q a t e d by c i r c u l a r d i c h r o i s m . A l l f ou r p o r p h y r i n s were found t o b i n d to the p o l y n u d e o t i d e s as shown by the I n d u c t i o n o f c i r c u l a r d i c h r o i s m 1n t h e i r So re t bands . F u r t h e r m o r e , t he s i g n o f t he Induced e l l i p t i d t y r e f l e c t s s e l e c t i v e o c c u p a t i o n o f b i n d i n g s i t e s by the p o r p h y r i n l i g a n d s . The c o n f o r m a t i o n a l l a b i l i t y o f p o ! y [ d ( A T ) ] *po l y [d ( A T ) ] was found t o be a p p r e c i a b l e as m i c r o m o l a r amounts o f m e s o s u b s t i t u t e d 4 N m e t h y l p y r I d y l , ...
... Resolution studies in diffusion tomography. Author(s): Thomas R. Lucas; Michael V. Klibanov; ... more ... Resolution studies in diffusion tomography. Author(s): Thomas R. Lucas; Michael V. Klibanov; Robert M. Frank. Real inversion of a ... Regularization of inverse problem by singular value filtration. Author(s): Vitalij N. Kurashov; Alexandr G. Chumakov; Andry V. Kovalenko. Stable ...
ABSTRACT Ashley R, Carvlin M, Lucas T, Olukotun A. Addressing cost-containment and cost-effective... more ABSTRACT Ashley R, Carvlin M, Lucas T, Olukotun A. Addressing cost-containment and cost-effectiveness in magnetic resonance contrast agent development. Invest Radiol 1994;29:S257-S259.
Proceedings of Spie the International Society For Optical Engineering, Oct 1, 1995
... wise continuous models for electromagnetic inverse problems. Author(s): Hugo Hidalgo Silva; J... more ... wise continuous models for electromagnetic inverse problems. Author(s): Hugo Hidalgo Silva; Jose L. Marroquin Zaleta; Enrique Gomez-Trevino. Imaging experimental data from optical tomography by the elliptic systems method. Author(s): Thomas R. Lucas; Michael V. Klibanov ...
The safety and efficacy of a new, low-osmolal magnetic resonance imaging contrast medium, gadoter... more The safety and efficacy of a new, low-osmolal magnetic resonance imaging contrast medium, gadoteridol injection, were evaluated in a phase II, open-label study at doses ranging from 0.05 to 0.30 mmol/kg. Eighty-six patients with a diagnosis of intracranial tumor received gadoteridol injection followed by magnetic resonance imaging. Two adverse events (headache, taste disturbance) in 2 of 86 (2.3%) patients were reported. Both were of mild intensity and resolved without treatment and without residual effects. In 4 of 86 (4.7%) patients, 5 laboratory changes were reported by the investigators as possibly related to gadoteridol injection. Efficacy evaluation was conducted in 80 of the 86 patients who received gadoteridol injection. In these patients, a total of 119 lesions was identified, and each was evaluated at four time points after contrast administration, yielding a total of 476 lesion studies. Marked enhancement was demonstrated in 402 of 476 (84%) lesions, whereas slight enhancement was demonstrated in 62 of 476 (13%) lesions. The difference in both the incidence and degree of enhancement of pathology between the predose and postdose images was highly significant (P less than .001). Overall, enhanced images provided more diagnostic information and facilitated detection of more lesions than precontrast images. Gadoteridol injection at doses up to 0.3 mmol/kg is a safe and effective magnetic resonance imaging contrast agent for use in patients with intracranial tumors.
Journal of Computer Assisted Tomography, May 1, 1987
Sequential fast magnetic resonance (MR) images (repetition time = 33 ms, echo time = 7 ms, alpha ... more Sequential fast magnetic resonance (MR) images (repetition time = 33 ms, echo time = 7 ms, alpha = 22 degrees, one image every 12 s) were acquired using gadolinium-diethylenetriamine pentaacetic acid (Gd-DTPA) (10 or 100 mumol/kg) to study perfusion and concentrating ability in normal rabbit kidneys and in kidneys with HgCl2-induced acute tubular necrosis (ATN). In normal rabbits receiving 100 mumol Gd-DTPA/kg a concentric region of decreased MR signal was observed. In sequential images the dark ring pattern migrated centripetally through the kidney moving from the corticomedullary junction to the inner medulla. The decrease in MR signal intensity occurred as a consequence of T2 relaxation (magnetic susceptibility) due to high concentration of Gd-DTPA within the tubules. This suggests that the dark ring pattern may serve as a qualitative feature indicative of the ability of the kidneys to concentrate. With the onset of HgCl2-induced ATN the pattern of enhancement due to Gd-DTPA administration changed markedly. Although the kidneys with ATN did continue to be perfused, the concentric dark ring pattern seen in normal kidneys receiving 100 mumol Gd-DTPA/kg was not observed. These results suggest that Gd-DTPA and fast imaging MR may provide a method of assessing perfusion and concentrating ability within the healthy or diseased kidney.
The paramagnetic magnetic resonance (MR) imaging contrast agent gadolinium diethylenetriaminepent... more The paramagnetic magnetic resonance (MR) imaging contrast agent gadolinium diethylenetriaminepentaacetic acid (DTPA) is freely filtered at the glomerulus and is neither secreted nor reabsorbed by the renal tubules. Fast MR imaging techniques, either gradient-echo or spin-echo, can be used to document the passage of Gd-DTPA through the renal tubules, as reflected by alteration in the MR signal intensity within the different anatomic regions of the kidney. Gradient-echo (repetition time of 35 msec, echo time of 7 msec, flip angles of 10 degrees-100 degrees) and spin-echo (repetition time of 35 msec, echo time of 8 msec) pulse sequences were used to acquire 20 consecutive images, one every 12 seconds, of the rabbit kidney. Both pulse sequences depicted the time course of Gd-DTPA distribution through the kidney but with distinctly different patterns of MR signal change. These dynamic MR images provide an MR nephrogram that directly demonstrates renal morphology and indirectly reflects the functional status of the renal vasculature, renal perfusion, and tubular concentrating ability.
Even though the intrinsic soft tissue contrast sensitivity of magnetic resonance imaging (MRI) af... more Even though the intrinsic soft tissue contrast sensitivity of magnetic resonance imaging (MRI) affords excellent visualization of anatomic detail, certain pathologic processes may be diagnosed earlier with the administration of a contrast-enhancing agent. At present there is one agent, gadopentetate dimeglumine, GdDTPA, that has received FDA approval for use in the MR scanning of the brain and spine in human patients. This paramagnetic chelate distributes throughout the extracellular fluid space as dictated by capillary permeability so that abnormal vascularity and sites of blood-CNS barrier breakdown are highlighted. Primary neoplastic disease, metastases, meningeal extension, residual and recurrent tumor have been found to be better distinguished in MR images acquired after administration of GdDTPA. Routine administration of GdDTPA for cranial imaging has resulted in the discovery of otherwise occult lesions in approximately 3 of patients. Although the clinical utility and high therapeutic safety index of the first approved magnetic resonance contrast agent, GdDTPA, have been well established, other contrast agents, having different physical, chemical and biological properties, may offer improved sensitivity and bio-specificity. Agents currently being evaluated in vivo include: low osmolal paramagnetic chelates, superparamagnetic particles, metalloporphyrins, liposome encapsulated agents, perfluorocarbons, intravascular macromolecular chelate complexes and labeled monoclonal antibodies. Concurrent with advances in the development of new compounds, innovations in scanning hardware, pulse sequence design and image post-processing are helping to extend the efficacy of contrast media. Additional clinical experience will indicate which contrast agents and which MR techniques can best facilitate the early detection of specific neoplastic lesions.
Small, multiple foci of increased signal intensity (T2 weighted images) in the centrum semiovale ... more Small, multiple foci of increased signal intensity (T2 weighted images) in the centrum semiovale and basal ganglia are frequently-observed on magnetic resonance images of the brain. Often, these findings are of doubtful significance with respect to the patient’s clinical state. Several explanations for this phenomenon have been advanced and much controversy surrounds this issue. We correlated images of 5 fresh and fixed brains obtained at 1.5 T and 4.7 T and of 10 fixed brains obtained at 1.5 T with pathologic analysis of these brains and also with an evaluation of the perivascular spaces in fixed brain specimens from the Yakovlev collection of the Armed Forces Institute of Pathology (AFIP). These foci of hyperintensity in part correlated with the location of the deep penetrating arteries and probably represent extracellular water in the perivascular (Virchow-Robin) spaces. These spaces typically enlarge with aging and with various systemic disorders such as hypertension. We then retrospectively reviewed 100 MR scans of patients with various clinical/pathologic conditions and found that these hyperintense foci were frequent findings. It is our conclusion that many of the hyperintense foci in the centrum semiovale and basal ganglia represent extracellular water in the Virchow-Robin spaces.
The I n t e r a c t i o n s o f two p o s i t i o n a l 1somers and one ana logue o f m e s o t e... more The I n t e r a c t i o n s o f two p o s i t i o n a l 1somers and one ana logue o f m e s o t e t r a ( 4 N m e t h y l p v r i d v l ) p o r p h i n e , w i t h the s y n t h e t i c p o l y n u d e o t i d e s p o l y [ d ( A T ) ] p o l y C d U T ) ] and po l y [ d (G-C ) ] • p o l y [ d ( G C ) ] have been I n v e s t i q a t e d by c i r c u l a r d i c h r o i s m . A l l f ou r p o r p h y r i n s were found t o b i n d to the p o l y n u d e o t i d e s as shown by the I n d u c t i o n o f c i r c u l a r d i c h r o i s m 1n t h e i r So re t bands . F u r t h e r m o r e , t he s i g n o f t he Induced e l l i p t i d t y r e f l e c t s s e l e c t i v e o c c u p a t i o n o f b i n d i n g s i t e s by the p o r p h y r i n l i g a n d s . The c o n f o r m a t i o n a l l a b i l i t y o f p o ! y [ d ( A T ) ] *po l y [d ( A T ) ] was found t o be a p p r e c i a b l e as m i c r o m o l a r amounts o f m e s o s u b s t i t u t e d 4 N m e t h y l p y r I d y l , ...
... Resolution studies in diffusion tomography. Author(s): Thomas R. Lucas; Michael V. Klibanov; ... more ... Resolution studies in diffusion tomography. Author(s): Thomas R. Lucas; Michael V. Klibanov; Robert M. Frank. Real inversion of a ... Regularization of inverse problem by singular value filtration. Author(s): Vitalij N. Kurashov; Alexandr G. Chumakov; Andry V. Kovalenko. Stable ...
ABSTRACT Ashley R, Carvlin M, Lucas T, Olukotun A. Addressing cost-containment and cost-effective... more ABSTRACT Ashley R, Carvlin M, Lucas T, Olukotun A. Addressing cost-containment and cost-effectiveness in magnetic resonance contrast agent development. Invest Radiol 1994;29:S257-S259.
Proceedings of Spie the International Society For Optical Engineering, Oct 1, 1995
... wise continuous models for electromagnetic inverse problems. Author(s): Hugo Hidalgo Silva; J... more ... wise continuous models for electromagnetic inverse problems. Author(s): Hugo Hidalgo Silva; Jose L. Marroquin Zaleta; Enrique Gomez-Trevino. Imaging experimental data from optical tomography by the elliptic systems method. Author(s): Thomas R. Lucas; Michael V. Klibanov ...
The safety and efficacy of a new, low-osmolal magnetic resonance imaging contrast medium, gadoter... more The safety and efficacy of a new, low-osmolal magnetic resonance imaging contrast medium, gadoteridol injection, were evaluated in a phase II, open-label study at doses ranging from 0.05 to 0.30 mmol/kg. Eighty-six patients with a diagnosis of intracranial tumor received gadoteridol injection followed by magnetic resonance imaging. Two adverse events (headache, taste disturbance) in 2 of 86 (2.3%) patients were reported. Both were of mild intensity and resolved without treatment and without residual effects. In 4 of 86 (4.7%) patients, 5 laboratory changes were reported by the investigators as possibly related to gadoteridol injection. Efficacy evaluation was conducted in 80 of the 86 patients who received gadoteridol injection. In these patients, a total of 119 lesions was identified, and each was evaluated at four time points after contrast administration, yielding a total of 476 lesion studies. Marked enhancement was demonstrated in 402 of 476 (84%) lesions, whereas slight enhancement was demonstrated in 62 of 476 (13%) lesions. The difference in both the incidence and degree of enhancement of pathology between the predose and postdose images was highly significant (P less than .001). Overall, enhanced images provided more diagnostic information and facilitated detection of more lesions than precontrast images. Gadoteridol injection at doses up to 0.3 mmol/kg is a safe and effective magnetic resonance imaging contrast agent for use in patients with intracranial tumors.
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