Albumin is a macromolecule that remains largely confined to the vascular space after intravenous administration. Human serum albumin was paramagnetically labeled by covalently binding from nine to 18 gadolinium-DTPA (diethylenetriaminepentaacetic acid) chelates per protein molecule. This conjugate was tested in varying doses for in vivo biodistribution and effectiveness in tissue relaxation. After intravenous injection of the agent in rats, T1 relaxation times were significantly reduced in samples of the blood and in lung, heart, spleen, kidney, and brain tissue. These effects persisted at a relatively constant level for the next 30 minutes. In vivo magnetic resonance imaging of the heart and lungs of rats and rabbits confirmed the prolonged contrast-enhancing effect of the labeled albumin. These preliminary studies indicate that paramagnetically labeled macromolecules that distribute in the intravascular space may be effective for MR imaging evaluation of tissue blood volume.
The appearance of the normal penis and of a variety of penile abnormalities on magnetic resonance (MR) images was studied in 55 patients with either medium (0.35 T) or high (1.5 T) magnetic field strengths. Penile morphologic characteristics with anatomic detail of the corpora cavernosa and corpus spongiosum were demonstrated in each patient. MR images clearly displayed congenital anomalies (n = 6), penile prostheses (n = 7), fibrous tissue or hematoma due to trauma (n = 8), and fibrous plaque in Peyronie disease (n = 3). MR imaging also demonstrated urethral (n = 6) and penile (n = 5) neoplasms and allowed tumor staging, thus facilitating the surgical approach.
The diagnostic value of MR contrast between renal cortex and medulla (CMC) as an indicator of renal disease was retrospectively studied in 51 patients (9 patients with obstructive disease, 7 with inflammatory disease, 12 with various noninfectious parenchymal medical disease, 5 with vascular disease, 2 with diffuse neoplastic disease, 7 with hemosiderosis, and 10 with renal trauma [blunt trauma and 9 postlithotripsy]). Additionally, normal kidneys from 20 control subjects were studied. On T1-weighted spin-echo images (SE 500/30), CMC was visible in all the normal kidneys (19% contrast +/- 2% SD). A decrease in or an absence of CMC on T1-weighted images (SE 500/28) was found to be a sensitive but nonspecific sign in most of the renal diseases studied. CMC was visibly preserved at normal levels in 7 of the 9 kidneys traumatized by lithotripsy and in all 4 kidneys with acute renal obstruction; CMC was above normal in kidneys with hemosiderosis. In conclusion, alteration in CMC is a sensitive but nonspecific indicator of renal disease. Furthermore, normal CMC can be seen in the presence of renal pathology.
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