Paramagnetic macrocyclic complexes as contrast agents for MR imaging: proton nuclear relaxation rate enhancement in aqueous solution and in rat tissues

Paramagnetic macrocyclic chelates show promise as magnetic resonance (MR) imaging contrast agents due to stability and relaxivity comparable to those of DTPA-type chelates. For the three copper and manganese macrocyclic complexes studied in aqueous solution, T1 and T2 relaxivities ranged from 0.14 to 5.88 mM-1sec-1 at 6.25 MHz. In rats, the intravenous administration of 16 mumol/kg of Mn(cyclam) caused the liver T1 relaxation rate to double at 15 minutes after injection. T1 measurements by pulsed MR imaging and manganese analyses on excised tissue showed that both relaxation rate (1/T1) and manganese content of liver and kidney increase linearly with the dosage of Mn(cyclam). The linear relationship between 1/T1 and manganese content can be considered an "in tissue" relaxivity plot for the agent. The resulting relaxivity is 54 mM-1sec-1 in liver, compared with 3.1 mM-1sec-1 in aqueous solution. Although this work is preliminary, the implication for medical MR imaging applications is that macrocyclic contrast agents can be effective at approximately one-tenth the current typical dose used for gadolinium DTPA.     

Simultaneous radical nephrectomy and repair of abdominal aortic aneurysm

Objectives

The combination of abdominal aortic aneurysm repair with other intra-abdominal surgery is controversial. Most studies have shown that a variety of procedures can be performed at the same time as an aneurysm repair with little change in mortality or complication rates. We conducted a retrospective study to determine if aneurysm repair could be safely and effectively combined with radical nephrectomy.

Methods

We studied 10 patients who underwent combined abdominal aortic aneurysm repair and radical nephrectomy during a 4-year period. Results from this group were compared to a separate control group of 10 patients who underwent radical nephrectomy alone and another of 12 patients who underwent abdominal aortic aneurysm repair alone, during the same time period.

Results

The overall mortality was 10% and significant complications occurred in an additional 10% of patients. Minor, self-limiting complications occurred in 30% of patients. There were no aortic graft infections that occurred in the entire series of patients at 18 months of mean follow-up. There were no remarkable differences in length of stay, age, operating time, blood loss, morbidity, and mortality between this series of patients and the combined values in a separate group of control patients who had undergone either procedure alone.

Conclusions

Simultaneous radical nephrectomy for presumed renal cell carcinoma can be safely combined with repair of abdominal aortic aneurysm in selected patients.