CT fluoroscopy (CTF) is a useful tool for guiding abdominal pelvic interventions. It decreases the time to place needles into target lesions and may be helpful in targeting small and/or deep lesions. However, radiation exposure to the patient and operator may be substantial. We review the different methods of CTF use to guide abdominal pelvic biopsies and fluid aspiration/drainages. Ways of decreasing exposure are discussed, and a CTF radiation safety policy adapted at our institution is presented.
The toxic manifestations of modern intravascular contrast agents have been extensively studied in many parts of the body (1–4). In most areas their predominant toxic effect seems related to their hypertonicity (1, 5, 6). The purpose of this paper is to report the toxic effects of the modern intravascular contrast agents on the sinus node of the canine heart. Methods And Materials An experimental model was designed for this study by modifying one used by Dr. Thomas James for the study of pharmacologic agents (7). The heart was exposed through an anterior bilateral thoracotomy in the fourth intercostal space while the respiration was supported with an intratracheal tube and a respirator. The pericardium was opened over the right coronary atrioventricular groove, and the sinus node artery was identified arising from the right coronary ar-tery, coursing dorsally and then cephalad to perforate the sinus node tissue. The sinus node artery was then ligated just distal to its origin, and a small cannula (I.D. 0.015) was tied in place beyond the ligature (Fig. 1). The injections were made by means of a pair of Harvard infusion pumps connected through a three-way stopcock to the cannula in the sinus node artery. One of the pumps was used for a timed infusion at a known rate of the substance to be tested. The other was used for a timed flushing of the tested substance with normal saline or Ringer's solution. The following data were recorded on a polygraph: one lead of the electrocardio-gram; cardiac rate; aortic pressure; and time of injection or flush. This provided a model for selective perfusion of the sinus node tissue with contrast agents. The right coronary artery remained intact, and the electrocardiogram was not altered by this preparation of the sinus node artery. Between injections into the sinus node artery the collaterals from the atrial branches and from the circumflex branch of the left coronary artery supplied blood to the perfused area as indicated by back bleeding into the cannula. Studies were performed in 45 dogs. Injections of the test substances were made in ordered and randomized series in varying concentrations. Intermittently, saline was used in fixed concentrations as a control to validate the continued usefulness of the particular animal. The return of the animal's circulation to a stable rate was used as a criterion for beginning the next injection. At least two minutes were also allowed between injections. Subsequently, the experiment was extended by atropinizing the animals (1 mg/kg) and/or cutting the vagus nerves after the typical response had been obtained with a test substance injection. These animals were then reinjected with the same test substance. Results 1. Type of Infusions Eliciting a Response: Two types of responses were observed, one to variations in speed of injection, the other to variations in the composition of the injectate.
Both I-123 IMP scintigraphy and MRI have been suggested as sensitive detectors of changes shortly after acute cerebral infarction. We compared the uptake of N-isopropyl I-123 p-iodoamphetamine (IMP) and MR spectroscopy of the brain after internal carotid artery ligation. Thirteen gerbils were lightly anesthetized with ether. After neck dissection, an internal carotid artery was occluded. After 2.8 hours, 100 µCi I-123 IMP was injected intravenously into the 13 experimental animals plus three controls. Seven gerbils remained asymptomatic while six developed hemiparesis. At 3 hours after ligation, the animals were killed. The brains were bisected and T1 and T2 relaxation times were determined for the right and left hemispheres by MR spectroscopy immediately after dissection. I-123 IMP uptake was then determined in the samples. Interhemispheric differences in uptake for I-123 IMP were 0.1 ± 1.7% (SEM) in the control, 33.5 ± 10% in the asymptomatic and 54.6 ± 9.7% in the symptomatic animals. Significant differences were seen with I-123 IMP in 6/7 asymptomatic and 6/6 symptomatic animals. In conclusion, I-123 is more sensitive than T1 or T2 relaxation times for the detection of cerebral perfusion abnormalities. Prolongation in T1 and T2 relaxation times correlates closely with increased brain tissue water content and the development of symptoms, indicators of structural brain damage and probable infarction.
