Thomas J. O'Dea

RADIATION DOSE IN INTERVENTIONAL FLUOROSCOPIC PROCEDURES

Vascular interventional procedures carried out under fluoroscopic guidance often involve high radiation doses. Above certain thresholds, radiation can cause significant damage to the skin including hair loss and severe necrosis. Such damage has been reported by several investigators. Many attempts have been made to quantitate the radiation doses to the skin involved with these procedures, but dosimetry methods are often flawed. To improve the situation better monitoring of radiation doses, fluoroscopist education, and changes in technology and methods are needed.

The potential for radiation‐induced skin damage in interventional neuroradiological procedures: A review of 522 cases using automated dosimetry

The Food and Drug Administration (FDA) has recommended the monitoring of radiation skin dose to patients during procedures having the potential for radiation damage. Radiologists need information about typical radiation doses during interventional procedures. The skin doses to patients during 522 interventional neuroradiological procedures have been monitored using an automated dosimetry system. Estimated entrance skin doses (ESD) were binned into 0.5 Gy increments and compared to FDA recommended thresholds for inclusion in the patient record. Percentages of procedures exceeding the above mentioned thresholds are presented. In addition, the percentage of dose in each view and the percentage of dose in fluoroscopic and digital angiographic modes are shown. Six percent of embolization procedures and one percent of cerebral angiograms are estimated to have potential for main erythema (ESD>6 Gy). All types of procedures have potential for temporary erythema and exceed the threshold for inclusion in the patient record (ESD> 1 Gy) at the 95% percentile. The types of procedures with most potential for skin damage also have significant percentages of dose in the digital angiographic mode. Thus, monitoring fluoroscopic time alone underestimates the potential for skin injury. On the other hand, combining the doses in the posterior-anterior and lateral views, tends to overestimate the potential for radiation injury.

Effect Of Plasma Cholesterol On Red Blood Cell Oxygen Transport

1. Oxygen (O2) transfer from the blood to tissues is a function of the red blood cell (RBC) O2 saturation (SO2), the plasma O2 content being negligible. Under conditions of increased tissue O2 demand, the SO2 of arterial blood does not change appreciably (97%); however, the SO2 of mixed venous blood, equal to that of the perfused tissues, can go as low as 20%.

Pilot study of oxygen transport rate of banked red blood cells

Background and Objectives  Dynamic oximetry provides a new way to assess the effect of blood storage on the oxygen transport rate (OTR).

Establishing a quality control program for an automated dosimetry system.

Automatic dosimetry systems can provide instantaneous dose and dose-rate information during fluoroscopic procedures as well as long-term records of patient doses. For this information to be useful, it is necessary that the accuracy of such systems be maintained through a rigorous quality control program. Daily and weekly quality control checks were performed on a PEMNET automated dosimetry system to determine its stability and the value of such tests in a quality control program. Weekly tests included monitoring the accuracy of the measured doses under a variety of conditions. The results of the tests indicate possible improvements in test methodology and real and potential sources of system failure and provide a statistical basis for setting quality control limits for future system monitoring.

A novel method for measuring the cross-sectional area of and flow rate through the upper gastrointestinal system a feasibility study

Ascertaining the success of metabolic/bariatric surgery procedures and modifying their dynamics today lack noninvasive, accurate, and objective assessment technology. The feasibility of a method for measuring the cross-sectional area of and flow through the upper gastrointestinal system by electromagnetic induction is described. Our method depends on the change in resonance frequency of a series circuit (capacitor, inductor, and resistor) when changing the induction parameters. This is done by placing a coil constructed of multiple loops of wire around a substance of high magnetic permeability. A large coil and a 52-in-circumference simulation, 2-chambered, cylinder and a small coil and a test tube were used for these studies. Five feasibility experiments were performed using a standard protocol. Results demonstrated that using both the large coil and the small coil apparatus, the magnetic permeability compared with air of 3 paramagnetic substances—iron filings, Ferrite 75, and Ferrite 78—were roughly equivalent, although the results showed greater differentiation with the small coil; lactated Ringer solution in the middle chamber of the large coil cylinder showed no change in various resonance frequencies; and sensitivity discrimination using the small coil between a 2-cm and a 1.5-cm tube filled with iron filings demonstrated reasonable sensitivity for the system, with comparable outcomes for the large coil. This feasibility study has been successful and serves as incentive to broaden simulation testing of our concept and device with eventual human application.

Mucus Clearance from the Pulmonary System by Mechanical Means: A Dual-Excitation Approach

A dual-excitation approach to mechanical clearance of mucus from the pulmonary system is described. The approach employs independently controlled vibratory and constrictive pressure stimulations to the thorax. Patient cooperative efforts are integrated into the therapy regimen as a means of enhancing the efficacy of the treatment. An engineering model that demonstrates the capability to generate vibratory and constrictive pressure variations at specified levels is described.

A novel device for measuring the effect of cholesterol on the release of oxygen from red blood cells

A novel method has been devised to measure the effect of cholesterol on the release of oxygen (O/sub 2/) from the red blood cell (RBC) into a tailored environment, which can be made to mimic myocardial tissue. Cholesterol affects the cell membrane of RBCs and thus the release of O/sub 2/ into tissue. While this is true of all tissue, the myocardium is especially sensitive because of its critical nature, high O/sub 2/ requirements, and the shortness of time that arterial blood spends in the muscle. Calculations are presented that show that the release time for O/sub 2/ from RBCs is close to the residence time of the RBC in the coronary system. Sequential measurements of blood oxygen saturation (SO/sub 2/) are made when oxygenated blood is subjected to conditions similar to the myocardium. The natural logarithm of the relative value of the SO/sub 2/ at time t compared to the initial value of the SO/sub 2/ can be fitted to a straight line whose slope is proportional to the parameters of the RBC membrane, the sample size, the hematocrit and the diffusion parameters of the apparatus. This value is used to estimate the effect of cholesterol lowering treatments on O/sub 2/ release. This test will serve as a valuable adjunct to or replacement for stress tests in the evaluation of coronary artery disease, especially in patients whose physical condition make standard stress testing painful or risky.