Thorkild Mygind

A Dose-Reducing Fluoroscopy System: Dose Measurements and Clinical Evaluation

Abstract A system based on pulsed fluoroscopy and image storage on a video disc recorder was developed to reduce fluoroscopic x-ray dose. It can be applied to any radiologic examination requiring fluoroscopy. An MVR disc recorder was used in connection with a conventional x-ray unit. Separate dose measurements for fluoroscopy and film-exposure radiation were obtained during 50 examinations of the stomach. The results were compared to those in 50 conventional television fluoroscopy studies. Average 90% reduction in fluoroscopy dosage was obtained, using 1 forty-msec x-ray pulse/second. Stepwise changing of the fluoroscopic images permitted sufficient impression of gastric dynamics.

Cardiovascular adjustments to pulmonary vascular injury in dogs.

The hemodynamic effects of blood volume augmentation and mechanical ventilation (MV) with positive end-expiratory pressure (PEEP) were studied in nine Beagles anesthetized with halothane before and after thrombin-induced pulmonary hypertension. The effect of therapy with dopamine, norepinephrine with and without nitroglycerine (NTG), and intraaortic balloon pumping (IABP) were studied in a second series of six Beagles. Before thrombin, dextran (35 ml · kg−1) caused a significant increase in right and left ventricular end-diastolic and end-systolic volumes (RV and LVEDV, and RV and LVESV). However, RV and LV performance, as estimated by ejection fraction, was unchanged during volume loading and MV with PEEP when the pulmonary vasculature was intact. The response to volume loading and MV with PEEP was altered significantly once PVR bad been increased with the administration of thrombin. Stroke volumes were decreased, and remained so, despite volume loading and MV with PEEP. LVEDV decreased without a decrease in LVEDP, indicating a decreased LV compliance. Dopamine and norepinephrine with and without NTG increased stroke volumes and RV ejection fraction in contrast to IABP. Assessment of LV performance, according to the Frank-Starling mechanism, requires a measure of end-diastolic volume when diffuse pulmonary vasoconstriction leads to RV distension and LV hypovolemia secondary to septal shift. Measurement of LV filling pressures can provide misleading values to estimate changes in LV volume in this setting. Measurement of ventricular volumes is required for optimal management of patients with severe acute respiratory failure and pulmonary hypertension.

Do contrast media aggravate Fanconi's syndrome in rats? A comparison of diatrizoate, iohexol, and ioxilan.

Thomsen HS, Dorph S, Mygind T, Nielsen H, Rygaard H, Larsen S, Skaarup P, Hemmingsen L, Holm J. Do contrast media aggravate Fanconis syndrome in rats? A comparison of diatrizoate, iohexol, and ioxilan. Invest Radiol 1988;23(Suppl 1):S164‐S167. Urine profiles (albumin, glucose, N‐acetyl‐&bgr;‐D‐glucosaminidase [NAG], lactate dehydrogenase [LDH], L‐&ggr;‐glutamyltransferase [GGT], sodium, and phosphate) were followed for seven days after intravenous (IV) administration of either diatrizoate, iohexol, ioxilan, or saline in 24 Wistar rats with a tubular dysfunction induced by IV sodium maleate. Ioxilan and saline had a similar effect on albumin excretion, iohexol had an intermediate effect, and diatrizoate increased it significantly from day 2 to day 7. Glucosuria was significantly greater after diatrizoate than after the nonionic contrast media (CM) or saline. Diatrizoate delayed normalization of enzymuria, whereas iohexol and ioxilan did not. None of the CM affected urinary sodium or phosphate excretion. It is concluded that Fanconis syndrome is significantly aggravated only by diatrizoate.

Urine profiles following intravenous diatrizoate, iohexol, or ioxilan in rats.

Thomsen HS, Dorph S, Mygind T, Hemmingsen L, Holm J, Larsen S, Nielsen H, Rygaard H, Skaarup P. Urine profiles following intravenous diatrizoate, iohexol, or ioxilan in rats. Invest Radiol 1988;23(Suppl 1):S168‐S170. The effects of intravenous diatrizoate, iohexol, ioxilan, or saline on albumin, glucose, sodium and the enzymes N‐acetyl‐&bgr;‐D‐glucosaminidase (NAG), lactate dehydrogenase (LDH), and L‐&ggr;‐glutamyltransferase (GGT) in the urine of 24 normal Wistar rats were followed for seven days. During the first two hours after administration of diatrizoate, all profile components changed markedly; the albumin excretion was significantly greater than following ioxilan and iohexol; glucose, LDH, and GGT excretions were significantly greater than following ioxilan. Iohexol and ioxilan caused a higher excretion of albumin, LDH, and GGT than saline. Iohexol also increased glucose and sodium levels. Glucose and GGT were significantly higher following iohexol than following ioxilan. Both high osmolar and low osmolar contrast media may cause temporary glomerular and tubular damage. Urine profile components are affected most by diatrizoate, less by iohexol, and least by ioxilan.

Ventricular volumes determined from indicator dilution curves

A bolus of indicator substance injected into a ventricle or an atrium will be diluted in a stepwise manner according to the pulsatile nature of bloodflow. Provided the indicator is dispersed immediately and uniformly in the ventricle or atrium the time course of the indicator can be predicted. Dilution curves recorded in three dog experiments demonstrate a stepwise change of the indicator concentration in the ascending aorta following a bolus injection into the left atrium. The information thus retrieved is entered into equations describing the mathematical model in order to calculate the distribution volumes of the indicator in the left atrium and ventricle.