Sven Dorph

Evaluation of Treatment Response in Active Crohn's disease by low-field magnetic resonance imaging

AbstractBackground: To evaluate low-field magnetic resonance imaging (MRI) in detecting therapeutic response in active Crohns disease during treatment with systemic steroids. Methods: Eight patients with active Crohns disease were examined before and during treatment with systemic steroids (1 mg/kg/day) using low-field MRI (0.1 T) in transverse and coronal planes before and after an intravenously administered bolus of gadodiamide. Five healthy persons were once examined in the same way. MRI images were evaluated without knowledge of diagnosis, treatment, or findings of endoscopy, conventional radiography, and surgery. Proximal and mid small bowel, terminal ileum, right-sided colon, transverse colon, and left-sided colon were evaluated separately. Results: Statistically significant differences were shown for both signal intensity on T2- (SIT2) and increment in signal intensity on T1-weighted images after contrast (%SIT1) when comparing diseased bowel segments with both nondiseased bowel segments (SIT2: p= 0.0001; %SIT1: p= 0.0009) and segments from the control group (SIT2: p < 0.00005; %SIT1: p < 0.00005). In 53 of 56 bowel segments evaluated (95%), agreement was found between findings by MRI, conventional radiography, endoscopy and/or surgery regarding disease extension. Extension was underestimated in two patients. All bowel segments in the control subjects were evaluated to be normal on MRI. Significant correlation was found between both SIT1 (p < 0.0025) and %SIT1 (p < 0.025) versus endoscopic activity gradings. During treatment, significant decrements of both SIT2 (p < 0.00005), %SIT1 (p= 0.002), and bowel wall thickness (p= 0.03) were found. Conclusions: Low-field MRI seems to be a promising noninvasive method in the evaluation of response regarding both disease extension and activity in Crohns disease during treatment with systemic steroids.

Inflammatory bowel disease evaluated by low-field magnetic resonance imaging: Comparison with endoscopy, 99mTc-HMPAO leucocyte scintigraphy, conventional radiography and surgery

Background: To evaluate the use of low-field magnetic resonance imaging (MRI) in active inflammatory bowel disease (IBD). Methods: MRI was executed in a consecutive cohort of 28 patients with Crohn disease (CD) and in 17 with ulcerative colitis (UC) prior to glucocorticoid treatment (1 mg prednisolone orally/kg body weight/day). MRI was repeated after 2-3 weeks (22 CD, 12 UC), and again after treatment completion or prior to surgery (18 CD, 6 UC). Five bowel segments were evaluated separately. MRIs were blindly evaluated by two observers, and findings compared with 39 leucocyte scintigraphies, 38 endoscopies, 15 double-contrast barium enemas, 66 small-bowel radiographic examinations and surgery in 23 patients. Results: In CD, blinded evaluation revealed a kappa ( s ) of 0.84 (95% confidence interval (CI) 0.78-0.91). In UC, s was 0.66 (95% CI 0.55-0.78). Agreements regarding disease extension between MRI and other modalities in CD were found in 345 bowel segments out of 391 (88.2%) at risk, and in UC in 209/235 (88.9%). Colonic disease activity gradings by radiography and endoscopy correlated significantly with T2-signal intensity (SI T2 ) and increments in T1-signal intensity (%SI T1 ) in both diseases. Significant correlations between MRI indices of disease activity and CDAI in CD (MRI-SI T2 : P < 0.0001; MRI% SI T1 : P = 0.0008) and the Powell-Tuck index in UC (MRI% SI T1 : P = 0.008) were found. Conclusions: With low interobserver variation and high concordance of findings with other examinations, low-field MRI seems a valuable modality in active IBD. In addition, MRI expressions of disease activity correlate to clinical, radiographic and endoscopic disease activity.

High-osmolar and low-osmolar contrast media. An update on frequency of adverse drug reactions.

During the past 3 years a great number of papers about adverse drug reactions to intravascular injection of high-osmolar and low-osmolar iodinated contrast media (CM) have been published. They include observational studies, randomized trials, meta-analyses and committee reports. Thorough analysis of this material substantiates an improvement in safety of at least 6-fold using nonionic low-osmolar CM compared with ionic high-osmolar CM. The point where only a small minority is continuing to argue effectively that low-osmolar CM are not better than conventional high-osmolar CM has now been reached. High-osmolar CM are used less and less for intravascular purposes, and, in fact, have been totally replaced by low-osmolar CM in 4 countries.

Why does kidney size change during I.V. urography

Meglumine iothalamate (280 ml I/ml) and sodium iothalamate (400 mg I/ml) in doses of 700 mg I/kg bw, were injected i.v. as a bolus in dogs. Renal size, urine flow rate, arterial pressure, renal blood flow and mean transit time and renal blood volume were measured before and after injection. All changes were qualitatively and quantitatively identical for both drugs. They produced a small transient renal shrinkage followed by a greater and prolonged renal enlargement. During the period of renal enlargement, urine flow increased. The time course of the enlargement paralleled the increase of urine flow rate. Renal blood flow also increased but both the mean transit time and renal vascular volume decreased. Therefore, the kidney size increase after i.v. injection of large doses of urographic contrast media cannot be attributed to an increased volume of the vessels. Most likely it is caused by diuresis-induced increase in the volume of the tubules.

QUALITY OF UROGRAPHY AND RENAL CLEARANCE OF IONIC AND NONIONIC CONTRAST MEDIA

Thomsen HS, Vcstergaard A, Dorph S. Quality of urography and renal clearance of ionic and nonionic contrast media. Invest Radiol 1992;27:40–44.The authors evaluated whether urographic quality correlated with patient hydration and the level of their renal function, depending on whether they received ionic or nonionic contrast media. One hundred patients with normal serum creatinine levels were randomly assigned to receive intravenous urography with either an ionic high-osmolar or a nonionic low-osmolar contrast medium. Patient hydration was evaluated by measuring urine osmolality in a sample voided just before the examination. The plasma concentration of iodine was determined in a single blood sample drawn approximately 3 hours later. From these determinations the plasma clearance of contrast medium was calculated. The urograms were assessed blindly with regard to nephrographic and pyelography opacification, as well as overall diagnostic quality. The clearance varied between 42 and 115 ml. x minutes−1 x 1.73 m−2. No systematic correlation or practical significance was found between the clearances and the urogram quality. A high urinary osmolality before the examination tended to improve quality with both media. It is not possible to assess glomerular filtration rate from nephrographic and pyelographic opacification, or from overall quality of routine urograms in patients with normal serum creatinine levels.

Urine profiles and kidney histology after intravenous injection of ionic and nonionic radiologic and magnetic resonance contrast media in normal rats

RATIONALE AND OBJECTIVES Previous studies showed that both high-osmolality and low-osmolality iodinated contrast media cause temporary albuminuria and enzymuria (presence of enzymes in urine) in normal rats. Whether the same is true with ionic high-osmolality and nonionic low-osmolality magnetic resonance (MR) contrast media is unknown. We studied urine profiles and histology after intravenous injection of four types of contrast media in rats with normal kidneys. METHODS Urine profiles were monitored 4, 24, 48, and 72 hr after intravenous injection of saline, diatrizoate, iohexol, gadopentetate dimeglumine, and gadodiamide (4.59 mmol/kg of body weight) in normal rats. Each group included 20 male rats. After sacrifice, both kidneys were removed for examination by light microscopy (LM) and electron microscopy (EM). RESULTS All four contrast agents caused a temporary (< 22 hr) increase in the excretion of albumin (2-5 times) and of cytoplasmic (30-100 times) and brush border (10-100 times) renal enzymes when compared with saline. The degree of albuminuria correlated well (r = 0.90) with the osmolality of the injected media, whereas the increased level of enzymuria was unrelated to the osmolality. No major differences in the enzymuric effects of the four agents were noted. LM revealed vacuoles in all kidneys exposed to radiologic contrast media but not in kidneys exposed to MR contrast media or saline. Slight vacuolation was revealed by EM after the use of MR contrast media, and significant vacuolation was evident via EM after the use of radiologic contrast media. No difference between ionic and nonionic media within each drug group was detected by either LM or EM. CONCLUSIONS Transient renal effects are induced by both ionic and nonionic high-osmolality and low-osmolality radiologic and MR contrast media in normal rats. Both osmotic (e.g., albuminuria) and chemotoxic (e.g., enzymuria) mechanisms seem to be involved. From a morphologic point of view, the chemotoxic mechanisms seem to be of major importance.

Variations in size of the normal kidney following intravenous administration of water-soluble contrast medium and urea

Abstract Variations in kidney area were measured on X-ray films following the injection of contrast medium and urea. A mean increase of 7·8 per cent following contrast-medium injection was demonstrated in hypertensive patients with normal renal arteries. In normotensive patients the mean increase was 4·8 per cent. Additional infusion of urea (washout urography) in the hypertensive group produced a further increase in renal area to an average maximum of 11·4 per cent. A rise in interstitial pressure associated with intrarenal vasodilatation is a possible explanation. The response has physiological and clinical implications.

The Transplanted Kidney: Diagnostic and Interventional Radiology

Following kidney allotransplantation a great number of complications threaten the patient and his graft, e.g. acute tubular necrosis, acute and chronic rejection, urologic and vascular complications and complications due to the immunosuppressive treatment. During the last decade a number of technical developments in radionuclide, ultrasonographic and radiographic imaging and intervention has significantly improved the possibility of early recognition and handling of such complications. Knowledge of the capability and limitations of the various techniques is of vital importance for their rational use. The aim of this review article is to give a short description of the various imaging modalities, the rational monitoring of the post-transplant patient, and possible handling of complications by the aid of imaging techniques.

Pyelorenal backflow in normal and ischemic rabbit kidneys.

Pyelorenal backflow during retrograde pyelography was studied in 68 kidneys of anesthetized rabbits. Thirty-three of the experiments were performed during or shortly after temporary renal arterial clamping. Pyelosinous backflow was observed in 67 and pyelovenous backflow in 65 of the 68 kidneys, occurring at an average intrapelvic pressure of 70 mmHg. This was true in intact kidneys and during arterial occlusion. Intrarenal backflow--intrusion of contrast material into the renal parenchyma--could be produced in only one of 35 experiments on intact kidneys, and occurred at an intrapelvic pressure of 119 mmHg. During arterial clamping, intrarenal backflow was observed in eight of nine experiments, occurring at intrapelvic pressures of about 70 mmHg. After removal of the clamp, intrarenal backflow was less frequent with shorter periods of arterial clamping and longer time between restoration of arterial flow before pyelography. Subcapsular extravasation of the medium with total blurring of the kidneys shadow and a prompt fall in intrapelvic pressure was the ultimate result of prolonged and extreme overdistension of the renal pelvis. It occurred at an average intrapelvic pressure of 80 mmHg. Histologic examination revealed tears in the fornix of the pelvic cavity in cases with pyelosinous backflow. If intrarenal backflow was present, there were tears leading from the pelvic cavity into the renal parenchyma. Supplementary experiments using a contrast material that could be demonstrated histologically (barium sulfate with gelatin) showed that the contrast filled the intertubular capillaries and venules. There was no evidence of backflow through the canalicular route.

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.