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R Kivisaari

Publications and source records attributed to R Kivisaari.

10 recordsLinked to original sources
PubMed2000

Detection of severe acute pancreatitis by contrast-enhanced magnetic resonance imaging.

The aim of the study was to assess the ability of MRI to differentiate between the two forms of severity of acute pancreatitis (AP), which is important for the detection of patients who require intensive monitoring and therapy. The second objective was to evaluate whether the distinction would be possible regardless of the MRI equipment. Magnetic resonance imaging was performed before and after intravenous administration of a gadolinium (Gd) chelate at 1.0 T using the breath-hold multislice rapid gradient-echo turbo fast low-angle shot (FLASH) sequence in 14 patients, and at 1.5 T with the 2D FLASH(50) sequence with fat saturation in 18 patients with acute pancreatitis early in the course of the disease. The patients were classified according to the Atlanta classification system as having the mild (MAP) or severe (SAP) form of the disease. At 1.0 T with use of a body coil, contrast-enhanced MRI failed to distinguish mild from severe pancreatitis. At 1.5 T with a phased-array body coil, the signal intensities of the patients with SAP were statistically significantly lower than those of the MAP group. Our initial clinical experience suggests that MRI with a sufficient magnetic field gradient strength may be useful for separating the two forms of acute pancreatitis in their early phases.

Acute Disease↗
PubMed1998

Multiphase segmented k-space velocity mapping in pulsatile flow waveforms.

The aim of the present study was to obtain the precision of flow measurement in breath-hold segmented k-space flow sequences. The results are based on studies of pulsatile flow in a phantom tube. The ultimate purpose is to use these sequences to measure coronary flow. In abdominal and cardiothoracic magnetic resonance imaging the image quality is degraded due to respiratory motion. In the segmented k-space acquisition method, one obtains many phase-encoding steps or views per cardiac phase. This shortens imaging time in the order of phase-encoding lines and makes it possible to image in a single breath-hold, thereby eliminating respiratory artefacts and improving edge detection. With breath-hold multiframe cine flow images it is possible to evaluate flow in all abdominal and cardiothoracic areas, including the coronary arteries. Our study shows that velocity curves shift in time when the number of k-space ky-lines per segment (LPS) are varied; this shift is linear as a function of LPS. The mean velocity Vmean in the center of mass of the pulsatile peak is constant (Vmean = 40.1 +/- 2.9 cm/s) and time t = -10.1 x LPS + 268 (r = 0.993, p < 0.0001). Correlation between theoretical and experimental flow curves is also linear as a function of LPS: C = -0.977 * LPS (r = 0.987, p < 0.0001). It is concluded that velocity curves move with LPS and are smoothed when the breath-hold velocity mapping is used. The more LPS is gathered the more inaccurate results are. LPS 7 or more cannot be considered clinically relevant.

Artifacts↗
PubMed1997

Contrast-enhanced magnetic resonance imaging for the detection of acute haemorrhagic necrotizing pancreatitis.

Eleven piglets with haemorrhagic necrotizing pancreatitis and nine piglets with oedematous pancreatitis were imaged using a multi-breath-hold TurboFLASH (TR 6.5 ms, TE 3 ms, TI 300 ms, flip angle 8 degrees , three slices) pre-excited T1-weighted sequence with an IV bolus injection of gadopentetate dimeglumine (Gd-DTPA, 0. 3 mmol/kg) as a contrast agent to show dynamic contrast enhancement of the pancreas by MRI. All piglets were imaged according to the same protocol before inducing the disease. Following the IV Gd-DTPA bolus, time-enhancement curve of the pancreas during haemorrhagic necrotizing pancreatitis was significantly lower than during oedematous pancreatitis. The enhancement curves for the healthy piglets and piglets with oedematous pancreatitis did not differ significantly. Each piglet served as its own control. Because the results of this initial study are similar to those obtained with contrast-enhanced CT, we conclude that our results may encourage further clinical trials, and contrast-enhanced dynamic MRI may be an alternative to the established method of CT for diagnosing acute haemorrhagic necrotizing pancreatitis.

Animals↗
PubMed1997

Structural changes in the renal proximal tubular cells induced by iodinated contrast media.

The renal morphologic changes induced by intravenously injected contrast media (CMs) were studied in 40 Wistar rats which had been deprived of water 24 h before the CM injection. In the first part of the investigation, the kidneys were fixed by perfusion for light and electron microscopy 2 h after injection of 3 g iodine/kg of iopamidol, iobitridol or iohexol. Control animals received physiologic saline. In the second part of the study, the fixation was performed 48 h after the injection of the corresponding dose of iobitridol or iohexol. The structural changes were semiquantitatively evaluated by two independent observers unaware of the agent injected. The lysosomes of the proximal convoluted tubular cells showed moderate changes 2 h after the iopamidol injection. Iobitridol and iohexol induced prominent lysosomal alterations with signs of cytoplasmic injury. After 48 h, the changes induced by iobitridol had almost disappeared, whereas the iohexol group still showed a statistically significant vacuolization. Although the general physicochemical properties of iobitridol and iohexol appear similar in vitro, the different lysosomal alteration might reflect differences in their characteristics in vivo.

Animals↗
PubMed1995

Dynamic high-field MR imaging in experimental porcine acute pancreatitis.

The effects of acute pancreatitis on MR imaging signal intensities (SIs) were determined in an experimental study at 1.0 T. Oedematous pancreatitis was induced in 9 piglets and haemorrhagic pancreatitis in 11 piglets. Each animal served as its own control for MR imaging before and after induction of pancreatitis. T1-weighted spin echo (450/15 ms) and dynamic turbo FLASH (flip angle 8 degrees) sequences were used without contrast medium in testing the stability of the SI measurements. There was no significant difference in the SI-versus-time curves of the pancreas in piglets with oedematous and haemorrhagic pancreatitis. However, the difference in mean SIs between healthy and diseased piglets was significant. Thus, although non-contrast MR may be useful in the diagnosis of acute pancreatitis, it does not distinguish between oedematous and haemorrhagic pancreatitis.

Acute Disease↗
PubMed1993

Contrast media-induced renal morphologic lesions in diabetic rats.

Diabetes mellitus was induced in rats with streptozotocin and after 3 months the animals (n = 48) received an i.v. injection of 1 or 3 g I/kg in the form of high-osmolar diatrizoate, low-osmolar iopromide or iohexol, or of 0.6 g I/kg of high-osmolar Gd-DTPA. The controls were given an i.v. injection of physiologic saline. After 2 hours the kidneys were fixed by perfusion and the renal morphologic changes were semiquantitatively analyzed by two independent observers unaware of the agent administered. The contrast media (CM) induced pronounced cytoplasmic vacuolization in the proximal convoluted tubular cells. Such a lysosomal alteration may indicate CM uptake into the cell, and the ultrastructural evaluation revealed intracellular injuries related to the process. The alterations were most marked following administration of iohexol, but diatrizoate also induced a statistically highly significant vacuolization (p < 0.001). The lysosomal alterations following iopromide administration were not as striking, and Gd-DTPA induced only minor changes.

Animals↗
PubMed1992

Contrast media-induced renal morphologic changes in rats with acute edematous pancreatitis.

OBJECTIVES: Contrast media (CM)-induced renal morphologic changes were studied in rats during acute edematous pancreatitis. METHODS: The histologically verified, mild pancreatitis was caused in Wistar rats (n = 54) by an injection of peanut oil into the pancreatic duct. After 24 hours, the animals received an intravenous (IV) injection of 1.0 or 3.0 g iodine (I)/kg of high-osmolality diatrizoate, low-osmolality iopromide or iohexol, or 0.2 or 0.6 g/kg of high-osmolality magnetic resonance (MR) CM, gadolinium-DTPA (Gd-DTPA). The controls received physiologic saline. The kidneys were fixed by perfusion after 2 hours, and changes in renal morphology were analyzed semiquantitatively by two independent observers blinded to the treatment. RESULTS: The smaller dose of iohexol and the larger dose of all other CM induced a statistically significant (P less than .05) cytoplasmic vacuolization in the proximal convoluted tubule cells. The changes were most prominent after iohexol (P less than .001). When compared with the authors' earlier findings on healthy rats, the CM-induced renal structural injury was more severe. CONCLUSIONS: Pancreatitis potentiates the renal microstructural changes associated with CM; although the animals' fluid and electrolyte status was not specifically assessed, the enhanced abnormalities may be related to the hypovolemia associated with pancreatitis.

Acute Disease↗
PubMed1992

Contrast media-induced renal morphologic lesions during experimental hemorrhagic necrotizing pancreatitis.

RATIONALE AND OBJECTIVES: Contrast media-induced renal morphologic changes were studied in rats. Hemorrhagic pancreatitis was induced as a means of sensitizing the animals to the effects of contrast media. METHODS: The histologically verified hemorrhagic pancreatitis was induced in Wistar rats (n = 66) by injecting 6% sodium taurocholate into the pancreatic duct. After 2 hours, the animals received intravenously 1.0 or 3.0 g iodine/kg of high-osmolal osmolal diatrizoate, low-osmolal iopromide or iohexol, iso-osmolal iotrolan or 0.2 or 0.6 g/kg of high-osmolal magnetic resonance contrast agent, gadolinium-DTPA (Gd-DTPA). Control animals received physiologic saline. The kidneys were fixed by perfusion 2 hours later, and the morphologic changes were reviewed by two independent observers blinded to the injected agent. RESULTS: The smaller dose of iohexol and the larger dose of all the contrast media induced a statistically significant (P < .001 or .01) cytoplasmic vacuolization in the proximal convoluted tubule (PCT) cells. The nonionic, low- and iso-osmolal contrast media caused as much or even significantly more vacuolization than diatrizoate. CONCLUSIONS: Hemorrhagic pancreatitis potentiates the contrast media-induced renal morphologic changes, which depend on the type and dose of the injected contrast media.

Animals↗
PubMed1991

Contrast media-induced renal tubular vacuolization. A light and electron microscopic study on rat kidneys.

The morphologic changes in healthy rat kidneys (n = 102) were studied 2 or 48 hours after intravenous injection of 1 or 3 g iodine (I)/kg of high-osmolality diatrizoate, low-osmolality iopromide and iohexol, or iso-osmolality iotrolan, as well as after 0.2 or 0.6 g/kg of the high-osmolality magnetic resonance contrast medium gadolinium DTPA. Physiologic saline was injected in controls. The kidneys were fixed by perfusion and the specimens were analyzed semiquantitatively by two independent observers blinded to the treatment. A statistically significant (P less than .01) cytoplasmic vacuolization was noticed in the proximal convoluted tubule cells 2 hours after injection of 3 g I/kg of diatrizoate or iopromide. Iohexol and iotrolan induced an even more significant (P less than .01) and longer-lasting vacuolization, but gadolinium DTPA did not produce lysosomal alterations. Although the vital cell organelles remained intact, reversible lysosomal alterations may represent the first structural signs of a threatening cellular injury.

Acute Kidney Injury↗