Diffuse contrast enhancement

Fig. 6. Delayed CT 48 h after the administration of contrast medium. The serum creatinine level was high (5.5mg/dl), and the contrast-enhanced areas were more extensive than those in Fig. 2 (serum creatinine 1.6mg/dl). Patchy contrast enhancement changed to diffuse contrast enhancement...

The area of wedge-shaped contrast enhancement increased with the increase in serum creatinine level. When the serum creatinine level exceeded 5 or 6 mg/dl, diffuse contrast enhancement involved the entire kidney. However, even in patients with diffuse contrast enhancement, delayed CT confirmed patchy wedge-shaped contrast enhancement again when the serum creatinine level decreased to 1.2-3.5 mg/dl in the recovery phase (refer to Patient 2 in Fig. 59, Chap. 10, Sect. 1). This finding in the recovery phase cannot be explained by tubular obstruction. 

Subsequently, we examined whether it is only patients with exercise-induced acute renal failure (ALPE) who show wedge-shaped contrast enhancement [15-18]. We performed delayed CT on a patient with ALPE and a patient with myoglobin uric acute renal failure (due to a malignant syndrome) when their serum creatinine levels were 3.0 and 1.5mg/dl, and compared the results. Wedge-shaped contrast enhancement was observed only in the patient with ALPE (Patient 19), and not in the patient with myoglobinuric acute renal failure. Diffuse contrast enhancement was noted (serum creatinine level, 3mg/dl) (Fig. 17). 

Fig. 17. Comparison of contrast enhancement 24h afterthe administration of contrast medium between exercise-induced acute renal failure (ALPE) and myoglobinuric acute renal failure (serum creatinine 3mg/dl). The patient with ALPE showed patchy wedge-shaped contrast enhancement, and the patient with myoglobinuric acute renal failure showed diffuse contrast enhancement...

Myoglobinuric acute renal failure developed after continued strenuous exercise. Marked muscular destruction (rhabdomyolysis) resulted in dark urine. However, there was no pain, and dehydration was marked. The CPK level showed a 10- to 20-fold increase compared with the reference value. Delayed CT showed diffuse contrast enhancement (Fig. 74). 

Contrast-enhanced MRI with Gd-DTPA has been applied to the evaluation of several compounds in man, some focusing on the hemodynamic effects of the drugs on cerebral blood volumes. Kolbtisch and others compared the anesthetic agents nitrous oxide and sevofhirane, noting them to produce compound-specific patterns of diffuse increases in cerebral blood volume (Kolbitsch et al., 2001). Intravenous cocaine, on the other hand, was observed to produce dose-dependent vasoconstriction of cerebral blood vessels (Kaufman et ul., 1998). 

Iontophoresis by definition is the process of transport of ions into or through a tissue by the use of an applied potential difference across the tissue [52], Depending on the physicochemical characteristics of a molecular species, electrorepulsion is usually the primary mechanism of transdermal transport for ions, whereas electroosmosis and increased passive diffusion (as a result of the reduced barrier properties) are more prominent for neutral species [53]. In contrast, enhancement in flux for neutral or weakly charged species during electroporation arises predominantly from the reduced barrier properties of the membrane, whereas direct electrorepulsion is usually of secondary importance [25],... 

This patient was the first case in our series in which acute renal failure developed after an athletics meeting. After he had participated in a 200-m race, loin pain occurred, leading to acute renal failure. Delayed computed tomography (CT) showed diffuse to patchy contrast enhancement. The details are given in Chap. 2, Sect. 2. 

Also technical aspects may contribute to the variable incidence of parenchymal enhancement in acute human stroke. With double dose contrast medium and a time lag between injection and imaging, every fourth stroke patient showed tissue enhancement within 24 h of stroke onset (Karonen et al. 2001). Widespread parenchymal enhancement in Tl-w images seems to gradually develop over the first week when simultaneously the diffusion changes tend to pseudonormalize. Without precise clinical history confounding with tumor enhancement may occur and should be ruled out by observation of the time profile of MR contrast enhancement and DWI. 

Norton GA, Kishore PR, Lin J (1978) CT contrast enhancement in cerebral infarction. Am J Roentgenol 131 881-885 Olah L, Wecker S, Hoehn M (2000) Secondary deterioration of apparent diffusion coefficient after 1-hour transient focal cerebral ischemia in rats. J Cereb Blood Flow Metab 20 1474-1482... 

The phenomenon of the contrast enhancement is caused by side-directed diffusion of silver atoms into the exposed areas because of the decrease of chemical potential in the areas. Silver atoms diffusion from the unexposed areas into the exposed ones compensates the influence of diffraction effects. As a result of diffusion, resolution may be considerably improved. 

Another interesting variation on negative diazo resists involves compositions of aqueous acetic acid solution of 4-dimethylaminophenyldiazonium chloride and zinc chloride in a poly(N-vinyl pyrrolidone) binder this is coated over cresol novolac film on a silicon wafer substrate. " The diazonium compound diffuses into the phenolic layer and is eventually partitioned in a uniform layer between the top layer and the phenolic resin. On exposure, the diazonium compound in the top layer bleaches and acts as a contrast-enhancement dye, while in the bottom it decomposes to the nonpolar 4-dimethylaminochlorobenzene, which acts as a dissolution inhibitor of the phenolic resin during development in aqueous-base solution. Line and space feature resolution of 0.5 p-m has been reported for this material. 

A 15-year-old girl with Crohn s disease developed ataxia and dystonia after taking metronidazole for 7 days [20 ]. An MRI scan showed bilateral symmetric T2/FLAIR hyper-intense lesions in the dentate nuclei. The lesions did not show contrast enhancement or restricted diffusion and resolved completely after withdrawal of metronidazole. 

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