Biomedical subjects

Mario Ries

Publications and source records attributed to Mario Ries.

3 recordsLinked to original sources

PubMed2003

Renal diffusion and BOLD MRI in experimental diabetic nephropathy. Blood oxygen level-dependent.

PURPOSE: To investigate the possibility of using combined blood oxygen level-dependent (BOLD) imaging and diffusion-weighted imaging (DWI) to detect pathological and physiological changes in renal tissue damage of the kidney induced by chronic renal hyperfiltration. MATERIALS AND METHODS: The apparent diffusion coefficient (ADC) and the T(2)* value within the inner compartments of the kidneys of 17 rats with diabetes mellitus were compared with the results obtained from a control group (N = 16). The influence of dynamic changes of the renal function on the blood-oxygen saturation was evaluated by comparing the T(2)* values before and after the active reduction of tubular transport by furosemide injection. RESULTS: All compartments of the diabetic kidney showed significantly (P < 0.05) lower T(2)*-values compared to the control group. In particular, the very low values in the outer stripe (OS) of the outer medulla (OM) (T(2)*-normal: 69.4 +/- 10.9 msec; T(2)*-diabetic: 51.4 +/- 13.9 msec) indicated either hypoxia due to hyperfiltration, or renal blood volume changes. Diffusion imaging of the same area showed significantly lower ADC values (ADC-normal: 1.45 +/- 0.26; ADC-edema: 1.19 +/- 0.25 [10(-9)m(2)/s]) that correlated with pathological findings on histopathology. The injection of furosemide significantly (P < 0.05) increased T(2)* in all compartments of both populations while the ADC remained unchanged. CONCLUSION: BOLD-contrast imaging appears to be able to depict tissue at risk from ischemia by revealing information about the balance between tubular workload and delivery of oxygen, and thus may reflect a measure of the reserve capacity. The diffusion measurements apparently reveal complementary information. Although ADC imaging is not sensitive to the current energy metabolism, it appears toreflect the pathological changes within the issue. Therefore, ADC measurements may be a sensitive indicator of the severity of ischemic lesions.

Animals↗

PubMed2003

Diffusion-weighted MR imaging with apparent diffusion coefficient and apparent diffusion tensor maps in cervical spondylotic myelopathy.

PURPOSE: To evaluate diffusion-weighted magnetic resonance (MR) imaging in patients with cervical spondylosis and/or myelopathy. MATERIALS AND METHODS: A multishot echo-planar imaging sequence with calculation of apparent diffusion coefficient (ADC) and apparent diffusion tensor (ADT) was applied in 36 patients with symptomatic cervical spondylosis. Diffusion-weighted images read by two neuroradiologists were compared with T2-weighted fast spin-echo images read independently by three neuroradiologists with regard to clinical status (n = 36). MR findings in a selected subgroup of 20 patients whose clinical status was confirmed by electrophysiologic examination also were compared. Sensitivity, specificity, positive predictive value, and negative predictive value of both T2-weighted imaging and diffusion-weighted imaging (ADC and ADT) were calculated and compared. RESULTS: Patients with myelopathy had abnormal ADC (17 of 21) and ADT (15 of 19) maps with increased ADC and ADT values and decreased anisotropy. For the detection of myelopathy, diffusion-weighted ADC maps had a sensitivity of 80% (17 of 21), while T2-weighted images had a sensitivity of 61% (13 of 21). The negative predictive value was 63% (seven of 11) and 60% (12 of 20) for ADC maps and T2-weighted images, respectively. Conversely, the specificity of diffusion-weighted images (53%; seven of 13) was lower than that of T2-weighted images (92%; 12 of 13). In patients with myelopathy confirmed at electrophysiologic examination, the sensitivity of diffusion-weighted images increased to 92% (12 of 13) and the negative predictive value increased to 75% (three of four), while T2-weighted images had a 53% (seven of 13) sensitivity and a 50% (six of 12) negative predictive value. CONCLUSION: Diffusion weighting improved the sensitivity of imaging in cervical spondylotic myelopathy.

Adult↗

PubMed2002

Imaging the changes in renal T1 induced by the inhalation of pure oxygen: a feasibility study.

The effect of the inhalation of pure oxygen on the kidney was evaluated by measuring monoexponential T1 and T2* relaxation times in nine volunteers using a multiple-shot turbo spin echo and multiple echo gradient echo sequences, respectively. The T1 of the renal cortex decreased significantly when breathing pure oxygen as compared to normoxia (from 882 +/- 59 to 829 +/- 70 msec, P < 0.05), while that of the renal medulla was unchanged. No significant changes were seen in the T2* of either compartment. Dynamic imaging using an inversion recovery sequence with an optimized inversion time typically produced signal changes of 20% in the renal cortex. Studies to assess if oxygen-induced changes in flow contributed to this effect showed that the flow contribution was not significant. Although longer inversion times (880 ms) produced optimal contrast, acceptable contrast was also obtained at shorter inversion times (450 msec) in the renal cortex, spleen, and lung, with the latter being of opposite polarity to the other two tissues, implying a shorter parenchymal T1 than previously reported in the literature. The results are consistent with oxygen acting as an intravascular contrast agent which induces a shortening of T1 in the arterial blood volume.

Feasibility Studies↗