Uwe H. Melchert

Motion-triggered cine MR imaging of active joint movement

MRI cine studies of active physiological joint movement can provide additional functional information as a supplement to standard examinations. With the ankle joint as an example, it is shown that it is possible to measure kinematic MRI presentations of active joint movement. A pneumatic pressure transducer, a respiratory monitor, and an active differentiator transformed the skin muscle shifting of periodically performed joint movement to a pseudo-ECG, which finally triggered the MRI scanner as in cardiac cine MR imaging.

Lumbar neurolytic sympathetic blockades provide immediate and long-lasting improvement of painless walking distance and muscle metabolism in patients with severe peripheral vascular disease

Thirty patients with angiographically proven peripheral vascular disease (PVD) and intermittent claudication were treated with percutaneous lumbar neurolytic sympathetic blockade (NSB) using 1.5 mL ethanol 95%. Claudication had been progressive in all patients during conservative treatment. Median (range) painless walking distance increased from 95 (10-200) meters (m) before to 355 (25-1003) m immediately after NSB. Further improvement was seen during the 1-year follow-up, with two exceptions: one patient lost a leg after acute arterial embolism and another patient deteriorated after 6 months. In the latter case, a second NSB improved the walking distance again. One case of transient mild neuralgia of the L3 dermatome occurred. 31P-magnetic resonance investigations of the calf muscles before, during, and after a treadmill exercise were performed in seven patients: 1 week after NSB, the postexercise recovery of phosphocreatine was accelerated in all patients compared to the pre-NSB values. The accelerated recovery suggests an improved post-ischemic metabolic situation after chemical sympathectomy.

A study of T1-weighted 31phosphorus MR-spectroscopy from patients with focal and diffuse liver disease.

31P-MR-Spectroscopy was performed in 28 patients with focal (n = 23) and diffuse (n = 5) liver disease and in 18 healthy volunteers. The spectra were obtained with a whole body scanner operating at 1.5 T by using a surface coil. To get T1-weighted 31P-spectra a short TR of 600 msec was taken, because T1-weighted spectra of focal liver disease were more significantly different from spectra from healthy volunteers than density weighted ones. The VOI from patients with focal superficial alterations showed a mean volume of 172 ml, with diffuse liver disease 196 ml, and from volunteers 158 ml. Focal tumors filled up the VOI on an average of 70%. This investigation demonstrated that PME/beta-ATP- and PDE/beta-ATP-ratios were sensitive indicators for focal liver disease. As a result of this study we could establish a significant increase of PME/beta-ATP- (0.75 +/- 0.30) and PDE/beta-ATP-ratios (1.68 +/- 0.62) in patients with superficial focal liver metastases (n = 19) compared to the control group (PME/beta-ATP: 0.49 +/- 0.17, PDE/beta-ATP: 1.24 +/- 0.24; t-test: p < 0.02). Patients with a hemangioma (n = 1), liver infarction (n = 1), empyema of gallbladder (n = 1) and a hepatic involvement by a malignant lymphoma (n = 1) showed a similar increase of PME/beta-ATP and/or PDE/beta-ATP. Up to now spectral changes seemed to be non-specific. The ratios of 31P metabolites of the cirrhoses (n = 4) and the fatty liver (n = 1) did not show any characteristic changes versus the volunteers.

In vivo P-31-MR-spectroscopy of focal hepatic lesions. Effectiveness of tumor detection in clinical practice and experimental studies of surface coil characteristics and localization technique.

RATIONALE AND OBJECTIVESThe influence of partial tumor sampling in a volume of interest (VOI) on the ratios of phosphorus metabolites was examined by localized phosphorus magnetic resonance spectroscopy (P-31-MRS). Experiments were performed to investigate the characteristics of the surface coil used and precession of spatial localization. METHODSA total of 24 patients with liver metastases and 20 volunteers were studied by P-31-MRS. Patients were divided in two groups: VOI < 50% (n = 8) and VOI > 50% (n = 16) occupied by tumor. For evaluation of the surface coil and localization method (image selected in vivo spectroscopy), phantom studies were performed. RESULTSSuperficial focal liver tumors were detectable with a surface coil at a distance within the coil radius. The image selected in vivo spectroscopy permitted the study of phosphorus metabolism in a defined VOI. phosphomonoester/β-adenosine triphosphate and phosphodiester/β-adenosine triphosphate were elevated significantly in spectra of both patient groups.CONCLUSIONS. Detection of small tumor volumes within a VOI filled by less than 50% of the tumor is possible, with results statistically different from that in normal volunteers.

APPLICATION OF THE MAXIMUM ENTROPY METHOD FOR EVALUATING PHOSPHORUS-31-MAGNETIC RESONANCE SPECTRA IN PATIENTS WITH LIVER METASTASES

RATIONALE AND OBJECTIVES.The clinical feasibility and application of the maximum entropy method for data analysis from in vivo phosphorus-31–magnetic resonance (P-31–MR) spectra of the liver were determined. METHODS.Image-guided localized P-31–MR spectroscopy was performed in 24 patients with liver metastases and in 20 healthy volunteers. The spectra were obtained with a whole body scanner operating at 1.5 T using a surface coil. Phosphomonoester/ β-adenosine triphosphate (ATP), phosphodiester/ β-ATP, and inorganic phosphate/β-ATP were calculated from the maximum entropy method-spectra and from spectra evaluated with standard data processing (Fourier transformation spectra). RESULTS.Phosphomonoestcr/β-ATP and phosphodiester/ β-ATP were increased significantly with both methods in patients spectra. Maximum entropy method spectra showed a distinct pattern with low noise. It was easier to determine peak borders and to attach resonances to the different metabolites using this method. CONCLUSIONS.Maximum entropy method is an alternative method for evaluation and quantification of P-31–MR spectra data and is preferred to standard data processing with Fourier transformation in cases of reduced signal-to-noise ratio of spectra.

Influence of different fasting periods on P-31-MR-spectroscopy of the liver in normals and patients with liver metastases

The purpose of this study was to determine the influence of different fasting periods on the in vivo P-31-MR spectroscopy of the healthy liver and patients with liver metastases. Image-guided localized P-31-MRS was performed in 24 patients with liver metastases and in 20 healthy volunteers. The spectra were obtained with a whole body scanner operating at 1.5 T using a surface coil. The P-31-MRS was performed after a fasting period of 3–5 h (group 1) and after overnight fasting (group 2). The PME/β-NTP, PDE/β-NTP and Pi/β-NTP were calculated from P-31-MR spectra and were compared in relation to the nutrition status of the volunteers and patients. The PME/β-NTP and PDE/β-NTP were significantly increased in spectra of patients with metastases. There were no significant changes in the ratios of phosphorus metabolites in healthy liver tissue or in liver metastases after a fasting period of 3–5 h as compared with overnight fasting.

THE TOTAL ENTROPY FOR EVALUATING 31P-MAGNETIC RESONANCE SPECTRA OF THE LIVER IN HEALTHY VOLUNTEERS AND PATIENTS WITH METASTASES

RATIONALE AND OBJECTIVESnThe authors describe the clinical status of liver tissue with only a single numerical quantity (total entropy) derived from spectroscopic data of 31P-magnetic resonance (MR) spectra.nnnMETHODSnTwenty-four patients with liver metastases and 20 volunteers were investigated with image-guided volume selective 31P-MR spectroscopy on a 1.5-T whole body scanner. From each in vivo 31P-MR spectrum, the ratios of phosphomonoester (PME)/beta-adenosine triphosphate (ATP), inorganic phosphate (Pi)/beta-ATP and phosphodiester (PDE)/ beta-ATP and the total entropy (H*) were calculated. Mean values and standard deviations were determined and significance of the differences were tested with Students t test.nnnRESULTSnFor patients, the H* = 4.7 +/- 4.3, PME/beta-ATP 0.72 +/- 0.28, Pi/beta-ATP = 1.00 +/- 0.39, PDE/beta-ATP = 1.68 +/- 0.59. For the volunteers, H* = 7.6 +/- 2.5, PME/beta-ATP = 0.39 +/- 0.15, Pi/beta-ATP = 0.90 +/- 0.19, PDE/beta-ATP = 1.25 +/- 0.28. The total entropy of patients spectra showed significantly lower values compared with those of volunteers. PME/beta-ATP and PDE/beta-ATP of the patients increased and differed significantly from volunteer data.nnnCONCLUSIONSnIt was demonstrated that the results of in vivo 31P-MR spectroscopy may be described with a single criterion by means of the total entropy.