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Biomedical subjects

F Schick

Publications and source records attributed to F Schick.

At least 37 records · Page 2Linked to original sources
PubMed2000

[The MR characterization of the composition of the hematopoietic bone marrow. The findings in generalized neoplasms and the monitoring of therapy].

PURPOSE: Methodological work was performed in the field of magnetic resonance imaging (MRI) and spectroscopy (MRS) in order to develop suitable tools for non-invasive characterization of hematopoietic bone marrow. The methods were applied for the assessment of normal values in healthy persons and to examine patients with generalized hematological diseases or to monitor effects of therapies influencing the composition of bone marrow. METHODS: Besides standard techniques of MRI as T1- or T2-weighted methods, chemical shift techniques for selective visualization of water or lipid components were applied. The method of magnetization transfer (MT) contrast was used with the intention to differentiate between multiple water containing tissue compartments (intra- vs. extracellular space). A further approach was the determination of the magnetic field distribution within spongy bone marrow. Besides investigations in healthy volunteers, prospective clinical studies were carried out in patients suffering from acute leukemia during their initial treatment and in patients who underwent high-dose therapy with following peripheral blood stem cell transplantation (PBSCT). RESULTS: Especially MR techniques for selective imaging of water of fat signals and proton spectroscopy yielded a high sensitivity to primarily pathological or therapeutically induced changes of hematopoietic bone marrow. Application of MT allowed an improved differentiation of the tissue compartments under PBSCT, which might result in temporary edema. Storage of hemosiderin in bone marrow after blood transfusions and simultaneous hematopoietic insufficiency could be revealed by methods sensitive to magnetic field inhomogeneities. CONCLUSIONS: Methods of MRI and MRS allow to non-invasively characterize hematopoietic bone marrow in the course of hematological diseases and during therapy. Marked changes in the composition of hematological bone marrow are detectable for extensive marrow areas. The prognostic relevance of the findings has to be evaluated in future follow-up studies.

Adult↗
PubMed2000

Conventional high resolution versus fast T(2)-weighted MR imaging of the heart: assessment of reperfusion induced myocardial injury in an animal model.

Cardiac image quality in terms of spatial resolution and signal contrast was assessed for conventional and newly developed T(2)-weighted fast spin-echo imaging with high k-space segmentation. The capability in revealing regional myocardial edema and cellular damage was examined by a porcine model using histopathologic correlation. Twelve porcine hearts were excised from slaughtered animals and instantly perfused with 1000 mL cold cardioplegic solution. After 4 h of cold ischemia the hearts were reperfused for one hour using a "Langendorff" perfusion model followed by MR imaging at 1.5 Tesla. Three additional pig hearts served as controls and were studied by MR directly after harvesting. Histopathological analysis of regional tissue changes was performed macro- and microscopically. Short axis T(2)-weighted (3000/45 and 90) high quality fast spin-echo (FSE) images were recorded without cardiac action and signal intensity was correlated with histology. These images also served as gold standard for evaluation of newly developed faster sequences allowing measuring times shorter than 20 s. Fast T(2)-weighted imaging comprised single-slice fast spin echo (moderate echo train length of 23 echoes, FSE(m)), and multi-slice single-shot half-Fourier fast spin-echo (71 echoes, FSE(HASTE)) sequences, supplemented by versions with inversion recovery preparation (FSE(m)IR and FSE(HASTE)IR). Systolic function after reperfusion was restored in 10 porcine hearts. Tissue alterations included myocardial edema and contraction band necrosis which was found to be most severe in myocardium with maximum T(2) SI. Especially FSE(m) and FSE(m)IR sequences allowed differentiation of all categories of tissue damage on a high level of significance. In contrast, single-shot FSE(HASTE) and FSE(HASTE)IR sequences did not provide sufficient image quality to discriminate moderate and severe myocardial damage (p > 0.05). Different degrees of myocardial injury after ischemia and reperfusion can be staged by MR imaging, especially using conventional high resolution T(2)-weighted FSE sequences. The animal study indicates that fast T(2)-weighted FSE(m) and FSE(m)IR sequences lead to superior image quality and diagnostic accuracy compared to FSE(HASTE) and FSE(HASTE)IR imaging.

Analysis of Variance↗
PubMed2000

An interleaved sampling strategy for MR spectroscopy in vivo: applications on human calf musculature.

Assessment of relaxation times, magnetization transfer rates, or apparent diffusion coefficients by volume selective (1)H MR spectroscopy requires data from several single spectra with variable sequence parameters. Unintentional movements during the examination lead to inaccuracies, especially if the spatial distribution of concentrations is inhomogeneous. Improved comparability of the single spectra in a series recorded in vivo were obtained using a modified spectroscopic technique with INTerleaved ACquisiTion of multiple SPECtra (INTACTSPEC). INTACTSPEC series of spectra from the tibialis anterior muscle (m. tib. ant.), soleus muscle (m. soleus), and tibial bone marrow of 20 healthy volunteers were analyzed. Transverse relaxation times T(2) of methylene signals in muscular lipid stores ranged from 77 ms (intramyocellular methylene component in m. tib. ant.) to 88 ms (intramyocellular methylene component in m. soleus) and were similar to those from yellow tibial bone marrow (T(2) = 84 ms). Echo time-dependent signal intensities of choline and creatine deviated markedly from a monoexponential behavior in m. tib. ant., but were nearly exponential in m. soleus. Results from water diffusion measurements parallel and perpendicular to the axis of the lower leg showed significant differences between m. tib. ant. and m. soleus, probably due to the spatial orientation of the muscle fibers. Apparent diffusion coefficients along the leg axis were found to be higher in m. tib. ant. (2.10 +/- 0.08 x 10(-3) mm(2)/s) compared to m. soleus (1.78 +/- 0.11 x 10(-3) mm(2)/s), but m. soleus showed less restricted diffusion in perpendicular orientation (1.59 +/- 0.19 x 10(-3) mm(2)/s versus 1.20 +/- 0.08 x 10(-3) mm(2)/s in m. tib. ant.). Magnetization transfer experiments with various RF preparation pulse amplitudes led to very similar results for m. tib. ant. and m. soleus.

Adult↗
PubMed2000

[MRI-guided percutaneous radiofrequency ablation of hepatic neoplasms--first technical and clinical experiences].

PURPOSE: To evaluate the safety and efficacy of MR-guided radiofrequency ablation (RFA) of hepatic neoplasms. MATERIAL AND METHODS: 16 hepatic neoplasms (1.3-3.0 cm in diameter) in 11 patients were treated by 22 percutaneous RFA sessions during a prospective study. 16 G, MR-compatible cooled-tip electrodes with active lengths of 2 cm and 3 cm, respectively, were placed under MR-guidance in an open 0.2 Tesla MR system (Magnetom Open, Siemens, Erlangen) using fast T1-weighted sequences. Pretreatment studies, evaluation of tumor necrosis (one week after last RFA), and further follow-up studies every 3 months were performed using 1.5 Tesla MR systems. RESULTS: The mean procedure time was 2.8 (1.5-3.3) h. Complications related to percutaneous treatment were not encountered. 14 of 16 neoplasms (87%) showed no CM enhancement during MRI after the last RFA and were judged to be completely necrotic. In 11 tumors one treatment session was necessary, in 4 tumors two and in one tumor three. Follow-up studies revealed persistent complete necrosis in 13 of 14 (93%) tumors during a period of 3-18 (median: 11.8) months. In 5 patients new intrahepatic tumors developed that were not suitable for further RFA treatment because of their number, size and location. CONCLUSION: MR-guided RFA using single cooled tip electrodes is safe and technically effective for treatment of hepatic neoplasms up to 3 cm in size, however further improvements are necessary.

Adult↗
PubMed2000

[The MR signal behavior of a 4-week-old occlusive myocardial infarct in an animal experiment].

PURPOSE: To correlate signal behaviour in T1- and T2-weighted images after Gd-DTPA with regional histopathology in occlusive myocardial infarction (MI). METHODS: Ligation of a diagonal branch of the LAD was performed in seven sheep. Four weeks later 0.1 mmol Gd-DTPA/kg were injected in five sheep 15 min before cardiac arrest and the sheep were slaughtered. In vitro imaging was performed at 1.5 T included T1- and T2-weighted spin echo sequences in long and short axis views. Signal intensities (SI) were determined in 36 myocardial segments per slice and compared to macro- and microscopy. RESULTS: In all animals an antero-lateral infarct region was evident histologically. This region presented with increased T2 SI and T1 SI after Gd-DTPA. The number of segments with increased SI in T1-weighted images was higher (n = 195 segments) compared to segments with increased T2 SI (n = 122 segments). Granulation tissue could be differentiated from rarely vascularized connective tissue at a high level of significance (p < 0.001) by T1 and T2 SI analysis. Wall thickness was significantly decreased in necrotic myocardium (3.8 +/- 1.2 mm) compared to normal tissue (9.8 +/- 1.1 mm, p < 0.001). CONCLUSION: In four-week-old occlusive MI the extent of necrosis can be accurately assessed by analysis of post contrast T1-weighted images. Considering regional T2 SI, granulation tissue can be differentiated from regions with predominant fibrous organisation.

Animals↗
PubMed2000

[Variability in the MR tomographic determination of myocardial function and perfusion parameters in health subjects].

PURPOSE: The aim of the study was to evaluate myocardial function and perfusion patterns using magnetic resonance imaging in normal subjects. MATERIALS AND METHODS: 22 healthy volunteers were examined. Cine-mode acquisitions along all three axes of the heart were generated and perfusion was measured on a mid-ventricular short-axis view. Myocardial wall thickening was scored and contrast enhancement during the first pass was analysed. RESULTS: For myocardial wall thickening increasing values from base (24-86%) to apex (63-106%) were found. Contrast enhancement patterns showed regional variability. In addition marked individual differences were detectable. CONCLUSION: Perfusion patterns should be interpreted only in combination with functional parameters. Standard values for perfusion measurements cover very large range as a result of the high individual variability.

Adult↗
PubMed2000

[Percutaneous radiofrequency ablation of hepatic neoplasms using a "cluster" electrode--first clinical results].

PURPOSE: To evaluate feasibility, safety and efficacy of percutaneous radiofrequency ablation (RFA) of hepatic neoplasms using a clustered electrode. MATERIAL AND METHODS: Percutaneous, CT-guided RFA using a clustered electrode was performed in 12 patients with a total of 15 hepatic neoplasms (2.0-6.0 cm in diameter). RESULTS: A total of 17 percutaneous RFA was performed. The mean total procedure time was 2.0 h (1.5-2.5 h). Placement of the clustered electrode within the neoplasms using a inter- or subcostal approach under local anesthesia was possible in all cases. Complications related to percutaneous treatment and technical problems were not encountered. Diameter of the ablated areas ranged between 3.0-7.0 cm. Technical success was observed in 13 of 15 neoplasms (86.6%). During a mean follow-up of 7.25 months (range 3-12 months) 8 of 12 neoplasms showed a complete necrosis. CONCLUSION: Percutaneous RFA using a clustered electrode is a feasible, safe and effective procedure for the treatment of hepatic neoplasms up to 6 cm in size.

Adult↗
PubMed2000

Dynamic MR imaging of liver metastases with Gd-EOB-DTPA.

PURPOSE: To assess liver and lesion enhancements by dynamic MR imaging after bolus injection of the hepatobiliary contrast agent gadolinium ethoxybenzyl-diethylenetriamine-pentaacetic acid (Gd-EOB-DTPA) in patients with liver metastases and to compare the effect of different doses. MATERIAL AND METHODS: A randomized double-blinded trial with doses of 12.5, 25 and 50 micromol/kg Gd-EOB-DTPA was performed in 35 patients with liver metastases. Liver enhancement, tumor enhancement and liver lesion contrast-to-noise (C/N) ratios were calculated from breath-hold gradient echo images (100/5/80 degrees) recorded precontrast and at different times up to 10 min postcontrast. RESULTS: Normal liver showed a characteristic enhancement pattern, with a rapid enhancement in the first 45 s postcontrast and a slight but significant further increase up to 600 s. The initial enhancement in the lesions was also pronounced, but the enhancement was slightly decreased after 240 s postcontrast. At dose levels of 12.5 and 25 micromol/kg Gd-EOB-DTPA, C/N ratios significantly increased compared to baseline from 90 to 600 s. Postcontrast C/N-values obtained using 50 micromol/kg Gd-EOB-DTPA were not significantly increased, except for the examinations 480 s postcontrast. CONCLUSION: In liver metastases, C/N ratios obtained with doses of 12.5 and 25 micromol/kg Gd-EOB-DTPA were slightly superior to 50 micromol/kg Gd-EOB-DTPA. This finding is probably due to a more pronounced extracellular effect of the contrast medium at higher doses.

Adult↗
PubMed2000

Fat- and water-selective MR cine imaging of the human heart: assessment of right ventricular dysplasia.

RATIONALE AND OBJECTIVES: The purpose of this study was to develop and implement MR sequences for chemical shift-selective breath-hold cine imaging of the heart. Fibroadipose conversion of myocardium in cases suspected of right ventricular dysplasia should be revealed in fat- and water-selective MR images of high quality. METHODS: Frequency-selective saturation of one chemical shift component was applied in modified k-space-segmented, electrocardiography-gated sequences, allowing high-quality cine imaging of the human heart in a single breath-hold. Phantom studies and human examinations in eight normal subjects (aged 24-62 years) and in seven patients (aged 31-47 years) with suspected right ventricular dysplasia were performed. The patients showed suspicious findings, such as a dyskinetic and dilated right ventricle combined with ventricular arrhythmia, and underwent MR imaging after exclusion of other possible reasons (eg, coronary artery disease or pulmonary hypertension). RESULTS: High selectivity to the desired chemical shift component was confirmed by test measurements in a phantom containing water and lipids. In the human subjects, minor problems with magnetic field inhomogeneities appeared in the thoracic walls only. Four patients with suspected right ventricular dysplasia showed clearly abnormal signal behavior of the right myocardial wall in both fat- and water-selective cine images. Bright transmural structures were exhibited in fat-selective images, but the origin of the fat (epicardium or infiltrated myocardium) was often difficult to assess. CONCLUSIONS: Right ventricular areas with fibrosis and fatty degeneration often show normal signal intensity in standard T1-weighted images but can be differentiated from normal tissue by the new chemical shift-selective breath-hold cine techniques.

Adipose Tissue↗
PubMed2000

Magnetic resonance osteodensitometry in human heel bones: correlation with quantitative computed tomography using different measuring parameters.

RATIONALE AND OBJECTIVES: Density of trabecular bone structures in human heel bones was assessed by 3D magnetic resonance (MR) gradient echo imaging (GEI) with multiple echoes. Different spatial resolutions were applied to investigate the influence of the pixel size on signal characteristics in GEI and to find suitable measuring parameters for a maximum correlation between GEI and bone mineral density obtained by quantitative computed tomography (QCT). METHODS: Thirty-five patients aged 31 to 65 years with suspected osteoporosis underwent MR and QCT examinations of the heel bones. The MR protocol included 3D GEI with three echo times (TE1 = 9.3, TE2 = 27.9, and TE3 = 46.5 ms) and isotropic pixel sizes of (0.6 mm)3, (1.2 mm)3, and (2.4 mm)3. Several subregions in the heel bones were analyzed. For determination of signal reduction with increasing TE, signal intensity ratios were calculated pixelwise from images with TE2/TE1 and TE3/TE1. RESULTS: All examinations showed that the T2*-related signal decrease was more pronounced for lower spatial resolution. In the dorsal part of the heel bones, the correlation between signal ratios in GEI and QCT-based bone mineral density values was between r = -0.86 for a spatial resolution of (0.6 mm)3 and r = -0.73 for (2.4 mm)3. Areas with low trabecular density in the ventral part of the heel bones showed clearly lower correlation coefficients (-0.65 < r < -0.67). CONCLUSIONS: Spatial resolution in 3D GEI clearly influences the T2*-related signal characteristics. Despite measuring different physical properties of spongy bone by GEI and QCT, a relatively high correlation between GEI with small pixel sizes and QCT was obtained in the dorsal part of the heel bones, but not in the ventral part with partly thickened trabeculae and irregular distribution. However, standardized measuring protocols with preferably small pixel sizes (as low as [0.6 mm]3) should be applied, and correlation curves must be determined, dependent on the actual bone marrow site, before clinical routine MR osteodensitometry becomes possible.

Absorptiometry, Photon↗
PubMed2000

Magnetic resonance imaging guided corticosteroid injection of the sacroiliac joints in patients with therapy resistant spondyloarthropathy: a pilot study.

OBJECTIVE: To evaluate magnetic resonance imaging (MRI) guided corticosteroid injections of inflamed sacroiliac (SI) joints in patients with spondyloarthropathy with therapy resistant sacroiliitis. METHODS: We performed 16 injections in 9 patients on an outpatient basis (6 men, 3 women, mean age at onset 24.7 +/- 7.5 yrs). All patients had MRI guided injection of 40 mg triamcinolone acetonide into SI joints using an open 0.2 Tesla unit. Before and 3 months after corticosteroid injection they underwent an MRI examination with a closed 1.5 Tesla unit. RESULTS: Seven of 9 patients reported subjective improvement that lasted at least a mean of 10.8 +/- 5.6 months. Subchondral bone marrow edema on fat suppressed images resolved in 8 patients after corticosteroid injection. CONCLUSION: MRI guided corticosteroid injection of SI joints appears to be an effective and safe procedure without exposure to radiation. It is a useful therapeutic modality, especially in young patients with severe isolated sacroiliitis.

Adolescent↗
PubMed1999

Excitation of narrow frequency bands with reduced relaxation-related signal losses: methodology and preliminary applications.

Selective excitation of a narrow frequency band is usually obtained by a long-duration, symmetrical-shaped RF pulse or by a series of short pulses with a symmetrical envelope. In species with fast transverse relaxation, both approaches lead to marked signal losses. Asymmetrical excitations applying truncated shaped pulses or half-Gaussian envelopes for trains of equidistant hard pulses were reported to provide higher signal intensity, but the frequency response is clearly inferior to the corresponding symmetrical excitations. Methods allowing asymmetrical excitation, but excellent frequency response are described in the present work. An additional 90 degree pulse is applied after a train of equidistant hard pulses with a half-Gaussian envelope. Suitable timing in the entire sequence of pulses and a phase cycle with length 2 only for the additional 90 degree pulse combined with an even number of scans allow the removal of undesired transverse magnetization outside narrow frequency bands. Thus, a periodical excitation with a very small bandwidth is obtained. In imaging sequences with standard 2D Fourier reconstruction the new excitation strategies can be included to generate a normal image representing morphology beside a band pattern with chemical information, if an odd number of scans is used. The separation of both parts in the final image is based on the principle of alternated line scanning. Macroscopic and microscopic field inhomogeneities in tissue are assessable in a single experiment. Preliminary applications on specimens with limited homogeneity of the magnetic field and on human tissue are demonstrated.

Adult↗
PubMed1999

[Cardiac MRI for determining functional left ventricular parameters].

PURPOSE: To prove the accuracy of MR methods in the determination of left ventricular (LV) functional parameters and anatomy. MATERIALS AND METHODS: At 1.5 T, 20 healthy volunteers and 22 patients with aortic valvular disease (stenosis n = 15, regurgitation n = 7) were examined. Functional parameters like cardiac output, ejection fraction, end-diastolic volume, aortic flow maximum, and time interval from the R-wave to maximum flow were obtained using a velocity encoding 2D FLASH sequence (TR 24 ms, TE 5 ms, venc 250 cm/sec) and segmented breath-hold cine FLASH 2D technique (TR 100 ms, TE 4.8 ms, flip angle 25 degrees, temporal resolution 50 ms). Invasive measurements (Fick principle) served as gold standard, intra- and interobserver variability were determined. RESULTS: Differences of functional parameters between normal volunteers and patients were detectable at a high level of significance (p < 0.0001). For cardiac output a superior correlation with the gold standard was found using flow measurements (r = 0.66, p < 0.0007) compared to volumetric calculations from cine studies (r = 0.47, p < 0.02). Interobserver variability was 2.5 +/- 2.7%/4.5 +/- 6.9% (flow quantification/calculations from cine studies), intraobserver variability was 1.7 +/- 1.6%/3.3 +/- 2.2%. CONCLUSIONS: MRI is an appropriate tool for determining LV functional parameters and anatomy. Differences between normal volunteers and patients with aortic valvular disease can be detected reliably. Flow measurements turned out to be more accurate than calculations from cine images. Therefore, flow quantification techniques should be preferred for clinical use.

Adult↗
PubMed1999

[Optimization of numerical measurement parameters for ECG-triggered MRI snapshot-FLASH myocardial perfusion studies].

BACKGROUND AND AIMS: In MR examinations of myocardial perfusion by the use of Snapshot-FLASH sequences it is of major importance that the achievable signal difference between pre- and normal postcontrast myocardium be maximized. METHODS: In ECG-triggered Snapshot-FLASH sequences the signal intensity of the myocardium depends on the flip angle alpha, the inversion time TI and the trigger delay TD (both depending on the cardiac frequency f) for unchanged slice thickness (SL), matrix size (MA), repetition time (TR) and echo time (TE). Therefore a simulation of the signal behavior of pre- and postcontrast myocardium based on Bloch's equations was performed by varying the flip angle alpha, TI and TD for different cardiac frequencies in order to determine an optimized combination of the measurement parameters. RESULTS: In normal heart rates (50-70 beats/min) maximal signal differences between pre- and normal postcontrast myocardium can be reached for inversion times TI = 170-200 ms and a flip angle alpha = 11 degrees. For higher heart rates again alpha = 11 degrees and TI = 200-220 ms with shortened TD (TD = 0 for f > 90 beats/min) were found to be optimal. The calculated values were semiquantitatively confirmed in phantom and volunteer measurements. CONCLUSIONS: The described method allows cardiac frequency dependent optimization of the Snapshot-FLASH measurement parameters alpha, TI and TD in order to reach a maximum in signal contrast between normal and malperfused myocardium.

Computer Graphics↗
PubMed1999

[Diagnosis of renal artery stenosis in 1.0 T using 3D phase contrast magnetic resonance angiography and dynamic contrast medium perfusion].

PURPOSE: To assess renal artery stenosis (RAS) by 3D phase contrast (PC) MR angiography and dynamic perfusion imaging of the kidneys. METHODS: On a standard 1.0 T MR imaging system (Magnetom Expert, Siemens), 32 patients with angiographically proven unilateral RAS were examined using a 3D PC sequence (TR 40 ms/TE 9 ms/venc 30 cm/s). An ECG-gated Turbo-FLASH 2D sequence (TR 4.5 ms/TE 2.2 ms/TIeff. 400 ms) was applied to study the first pass of paramagnetic contrast agent (0.1 mmol Gd-DTPA/kg) through the kidneys. Signal intensity (SI) over time curves of the renal cortex were obtained and evaluated considering temporal relation and percentage of maximum SI compared to the aorta and normal kidneys. Analysis of the MRA was performed by two independent blinded readers. The gold-standard DSA was interpreted by consensus reading of two experienced radiologists. RESULTS: RAS was detected by 3D PC MRA with a sensitivity of 93% and specificity of 81% (ppv 82%, npv 93%, accuracy 87%, kappa = 0.61). Maximum SI in RAS was significantly decreased (p < 0.001-0.0001). A temporally delayed enhancement of 1.5 +/- 1.3 s was found for RAS > 75% (p < 0.002) but not for RAS < 75% (p > 0.1). CONCLUSIONS: 3D PC MRA is capable of detecting RAS in a high percentage of patients. Dynamic perfusion imaging of the kidneys, applied additionally, can confirm the diagnosis and give valuable information about the hemodynamic relevance of RAS in suspected unilateral disease.

Contrast Media↗
PubMed1999

[MR tomography of the bone marrow changes after high-dosage chemotherapy and autologous peripheral stem-cell transplantation].

PURPOSE: Evaluation of MR standard imaging and short time inversion recovery (STIR) imaging to assess changes in red bone marrow cellularity after high-dose chemotherapy (HDC) and peripheral blood stem cells transplantation (PBSCT). MATERIALS AND METHODS: Sixty-one magnetic resonance (MR) studies were performed in 15 patients (8 female and 7 male, average age 45 years) who received HDC and PBSCT for therapy of either a solid tumor or multiple myeloma. All patients underwent MR examinations of the lumbar region and both femora with T1- and T2-weighted turbo spin-echo (TSE) and STIR sequences at predefined time intervals. Qualitative analysis of the signal intensity was performed by consensus reading of four radiologists. MR results were correlated with results of blood smears and marrow histology. RESULTS: STIR sequences demonstrated marked changes in signal intensity not only until the aplasia occurred but also during bone marrow repopulation. An increased signal intensity was observed after HDC in 13/15 patients (87%), followed by a decrease in signal intensity immediately after aplasia in 14/15 patients (93%). Signal intensity further changed parallel to marrow engraftment in 11/15 patients (73%). T2-TSE only showed clear changes during repopulation in 8/15 patients (53%). The individual course of the signal in T1-TSE was markedly inhomogeneous. CONCLUSIONS: STIR sequences show bone marrow edema during aplasia and marrow cellularity during reconstitution and are suitable for characterisation of red bone marrow after HDC and autologous PBSCT.

Adult↗
PubMed1999

Measurement of intracellular triglyceride stores by H spectroscopy: validation in vivo.

We validate the use of 1H magnetic resonance spectroscopy (MRS) to quantitatively differentiate between adipocyte and intracellular triglyceride (TG) stores by monitoring the TG methylene proton signals at 1.6 and 1.4 ppm, respectively. In two animal models of intracellular TG accumulation, intrahepatic and intramyocellular TG accumulation was confirmed histologically. Consistent with the histological changes, the methylene signal intensity at 1.4 ppm increased in both liver and muscle, whereas the signal at 1.6 ppm was unchanged. In response to induced fat accumulation, the TG concentration in liver derived from 1H MRS increased from 0 to 44.9 +/- 13.2 micromol/g, and this was matched by increases measured biochemically (2.1 +/- 1.1 to 46.1 +/- 10.9 micromol/g). Supportive evidence that the methylene signal at 1.6 ppm in muscle is derived from investing interfascial adipose tissue was the finding that, in four subjects with generalized lipodystrophy, a disease characterized by absence of interfacial fat, no signal was detected at 1.6 ppm; however, a strong signal was seen at 1.4 ppm. An identical methylene chemical shift at 1.4 ppm was obtained in human subjects with fatty liver where the fat is located exclusively within hepatocytes. In experimental animals, there was a close correlation between hepatic TG content measured in vivo by 1H MRS and chemically by liver biopsy [R = 0.934; P <.0001; slope 0.98, confidence interval (CI) 0.70-1.17; y-intercept 0.26, CI -0.28 to 0. 70]. When applied to human calf muscle, the coefficient of variation of the technique in measuring intramyocellular TG content was 11.8% in nonobese subjects and 7.9% in obese subjects and of extramyocellular (adipocyte) fat was 22.6 and 52.5%, respectively. This study demonstrates for the first time that noninvasive in vivo 1H MRS measurement of intracellular TG, including that within myocytes, is feasible at 1.5-T field strengths and is comparable in accuracy to biochemical measurement. In addition, in mixed tissue such as muscle, the method is clearly advantageous in differentiating between TG from contaminating adipose tissue compared with intramyocellular lipids.

Adipose Tissue↗