Biomedical subjects

I Zuna

Publications and source records attributed to I Zuna.

97 records · Page 6Linked to original sources

PubMedDate not supplied

Quantitative characterization of color Doppler images: reproducibility, accuracy, and limitations.

A computer-based quantitative analysis for color Doppler images of complex vascular formations is presented. The red-green-blue-signal from an Acuson XP10 is frame-grabbed and digitized. By matching each image pixel with the color bar, color pixels are identified and assigned to the corresponding flow velocity (color value). Data analysis consists of delineation of a region of interest and calculation of the relative number of color pixels in this region (color pixel density) as well as the mean color value. The mean color value was compared to flow velocities in a flow phantom. The thyroid and carotid artery in a volunteer were repeatedly examined by a single examiner to assess intra-observer variability. The thyroids in five healthy controls were examined by three experienced physicians to assess the extent of inter-observer variability and observer bias. The correlation between the mean color value and flow velocity ranged from 0.94 to 0.96 for a range of velocities determined by pulse repetition frequency. The average deviation of the mean color value from the flow velocity was 22% to 41%, depending on the selected pulse repetition frequency (range of deviations, -46% to +66%). Flow velocity was underestimated with inadequately low pulse repetition frequency, or inadequately high reject threshold. An overestimation occurred with inadequately high pulse repetition frequency. The highest intra-observer variability was 22% (relative standard deviation) for the color pixel density, and 9.1% for the mean color value. The inter-observer variation was approximately 30% for the color pixel density, and 20% for the mean color value. In conclusion, computer assisted image analysis permits an objective description of color Doppler images. However, the user must be aware that image acquisition under in vivo conditions as well as physical and instrumental factors may considerably influence the results.

Algorithms↗

PubMedDate not supplied

Pharmacokinetic MRI for assessment of malignant glioma response to stereotactic radiotherapy: initial results.

The purpose of this study was to assess the value of dynamic, contrast-enhanced MRI in patients with malignant glioma (a) to predict before stereotactic radiotherapy local tumor control, (b) to investigate temporal changes in tumor microcirculation after stereotactic radiotherapy, and (c) to analyze whether malignant glioma response may be predicted earlier by alterations in the tissue pharmacokinetics rather than in terms of tumor volume. Ninety MRI studies were performed of 18 patients with malignant glioma before and 6, 18, 26, 52, and 72 weeks after the end of stereotactic radiotherapy. The signal time courses of the contrast-enhanced tumors were analyzed using a pharmacokinetic two-compartment model that calculates for the parameter A, reflecting the degree of MRI signal enhancement [no units] and the exchange rate constant k21 [min(-1)]. Before radiotherapy, the amplitude A was significantly (P < .05) lower in patients with subsequent local tumor control (n = 8; mean A = .34 +/- .15) compared to patients without subsequent local tumor control (n = 10; mean A = .94 +/- .71). In the local tumor control group, early after stereotactic radiotherapy (at 6-18 weeks), there was a significant (P < .05) time-dependent decrease in the parameter k21, whereas there was still no alteration in the tumor volume. A low amplitude A before radiotherapy, combined with an early drop of k21 after stereotactic radiotherapy, reliably characterized the group of patients with subsequent tumor volume decrease. Our preliminary results suggest that two contrast-enhanced dynamic MR studies, one before and one early after stereotactic radiotherapy, offer important information on local tumor control within the first 6 to 18 weeks after stereotactic radiotherapy. Moreover, this response may be evidenced before tumor volume changes and provides a therapeutic window to broaden treatment options and to improve treatment outcome.

Brain↗

PubMedDate not supplied

Fast fluid-attenuated inversion-recovery (FLAIR) MRI in the assessment of intraaxial brain tumors.

This study demonstrates the value of a fast fluid-attenuated inversion-recovery (FLAIR) technique in the assessment of primary intraaxial brain tumors. Twenty-one patients with primary intraaxial brain tumors were examined by T2-weighted, proton-density-weighted fast spin echo, fast FLAIR, and contrast-enhanced T1-weighted spin echo using identical slice parameters. The images were evaluated using quantitative and qualitative criteria. Quantitative criteria were tumor-to-background and tumor-to-cerebrospinal fluid (CSF) contrast and contrast-to-noise ratio (CNR). The qualitative evaluation was performed as a multireader analysis concerning lesion detection, lesion delineation, and image artifacts. In the qualitative evaluation, all readers found the fast FLAIR to be superior to fast spin echo in the exact delineation of intraaxial brain tumors (P < .001) and the delineation of enhancing and nonenhancing tumor parts. Fast FLAIR was superior in the delineation of cortically located and small lesions but was limited in lesions adjacent to the ventricles. Fast FLAIR provided a significantly better tumor-to-CSF contrast and tumor-to-CSF CNR (P < .001). The tumor-to-background contrast and tumor-to-background CNR of the fast FLAIR images were lower than those of T2-weighted spin-echo images but higher than those of proton-density-weighted spin-echo images. FLAIR images had more image artifacts influencing the image interpretation in only two patients. Signal hyperintensities at the ventricular border were present in 92% of the patients. They are common findings in fast FLAIR and should be included into the image interpretation.

Adult↗

PubMedDate not supplied

Multiexponential proton spin-spin relaxation in MR imaging of human brain tumors.

In vivo measurements of proton relaxation processes in human brain tumors have been performed by magnetic resonance (MR) imaging using a whole-body superconductive MR scanner, operating at 1.5 T. The T1 and T2 relaxation time measurements were based on a combined Carr-Purcell/Carr-Purcell-Meiboom-Gill sequence with two interleaved repetition times and 32 echoes. First, comparative measurements in the imager and with the spectrometer of relaxation times were performed on phantoms containing fluids of different T1 and T2 to evaluate accuracy. A maximum deviation of approximately 10% was found. Multislicing with a gap width of one slice thickness influenced the accuracy of T1 relaxation measurement. A gap width of at least two times the slice thickness was necessary for reliable determination of T1. No influence on T2 values was observed by multislicing. Second, in human head imaging the multiexponential behavior of the T2 decay curves has been analyzed in each pixel, where the mean square deviation has been used as a criterion to discriminate between mono- and biexponential behavior. Mean values of monoexponential T1 and multiexponential T2 relaxation data for white matter, gray matter, CSF, edema, and tumor were sampled in 12 patients with brain tumors. T2 showed monoexponential behavior in white and gray matter, whereas CSF, edema, and tumor showed distinct biexponentiality. The biexponential analysis generally yields "fast" and "slow" components with T2f = 80 +/- 17 ms and T2s = 2,030 +/- 210 ms for CSF (partial volume effect), T2f = 104 +/- 25 ms and T2s = 677 +/- 152 ms for edematous tissues, T2f = 97 +/- 19 ms and T2s = 756 +/- 99 ms for tumor tissues, respectively. Using a stepwise discriminant analysis by forward selection, the two best discriminating parameters of the multiexponential relaxation analysis for each pair of classification groups have been selected. For the discrimination of edematous and tumor tissues a retrospective overall accuracy of 94% has been found.

Brain↗

PubMedDate not supplied

Systemic bone marrow disorders: characterization with proton chemical shift imaging.

In a prospective clinical study, 26 patients (22 with malignant lymphoma and 4 with myelofibrosis) and 9 healthy volunteers were examined by conventional magnetic resonance and proton chemical shift imaging (CSI; modified Dixon method). On the basis of the CSI data, a quantitative evaluation of the relative fat and water signal fractions in regions of interest of the femur, pelvis, and spine was performed. In 16 of 17 patients with biopsy-proven bone marrow disorders, CSI revealed a significant reduction in the fat fraction of the bone marrow relative to that of normal volunteers. The visual assessment could detect only 14 of the 17 pathological cases.

Bone Marrow↗

PubMedDate not supplied

Systemic chemotherapy with epirubicin for treatment of advanced or multifocal hepatocellular carcinoma.

BACKGROUND: The purpose of this retrospective study was to determine the response rate and effect on survival of chemotherapy with epirubicin in non-resectable advanced hepatocellular carcinoma (HCC). METHODS: Fifty-two patients with non-resectable disease were treated with epirubicin. A treatment cycle consisted of 20 mg/m(2) i.v. on days 1, 8 and 15 and was repeated every 4 weeks to a maximum dose of 1,000 mg/m(2). Forty-four patients were eligible for analysis. RESULTS: Out of 44 patients, 1 (2.3%) achieved a complete response, 3 (6.8%) had partial responses and 16 (36%) had stable disease (SD). For patients with successful disease control (complete and partial responders and patients with SD), the median survival was 16.2 months; for non-responders, it was 6.1 months (p < 0.003). Eight (88.9%) of 9 patients with alpha-fetoprotein (AFP) levels <50 microg/l achieved successful disease control compared to 12 (34.9%) out of 35 patients with initially elevated AFP (p < 0.0001). CONCLUSION: Epirubicin appears to be an active therapeutic option for patients with non-resectable HCC. Especially the subgroup of patients with low levels of AFP may benefit from this treatment.

Adult↗

PubMedDate not supplied

Locally advanced breast carcinoma: evaluation of mammography in the prediction of residual disease after induction chemotherapy.

BACKGROUND: We aimed to assess the mammographic features of locally advanced breast carcinoma treated with neoadjuvant chemotherapy and to evaluate morphological criteria that determine the value of mammography in therapy monitoring. MATERIALS AND METHODS: We reviewed the pre- and post-therapeutic mammograms of 44 patients with stage III-breast carcinoma with regard to tumor characteristics and malignant calcifications and compared to histopathological results. RESULTS: Delineation of the tumor proved to be the most significant criterion. In 34 tumors more than 50% of the lesion was defined; these showed a high correlation between the mammographically determined tumor diameter and that determined on histopathological examination (r = 0.77). Less than 50% of the mass was definable in 14 tumors; here the correlation between mammographically and histopathologically determined tumor diameter was low (r = -0.19). CONCLUSIONS: The diagnostic value of mammography in the evaluation of tumor response to induction chemotherapy depends primarily on the extent to which the tumor can be delineated from the adjacent breast tissue. For tumors whose margins can be defined by more than 50% on the baseline mammogram, the diagnostic reliability of mammography is high. Ill-defined masses should preferably be assessed with other imaging procedures such as ultrasonography or magnetic resonance imaging.

Antineoplastic Combined Chemotherapy Protocols↗