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Biomedical subjects

P E Peters

Publications and source records attributed to P E Peters.

At least 19 recordsLinked to original sources
PubMed2000

Screening for asymptomatic early bronchogenic carcinoma with low dose CT of the chest.

BACKGROUND: Survival of patients with lung carcinoma is very poor, particularly for patients with advanced disease. There are no early clinical symptoms, and screening with chest radiography has not been recommended. Computed tomography (CT) is superior to radiography for detection of pulmonary nodules but usually is associated with relatively high radiation exposure. Recently, accuracy of low dose CT has been shown to be similar to conventional dose CT. The goal of the current study was to assess the findings of low dose CT of the chest in heavy smokers. METHODS: More than 700 heavy smokers (> 20 pack years; age: > 40 years) underwent unenhanced low dose CT of the chest. Detected nodules were classified according to their density (soft tissue, calcified, fat) and size (< 6 mm, 6-10 mm, > 10 mm). In nodules larger than 10 mm with no CT features to suggest a benign lesion, histology was obtained. RESULTS: In approximately 40% of smokers, nodules smaller than or equal to 10 mm were detected. None was resected. In less than 3% of individuals, lesions larger than 10 mm were detected; 8 were bronchogenic carcinoma. All eight carcinomas were resectable. Lesions for which no histology was obtained were followed with low dose CT. CONCLUSIONS: Low dose CT detected 8 bronchogenic carcinomas in more than 700 heavy smokers. All eight were resectable. Pulmonary nodules measuring up to 10 mm were found in 40% of smokers. The significance of these small lesions has remained unclear.

Adult↗
PubMed1999

Pulmonary nodules: experimental and clinical studies at low-dose CT.

PURPOSE: To compare the number of pulmonary nodules detected at helical low- and standard-dose computed tomography (CT) and to investigate the diagnostic value of low-dose CT with a radiation exposure equivalent to that used at chest radiography. MATERIALS AND METHODS: Two radiologists recorded pulmonary nodules at standard-dose (250 or 100 mA, pitch of 1; 200 mA, pitch of 2) or low-dose CT (50 or 25 mA, pitch of 1 or 2) in five postmortem specimens and 75 patients. Nodules were assessed by size (5 mm or smaller, 6-10 mm, or larger than 10 mm) and by diagnostic confidence ("definite nodule," "definite lesion, not classic nodule," or "questionable lesion, possibly representing a vessel") with the Wilcoxon signed rank test. Artifacts depicted at low-dose CT were recorded. RESULTS: There were no statistically significant differences in the number of nodules detected at standard- or low-dose CT except in nodules 5 mm or smaller that were assessed as definite nodules at standard- or low-dose CT (25 mA, pitch of 2) (472 vs 397, P < .05). Artifacts that possibly interfered with nodule detection were observed exclusively at CT with 25 mA and a pitch of 2. CONCLUSION: Pulmonary nodules were detected reliably at CT with 50 mA and pitch of 2 or with 25 mA and a pitch of 1. However, further reduction of the dose to that used at chest radiography was associated with a significant decrease in the number of nodules 5 mm or smaller that were detected, possibly due to artifacts.

Adult↗
PubMed1998

Study of susceptibility-induced artefacts in GRASE with different echo train length.

The aim of this study was to evaluate the sensitivity of gradient-and-spin-echo (GRASE) sequences to susceptibility effects. GRASE sequences with 21 and 33 echoes per echo train were compared with a T2-weighted FSE sequence with an echo train length of 5 by means of MRI in phantoms, volunteers (n = 10), and patients (n = 19) with old hemorrhagic brain lesions. All experiments were performed on a 1.0-T clinical MR system (Impact Expert, Siemens AG, Erlangen, Germany) with constant imaging parameters. Contrast-to-noise ratios (CNRs) of tubes doped with iron oxides at different concentrations, of brain areas with physiological iron deposition (red nucleus, substantia nigra), and of areas of old brain hemorrhage were calculated for FSE and GRASE pulse sequences. Areas of old brain hemorrhage were also qualitatively analyzed for the degree of visible susceptibility effects by blinded reading. The CNR of iron oxide tubes and iron-containing brain areas decreased with increasing echo trains of GRASE sequences. The CNR of GRASE sequences decreased when compared with CNR of their FSE counterparts (GRASE 21 echo trains 23.8 +/- 0.8, FSE 5 echo trains 26.7 +/- 0.9; p </= 0.01). Qualitative analysis confirmed these measurements. FSE with an ETL of 5 demonstrated significantly stronger susceptibility effects than their GRASE counterpart with an ETL of 21. The results demonstrate that GRASE sequences do not necessarily compensate for the reduced sensitivity of FSE to susceptibility effects. The complex signal behavior of GRASE makes conventional SE, gradient echo, or FSE sequences containing shorter echo trains preferable when patients with intracranial hemorrhage are clinically evaluated.

Adult↗
PubMed1998

[T1-weighted dynamic MRI with new superparamagnetic iron oxide particles (Resovist): results of a phantom study as well as 25 patients].

PURPOSE: Evaluation of the diagnostic usefulness of the T1-effect of Resovist (SPIO) for dynamic MRI of the liver. METHOD: In-vitro measurements of a dilution series with T1-weighted FLASH and SE sequences and investigation of 25 patients with known focal liver lesions with a T2-weighted TSE sequence and a dynamic T1-FLASH sequence. RESULTS: T1-weighted MRI with Resovist in vitro showed a positive enhancement at low concentrations and a negative enhancement at higher concentrations. In-vivo T1-weighted dynamic MRI liver parenchyma demonstrated a positive enhancement 30 s post contrast, followed by a continuous slope of signal intensity and a negative enhancement (> or = 60 s). Spleen, portal venous vessels and haemangiomas showed an early increase in signal intensity followed by a decreasing positive enhancement, but without negative enhancement. During the perfusion phase metastases showed a small but not significant increase in signal intensity. In 80% a positive ring enhancement could be observed around metastases. CONCLUSION: Resovist exhibits a diagnostically useful T1-effect. An evaluation of the perfusion of focal liver lesions during the distribution phase is possible with dynamic T1-weighted MRI. This approach may further improve characterisation of focal liver lesions.

Adult↗
PubMed1998

[Combined use of ECK-triggered 2D-phase contrast MR angiography and 2D-time-of-flight MR angiography for planning and follow up before and after vascular intervention of pelvic and leg arteries].

PURPOSE: To develop a strategy for the complete work-up of vessel lumen and vessel wall for planning and follow-up of radiological interventions of lower extremity arteries. METHODS: A total of 36 patients (21 pre-, 8 post- and 7 pre- and postinterventional) were studied. MRA studies were performed using an ECG-triggered phase contrast technique for the demonstration of intraluminal flow and an axial high resolution time-of-flight technique to assess the vascular wall. All MRA studies were analysed by intraindividual DSA comparison for the assessment of flow and wall structures. RESULTS: Combined MRA techniques provided a good correlation with DSA for the assessment of vascular flow. The kappa test revealed a value of greater than 0.61 for most on the vessel segments proving a good correlation of both methods. Orthogonal high-resolution TOF-MRA provided additional information for the assessment postinterventional wall haematomas and hard plaques. CONCLUSION: Combination of PCA to study flow and axial TOF to study wall pathology improves the usefulness of peripheral MRA.

Adult↗
PubMed1998

T1 effects of a bolus-injectable superparamagnetic iron oxide, SH U 555 A: dependence on field strength and plasma concentration--preliminary clinical experience with dynamic T1-weighted MR imaging.

PURPOSE: To investigate the field strength dependency of relaxivity values with SH U 555 A, concentration-dependent T1 effects, and findings at dynamic T1-weighted magnetic resonance (MR) imaging in patients with focal liver lesions. MATERIALS AND METHODS: Longitudinal relaxivity (r1) with SH U 555 A was measured in human plasma (0.02-300.00 MHz), and transverse relaxivity (r2) was measured at 10, 20, and 40 MHz. Second, a dilution series in human plasma was used at 1-T, T1-weighted, spin-echo or fast low-angle shot (FLASH) imaging. In 22 patients with focal liver lesions, imaging with the latter sequence was performed with a dose of SH U 555 A of 10 mumol Fe/kg. RESULTS: The r1 of SH U 555 A decreased with increasing field strength, but was higher at high field strengths than r1 values for gadolinium chelates. Enhancement calculations for different iron concentrations in human plasma demonstrated positive enhancement at concentrations less than 700 mumol Fe/L. Enhancement increased with the degree of T1 weighting and was highest for the FLASH sequence with the shortest TE (+81.4% with 300 mumol Fe/L). Enhancement was positive in the liver for at least 30 seconds and in the spleen for at least 480 seconds. CONCLUSION: Signal intensity changes at dynamic T1-weighted MR imaging after bolus injection of SH U 555 A can be explained by dynamic changes in iron-plasma concentration.

Contrast Media↗
PubMed1998

Effects of testosterone replacement therapy on cortical and trabecular bone mineral density, vertebral body area and paraspinal muscle area in hypogonadal men.

Loss of bone and muscle mass are major findings of male hypogonadism. In order to determine the long-term effect of testosterone replacement therapy on spinal bone and muscles, the trabecular and cortical bone mineral density, vertebral body area and paraspinal muscle area were assessed by quantitative computed tomography in 32 testosterone-substituted patients, aged 18-74 years, with idiopathic hypogonadotropic hypogonadism (n=6), pituitary insufficiency (n=5), Klinefelter syndrome (n=12) or other forms of primary hypogonadism (n=9). They were followed for a mean period of 3.2+/-1.7 years (mean+/-S.D.), ranging from 1 to 7 years. A significant correlation between initial serum testosterone levels and bone mineral density was found in patients with congenital forms (r=0.58; P<0.05) but not in those with acquired forms. A significant increase in trabecular and cortical bone mineral density (P<0.001) was documented in the course of replacement therapy in all patients regardless of the type of hypogonadism and age of patients. A slight but significant increase in paraspinal muscle area was observed if all patients were taken together (P<0.01). The area of paraspinal muscle correlated with body weight (r=0.58; P<0.001) and moderately with trabecular bone mineral density (r=0.4; P<0.01). Its increase did not correspond to the change observed for trabecular and cortical bone mineral density. Vertebral body area did not change over time. It correlated only with height and weight but not with bone mineral density. In conclusion, testosterone therapy of hypogonadal men improves both trabecular and cortical bone mineral density of the spine independently of age and type of hypogonadism while vertebral area remains unchanged. The effects seen on paraspinal muscles emphasize the clinical benefit of adequate replacement therapy for the physical fitness of hypogonadal men.

Adolescent↗
PubMed1997

[Radiologic performance in night and emergency care].

This report deals with radiologic examinations outside official working hours in a German university hospital and the influence of new government regulations. A total of 65,113 radiologic examinations were requested and performed outside official working hours between 1 July 1990 and 30 Juni 1994. The data were analyzed according to the age and sex of this patient population compared with the entire population studied within this 4-year period. Further analysis included the time of the study, the organ systems investigated, and the radiologic technique. About one-third of requests occurred between 16.00 and 20.00 hours on normal working days and, thus, could be taken care of by late shifts. Another third covers the time between 20.00 and 08.00 hours in the morning, which requires inhouse staff (medical and technical). The remainder of the requests occurred during holidays and weekends in the daytime. The most common request in this analysis was for portable chest examination. About 50% of all portable chest examinations were performed outside regular working hours. In all, 17.2% of all requests involved CT and MRT studies. Government regulation did not change the number, technique, and frequency of radiologic examinations outside official working hours.

Adolescent↗
PubMed1997

[Magnetic resonance tomography without and with gadolinium-DTPA for evaluating kidney transplants].

PURPOSE: To determine the value of MR imaging in differentiating the various causes of human renal allograft dysfunction. METHODS: A total of 123 human renal allografts (normal n = 20, acute rejection n = 57, acute tubular necrosis n = 14, interstitial fibrosis n = 11, chromic allograft glomerulopathy n = 11, cyclosporine nephrotoxicity n = 3, cortical necrosis n = 7) were investigated by means of MR imaging. Axial T1-weighted spin-echo images and coronal T1-weighted gradient-echo images were obtained before and after Gd-DTPA injection. Diagnostic parameters included corticomedullary contrast and allograft size and shape on the pre-contrast sequences. RESULTS: None of the diagnostic parameters used could differentiate among the various diagnostic groups. Diagnostic of cortical necrosis could be made only on post-contrast scans. Contrast-enhanced scans were superior to pre-contrast images in detection of focal allograft lesions. Otherwise, contrast-enhanced scans did not provide any more information than pre-contrast studies. Spin-echo and gradient-echo sequences displayed the same diagnostic value. CONCLUSIONS: MR imaging has a limited value in differentiating the various causes of renal allograft dysfunction.

Adult↗
PubMed1997

[Phase-contrast MR angiography of the lower extremity. Comparison of methods and clinical application].

PURPOSE: To investigate whether phase-contrast MRA is a clinically suited approach to examine arteries of the pelvis and lower extremities. METHODS: The study was divided into two parts, a volunteer study and patient study. Three MRA techniques-2D TOF with venous saturation, 3D magnitude contrast and 2D phase contrast with ECG triggering-were intraindividually compared in 15 volunteers and evaluated by three blinded readers. Subsequently, a total of 230 vessel segments of 45 MRA studies using ECG-triggered phase contrast were compared with intraarterial DSA. All vessel segments were scored by three blinded readers using a five-point scale with DSA serving as the gold standard. RESULTS: ECG-triggered phase contrast provided better image quality than the other MRA techniques as assessed by the Friedman test. Clinical studies demonstrated a significant correlation of DSA and MRA as assessed by the Spearman correlation and kappa statistics for individual readers. CONCLUSION: MRA of the pelvis and lower extremities may be performed with 2D ECG-triggered phase-contrast MRA within a reasonable time frame (< 30 min). MRA slabs provide orientation similar to that with DSA projections and good to very good correlation of vessel pathology as shown by kappa statistics.

Angiography, Digital Subtraction↗
PubMed1997

Enhancement characteristics of liver metastases, hepatocellular carcinomas, and hemangiomas with Gd-EOB-DTPA: preliminary results with dynamic MR imaging.

Our objective was to study Gd-EOB-DTPA for the characterization of focal liver lesions by means of dynamic MR imaging. A double-blind and randomized dose-ranging phase-2 clinical trial was performed in 31 patients (liver metastases n = 23, hepatocellular carcinoma n = 4, and hemangioma n = 4) at a field strength of 1.0 Tesla. Gd-EOB-DTPA (Schering AG, Berlin, Germany) was administered as an IV bolus (12.5, 25, or 50 micromol/kg body weight) with dynamic T1-weighted MRI during the distribution and cellular uptake of the contrast agent at multiple time points up to 45 min post contrast. Dynamic changes in tumor signal intensity, tumor-liver contrast, enhancement patterns, side effects, and adverse events were evaluated. Monitoring of vital signs revealed no significant changes during bolus injection of Gd-EOB-DTPA. Liver metastases demonstrated an inhomogeneous uptake of Gd-EOB-DTPA during the distribution phase with a washout effect on delayed images > 3 min and highest tumor-liver contrast 20 and 45 min post contrast. Hepatocellular carcinomas showed prolonged enhancement as compared with metastases and hemangiomas. Hemangiomas exhibited an early peripheral-nodular enhancement with subsequent partial or complete filling, persisting enhancement < 10 min following injection of Gd-EOB-DTPA, and delayed washout as compared with liver metastases. Initial clinical experience suggests that Gd-EOB-DTPA as a bolus injectable hepatobiliary MR contrast agent may offer useful features for the characterization of focal liver lesions.

Carcinoma, Hepatocellular↗
PubMed1997

Evaluation of myelination and myelination disorders with turbo inversion recovery magnetic resonance imaging.

The aim of our work was to determine the efficacy of turbo inversion recovery spin echo (TIRSE) pulse sequences in differentiating patients with normal and abnormal myelination. Twenty neurological normal children (aged 5 months to 12 years) as well as 65 children presenting clinically with neurologic developmental deficits (aged 2 months to 10 years) were examined using TIRSE, T1-weighted SE, and T2-weighted turbo SE pulse sequences. Contrast-to-noise-ratio (CNR) between myelinated white and gray matter was compared for the different pulse sequences. In addition, two readers analyzed all images qualitatively by consensus. The CNR values were significantly higher on TIRSE images as compared with conventional images (p < 0. 05). Forty-two neurologically abnormal patients displayed a normal myelination on all sequences, whereas 23 showed an abnormal myelination. The TIRSE sequence provided a sensitive and specific depiction of an abnormal myelination in all of these patients. The TIRSE sequence provided additional information to conventional pulse sequences in determining myelination disorders in children, especially in children older than 2 years.

Adolescent↗
PubMed1997

Artificially produced cartilage lesions in small joints: detection with optimized MRI-sequences.

The purpose of this study was to evaluate different magnetic resonance imaging (MRI) pulse sequences in the detection of artificial cartilage lesions in small joints using an animal model. A total of 32 artificial cartilage lesions were created in the knee joints of 20 rabbits. Twenty lesions were produced 4 weeks and 12 lesions 1 h before the MRI examination, performed in an extremity coil at 1.0 T. All joints were examined with five imaging sequences: (1) a conventional T1-weighted spin-echo (SE)-sequence (repetition time [TR] 600 ms, echo time [TE] 15 ms), (2) a T2-weighted turbo-SE-sequence (TR 2000 ms, TE 85 ms), (3) a two-dimensional (2D) gradient echo (GE)-sequence (TR 440 ms, TE 10 ms, flip angle 60 degrees) and (4,5) two three-dimensional (3D) GE-sequences (TR 40 ms, TE 7 ms, flip angle 40 degrees, with fat suppression (FS) and TR 30 ms, TE 9 ms, flip angle 40 degrees). Two examinations had to be excluded because of insufficient image quality and the remaining examinations were analyzed by two experienced radiologists. The MRI images were correlated with the pathologic findings and anatomical structures were scored according to a 5-level scale. Direct comparison of the pathological and MRI findings showed that 19 of the 30 artificially induced cartilage lesions were detected with the FS 3D GE-sequence, 13 with the 2D GE-sequence, 11 with the 3D GE-sequence, 3 with the T1-weighted SE-sequence, and 2 with the T1-weighted SE-sequence. The highest percentage of artificial cartilage lesions was demonstrated using a fat-suppressed 3D GE-sequence. However, the analysis of cartilage defects in small joints with optimized sequences as well as clinical routine hardware and software had limitations. Therefore a pilot study was performed analyzing newly developed high resolution FS 3D GE images obtained from 5 rabbit knees with 10 cartilage lesions at 1.5 T. Two sequences were used with 1.0 and 0.5 mm slice thickness, a matrix of 256 x 256 and 512 x 256 and a field of view of 12 x 6 and 8 x 6 cm. In this small subset detection rates were substantially higher than in the 30 rabbit knees examined before.

Animals↗
PubMed1997

Texture analysis of direct magnification radiographs of vertebral specimens: correlation with bone mineral density and biomechanical properties.

RATIONALE AND OBJECTIVES: The authors used direct magnification radiographs, combines with texture analysis, to investigate the trabecular structure of human vertebral specimens and compared these techniques with measurement of bone mineral density (BMD) by using quantitative computed tomography to predict bone strength. METHODS: Direct magnification radiographs and BMD measurements were obtained from 38 motion segments from the thoracolumbar spines of 11 female human cadavers. Maximum compressive strength (MCS) was determined with a materials testing machine. Morphologic parameters, digital skeletons, and fractal dimension were obtained from the radiographs in three different regions of interest. RESULTS: Correlations between BMD and MCS were statistically significant (r = .81, P < .01). With morphologic parameters, correlation coefficients of up to .64 (P < .01) were obtained. Use of multivariate regression analysis with one morphologic parameter (the width of the black pixels, or thicknessB) in addition to BMD improved correlations versus MCS (P < .01). CONCLUSION: In an experimental setting, BMD showed statistically significant correlation with bone strength, whereas the structural parameters demonstrated only modest correlations. BMD together with one of these measures (thicknessB), however, showed the highest correlation.

Adult↗