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K Hoffmann

Publications and source records attributed to K Hoffmann.

At least 55 records · Page 3Linked to original sources
PubMed2003

[CT-colonography with the 16-slice CT for the diagnostic evaluation of colorectal neoplasms and inflammatory colon diseases].

PURPOSE: Comparison of the performance of virtual and conventional colonoscopy for the detection of colorectal polyps and inflammatory colon diseases using a 16-slice spiral CT scanner. Furthermore, presentation of the first experiences with a new three-dimensional reconstruction mode ("colon-dissection") that dissects the colonic wall like a pathologic-anatomic preparation to increase the sensitivity. MATERIALS AND METHODS: Forty patients were studied using a 16-slice spiral CT (Lightspeed 16, General Electric Medical Systems, Milwaukee, Wisconsin 53201, USA). The examination was performed after standard oral preparation for colonoscopy. The colonic distension was achieved with room air and intravenous butylscopolamine. Images were obtained in supine and prone position using a detector configuration of 16 x 0.625 mm, pitch 1.7, rotation time 0.5 s, 160 mAs and 120 kV. Axial reconstruction with a slice thickness of 0.625 mm. The CT data were assessed by two radiologists on an Advantage Workstation (Volume Analysis 2, USA) using a software with the capabilities of axial, multiplanar and volume rendering, virtual endoscopy, and colon dissection. Conventional colonoscopy was used to determine the sensitivity. RESULTS: A total of 30 polyps were found in 8 patients and a carcinoma was detected in two patients. Colonography identified 4 polyps with a diameter of 10 mm or more, 6 polyps with a diameter of 5 mm to 9.9 mm, 11 polyps with a diameter of 3 to 4.9 mm and 9 polyps with a diameter of 3.0 mm or less. There were two false negative findings (one polyp of 3 mm and one of 4 mm had been overseen) and two false positive findings for polyps (polyps of 4 mm and 6 mm). The sensitivity and specificity for the detection of colonic polyps were 93% and 94% with the "colonic-dissection" mode, 87 % and 94 % with the "virtual-endoscopy" mode and 63 % and 97 % with multi-planar reconstruction, respectively. Depending on the diameter of the colonic polyps, the "colon-dissection" mode ("virtual-coloscopy") had a sensitivity and specificity of 100 % and 100 % for polyps with a diameter over 5.0 mm, 91 % and 82 % for polyps with a diameter from 3.0 to 4.9 mm and 89 % and 78 % for polyps with a diameter under 3.0 mm, respectively. Inflammatory colon diseases presented as thickening of the colon wall over 5 mm. CONCLUSIONS: Virtual colonoscopy with 16-slice spiral CT allows accurate detection of colonic polyps, including small polyps below a diameter of 3 mm. In comparison with the 2D- and 3D-"virtual-endoscopic" reconstruction, the 3D-reconstruction software "colon-dissection" achieves the highest sensitivity for the detection of colonic masses. Therefore, the combination of a 16-slice spiral CT and the "colon-dissection" reconstruction software provides a high resolution in the z-axis for detecting colonic masses and polyps down to a diameter of less than 2 mm, with a sensitivity of about 90 %. This sensitivity is much higher than the sensitivity achievable with 4-slice spiral CT and without "colon-dissection" mode. A thickened colon wall over 5 mm indicates inflammatory colon disease.

Colonic Polyps↗
PubMed2003

Comparison of high frequency ultrasound and optical coherence tomography as modalities for high resolution and non invasive skin imaging.

High frequency ultrasound (HFUS) and optical coherence tomography (OCT) are techniques for high resolution imaging of tissues. The penetration depth of these modalities is limited, but it is sufficiently large enough for non invasive skin imaging. HFUS and OCT are based on the same concept. Waves (ultrasonic waves, respectively light waves) propagate along a narrow beam, are backscattered at tissue inhomogeneities and analyzed over time of flight to obtain spatially resolved morphological information. The objective of this paper is to compare HFUS and OCT in terms of resolution, dynamic range and contrast and to assess their value as tools for high resolution skin imaging. Measurements on phantoms and in vivo have been performed with a 100 MHz ultrasound system and an OCT-scanner working in the near infrared spectrum at 1300 nm wave-length. From the measurements, it can be concluded that OCT delivers an almost isotropic resolution (axial resolution about 5.8 microns, lateral resolution about 4.1 microns), whereas the resolution of the investigated HFUS system is more anisotropic (axial resolution about 9.3 microns, lateral resolution about 60 microns). HFUS and OCT show different penetration depths and a different contrast. Both techniques can, therefore, be combined advantageously in a multimodality approach to account for their individual characteristics.

Hair↗
PubMed2002

[In vivo differentiation of pigmented skin tumors with laser Doppler perfusion imaging].

BACKGROUND AND OBJECTIVE: Malignant melanomas show a higher heterogeneity in their architecture and a higher vessel density because of neovascularization compared to benign melanocytic skin tumours. In this study the validity of the newly developed Laser Doppler Perfusion Imager (LDPI) with a lateral resolution of 100 microns in the differential diagnosis of pigmented skin tumours was investigated. PATIENTS/METHODS: The perfusion of 116 pigmented skin tumours was s measured with LDPI; 44 malignant melanomas, five melanoma metastases, 59 dysplastic nevi and eight basal cell carcinomas were studied before excision for precise histological diagnosis. RESULTS: There is a significantly higher perfusion of the malignant melanomas (3.15 +/- 1.87 AU) compared to dysplastic nevi (1.14 +/- 0.97 AU) (p < 0.01). By calculating a ratio of the mean perfusion in the tumour and the mean perfusion in adjacent healthy skin, the potential source of error because of regional differences in perfusion is eliminated. The ratio of malignant melanomas (10.78 +/- 9.18) is significantly higher than these of melanoma metastases (4.20 +/- 1.66), basal cell carcinomas (3.24 +/- 1.32) and dysplastic nevi (2.85 +/- 1.32). CONCLUSIONS: The high resolution LDPI has the potential to be a non-invasive screening method for preoperative differential diagnosis of pigmented skin tumours. Besides the epiluminescence microscopy and sonographic determination of the tumour thickness, we have now the possibility to get preoperative information about tumour vascularization.

Adult↗
PubMed2002

Ultraviolet protection factor of fabrics: comparison of laboratory and field-based measurements.

BACKGROUND/PURPOSE: Spectrophotometry has become an accepted laboratory-based method for the determination of the ultraviolet protection factor (UPF) of fabrics. However, the validity of the UPF determined in the laboratory has been a controversial issue with regard to its significance in the field. To compare UPF values obtained by spectrophotometry, determination of the minimal erythema dose (MED), and biological dosimetry, we conducted laboratory and field-based measurements on various fabric materials. METHODS: One cotton, two viscose, and two polyester fabrics were enrolled into the study. Spectrophotometric (SP) testing was performed in accordance with the European standard. In vivo "on skin" (IV) testing on human subjects was performed with and without fabric protection. For determination of MED, a solar-simulator was used. In another part of the study, biological dosimetry (BD) testing was employed for laboratory testing with solar-simulated radiation (laboratory BD testing) as well as field-based measurements with natural sunlight in stationary (stationary BD testing) and "real life" exposure situations (mobile subject BD testing). For field-based measurements one light-weight polyester fabric was selected. RESULTS: The differences of the mean UPF values obtained by the laboratory-based methods were significant (MANOVA; P = 0.05), except for fabric no. 2 (MANOVA; P = 0.097). In 4 of the 5 fabrics tested, UPF values obtained by IV testing were significantly lower than those obtained by SP testing (t-test; P = 0.05). In 3 fabrics, SP testing revealed significantly higher UPF values in comparison to laboratory BD testing (t-test; P = 0.05). The differences of UPF values obtained by the laboratory and field-based measurements employed for the light-weight polyester fabric were significant (ANOVA; P = 0.05). In comparison to SP testing (UPF 3.8), stationary BD testing resulted in significantly lower (UPF 3.5) and mobile subject BD testing in a significantly higher UPF of 4.4 (t-test; P = 0.05). The UPF obtained by mobile subject BD testing differed significantly from the UPF obtained by stationary BD testing (t-test; P = 0.05). CONCLUSIONS: Comparison of the presented methods indicates that IV testing generally results in lower UPF values. By contrast BD testing in "real life" exposure situations reveals relatively high UPF values. Although an overestimation of the spectrophotometrically measured UPF has been observed in comparative laboratory testing, UPF values obtained by field-based measurements are in relatively good agreement, or even surpass UPF values obtained by spectrophotometry. It is, therefore, suggested that SP testing provides "safe" UPF values which may be also valid in extreme real exposure situations. Biological UV dosimetry is, however, a promising alternative method for UPF testing: the test is easily performed in realistic exposure situations, the test is relatively inexpensive, and the measurements are valid.

Analysis of Variance↗
PubMed2002

Investigation of basal cell carcinoma [correction of carcionoma] by confocal laser scanning microscopy in vivo.

BACKGROUND/PURPOSE: In vivo confocal laser scanning microscopy (CLSM) allows to study human skin up to 200 micro m deep non-invasively. Aim of this study was to investigate basal cell carcinoma (BCC) using in vivo CLSM, and to compare the micromorphologic features of BCC with uninvolved skin. METHODS: Twelve patients with histological diagnosis of BCC referred to our department for tumor excision were investigated on the lesion(s) and on clinically uninvolved sites preoperatively by in vivo CLSM using the Vivascope 1000 (Lucid Inc., Rochester, USA). The images were compared to histological examinations of the excised tissue. RESULTS: Typical changes in vasculature such as increase in number and diameter of the blood vessels, loss of the vascular architecture, parallelly and horizontally orientated vessels, and accumulation and rolling phenomena of bright reflecting cells of 11.88 +/- 1.75 micro m in diameter along the vessel wall were observed in all BCCs. The tumor stroma of the BCCs showed a strong reflectance mainly due to numerous bundles of collagen fibers encoating dark, cell-rich areas of tumor parenchym. In five patients, slim basaloid cells with relatively large, elongated dark nuclei were observed in the periphery of the tumor parenchym. In the fibrosing type of BCC, curled bundles of collagen with large cells represented the tumor stroma. CONCLUSIONS: BCC can be investigated by CLSM and provide typical features. Besides the tumor parenchym and stroma, typical changes in vasculature seem to be a sensitive criteria for BCC and may in future help in diagnosing BCC by CLSM as well as in assessing the margins of large tumors. We suggest that CLSM is a promising non-invasive tool for the diagnostics of BCC and the assessment of tumor margins prior to surgery.

Aged↗
PubMed2002

Estimating the distribution of usual dietary intake by short-term measurements.

OBJECTIVE: To estimate the habitual dietary intake distribution in a population on the basis of repeated short-term measurements, especially of multiple 24 h diet recalls. METHODS: Six different statistical methods were evaluated and compared. The comparison referred to theoretical assumptions, admitted data transformations, statistical foundations, available software packages, and applications to real data of dietary intake. RESULTS: The Nusser method and a simplified version of it proposed in the paper have proved to be universally applicable methods for estimating the usual intake distribution for food groups and nutrients. Also, the Buck method seemed to be a robust estimation procedure suitable for the description of food consumption data, whereas the other considered methods were only applicable for log-normally distributed intake data or required a comprehensive data simulation. Characteristics of the estimated usual intake distribution were a decreased standard deviation, increased lower percentiles, and decreased upper percentiles compared to the observed sample distribution of individual means. Empirical results concerning total fat and vegetable intake in three different European consumption surveys showed that the estimated percentiles of the usual intake distribution did not depend markedly on the number of sampling days. CONCLUSIONS: Repeated short-term measurements like 24 h diet recalls can be used to describe the habitual dietary intake distribution in food consumption surveys. Recommended is a sampling design of two non-consecutive sampling days. The sampling days of all participants should be selected in such a way that they cover all seasons and days of the week.

Data Interpretation, Statistical↗
PubMed2002

Recent weight changes and weight cycling as predictors of subsequent two year weight change in a middle-aged cohort.

OBJECTIVE: To evaluate the influence of recent weight changes (weight gain, loss and cycling) on subsequent weight changes. DESIGN: Prospective cohort study with 2 y of follow-up. Data analysis with a polytomous logistic regression model. SUBJECTS: A total of 18 001 non-smoking subjects, 6689 men and 11 312 women, from the general population. MEASUREMENTS: Body height and weight measurements and interview data on lifestyle habits and medical history at baseline. For follow-up, self-administered questionnaires for assessment of body weight and incident diseases. RESULTS: Recent changes in body weight, that is weight gain, weight loss and weight cycling, were significant predictors of subsequent weight changes in both men and women after controlling for age, baseline BMI and several lifestyle and behavioural characteristics as potential confounding factors. Weight cycling before baseline was the strongest predictor of subsequent large weight gain (> or =2 kg) with an odds ratio (OR) of 4.84 (95% confidence interval (CI) 3.34-7.02) in men. In women, prior weight loss was the strongest predictor of subsequent large weight gain (OR 4.77; 95% CI 3.63-6.03), followed by weight cycling (OR 3.02; 95% CI 2.15-4.25). CONCLUSION: These data indicate the need for thorough weight history assessment to identify those who are most likely to gain weight. Effective weight control before the development of obesity or after intentional weight loss due to obesity should be a primary goal in the management of obesity.

Adolescent↗
PubMed2002

Plasma levels of opioid peptides after sunbed exposures.

BACKGROUND: Previous studies have indicated that solar and artificial ultraviolet (UV) radiation have a positive influence on psychological variables such as mood and emotional state. Circulating opioid peptides have been suggested as being important in this effect. OBJECTIVES: To investigate in a controlled trial the influence of UVA radiation on opioid peptide levels. METHODS: We determined plasma levels of beta-endorphin immunoreactive material (IRM) and met-enkephalin in UV-exposed (n = 35) and non-exposed (n = 9) healthy volunteers. On the first day of the study, blood samples were taken from the volunteers (time A). UVA irradiation was subsequently administered with an air-conditioned tanning device. During the UV exposures the volunteers wore opaque goggles. Twenty minutes after UV exposure, blood samples were collected again (time B). Within the following 3 weeks the volunteers had a series of five UV exposures. On the last day of the study (24 h after the sixth UV exposure) blood samples were collected (time C). The cumulative UVA doses were 96 J cm-2 for skin type II and 126 J cm-2 for skin type III. The controls had no UV exposures. Plasma beta-endorphin IRM and met-enkephalin levels were determined using radioimmunoassays. RESULTS: At all times of blood collection (A, B, C), there were no significant differences in plasma levels of beta-endorphin IRM and met-enkephalin between UV-exposed and non-exposed volunteers (P > 0.05). CONCLUSIONS: UVA irradiation does not significantly elevate plasma levels of beta-endorphin IRM and met-enkephalin. Therefore we suggest that psychological benefits claimed to occur after UV exposure are unlikely to be mediated by the types of circulating opioid peptides measured in this study.

Adolescent↗
PubMed2002

Uncommon vascular naevi associated with focal acantholytic dyskeratosis.

Cutis marmorata telangiectatica congenita and vascular twin naevi are rare vascular anomalies in which focal acantholytic dyskeratosis is usually not observed. We describe a 44-year-old-man who presented for evaluation of skin lesions that had been present since birth. Physical examination revealed anaemic macules adjacent to a naevus telangiectaticus on the chest. Naevus anaemicus was also seen on the shoulders, arms, and left leg. There was bluish-reddish reticulate marking of the skin and cutaneous atrophy. Shortening and hypoplasia of the left leg was observed. Histologic examination of two biopsy specimens revealed focal acantholytic dyskeratosis. In vivo confocal laser scanning microscopy showed dilated capillaries and vessels of the upper dermal plexus in the telangiectatic and decreased capillary blood flow in the anaemic skin sites. The findings were consistent with a diagnosis of cutis marmorata telangiectatica congenita, vascular twin naevi, and incidental focal acantholytic dyskeratosis. The particularities of the present case are the following: firstly, the association of two rare vascular anomalies to which the genetic concept of mosaicism can be applied; secondly, the occurrence of incidental focal acantholytic dyskeratosis in sites of vascular naevi.

Acantholysis↗
PubMed2002

[Therapy of acute mastoiditis].

BACKGROUND: Acute otitis media is a common disease, mostly contracted at childhood. The development of acute mastoiditis has been decreased since the introduction of antibiotics. Currently it is only developed in 0.004 % cases of acute otitis media. But despite of this fact, even today one should not neglect this condition as the complications such as intracranial spread and lateral sinus thrombosis are still life threatening. METHODS AND PATIENTS: In a retrospective study from 01/96 - 09/00 we reviewed the cases of acute mastoiditis as a result of acute otitis media at our department. Additionally we compared study results out of 1972 until 1989 with our current results. RESULTS: Altogether mastoidectomy has been carried out at 157 patients. The cases have steadily increased since 1996. This is confirmed by comparison with study results of previous years. The majority of the patients were between 8 months and 3 years old (60 %). When the patients first presented at our department, the first signs of otitis media were 19.5 days ago in average. 38 % of the patients received no antibiotic treatment before admission. A thickened mucous membrane was seen by the mastoidectomy mostly (58 %). A subperiostal abscess we noted in 8.5 %. The most common isolated bacteria were Streptococcus pneumoniae (33 %) and Streptococcus pyogenes (11 %). The patients stayed at the department about 10 days. In comparison to recent study results the "typical" mastoiditis has decreased. The causative pathogens have not changed. CONCLUSIONS: In the last years we realised an increasing number of mastoiditis at our department. The isolated bacteria are the same as presented in the literature. Early surgery combined with an effective antibiotic treatment can avoid the known complications of mastoiditis.

Acute Disease↗
PubMed2001

Excitation of Rydberg series in C60.

Rydberg series of C60 are reported for the first time. The Rydberg states are seen in photoelectron spectra using ultrashort pulsed-laser excitation, where the excited states formed are ionized with one further photon from the same laser pulse. The structure is observed for pulse durations as short as 100 fs with indications of residual structure for even shorter pulse excitation. The production mechanism is discussed and the Rydberg states are modeled by analytically solving the Schrödinger equation with a simple jelliumlike potential for C60.

Journal Article↗