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Biomedical subjects

M Lenz

Publications and source records attributed to M Lenz.

At least 19 recordsLinked to original sources
PubMed2006

Searching for diabetes decision aids and related background information.

AIMS: Patient decision aids (DAs) are interventions designed to help patients making informed decisions. DAs are complex interventions comprising a number of active components each essential to the proper functioning of the aid. Critical appraisal of DAs therefore requires access to information describing the incremental assessment of each stage in their development, including information about the theoretical funding, development processes, efficacy trials and long-term implementation. We explored the feasibility of identifying such information with conventional database search strategies. Our study was conducted only in the field of diabetes care. METHODS: The 'Inventory of Existing Patient Decision Aids', medline (PubMed) and the World Wide Web were used to identify DAs relevant for diabetes care. For tracking information concerning each developmental stage, the reference lists of the DAs, home pages of the authors, medline, embase, PsycINFO, cinahl, and the Cochrane database were searched systematically. RESULTS: A total of 13 DAs relevant for diabetes care were identified. The search for publications concerning their development yielded more than 3000 results, only 10 of which referred to at least one of the 13 DAs. No additional background information was found on the home pages of the authors. CONCLUSIONS: Conventional database search strategies do not allow the extraction of information about the stages in development of a DA. To facilitate critical appraisal of DAs, we propose the creation of an electronic database which provides information about available DAs, together with the relevant background literature, or to incorporate such a system into existing databases.

Decision Making↗
PubMed2006

Phylogeny of Australian Coptotermes (Isoptera: Rhinotermitidae) species inferred from mitochondrial COII sequences.

Six Australian species of Coptotermes are traditionally recognized, but recent cuticular hydrocarbon studies suggest that some of these may represent more than one species. An understanding of the phylogenetic diversity of Australian Coptotermes, particularly the pest species, is likely to be important for the improvement of termite management strategies. A study of phylogenetic relationships among species of this genus was performed, based on the mitochondrial cytochrome oxidase (COII) gene, comparing the data with recent data from Asian species. Representatives of the species C. lacteus (Froggatt), C. frenchi Hill and C. michaelseni Silvestri were each found to form closely related monophyletic groups, however representatives of C. acinaciformis (Froggatt) were not. For C. acinaciformis, representatives from northern mound-building populations were found to form a distinct group to southern, tree-nesting forms. Among southern C. acinaciformis, two Western Australian representatives were found to be divergent from other populations. The results suggest that C. acinaciformis probably represents a complex of species rather than one, as has been suggested previously. One unidentified Coptotermes sp. taxon from Melbourne was found to be divergent from other taxa. Notably, some Australian species were more closely related to Asian species than other Australian species.

Animals↗
PubMed2002

Hypericin activated by an incoherent light source has photodynamic effects on esophageal cancer cells.

BACKGROUND AND AIMS: Photodynamic therapy (PDT) is a new treatment modality for early esophageal neoplasia. With two absorption maxima in the visible light range (550 and 588 nm) hypericin is a very promising photosensitizer for PDT with incoherent light sources. We studied the effects of photosensitizing hypericin in both primary cell cultures and cell lines (squamous: Kyse-140 and adenocarcinoma: OE-33) of human esophageal cancer using an incoherent white light source. MATERIALS AND METHODS: Esophageal cancer cells were preincubated (4-24 h) with hypericin (10 nM-1 micro M) and then irradiated with a light energy dose of 30 J/cm(2). RESULTS: Hypericin showed strong phototoxic effects and induced apoptosis in a dose-dependent fashion. The IC(50) value of hypericin phototoxicity was approximately 30 nM in both squamous and adenocarcinoma cells. In the concentrations used nonphotoactivated hypericin showed no toxic or apoptotic potency. The phototoxicity of hypericin was compared to that of delta-aminolevulinic acid (5-ALA), which is already being used for photodynamic therapy of gastrointestinal cancer. 5-ALA produced similar phototoxic effects but at a much higher dose (IC(50) 182+/-8 micro M in Kyse-140 and 308+/-40 micro M in OE-33 cells). Moreover, 5-ALA did not induce apoptosis to a relevant extent. CONCLUSION: Hypericin is a very promising new photosensitizer for innovative photodynamic therapy of esophageal cancer. Both the well known clinical safety of hypericin and the lower costs of broad band light sources argue in favor of clinical trials.

Adenocarcinoma↗
PubMed2000

The ootheca of Mastotermes darwiniensis Froggatt (Isoptera: Mastotermitidae): homology with cockroach oothecae.

The basal termite Mastotermes darwiniensis produces an egg mass, the nature of which is controversial. The debate centres on whether it is homologous with the oothecae of mantids and cockroaches and, if so, whether its simple structure is plesiomorphic or apomorphic within the Dictyoptera. To help resolve these issues we observed primary reproductives of M. darwiniensis during oviposition and examined the morphology of the reproductive product. Oviposition is cockroach-like in that the egg mass is assembled within the vestibulum and the eggs are issued externally in pairs. The reproductive product is an ootheca of the blattarian type. A distinct, tanned outer covering is stretched over the two parallel rows of eggs. No keel is present and no calcium oxalate crystals were apparent in the outer covering. We cannot rule out the possibility that the simple structure of the ootheca is plesiomorphic within Dictyoptera. However, based on (i) apomorphies shared by Mastotermes and Blattaria, and (ii) the life habits of Isoptera, a secondary reduction is the more plausible explanation.

Animals↗
PubMed2000

Phylogenetic analysis and trait evolution in Australian lineages of drywood termites (Isoptera, Kalotermitidae).

A phylogenetic analysis of Australian drywood termites (Isoptera, Kalotermitidae) based on partial sequence from the cytochrome oxidase II (COII) and cytochrome b genes is presented. In addition to providing new information on the evolutionary relationships among 25 species from seven genera, we evaluate the relative likelihoods of alternative topological hypotheses, including those derived from morphology-based classifications. We also test the applicability of a molecular clock for estimating the age of the Kalotermitidae and infer the evolution of species-specific variation for habitat type and soldier caste phragmosis by mapping this information onto the independently derived phylogeny. Maximum-likelihood analysis of both nucleotide and protein sequences from a multigene data set jointly support a single topology, which is shown to be the best estimate of the true phylogeny among the alternatives tested. Our results support the monophyly of all genera but question the discrimination between Procryptotermes and Cryptotermes. A basal dichotomy among generic groups suggests two principle lines of divergence within the family. Intergeneric relationships show mixed congruence to previous proposals, resulting in one morphology-based classification being rejected. A molecular clock hypothesis is not supported due to significant among-lineage rate heterogeneity in the COII gene. Patterns revealed through trait mapping suggest that the most recently diverged taxa tend to occupy the driest habitats and that these same taxa reflect a defensive transition away from large mandibulate soldiers toward small phragmotic soldiers. The association between habitat and defensibility supports the hypothesis that these two characters have been tightly linked throughout the social diversification of termites.

Animals↗
PubMed2000

[Atlanto-axial rotation and distance in small children. A postmortem study].

The aetiology of atlanto-axial rotatory subluxation is obscure. Therefore, a post mortem investigation was designed in order to evaluate the C 1-2 rotation and translation mobility and to clear the borderline between mobility and instability and to clear the role of the atlanto-axial joints in atlanto-axial rotatory subluxation. C 1-2 specimen of 2 months, 9 months and 53 months old children were used. In the intact specimen and after sequential decision of the atlanto-axial joint capsule, the atlanto-axial membrane, the transverse ligament of the atlas, and eventually the alar ligaments, the atlas was rotated and anteriorly translated over the axis. The end point of the movements was recorded radiographically. Decision of the anatomic structures increased the rotation of up to 25 degrees. The joint capsules are lax and wide thus allowing rotation with almost complete subluxation. The subluxation of atlanto-axial joints probably stays within the normal range of motion and is not a factor of atlanto-axial rotatory subluxation. Interlocking of the facets could not be observed. In atlanto-axial rotatory subluxation the atlanto-dental interval becomes asymmetric. Its radiographic projection is variable and therefore ist does not present a valuable radiographic parameter.

Age Factors↗
PubMed2000

Head and neck tumors: imaging recurrent tumor and post-therapeutic changes with CT and MRI.

OBJECTIVE: To evaluate criteria for detection of tumor recurrence and post-treatment changes in patients with head and neck malignancies in computed tomography (CT) and magnetic resonance imaging (MRI). METHODS AND MATERIALS: Thirty-nine patients with head and neck carcinoma receiving radiochemotherapy were examined before, during and after therapy with MRI. Changes in signal intensity were correlated to histology or clinical course. Three hundred and thirty-one patients with head and neck malignancies were examined with CT after therapy. CT diagnoses were correlated with histology or clinical course. RESULTS: Main criteria for recurrent/residual tumor in MRI was infiltrative mass with high signal intensity in T2-weighted images and enhancement after Gd-DTPA in T1-weighted images. Radiation-induced changes led to false positive diagnosis in 46% in the interval up to 3 months after therapy and in 58% in the interval 3-6 months after therapy. The combination of a circumscribed, infiltrative mass with contrast enhancement in CT had a sensitivity of 86% and a specificity of 80%. CONCLUSION: CT could accurately demonstrate postoperative changes and tumor recurrence. MRI had advantages in differentiation of tumor and scar, but edema after radiation therapy can spoil diagnosis.

Combined Modality Therapy↗
PubMed2000

2D and 3D visualisation of head and neck tumours from spiral-CT data.

PURPOSE: This paper intends to demonstrate the possibilities of two- and three-dimensional visualisation methods from spiral-CT data sets in the head and neck region and demonstrates their value based on various studies. MATERIAL AND METHODS: The scanner was a Somatom PLUS 4 (Siemens, Forchheim/Germany). The patients were scanned using a slice thickness of 3 mm and a table feed of 5 mm (pitch 1,6). The images were reconstructed with an increment of 1 mm. Contrast agent (150 ml) was applied intravenously with a flow of 2.5 ml/s and a start delay of 80 s. In one study the start delay was 20 s in order to visualise the carotid arteries (extracranial aneurysm). Volumetric data sets were postprocessed with 'Vitrea' and 'VoxelView' (Vital Images) volume rendering software on a Silicon Graphics O2 workstation (virtual laryngoscopy). Multiplanar reformation and colour-coded 3D-reconstruction were done on a Prominence workstation (Siemens/Forchheim/Germany). RESULTS: In every region of the head and neck MPRs are useful as additional planes (with the exception of the hypopharynx and the larynx), SSDs are always useful if there is extensive bony destruction (skull, spine, skeleton larynx). Colour-coded three-dimensional reformations may be done for extensive tumours and before multi-specialty surgery. Perspective volume rendering is already in use for virtual endoscopy of the paranasal sinuses and the virtual laryngoscopy. In temporal bone evaluation, perspective volume rendering is a new and promising method of the future to assess the inner ear. SUMMARY: Two- and three-dimensional displays are used to visualise pathological findings in their topographic relation to anatomical leading structures. Thus, the radiologist can point out to the clinician the pathological findings by some essential images without having to demonstrate all axial slices.

Aneurysm↗
PubMed2000

Imaging of head and neck tumors--methods: CT, spiral-CT, multislice-spiral-CT.

Spiral-CT is standard for imaging neck tumors. In correspondence with other groups we routinely use spiral-CT with thin slices (3 mm), a pitch of 1.3-1.5 and an overlapping reconstruction increment (2-3 mm). In patients with dental fillings a short additional spiral parallel to the corpus of the mandible reduces artifacts behind the dental arches and improves the diagnostic value of CT. For the assessment of the base of the skull, the orbital floor, the palate and paranasal sinuses an additional examination in the coronal plane is helpful. Secondary coronal reconstructions of axial scans are helpful in the evaluation of the crossing of the midline by small tumors of the tongue base or palate. For an optimal vascular or tissue contrast a sufficient volume of contrast medium and a start delay greater than 70-80 s are necessary. In our opinion the best results can be achieved with a volume of 150 ml, a flow of 2.5 ml/s and a start delay of 80 s. Dynamic enhanced CT is only necessary in some special cases. There is clear indication for dynamic enhanced CT where a glomus tumor is suspected. Additional functional CT imaging during i-phonation and/or Valsalva's maneuver are of great importance to prove vocal cords mobility. Therefore, imaging during i-phonation is an elemental part of every thorough examination of the hypopharynx and larynx region. Multislice-spiral-CT allows almost isotropic imaging of the head and neck region and improves the assessment of tumor spread and lymph node metastases in arbitrary oblique planes. Thin structures (the base of the skull, the orbital floor, the hard palate) as well as the floor of the mouth can be evaluated sufficiently with multiplanar reformations. Usually, additional coronal scanning is not necessary with multislice-spiral-CT. Multislice-spiral-CT is especially advantageous in defining the critical relationships of tumor and lymph node metastases and for functional imaging of the hypopharynx and larynx not only in the transverse plane but also in the coronal plane.

Glomus Tumor↗
PubMed2000

Methods: MRT.

MRI has become the imaging method of choice in special regions of the head and neck (e.g. nasopharynx, oropharynx, oral cavity, floor of the mouth). Superconducting MR-equipment with field strengths of 1.0-1.5 T are appropriate for the evaluation of the head and neck region. Signal acquisition is optimal with circular polarized head coils or with specially designed surface coils; the body coil is insufficient.When imaging tumors we need T1 contrast, T2 contrast and contrast medium information (enhancement information). For the T1 contrast T1-spin-echo is and remains the best sequence. For T2-contast T2 turbo-spin-echo with fat suppression has replaced the T2 spin-echo sequences because it is faster and shows good contrast between tumor and saturated fat tissue. Fat saturated T1 turbo-spin-echo enables best tissue contrast after Gd-DTPA application.

Contrast Media↗
PubMed2000

Paranasal sinuses and nasopharynx CT and MRI.

Neoplastic disease of the nose, paranasal sinuses, the nasopharynx and the parapharyngeal space requires thorough assessment of location and extent in order to plan appropriate treatment. CT allows the deep soft tissue planes to be evaluated and provides a complement to the physical examination. It is especially helpful in regions involving thin bony structures (paranasal sinuses, orbita); here CT performs better than MRI. MRI possesses many advantages over other imaging modalities caused by its excellent tissue contrast. In evaluating regions involving predominantly soft tissue structures (ec nasopharynx and parapharyngeal space) MRI is superior to CT. The possibility to obtain strictly consecutive volume data sets with spiral CT or 3D MRI offer excellent perspectives to visualize the data via 2D or 3D postprocessing. Because head and neck tumors reside in a complex area, having a 3D model of the anatomical features may assist in the delineation of pathology. Data sets may be transferred directly into computer systems and thus be used in computer assisted surgery.

Angiofibroma↗
PubMed2000

Oropharynx, oral cavity, floor of the mouth: CT and MRI.

Pretherapeutic staging of tumors of the oropharynx, the oral cavity and the floor of the mouth is important and should be thorough and exact to ensure appropriate therapy. Particularly important is the assessment of infiltration of deeper compartments and the topographic relationship of tumor to vascular structures (lingual artery and vein, hypoglossal nerve), or the presence of spread of the tumor across the midline. As spread of tumor may occur to a large degree underneath normal appearing mucosa, clinical assessment of the true tumor extent is difficult. In the last 20 years computed tomography (CT) has proved its value as a supplementary non-invasive method and established its role in modern diagnostic evaluation. Magnetic resonance imaging (MRI) is an non-invasive scanning method that offers excellent tissue contrast. Ultrasonography (US) is of secondary importance, but provides useful guidance due to its wide availability and its easy use. This paper aims to depict the possibilities of modern CT and MRI to provide 'one-stop-shopping' information to the clinician as a basis for the right therapeutic approach and correct estimation of the individual patient's prognosis. A clear problem oriented imaging strategy with standardized diagnostic criteria will lead to a cost effective evaluation.

Contrast Media↗
PubMed2000

[Diagnosis of glomus jugulare tumor recurrence with dynamic contrast medium flow in MRI].

PURPOSE: To evaluate the ability of dynamic MRI to differentiate residual tumor from scar after glomus jugulare (GJ) surgery. METHODS: 26 patients after GJ surgery were examined with dynamic contrast medium MRI on a 1.5 T Philips-Gyro-Scan NT. A T1-weighted TFE sequence was performed to localise the 5 slices for the dynamic study. Subsequently, a T1-weighted TFE sequence was used for the dynamic contrast medium study. We started contrast medium administration and TFE sequence at the same time. The time until acquisition of the first image was 7.4 s, and the interval between two images 7 s (total time 2.24 min). Intensity versus time studies were performed in the region of interest. RESULTS: 2 typical intensity versus time graphs were observed: residual tumors showed a rapid increase in signal intensity, followed by a "wash-out" phase, and a plateau phase in the later course. Scar showed a moderate increase in signal intensity, followed by a plateau phase on a low intensity level. In 9 patients, in whom tumor removal was subtotal, we saw the typical graph of a GJ tumor. 4 of 17 patients with complete tumor removal showed a typical graph like that of residual tumor, 13 of 17 patients showed the typical graph of a scar. CONCLUSION: With dynamic contrast medium MRI studies, differentiation between residual tumor and scar is possible in patients with prior GJ surgery.

Cicatrix↗
PubMed1999

[The morphological and functional diagnosis of the head-neck area with multiplanar spiral CT].

PURPOSE: To evaluate the improvement of multislice-spiral CT in the assessment of head and neck tumors. MATERIAL AND METHODS: 80 patients with suspected tumor in the head and neck region were examined with MSCT (Somatom Plus 4 VZ) after the administration of i.v. contrast material. Slice collimation was 4 x 1 mm with a pitch factor of 6. Additional multiplanar reformations were calculated in each case. RESULTS: The specific anatomy and pathways of tumor spread is difficult to demonstrate in cross-sectional imaging. Tumor infiltration of the base of the skull or the palate could be depicted or excluded on coronal MPR, additional coronal scanning was not necessary. The detection of pathologic lymph nodes was improved with MPR in 7 patients. DISCUSSION: The exact determination of tumor margins is mandatory for modern therapy concepts of limited surgery. High resolution datasets are basis for reformations in arbitrary planes, making additional coronal scanning not necessary. Functional imaging of the larynx and hypopharynx improve the diagnostic accuracy of CT, a short scan time is necessary to reduce motion artifacts. Conclusive assessment of tumor infiltration, lymphatic spread and functional alterations is improved with MSCT.

Contrast Media↗