[en] The Simplified Theory of Plastic Zones (STPZ) is a direct method based on Zarka's method, primarily developed to estimate post-shakedown quantities of structures under cyclic loading, avoiding incremental analyses through a load histogram. In a different paper the STPZ has previously been shown to provide excellent estimates of the elastic–plastic strain ranges in the state of plastic shakedown as required for fatigue analyses. In the present paper, it is described how the STPZ can be used to predict the strains accumulated through a number of loading cycles due to a ratcheting mechanism, until either elastic or plastic shakedown is achieved, so that strain limits can be satisfied. Thus, a consistent means of estimating both, strain ranges and accumulated strains is provided for structural integrity assessment as required by pressure vessel codes. The computational costs involved typically consist of few linear elastic analyses and some local calculations. Multilinear kinematic hardening and temperature dependent yield stresses are accounted for. The quality of the results and the computational burden involved are demonstrated through four examples. - Highlights: • A method is provided to estimate accumulated elastic–plastic strains. • A consistent method is provided to estimate elastic–plastic strain ranges. • Effect of multilinear kinematic hardening is captured. • Temperature dependent material properties are accounted for. • Few linear elastic analyses required

[en] A review of some of the main characteristics of present day induction linacs is given

No abstract available

[en] Purpose: Evaluation of the potential of MRI concerning dissection of the supra-aortic vessels after cervical trauma. Patients and methods: During the time period from August 1998 to February 2001, 148 patients with trauma were examined by means of MRI scan of the neck / cervical spine or skull concerning morphology of the cervical spine as well as the brain tissue. MRI sequences were weighted T₁ and T₂ before and after contrast medium in transverse and sagittal slices. Additional time of flight (TOF) sequences and contrast-enhanced angiography were acquired. The MRI images were examined by two experienced radiologists when tied consensus was reached. Results: 7 patients (4,7%) with a total of 9 dissections of the vertebral and/or internal carotid artery were found; diagnosis was done on TOF images, contrast enhances MR-angiography, transversal T₁- and T₂-weighted sequences as well as T₁-weighted images post-contrast medium. Therapy was changed accordingly in 4 cases and anticoagulation initiated. Conclusion: All patients with cervical injuries should be screened by MRI including MR-angiography, T₁-weighted images pre- and post-contrast agent to achieve a sure diagnosis concerning the precise size of the dissection. MRI has proven to be an excellent diagnostic tool for our patient group. (orig.)

[en] The relation between height of lumbar discs (measured from lateral radiographic views) and disc degeneration (classified from MR images) deserves attention in view of the wide, often parallel or interchanged use of both methods. The time sequence of degenerative signs and decrease of disc height is controversial. To clarify the issue, this cross-sectional study documents the relation between disc degeneration and disc height in a selected cohort. Forty-three subjects were selected at random from a cohort examined for potential disc-related disease caused by long-term lifting and carrying. From each subject a lateral radiographic view of the lumbar spine as well as findings from an MR investigation of (in most cases) levels T12/L1 to L5/S1 were available; thus, n = 237 lumbar discs were available for measurement and classification. Disc height was measured from the radiographic views with a new protocol compensating for image distortion and permitting comparison with normal, age- and gender-appropriate disc height. Degeneration as well as disc height were classified twice from MR images by independent observers in a blinded fashion. Disc degeneration classified from MR images is not related to a measurable disc height loss in the first stage of degeneration, whereas progressive degeneration goes along with progressive loss of disc height, though with considerable interindividual variation. Loss of disc height classified from MR images is on average compatible with loss of disc height measured from radiographs. In individual discs, however, classification of height loss from MR images is imprecise. The first sign of disc degeneration (a moderate loss of nucleus signal) precedes disc height decrease. As degeneration progresses, disc height decreases. Disc height decrease and progress of degeneration, however, appear to be only loosely correlated. (orig.)

No abstract available

No abstract available

[en] Since musculoskeletal tumours comprise a large heterogeneous group of entities with different biological behaviour, clinical diagnosis of such lesions can be very difficult. The aim of this prospective study was to assess the usefulness of 2-[F-18]-fluoro-2-deoxy-d-glucose (FDG) positron emission tomography (PET) in the non-invasive evaluation of soft tissue tumours. One hundred and two patients with suspected soft tissue neoplasms were investigated by FDG-PET. The uptake of FDG was evaluated semiquantitatively by determining the tumour to background ratio (TBR). All patients underwent biopsy, resulting in the histological detection of 39 high-grade sarcomas, 16 intermediate-grade sarcomas, 11 low-grade sarcomas, 25 benign tumours, 10 tumour-like lesions such as spontaneous myositis ossificans (n = 6) and one non-Hodgkin lymphoma. All lesions except for two lipomas disclosed an increased FDG uptake. Sarcomas showed significantly higher TBR values than latent or active benign lesions (P<0.001) and aggressive benign lesions (P<0.05). Using a TBR cut-off level of 3.0 for malignancy, sensitivity of FDG-PET was 97.0%, specificity 65.7% and accuracy 86.3%. From our data there are three main conclusions: (1) Except for patients with pseudotumoral myositis ossificans, lesions with a TBR >3 were sarcomas (91.7%) or aggressive benign tumours (8.3%). (2) Tumours with a TBR <1.5 were latent or active benign lesions, exclusively. (3) The group with intermediate TBR values (<3 and >1.5) comprised primarily latent or active benign lesions, but also four aggressive benign tumours and two low-grade sarcomas. Our data suggest that FDG-PET represents a useful tool for the evaluation of the biological activity of soft tissue neoplasms. (orig.)

[en] Aim and methods: The aim of the present study was to evaluate the MRI criteria of infectious spondylitis (spondylodiscitis). The MR images of 23 patients suffering from spondylodiscitis (78% unspecific, 22% specific) were retrospectively analyzed. Results: The height of the intervertebral discs involved was normal in 40%, reduced in 43% and increased in 17% of the cases. The most common findings can be summarized in an MR triad: (1) The vertebral bodies involved are hypointense in T1-weighted images (100%) with a lack of delineation of the intervertebral discs (53%). (2) The injection of Gd-DTPA yields an enhancement of the vertebral bodies involved and intervertebral discs (95% and 74% respectively). (3) The vertebral bodies and intervertebral discs are hyperintense in T2-weighted sequences (76% and 90% respectively). (orig.)

[en] The data of studies performed in the 1980s, applying standard X-ray diagnostics sometimes supplemented by tomography, for the diagnosis of the most frequently occurring lesions caused by infectious spondylitis have been found to be better in diagnostic value than the information obtained by CT. Magnetic resonance imaging has been found to be clearly better than skeletal scintigraphy and X-ray diagnostics. The advantage of MR imaging basically is the more accurate anatomic localization and visualization of findings. In addition, MR imaging achieves good imaging of the paravertebral soft tissue and the vertebral canal. Degenerative and neoplastic lesions can be better distinguished from a vertebral osteomyelitis by means of the MRI, as compared to Tc-99m MDP scintigraphy, or X-ray diagnostics. Accumulations occurring after surgery at the invertebral disks in the region of the vertebral column cannot be distinguished by scintigraphy from inflammatory reactions. CT, on the other hand, detects minor abscess calcifications as a result of tuberculous spondylitis better than MR imaging. Early diagnosis of spondylitis is possible by scintiscanning and MRI, but cannot be expected from X-ray diagnostics. (orig./VHE)