PubMed Health⌕ Search

Biomedical subjects

J Leupold

Publications and source records attributed to J Leupold.

7 recordsLinked to original sources
PubMed2006

Alternating repetition time balanced steady state free precession.

A novel balanced SSFP technique for the separation or suppression of different resonance frequencies (e.g., fat suppression) is presented. The method is based on applying two alternating and different repetition times, TR(1) and TR(2). This RF scheme manipulates the sensitivity of balanced SSFP to off-resonance effects by a modification of the frequency response profile. Starting from a general approach, an optimally broadened stopband within the frequency response function is designed. This is achieved with a TR(2) being one third of TR(1) and an RF-pulse phase increment of 90 degrees . With this approach TR(2) is too short ( approximately 1 ms) to switch imaging gradients and is only used to change the frequency sensitivity. Without a significant change of the spectral position of the stopband, TR(1) can be varied over a range of values ( approximately 2.5-4.5 ms) while TR(2) and phase cycling is kept constant. On-resonance spins show a magnetization behavior similar to balanced SSFP, but with maximal magnetization at flip angles about 10 degrees lower than in balanced SSFP. The total scan time is increased by about 30% compared to conventional balanced SSFP. The new technique was applied on phantoms and volunteers to produce rapid, fat suppressed images.

Humans↗
PubMed2005

Double average parallel steady-state free precession imaging: optimized eddy current and transient oscillation compensation.

Balanced steady-state free precession (SSFP) imaging is sensitive to off-resonance effects, which can lead to considerable artifacts during a transient phase following magnetization preparation or steady-state interruption. In addition, nonlinear k-space encoding is required if contrast-relevant k-space regions need to be acquired at specific delays following magnetization preparation or for transient artifact reduction in cardiac-gated k-space segmented CINE imaging. Such trajectories are problematic for balanced SSFP imaging due to nonconstant eddy current effects and resulting disruption of the steady state. In this work, a novel acquisition strategy for balanced SSFP imaging is presented that utilizes scan time reduction by parallel imaging for optimized "double average" eddy current compensation and artifact reduction during the transient phase following steady-state storage and magnetization preparation. Double average parallel SSFP imaging was applied to k-space segmented CINE SSFP tagging as well as nongated centrically encoded SSFP imaging. Phantom and human studies exhibit substantial reduction in steady-state storage and eddy current artifacts while maintaining spatial resolution, signal-to-noise ratio, and similar total scan time of a standard SSFP acquisition. The proposed technique can easily be extended to other acquisition schemes that would benefit from nonlinear reordering schemes and/or rely on interruption of the balanced SSFP steady state.

Algorithms↗
PubMed2001

Long-term results following ankle arthrodesis for post-traumatic arthritis.

BACKGROUND: Ankle arthrodesis is considered by many to be the standard operative treatment for end-stage ankle arthritis; however, the long-term effect of ankle arthrodesis on other lower-extremity joints remains largely unknown. The purpose of this study was to perform a clinical and radiographic review to determine the effect of ankle arthrodesis on the development of osteoarthritis in other lower-extremity joints. METHODS: Twenty-three patients who had had an isolated ankle arthrodesis for the treatment of painful posttraumatic arthritis of the ankle were followed for a mean of twenty-two years (range, twelve to forty-four years) after the operation. Each completed standardized, self-reported outcome questionnaires (the Foot Function Index, Western Ontario and McMaster University Osteoarthritis Index [WOMAC], and Short Form-36 [SF-36]), was examined clinically by two of the investigators, and underwent complete radiographic examination of the knee, ankle, and foot bilaterally. The radiographic grade of osteoarthritis was determined for each joint, and the levels of overall activity limitation, pain, and disability were determined for each patient from the clinical findings and questionnaire information. RESULTS: Osteoarthritis of the ipsilateral subtalar (p<0.0001), talonavicular (p<0.0001), calcaneocuboid (p<0.0001), naviculocuneiform (p = 0.0012), tarsometatarsal (p = 0.0009), and first metatarsophalangeal joints (p = 0.0012) was consistently more severe than the osteoarthritis of those joints on the contralateral side. Osteoarthritis did not develop more frequently in the ipsilateral knee or lesser metatarsophalangeal joints than it did on the contralateral side. Significant differences between the two sides were found with regard to overall activity limitation (p<0.0001), pain (p<0.0001), and disability (p<0.0001), with the involved side consistently more symptomatic. CONCLUSIONS: To our knowledge, the present series represents the longest follow-up study of ankle arthrodesis to date. Our cohort of patients all had isolated post-traumatic ankle arthritis, and each underwent a successful isolated ankle arthrodesis. At a mean of twenty-two years, the majority of the patients had substantial, and accelerated, arthritic changes in the ipsilateral foot but not the knee. They were often limited functionally by foot pain. Although ankle arthrodesis may provide good early relief of pain, it is associated with premature deterioration of other joints of the foot and eventual arthritis, pain, and dysfunction.

Activities of Daily Living↗
PubMed2001

Birth as a multidimensional experience: comparison of the English- and German-language versions of Salmon's Item List.

Results concerning satisfaction with the birth experience in different trials are difficult to compare, owing to a lack of internationally used research scales. Salmon's Item List (SIL) is easy-to-handle and would therefore be very helpful for research as well as for obstetric clinic quality control. Two hundred and fifty-one patients were investigated using a German-language version of SIL (SIL-ger); the statistical evaluation was carried out by means of a principal components analysis. Principal components analysis revealed two major findings: (1) as stated by other authors the birth experience is multidimensional, each aspect influencing the others in a non-linear way; (2) in addition to Salmon's dimensions (i.e. postnatal 'fulfillment', intranatal 'physical discomfort' and intranatal 'emotional distress') another postnatal dimension labeled 'negative emotional experience' was detected. Not only are intranatal experiences multidimensional, but so too are evaluative feelings afterwards. In addition to fulfillment, as developed by Salmon, a dimension of negative emotional experience needs to be taken into account. This dimension does not correlate in a linear way with fulfillment. It is appropriate to use SIL in research. Before using it for purposes of clinical quality control, however, larger samples need to be evaluated in order to prove the stability of the factor structure.

Cross-Cultural Comparison↗
PubMed1999

Sites of simian foamy virus persistence in naturally infected African green monkeys: latent provirus is ubiquitous, whereas viral replication is restricted to the oral mucosa.

Foamy viruses (FV), retroviruses of the genus Spumavirus, are able to infect a wide variety of animal species and replicate in nearly all types of cultured cells. To identify the cells targeted by FV in the natural host and define the sites of viral replication, multiple organs of four African green monkeys naturally infected with simian FV type 3 were investigated for the presence of FV proviral DNA and viral transcripts. All organs contained significant amounts of FV proviral DNA. In addition to proviruses containing the complete transactivator gene taf, proviral genomes carrying a specific 295-bp deletion in the taf gene were detected in all monkeys. As in the case of human foamy virus the deletion leads to the formation of the bet gene that is regarded to be instrumental in the regulation of viral persistence. FV RNA was detected by RT-PCR and in situ hybridization only in the oral mucosa of one monkey. No other samples contained detectable levels of viral transcripts. Histopathological changes were not observed in any of the tissue samples analyzed. Our results show that the natural history of FV is characterized by latent infection in all organs of the host and by minimal levels of harmless viral replication in the oral mucosa. The broad host cell range in vivo further encourages the development of FV-derived vectors for therapeutic gene delivery.

Animals↗