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J Rochelle

Publications and source records attributed to J Rochelle.

7 recordsLinked to original sources
PubMed2004

Lutetium oxyorthosilicate block detector readout by avalanche photodiode arrays for high resolution animal PET.

Avalanche photodiodes (APDs) have proven to be useful as light detectors for high resolution positron emission tomography (PET). Their compactness makes these devices excellent candidates for replacing bulky photomultiplier tubes (PMTs) in PET systems where space limitations are an issue. The readout of densely packed, 10 x 10 lutetium oxyorthosilicate (LSO) block detectors (crystal size 2.0 x 2.0 x 12 mm3) with custom-built monolithic 3 x 3 APD arrays was investigated. The APDs had a 5 x 5 mm2 active surface and were arranged on a 6.25 mm pitch. The dead space on the edges of the array was 1.25 mm. The APDs were operated at a bias voltage of approximately 380 V for a gain of 100 and a dark current of 10 nA per APD. The standard deviation in gain between the APDs in the array ranged from 1.8 to 6.5% as the gain was varied from 50 to 108. A fast, low-noise, multi-channel charge sensitive preamplifier application-specific integrated circuit (ASIC) was developed for the APD readout. The amplifier had a rise time of 8 ns, a noise floor of 515 e- rms and a 9 e- pF(-1) noise slope. An acquired flood image showed that all 100 crystals from the block detector could be resolved. Timing measurements with single-channel LSO-APD detectors, as well as with the array, against a plastic scintillator and PMT assembly showed a time resolution of 1.2 ns and 2.5 ns, respectively. The energy resolution measured with a single 4.0 x 4.0 x 10 mm3 LSO crystal, wrapped in four-layer polytetrafluoroethylene (PTFE) tape and coupled with optical grease on a single APD of the array, yielded 15% (full width at half maximum, FWHM) at 511 keV. Stability tests over 9 months of operation showed that the APD arrays do not degrade appreciably. These results demonstrate the ability to decode densely packed LSO scintillation blocks with compact APD arrays. The good timing and energy resolution makes these detectors suitable for high resolution PET.

Equipment Design↗
PubMed2001

No incremental benefit of multisite atrial pacing compared with right atrial pacing in patients with drug refractory paroxysmal atrial fibrillation.

OBJECTIVE: To evaluate the incremental antifibrillatory effect of multisite atrial pacing compared with right atrial pacing in patients with drug refractory paroxysmal atrial fibrillation paced for arrhythmia prevention alone. METHODS: In 20 of these patients (mean (SD) age 64 (8) years; 14 female, six male), a single blinded randomised crossover study was performed to investigate the incremental benefit of one month of multisite atrial pacing compared with one month of right atrial pacing. Outcomes included the number of episodes of paroxysmal atrial fibrillation, their total duration obtained from pacemaker Holter memory, and quality of life using a cardiac specific questionnaire (the modified Karolinska questionnaire). RESULTS: Comparing right atrial with multisite atrial pacing, there was no significant change in either the number of paroxysmal atrial fibrillation episodes (mean (SD): right atrial pacing 77 (98) episodes v multisite pacing 52 (78) episodes, NS) or their total duration (right atrial, 4.8 (5.4) days v multisite, 6.3 (9.8) days, NS). Quality of life scores compared with baseline status were equally improved by either pacing strategy (mean percentage improvement: right atrial, 38%, p = 0.003; multisite, 44%, p = 0.003). There was no significant difference in life scores comparing the two pacing modes. CONCLUSIONS: Multisite atrial pacing has no incremental antiarrhythmic effect compared with right atrial pacing in patients paced for drug refractory paroxysmal atrial fibrillation. Quality of life is equally improved with either pacing strategy, with no differences between them.

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PubMed1999

Evaluation of biatrial pacing, right atrial pacing, and no pacing in patients with drug refractory atrial fibrillation.

It has been suggested biatrial pacing may prevent the recurrence of atrial fibrillation (AF). To further evaluate this hypothesis, we performed a randomized, single-blinded study in 19 patients with drug refractory AF. The study compared biatrial pacing with conventional right atrial (RA) pacing and a control period of inhibited pacing. The pacing modes utilized were DDD with a base rate of 70 beats/min for biatrial and RA pace (with and without biatrial resynchronization, respectively) and 40 beats/min for the control period. The duration of each pacing mode was 3 months. The number of AF episodes and their duration were obtained from pacemaker Holter memory (Chorus RM ELA Medical). Comparison of the control period (n = 11) with either pacing strategy showed a significant decrease in the total duration of AF (control 27 +/- 35 days, biatrial 8 +/- 15 days p = 0.02, RA 11 +/- 27 days p = 0.04). However, there was no effect on the number of AF episodes (control 79 +/- 108, biatrial 36 +/- 75 p = 0.32, RA 41 +/- 80 p = 0.11). The total percentage of atrial pacing also significantly increased when the control period (6 +/- 9%) was compared with both RA pace (62 +/- 33%, p = 0.008) and biatrial pace (63 +/- 31, p = 0.003). When biatrial pacing was compared with RA pace (n = 19), there was no significant difference in either the duration of AF (biatrial 16 +/- 26 days vs RA 19 +/- 31 days, p = 0.7) or the number of AF episodes (biatrial 56 +/- 91 vs RA 87 +/- 106, p = 0.34). In conclusion, pacing (either type) at a base rate of 70 beats/min has an antifibrillatory effect when compared with inhibited pacing at 40 beats/min. No additional benefit of biatrial pacing over right atrial pacing was demonstrated in this study.

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PubMed1994

Rapid and efficient construction of yeast artificial chromosome contigs in the mouse genome with interspersed repetitive sequence PCR (IRS-PCR): generation of a 5-cM, > 5 megabase contig on mouse chromosome 1.

We have developed a new technique for the generation of YAC contigs in the mouse genome that is based on the ability to detect overlapping clones by hybridization of shared IRS-PCR products. As a demonstration of the technique, a 5-cM, > 5 megabase contig was developed on the distal half of mouse Chromosome (Chr) 1, spanning the region from Lamb2 to At3. The contig covers roughly 5% of the genetic distance of the chromosome and is comprised of more than 80 clones; 71 probes were assigned physical order to the chromosome, of which 59 were new markers generated in this study. Eight of the new probes were shown to be polymorphic between C3H/HeJ-gld and M. spretus. Three probes were mapped on a [(C3H/HeJ-gld x M. spretus) x C3H/HeJ-gld] interspecific backcross to integrate the physical map with a high-resolution genetic map of the region.

Animals↗
PubMed1994

A rate responsive pacemaker that physiologically reduces pacing rates at rest.

Current rate responsive pacemakers incorporate sensors such as minute ventilation (MV) for adapting to changing patient conditions during exercise and periods of exertion. However, for sleep and/or rest periods, the only pacemakers currently on the market that slow the pacing rate utilize an internal timer to determine a decrease in pacing rate. It would be advantageous if the pacing rate could be automatically lowered during periods of sleep or rest. This study utilized a rate responsive sensor, MV, to track the patient's sleeping and resting periods and to decrease the pacing rate at such times. A total of eight patients implanted with Sentri 1210 single chamber MV sensor pacemakers were studied. A sleep rate (SR) of 45 beats/min was selected. A sleep rate response function, which indicated the relationship between changes in MV and corresponding heart rate, was initially set at a value of 16 and continually and automatically updated in a 3-month study. Adaptation was based on the premise that 3 hours per day should be spent at the SR. The average decrease in pacing rates from onset to 3 month for the eight patients was 12.4% +/- 5.3%. Correspondingly, the histograms of the lowest datalog histogram (40-59 beats/min) increased from 0% to 15.4% +/- 0.9% of paced beats. Correlation between the patients' 24-hour diary and Holter recordings showed that the pacing rates during sleep were consistently lower than when the patients were awake and active. This was also the case with a patient whose nocturnal and daily routine was intentionally altered.(ABSTRACT TRUNCATED AT 250 WORDS)

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PubMed1993

Single-strand conformational polymorphism (SSCP) mapping of the mouse genome: integration of the SSCP, microsatellite, and gene maps of mouse chromosome 1.

Interspersed repetitive sequence (IRS) PCR and repetitive element-to-bubble (IRS-bubble) PCR have been utilized to rapidly generate large numbers of mouse-specific, chromosome 1-enriched STSs from mouse-hamster somatic cell hybrids. Single-strand conformational polymorphism (SSCP) has been used to localize 39 new repetitive element-linked STSs to the mouse map: 22 to Chr 1, 10 to Chr. 15, 2 each to Chrs 12 and 14, and three to Chr 7. In addition, we have integrated the SSCP, single-strand length polymorphism, and restriction fragment length polymorphism maps of mouse Chr. 1, resulting in a high-density map of the chromosome, containing over 100 loci, all typed on a single interspecific backcross.

Animals↗