Biomedical subjects

David J Schwartz

Publications and source records attributed to David J Schwartz.

5 recordsLinked to original sources

PubMed2005

Coordination copolymerization of severely encumbered isoalkenes with ethylene: enhanced enchainment mediated by binuclear catalysts and cocatalysts.

This contribution describes the implementation of the binuclear organotitanium "constrained geometry catalysts" (CGCs), (mu-CH(2)CH(2)-3,3'){(eta(5)-indenyl)[1-Me(2)Si((t)()BuN)](TiMe(2))}(2)[EBICGC(TiMe(2))(2); Ti(2)] and (mu-CH(2)-3,3'){(eta(5)-indenyl)[1-Me(2)Si((t)BuN)](TiMe(2))}(2)[MBICGC(TiMe(2))(2); C1-Ti(2)], in combination with the bifunctional bisborane activator 1,4-(C(6)F(5))(2)BC(6)F(4)B(C(6)F(5))(2) (BN(2)) in ethylene + olefin copolymerization processes. Specifically examined are the classically poorly responsive 1,1-disubstituted comonomers, methylenecyclopentane (C), methylenecyclohexane (D), 1,1,2-trisubstituted 2-methyl-2-butene (E), and isobutene (F). For the first three comonomers, this represents the first report of their incorporation into a polyethylene backbone via a coordination polymerization process. C and D are incorporated via a ring-unopened pathway, and E is incorporated via a novel pathway involving 2-methyl-1-butene enchainment in the copolymer backbone. In ethylene copolymerization, Ti(2) + BN(2) enchains approximately 2.5 times more C, approximately 2.5 times more D, and approximately 2.3 times more E than the mononuclear catalyst analogue [1-Me(2)Si(3-ethylindenyl)((t)BuN)]TiMe(2) (Ti(1)) + B(C(6)F(5))(3) (BN) under identical polymerization conditions. Polar solvents are found to weaken the catalyst-cocatalyst ion pairing, thus influencing the comonomer enchainment selectivity.

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PubMed2005

Factors associated with the frequency of self-intermittent catheterization after prostate brachytherapy.

PURPOSE: Urinary obstructive symptoms are the most common side effects of transperineal interstitial permanent prostate brachytherapy (TIPPB). Self-intermittent catheterization (SIC) can be used to relieve urinary retention. This study evaluated the factors associated with the probability of a patient performing SIC after TIPPB. METHODS AND MATERIALS: We prospectively evaluated 204 patients who underwent TIPPB at Mayo Clinic Scottsdale (MCS). All patients were taught to perform SIC before implant and were instructed to do so if they could not urinate at any time after the procedure. RESULTS: Of the 204 patients, 22 patients (11%) received (103)Pd seeds and 182 patients (89%) received (125)I. Thirty-seven (18%) patients received external-beam radiotherapy (XRT) in addition to the TIPPB. SIC was performed by 69 (34%) of the 204 patients. Factors that were significantly associated with a lower frequency of SIC were prostate volumes < or = 34.2 cm(3) (p = 0.005), < or = 137 seeds implanted (p = 0.04), prostate-specific antigen (PSA) levels < or = 6.35 (p = 0.03), American Urological Association (AUA) score < or = 10 (p = 0.01), the use of (125)I (p = 0.03), and the addition of XRT to the implant (p = 0.02). CONCLUSIONS: Significant associations were observed between the frequency of SIC and the number of seeds implanted, AUA scores, prostate volume, PSA levels, addition of XRT, and isotope used. Whereas the first four of these factors may be surrogates for prostate volume and obstructive symptoms in general, the last two factors are related to treatment decisions. These findings may aid in better patient selection and therapeutic decisions. Additionally, this information may provide a clearer understanding of the urinary side effects of TIBBP.

Analysis of Variance↗

PubMed2004

Selective identification of different brachytherapy sources, ferromagnetic seeds, and fiducials in the prostate using an automated seed sorting algorithm.

PURPOSE: Routine permanent prostate brachytherapy (PPB) includes CT-based postimplant dosimetry (PID). A method of identifying different source types from CT data in the same implant volume is described. METHODS AND MATERIALS: A previously described automatic method for seed localization using CT data is used in this study. Two cases were analyzed: a PPB case with (103)Pd followed by salvage (125)I implantation, both performed at another institution, and a cadaver case where 4 different seed types, including ferromagnetic seeds, and fiducials were implanted. RESULTS: Automatic segregation of different seed types with minimal manual correction is demonstrated using the described localization algorithm. The process is confirmed accurate by comparison of plain film radiographs to CT data and digitally reconstructed radiographs. CONCLUSION: Unique identification of different source types, including PPB seeds, fiducial markers, and ferromagnetic seeds in permanent implants is possible and permits dosimetric analyses that are spatially coincident.

Aged↗

PubMed2003

Radiation exposure to operating room personnel during transperineal interstitial permanent prostate brachytherapy.

PURPOSE: To identify factors associated with radiation exposure (RE) to operating room personnel during transperineal interstitial permanent prostate brachytherapy (TIPPB). METHODS AND MATERIALS: Between May 1998 and December 2000, 155 patients underwent TIPPB with fluoroscopic and ultrasound guidance. Data for each case included: operating room time (OT), anesthesia time (AT), fluoroscopy time (FT), number and type of seed implanted, total seed activity, and resident participation. RESULTS: Personnel RE per case, FT, OT, and AT decreased as case number increased. Whole body badge dose per case decreased from a mean of 0.15+/-0.01 mSv (15+/-1 mrem) in 1998 to 0.074+/-0.011 mSv (7+/-1 mrem) in 2000. Average FT per case decreased from a mean of 17:27 min (range, 10:40-28:23) in 1998 to 12:08 min (range, 6:40-31:00) in 2000. Resident participation was associated with increased FT. Mean whole body and ring badge doses for the treating radiation oncologist were 0.0076 mSv/min (0.76 mrem/min) and 0.05 mSv/min (5.26 mrem/min) of FT, respectively. CONCLUSIONS: FT was the predominant factor that related to RE during TIPPB. Treating radiation oncologists were exposed to less than 20 mSv per 100 cases, significantly less than other fluoroscopically guided procedures. Nonetheless, appropriate radiation exposure precautions during TIPPB should continue.

Body Burden↗

PubMedDate not supplied

Building a cardiology practice.

This study was designed to quantify the clinical and marketing effectiveness of the Pocket EKG Clinical Based Marketing Program by measuring its impact on new patient visits, patient satisfaction, payor negotiations, and patient management at Pikes Peak Cardiology (PPC), Colorado Springs, Colorado. New patient visits were found to increase by 22% for 6.5 consecutive years. Ninety-two percent of patients surveyed found that the Pocket EKG Card promoted loyalty to the cardiology practice. The Pocket EKG Patient Satisfaction Survey was proven to satisfy Health Plan Employer Data and Information Set (HEDIS) guidelines as required in payor contracting. Finally, access to a baseline electrocardiogram contributed to a 54% reduction in unnecessary hospitalization. The Pocket EKG Clinical Based Marketing Program proved to successfully market PPC to its three customers: patients, payors, and primary care physicians.

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