Search

Purpose: The authors are developing a system for calibrated breast density measurements using full field digital mammography (FFDM). Breast tissue equivalent (BTE) phantom images are used to establish baseline (BL) calibration curves at time zero. For a given FFDM unit, the full BL dataset is comprised of approximately 160 phantom images, acquired prior to calibrating prospective patient mammograms. BL curves are monitored serially to ensure they produce accurate calibration and require updating when calibration accuracy degrades beyond an acceptable tolerance, rather than acquiring full BL datasets repeatedly. BL updating is a special case of generalizing calibration datasets across FFDM units, referred to as cross-calibration. Serial monitoring, BL updating, and cross-calibration techniques were developed and evaluated. Methods: BL curves were established for three Hologic Selenia FFDM units at time zero. In addition, one set of serial phantom images, comprised of equal proportions of adipose and fibroglandular BTE materials (50/50 compositions) of a fixed height, was acquired biweekly and monitored with the cumulative sum (Cusum) technique. These 50/50 composition images were used to update the BL curves when the calibration accuracy degraded beyond a preset tolerance of ±4 standardized units. A second set of serial images, comprised of a wide-range of BTE compositions, was acquired biweekly to evaluate serial monitoring, BL updating, and cross-calibration techniques. Results: Calibration accuracy can degrade serially and is a function of acquisition technique and phantom height. The authors demonstrated that all heights could be monitored simultaneously while acquiring images of a 50/50 phantom with a fixed height for each acquisition technique biweekly, translating into approximately 16 image acquisitions biweekly per FFDM unit. The same serial images are sufficient for serial monitoring, BL updating, and cross-calibration. Serial calibration accuracy was maintained within ±4 standardized unit variation from the ideal when applying BL updating. BL updating is a special case of cross-calibration; the BL dataset of unit 1 can be converted to the BL dataset for another similar unit (i.e., unit 2) at any given time point using the 16 serial monitoring 50/50 phantom images of unit 2 (or vice versa) acquired near this time point while maintaining the ±4 standardized unit tolerance. Conclusions: A methodology for monitoring and maintaining serial calibration accuracy for breast density measurements was evaluated. Calibration datasets for a given unit can be translated forward in time with minimal phantom imaging effort. Similarly, cross-calibration is a method for generalizing calibration datasets across similar units without additional phantom imaging. This methodology will require further evaluation with mammograms for complete validation. [ABSTRACT FROM AUTHOR]

Purpose: The Breast Imaging Reporting and Data System (BI-RADS) breast composition descriptors are used for standardized mammographic reporting and are assessed visually. This reporting is clinically relevant because breast composition can impact mammographic sensitivity and is a breast cancer risk factor. New techniques are presented and evaluated for generating automated BI-RADS breast composition descriptors using both raw and calibrated full field digital mammography (FFDM) image data. Methods: A matched case-control dataset with FFDM images was used to develop three automated measures for the BI-RADS breast composition descriptors. Histograms of each calibrated mammogram in the percent glandular (pg) representation were processed to create the new BRpg measure. Two previously validated measures of breast density derived from calibrated and raw mammograms were converted to the new BRvc and BRvr measures, respectively. These three measures were compared with the radiologist-reported BI-RADS compositions assessments from the patient records. The authors used two optimization strategies with differential evolution to create these measures: method-1 used breast cancer status; and method-2 matched the reported BI-RADS descriptors. Weighted kappa (κ) analysis was used to assess the agreement between the new measures and the reported measures. Each measure's association with breast cancer was evaluated with odds ratios (ORs) adjusted for body mass index, breast area, and menopausal status. ORs were estimated as per unit increase with 95% confidence intervals. Results: The three BI-RADS measures generated by method-1 had κ between 0.25-0.34. These measures were significantly associated with breast cancer status in the adjusted models: (a) OR = 1.87 (1.34, 2.59) for BRpg; (b) OR = 1.93 (1.36, 2.74) for BRvc; and (c) OR = 1.37 (1.05, 1.80) for BRvr. The measures generated by method-2 had κ between 0.42-0.45. Two of these measures were significantly associated with breast cancer status in the adjusted models: (a) OR = 1.95 (1.24, 3.09) for BRpg; (b) OR = 1.42 (0.87, 2.32) for BRvc; and (c) OR = 2.13 (1.22, 3.72) for BRvr. The radiologist-reported measures from the patient records showed a similar association, OR = 1.49 (0.99, 2.24), although only borderline statistically significant. Conclusions: A general framework was developed and validated for converting calibrated mammograms and continuous measures of breast density to fully automated approximations for the BI-RADS breast composition descriptors. The techniques are general and suitable for a broad range of clinical and research applications. [ABSTRACT FROM AUTHOR]

The laser sheath uses optical fibers, delivering pulsed ultraviolet excimer laser light, to vaporize fibrotic tissue binding intravenous cardiac leads to the vein or heart wall during lead extraction from the implant vein. The total investigational experience with laser sheaths is reported. During the period from October 1995 to December 1999. 2,561 pacing and defibrillator leads were treated in 1,684 patients at 89 sites in the United States with three sizes of laser sheath. Endpoints were complete removal of the lead, partial removal (leaving the tip behind), or failure (abandoning the lead, onset of complications, change to transfemoral or transatrial approach). Minimal follow-up at 30 days was recorded. Of the leads, 90% were completely removed. 3% were partially removed, and the balance were failures. Major perioperative complications (tamponade. hemothorax, pulmonary embolism, lead migration, and death) were observed in 1.9% of patients with in hospital death In 13 (0.8%). Minor complications were seen in an additional 1.4% of patients. Multivariate analysis showed that implant duration was the only preoperative independent predictor of failure; female sex was the only multivariate predictor of complications. Success and complications were not dependent on laser sheath size. At follow-up, various extraction related complications were observed in 2% of patients. The learning curve showed a trend toward fewer complications with experience. Lead extraction with the laser sheath can be safely practiced with high success rates. Success is independent of laser sheath size. Major complications can be expected in < 2% of patients, and occur more often during an investigator's early experience. [ABSTRACT FROM AUTHOR]

Of the 400,000-500,000 permanent pacemaker leads implanted worldwide each year, around 10% may eventually fail or become infected, becoming potential candidates for removal. Intravascular techniques for removing problematic or infected leads evolved over a 5-year period (1989-1993). This article analyzes results from January 1994 through April 1996, a period during which techniques were fairly stable. Extraction of 3,540 leads from 2,338 patients was attempted at 226 centers. Indications were: infection (27%), nonfunctional or incompatible leads (25%), Accufix® or Encor® leads (46%), or other causes (2%). Patients were 64 ± 17 years of age (range 5-96); 59% were men, 41% women. Leads were implanted 47 ± 41 months (maximum 26 years), in the atrium (53%), ventricle (46%), or SVC (1 %). Extraction was attempted via the implant vein using locking stylets and dilator sheaths, and/or transfemorally using snares, retrieval baskets, and sheaths. Complete removal was achieved for 93% of leads, partial for 5%, and 2% were not removed. Risk of incomplete or failed extraction increased with implant duration (P < 0.0001), less experienced physicians (P < 0.0001), ventricular leads (P < 0.005), noninfected patients (P < 0.0005), and younger patients (P < 0.0001). Major complications were reported for 1.4% of patients (< 1% at centers with > 300 cases), minor for 1.7%. Risk of complications increased with number of leads removed (P < 0.005) and with less experienced physicians (P < 0.005); risk of major complications was higher for women (P < 0.01). Given physician experience, appropriate precautions, and appropriate patient selection, contemporary lead removal techniques allow success with low complication rates. [ABSTRACT FROM AUTHOR]

Septicemia necessitates extraction of chronic pacemaker leads. Using locking stylets and sheaths to extract leads via the implantation vein (subclavian, cephalic, or jugular) and maneuvering devices, sheaths, and retrieval baskets via the femoral approach, extraction of 228 leads implanted 5 days to 240 months (mean 55 months) was attempted in 136 patients (mean 62 years) at 134 institutions. In addition to septicemia (9%) and infection (39%), total 48%, indications included prophylaxis/replacement (40%), and other (12%). Seventy-seven leads were atrial, 151 ventricular; 147 were unipolar, 81 bipolar; 96 had silicone insulation, 127 polyurethane. 1 poly/silicone, and 2 undetermined. Fixation included tines or fins (160), screw (40), flange (12), and other (16). One hundred and ninety-four leads were completely extracted, 19 partly extracted, and 15 not extracted. Procedural complications were: torn atrium requiring open heart repair (1), hemothorax requiring a chest tube and blood transfusions (1), subacute hemothorax requiring drainage 18 days after discharge (1), thrombosis treated by drugs (1), and myocurdial avulsion without sequela (1), Important observations included the significant (raining required due to the large number of possible clinical variables, and the need to be prepared for life-threatening cardiovascular complications. With training, procedures done at higher volume and lower volume institutions met with similar success. Conclusion: intravascular lead extraction is a viable technique whose benefits outweigh the risks, given the proper intensive training and open heart surgical backup, and may obviate the need fur open heart surgery for lead extraction. [ABSTRACT FROM AUTHOR]

In this report we describe fatigue of the His-Purkinje system during retrograde stimulation of the His bundle by ventricular programmed stimulation. The patient underwent electrophysiologic evaluation for syncope. Antegrade conduction and supraventricular studies were normal with the exception of baseline left bundle branch block. During programmed ventricular stimulation, the patient developed intra-Hisian and infra-Hisian block with symptomatic 3:1 atrioventricular heart block requiring insertion of a permanent pacemaker. This case demonstrates the need for careful study of both antegrade and retrograde conduction properties of the His bundle and atrioventricular node when performing standard His bundle studies in evaluation of syncope. [ABSTRACT FROM AUTHOR]

To establish the efficacy of a temperature-based pacemaker control algorithm, right ventricular temperature and heart rate were measured for 12-70 hours in eight patients (51 ± 17 years) and in one normal volunteer (28 years) during a variety of activities including exercise, rest, sleeping, eating, drinking, and bathing. A diurnal variation in heart rate and temperature was observed. Drinking caused transient temperature changes (less than one minute); during eating, increases of 0.07-0.36°C over 3-12 minutes were observed. An increase of 0.24°C over 8.5 minutes was observed in one patient during bathing. An abrupt drop in temperature was typically observed at the onset of exercise, followed by a steady temperature rise. During treadmill exercise, after a drop (0.13-0.48°C, Bruce n - 4; 0A6-0.34°C, Naughton, n = 3) during the first 1-2 minutes, temperature rose steadily through the end of peak exercise (0.45-1.01°C, Bruce; 0.28-0.47°C, Naughton). A temperature dip was also observed when a patient was told exercise would start but the treadmill failed to turn on. The dip is probably secondary to changes in blood flow from the peripheral circulation to the central system at the onset of exercise. Repeated exercise separated by short rests caused progressive blunting of the initial dip. Right ventricular temperature changes in a predictable manner with daily activity, allowing a temperature algorithm to detect rest and exercise. [ABSTRACT FROM AUTHOR]

From December 1988 to April 1994, the extraction of 2,195 intravascular pacing leads from 1.299 patients was attempted at 193 centers. Indications were: infection (54%, including 10% septicemia), pacemaker reoperation with removal of nonfunctional or incompatible leads (40%), and other causes (6%). Extraction was attempted via the implant vein using locking stylets and dilator sheaths, via the femoral vein using snares, retrieval baskets, and sheaths, or via both approaches. Leads had been implanted for 0.2 months to 24 years (mean 56 months). At the conclusion of the intravascular procedure, 86.8% of the leads were completely removed, 7.5% were partially removed, and 5.7% were not removed. For physicians performing their first case, 12% of leads were not removed; for physicians who had performed more than 10 cases, only 2% of leads were not removed. Of the 189 leads where extraction attempts had previously failed, 75.1% were completely removed, 14.8% were partially removed, and 10.1% were not removed. Scar tissue increased in severity with implant duration, was a complicating factor, and was the main cause of failure to remove leads. Use of the femoral approach increased with implant duration (5% of leads implanted 12 months or less, 11% of leads 13 months to 3 years, 20% of leads 4-7 years, and 31% of leads 8-24 years), primarily because of increasingly abundant scarring and prior lead damage. Fatal and near fatal complications occurred in 2.5%. including 8 (0.6%) deaths (3 hemopericardium/tamponade, 1 hemothorax, 3 pulmonary embolus, 1 stroke). With experienced operators, appropriate precautions, and appropriate patient selection, modern techniques allow the successful extraction of up to nearly 98% of intravascular leads with a relatively low incidence of complications. [ABSTRACT FROM AUTHOR]