Biomedical subjects

R Wojcik

Publications and source records attributed to R Wojcik.

7 recordsLinked to original sources

PubMed2001

Preinjury warfarin does not impact outcome in trauma patients.

OBJECTIVE: The objective of this study was to determine whether the preinjury condition of anticoagulation had an adverse impact on patients sustaining injury. METHODS: A retrospective analysis was performed for prospectively collected registry data from 1995-2000 from all accredited trauma centers in Pennsylvania. The registry was queried for all trauma patients who had anticoagulation therapy as a preinjury condition (PIC). This group served as our experimental cohort. A control cohort (not having warfarin therapy as a PIC) was developed using case-matching techniques for age, sex, Glasgow Coma Scale (GCS), Injury Severity Score (ISS), A Severity Characterization of Trauma (ASCOT) score, and in the head injured patients, International Classification of Diseases, Ninth Revision, Clinical Modification (ICD-9-CM) diagnoses. Head and non-head injured patients were evaluated separately. The cohorts were examined for 28-day mortality, intensive care unit length of stay (ICU-LOS), hospital length of stay (HOS-LOS), PICs, occurrences, discharge destinations, and functional status at discharge. Chi2 and Student's t test were used to evaluate the data; p values < 0.05 were considered significant. RESULTS: Two thousand nine hundred forty-two patients were available for analysis. The prevalence of PICs was significantly greater in the warfarin group for both the head and non-head injured populations (p < 0.003 and p < 0.0001, respectively). The incidence of occurrences in the non-head injured population was statistically higher for the warfarin patients (p < 0.001), but showed no difference in the head injured group regardless of warfarin use (p = 0.15). Functional status at discharge demonstrated no clinically significant difference between the warfarin and non-warfarin groups in both head and non-head injured populations. There was no difference in discharge destination in the head injured population; however, in the non-head injured population a greater percentage of non-warfarin patients was discharged to home when compared with the warfarin patients. CONCLUSION: Our data suggest that the PIC of anticoagulation with warfarin does not adversely impact mortality or LOS outcomes in both head and non-head injured patients. In non-head injured patients, however, the occurrence rates and discharge destination were different. More research needs to be done to determine whether this is related to anticoagulation or other reasons (i.e., number of PICs). These data should be used when weighing risk/benefit ratios of prescribing chronic anticoagulation.

Aged↗

PubMed2001

Positron emission mammography-guided breast biopsy.

UNLABELLED: Positron emission mammography (PEM) is a technique to obtain planar images of the breast for detection of potentially cancerous, radiotracer-avid tumors. To increase the diagnostic accuracy of this method, use of minimally invasive methods (e.g., core biopsy) may be desirable for obtaining tissue samples from lesions detected with PEM. The purpose of this study was to test the capabilities of a novel method for performing PEM-guided stereotactic breast biopsies. METHODS: The PEM system consisted of 2 square (10 x 10 cm) arrays of discrete scintillator crystals. The detectors were mounted on a stereotactic biopsy table. The stereotactic technique used 2 PEM images acquired at +/-15 degrees and a new trigonometric algorithm. The accuracy and precision of the guidance method was tested by placement of small point sources of (18)F at known locations within the field of view of the imager. The calculated positions of the sources were compared with the known locations. In addition, simulated stereotactic biopsies of a breast phantom consisting of a 10-mm-diameter gelatin sphere containing a concentration of (18)F-FDG consistent with that reported for breast cancer were performed. The simulated lesion was embedded in a 4-cm-thick slab of gelatin containing a commonly reported concentration of FDG, simulating a compressed breast (target-to-background ratio, approximately 8.5:1). An anthropomorphic torso phantom was used to simulate tracer uptake in the organs of a patient 1 h after a 370-MBq injection of FDG. Five trials of the biopsy procedure were performed to assess repeatability. Finally, a method for verifying needle positioning was tested. RESULTS: The positions of the point sources were successfully calculated to within 0.6 mm of their true positions with a mean error of +/-0.4 mm. The biopsy procedures, including the method for verification of needle position, were successful in all 5 trials in acquiring samples from the simulated lesions. CONCLUSION: The success of this new technique shows its potential for guiding the biopsy of breast lesions optimally detected with PEM.

Biopsy, Needle↗

PubMed2000

Performance of a PSPMT based detector for scintimammography.

In breast scintigraphy, compact detectors with high intrinsic spatial resolution and small inactive peripheries can provide improvements in extrinsic spatial resolution, efficiency and contrast for small lesions relative to larger conventional cameras. We are developing a pixelated small field-of-view gamma camera for scintimammography. Extensive measurements of the imaging properties of a prototype system have been made, including spatial resolution, sensitivity, uniformity of response, geometric linearity and energy resolution. An anthropomorphic torso phantom providing a realistic breast exit gamma spectrum has been used in a qualitative study of lesion detectability. A new type of breast imaging system that combines scintimammography and digital mammography in a single upright unit has also been developed. The system provides automatic co-registration between the scintigram and the digital mammogram, obtained with the breast in a single configuration. Intrinsic spatial resolution was evaluated via calculation of the phase-dependent modulation transfer function (MTF). Measurements of extrinsic spatial resolution, sensitivity and uniformity of response were made for two types of parallel hole collimator using NEMA (National Electrical Manufacturers Association) protocols. Geometric linearity was quantified using a line input and least squares analysis of the measured line shape. Energy resolution was measured for seven different crystal types, and the effectiveness of optical grease coupling was assessed. Exit gamma spectra were obtained using a cadmium zinc telluride based spectrometer. These were used to identify appropriate radioisotope concentrations for the various regions of an anthropomorphic torso phantom, such that realistic scatter conditions could be obtained during phantom measurements. For prone scintimammography, a special imaging table was constructed that permits simultaneous imaging of both breasts, as well as craniocaudal views. A dedicated breast imaging system was also developed that permits simultaneous acquisition and superposition of planar gamma images and digital x-ray images. The intrinsic MTF is nonstationary, and is dependent on the phase relationship between the signal and the crystal array matrix. Averaged over all phases, the MTF is approximately 0.75, 0.57 and 0.40 at spatial frequencies of 1.0, 1.5 and 2.0 cycles per cm, respectively. The phase averaged line spread function (LSF) has a FWHM value of 2.6 mm. Following uniformity corrections, the RMS deviations in flood images are only slightly greater than is predicted from counting statistics. Across an 80 mm section of the active area, the differential linearity is 0.83 mm and the absolute linearity 2.0 mm. Using an anthropomorphic torso phantom with detachable breasts, scatter radiation similar to that observed exiting the breast of scintimammography patients was observed. It was observed that scattered gamma rays can constitute the majority of the radiation incident on the detector, but that the scatter-to-primary ratio varies significantly across the field of view, being greatest in the caudal portion of the breast, where scatter from the liver is high. Using a lesion-to-breast concentration ratio of 6:1, a 1.0 cm3 simulated breast lesion was detectable in lateral images obtained with both the developmental camera and with a clinical camera, while a 0.35 cm3 lesion was detectable in neither. Utilization of the dual x-ray transmission, gamma emission breast imaging system greatly increases the conspicuity of scintimammographic lesions relative to prone imaging, as well as greatly facilitating the localization and identification of structures in the gamma image. The prototype imaging gamma detector exhibits spatial resolution superior to that of conventional cameras, and comparable uniformity of response and geometric linearity. Because of light losses in the crystals, the energy resolution is inferior to that of single crystal NaI(Tl) came

Equipment Design↗

PubMed2000

Long-term follow-up of trauma patients with a vena caval filter.

BACKGROUND: Venous thromboembolism (VTE) is an important complication in blunt trauma patients. At our Level I trauma center, we had a deep venous thrombosis (DVT) rate of 3.2% from 1993 to 1997 despite an aggressive VTE prophylaxis program. During this time period, we placed vena caval filters (VCF) for both traditional and prophylactic indications. This project was developed to establish a VCF registry for trauma patients to determine the long-term complications of VCF placement. METHODS: A letter was sent to all trauma patients who had a VCF placed from 1993 through 1997. Patients were asked to return for a history and physical examination to detect signs and symptoms related to VTE, a duplex ultrasound of the inferior vena cava, and a plain abdominal radiograph to determine filter migration. RESULTS: There were 191 VCFs inserted in our trauma population from 1993 to 1997. There were 105 patients (75 male and 30 female) available for evaluation, with a mean follow-up of 28.9 months. Forty-one VCFs were placed in patients with DVT or pulmonary embolism, and 64 were placed in patients for prophylactic indications as per the guidelines developed by the Eastern Association for the Surgery of Trauma. There were no clinically identifiable complications related to insertion of the VCF. There were no pulmonary embolisms detected after VCF insertion. In follow-up, only one filter (0.95%) migrated, and this was minimal (1 cm cephalad). One (0.95%) vena cava was occluded, based on duplex ultrasonography, and 11 patients (10.4%) had signs or symptoms of leg swelling after hospital discharge. Twenty eight (44%) of the 64 patients with prophylactic VCFs developed a DVT after filter placement. CONCLUSION: VCFs placed in trauma patients have acceptable short- and long-term complication rates. Consideration should be given to prophylactic VCF placement in patients at high risk for VTE. Randomized controlled trials are needed to evaluate whether VCF insertion increases the risk for subsequent DVT.

Adolescent↗

PubMed2000

The potential role of positron emission mammography for detection of breast cancer. A phantom study.

Positron emission mammography (PEM) is a new, specialized imaging modality utilizing PET radiopharmaceuticals to detect breast cancer. The capabilities and limitations of PEM in detecting breast tumors were investigated with a series of phantom experiments. The PEM imager was mounted on a standard Lorad biopsy table (separated by 18 cm). In the initial phase of the investigation, basic scanner parameters (resolution, sensitivity, and scatter fraction) were measured. The effects of a number of breast imaging parameters (length of acquisition, breast thickness, and breast density) on detection of breast lesions were then explored utilizing special phantoms. Moderately compressed breasts were simulated with a block of gelatin containing amounts of FDG consistent with 370 MBq injections. Lesions were simulated with four hollow spheres (inner diameters=5 mm, 8 mm, 12 mm, and 15 mm) filled with amounts of FDG representative of uptake in malignant breast tumors (target-to-background concentration ratio=8.5:1). Resolution at the center of the imager was 3.9 mm, sensitivity was 0.059 kcps/kBq/ml and the Compton scatter fraction was approximately 12%. Objects as small as 8 mm in diameter could be detected after 30 s of data acquisition; 5 mm spheres were detectable after 300 s. Object detection capabilities were reduced with increasing breast thickness. In thin compressed breasts (2 cm) even the smallest sphere (5 mm in diameter) could be detected; increasing breast thickness increased the minimum detectable sphere diameter to 8 mm. Increased background activity caused by FDG uptake in metabolically active normal tissue more prevalent in radiodense breasts compared to "fatty" breasts was simulated and shown to reduce the minimum detectable lesion size to 12 mm for the densest breasts. These results demonstrate the potential of PEM for the detection of breast lesions. The addition of the system to a standard biopsy apparatus indicates its potential for use to guide some core biopsies of breast cancers.

Breast Neoplasms↗

PubMed1998

Using modern information technology to profile faculty activities.

Most academic medical centers (AMCs) have developed mechanisms for tracking the financing of their faculty members' research and clinical activities. However, information systems for managing and reporting financial data often do not provide fully accurate or complete pictures of the accomplishments of an institution or its faculty. Modern information technology can help AMCs integrate more extensive information about their faculties from many different sources; in particular, Web publishing technologies permit large numbers of users to have easy secure access to databases across different platforms. The authors briefly describe five faculty information systems now in use. They then describe in detail the development and implementation of one of these systems, The Johns Hopkins University School of Medicine Faculty Information System (FIS), which uses Web publishing technologies, collecting and making available information about the clinical, teaching, and research activities of faculty members.

Academic Medical Centers↗

PubMed1977

A quantitative echocardiographic study of champion childhood swimmers.

An echocardiographic evaluation of 77 members of a championship childhood swim team showed dimensional variations from normal in most athletes. Cardiac walls were thicker than the 95th percentile of normal: right ventricular anterior wall exceeded the 95th percentile in 100%, interventricular septum in 83% and left ventricular posterior wall in 91%. The left ventricular and left atrial cavities in diastole had mean values at the 50th percentile of normal but showed considerable scatter. The left ventricular cavity in systole had a mean value less than the 5th percentile of normal and also showed wide scatter. The aortic root and the aortic intercusp dimension exceeded the 95th percentile of normal in most subjects, 74% and 77%, respectively. No correlation existed between the coach's estimate of championship ability and echocardiographic wall or chamber sizes. Children who participate extensively in athletic training programs such as swimming may have echocardiograms which are quantitatively different from those of nonathletic younsters.

Adolescent↗