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Biomedical subjects

J M Pfaff

Publications and source records attributed to J M Pfaff.

11 recordsLinked to original sources
PubMed2000

The web browser as a unifying agent for radiology and the health care enterprise.

A variety of information systems in the health care enterprise are used to store patient information. The hospital information system (HIS), the picture archiving and communications system (PACS), the radiology information systems (RIS), and patient records, for example, are often supported by separate and distinct systems. A referring physician reviewing a radiologist's report often does not have convenient access to the original radiologic images. A radiologist interpreting a radiologic examination may not have convenient access to clinical information generated outside of the radiology department. Clearly, convenient and quick access to all relevant patient information is the ideal in delivering quality patient care. Recently, the web browser has become increasingly well accepted as the "universal client" for viewing a wide variety of information. We believe that the web browser may provide the universal "window" to the variety of distinct information sources required by the physician, and may provide unification of these information sources through hypertext links. We specifically looked at the feasibility of using the web browser to view scanned patient charts. A total of 5,200 patient charts (131,000 pages) were scanned into a structured query language (SQL) database. Access to these records was made available on the hospital local area network (LAN), and on the Internet over the worldwide web. Comparison measurements were made of the time required to access patient records using a dedicated viewing application and using a web browser.

Databases as Topic↗
PubMed1996

Mammographic features after conservation therapy for malignant breast disease: serial findings standardized by regression analysis.

OBJECTIVE: The purpose of this study was to determine the incidence and natural history of mammographic changes in patients within 5 years of conservation therapy for malignant breast disease. MATERIALS AND METHODS: We reviewed the records of 164 consecutive patients with a history of conservation therapy for malignant disease. We recorded mammographic changes related to treatment for each year after surgery. Linear regression analysis was applied to determine trends for progression, regression, or stability of findings. RESULTS: We evaluated 158 patients with 162 lesions for which initial mammographic evaluation had occurred within 5 years of surgery. Of these 158 patients, 121 (77%) underwent serial studies. A total of 152 patients (96%) showed changes on mammograms that represented scarring, usually in multiple locations. Findings at initial evaluation included architectural distortion (n = 110; 82%), increased regional density or scarring (n = 106; 79%), skin thickening (n = 73; 54%), masses (n = 16; 12%), and calcifications (n = 4; 3%). All findings except calcifications showed partial resolution over time, with architectural distortion showing the most significant resolution (p = .05). CONCLUSION: Mammographic features after conservation therapy for breast cancer are common at 1 year after treatment. With the exception of calcifications, we found that all changes showed decreased prominence during the next 5 years. Recognition of such trends during routine surveillance should facilitate the early identification of changes that represent recurrence or do novo malignancy.

Adult↗
PubMed1996

Mammographic changes after excisional breast biopsy for benign disease.

OBJECTIVE: The purpose of this study was to establish the incidence and natural history of mammographic changes in patients within 5 years of an excisional breast biopsy. MATERIALS AND METHODS: We reviewed the records of 428 consecutive patients who had undergone excisional biopsy for benign breast disease. We recorded year by year the mammographic changes seen after surgery. Because the site of surgery was known in each patient and because follow-up imaging continued for at least 2 years after biopsy, our analysis was able to exclude interval malignancy in the area of surgery. We then applied linear regression analysis to determine trends regarding progression, stability, or regression of changes after surgery. RESULTS: We evaluated 293 patients with 296 biopsies for which the initial mammographic study occurred within 5 years of surgery. Of those 293 patients, 237 (81%) underwent serial mammographic studies. Of the 293 patients studied, 146 patients (50%) showed no changes related to surgery. Of the remaining 147 patients (50%) who showed mammographic changes, the most common changes at initial mammographic follow-up were architectural distortion (98/205, 48%), skin thickening (35/205, 17%), and increased focal density (parenchymal scar) (30/205, 15%). Regression analysis showed no significant change of mammographic features in all patients during 5 years of follow-up (p > .2). CONCLUSION: Mammographic changes after excisional breast biopsy were seen in 50% of patients. When mammographic changes were seen, they remained stable during 5 years of follow-up. Recognition of such trends during routine surveillance should facilitate the identification of changes that represent developing malignancy.

Adult↗
PubMed1991

Digital angiographic impulse response analysis of regional myocardial perfusion. Estimation of coronary flow, flow reserve, and distribution volume by compartmental transit time measurement in a canine model.

A system impulse response function that describes the kinetics of radiographic contrast material transit through the coronary circulation was calculated from 175 selective digital angiograms of normal and stenotic arteries in 10 dogs during rest and hyperemia. The goal of the study was to determine if the flow and distribution volume characteristics of the epicardial coronary arteries and the myocardial microcirculation could be stimulated by specific mathematical compartments of a lagged normal density model impulse response function in which the flow/distribution volume ratio is the inverse of the mean transit time. The arterial compartment mean transit time correlated with flow (r = 0.75); however, the correlation was significantly improved in individual dogs (r = 0.83 +/- 0.13; p less than 0.005) and was highly dependent on the length of the conduit vessel. The microcirculation compartment mean transit time was distributed as two populations with respect to flow. There was a linear correlation during hyperemia (r = 0.87) and a nonlinear relation during rest, which was characteristic of an autoregulating system. Resting values of microcirculation compartment mean transit time correlated with coronary flow reserve (r = 0.84) and differed significantly between vessels that were normal and those with subcritical stenosis, critical stenosis, or total occlusion (p less than 0.01 for all comparisons). The estimated microcirculation compartment distribution volume increased from a minimum of 4.0 +/- 1.5 ml/100 g myocardium in normal vessels with resting flow to 11.2 +/- 3.5 ml/100 g during hyperemia. These data suggest that the model compartments functionally describe the physiological behavior of their anatomic analogues and permit the quantification of microcirculatory autoregulation from a single measurement at rest without provoking hyperemia.

Algorithms↗
PubMed1989

Digital angiographic impulse response analysis of regional myocardial perfusion: linearity, reproducibility, accuracy, and comparison with conventional indicator dilution curve parameters in phantom and canine models.

The system mean transit time (Tsys) of the impulse response function describing contrast material transit through the coronary circulation was determined from serial digital angiographic images. The linearity, reproducibility, and relations with regional myocardial perfusion and conventional time-density curve parameters, time to peak concentration (TPC), and exponential washout rate (k) were assessed in a dynamic flow x-ray phantom (n = 46) and in six open-chest dogs (n = 102) while coronary flow was altered by stenosis and/or hyperemic stimuli. In the phantom studies, the inverse of the system mean transit time (Tsys-1) closely predicted flow/volume (r = 0.99, slope = 0.99). In dogs, Tsys-1 was independent of the shape of the contrast bolus injection (single or double-peaked), class of contrast agent (ionic or nonionic), the type of hyperemic stimulus (dipyridamole, dipyridamole plus norepinephrine, transient total occlusion, or ionic contrast media), and was highly reproducible between adjacent myocardial regions served by the same artery (r = 0.98 +/- 0.01). There was a strong correlation between Tsys-1 and regional coronary flow for stenotic and/or hyperemic vessels (r = 0.94, distribution volume = 14.9 ml/100 g) over a wide range (0-514 ml/min/100 g). Tsys-1 performed better than conventional time-density curve parameters TPC-1 and k for predicting phantom flow/volume ratios and regional myocardial blood flow in the dog. These data suggest that both digital coronary angiography and coronary contrast transit can be modeled as linear systems and that impulse response analysis may provide accurate and reproducible estimates of regional myocardial blood flow.

Algorithms↗
PubMed1988

Computer analysis of Doppler color flow mapping images for quantitative assessment of in vitro fluid jets.

To determine the ability of Doppler color flow mapping to accurately and reproducibly assess the flow volume and kinetic energy of in vitro fluid jets, a Doppler color flow mapping system was interfaced with an image processing computer. An aliasing correction algorithm was used to extend the upper limit of measurable velocity to 184 cm/s. Images were analyzed for jet area (equal to the total number of image pixels) and jet energy (equal to the sum of all pixel velocities squared), both integrated over all frames of the injection and in single maximal frames. The Doppler flow mapping area and energy measurements were compared with known flow volume and delivered kinetic energy, and the effects of four experimental variables (orifice area, gain setting, chamber compliance and chamber size) were evaluated. Jet area correlated nonlinearly with flow volume and was markedly affected by each of these experimental variables, increasing by 40 to 150% from the smallest to the largest orifice size, 15 to 94% with the highest versus the lowest gain setting, 1 to 54% with greater chamber compliance and 7 to 70% in the large versus the small chamber. In contrast, jet energy correlated linearly with delivered kinetic energy up to 350,000 ergs, at which point velocities started to exceed the extended velocity range and second wrap aliasing occurred. The relation was not affected by orifice area, gain or compliance, and was only minimally affected by chamber size.(ABSTRACT TRUNCATED AT 250 WORDS)

Image Processing, Computer-Assisted↗
PubMed1986

Digital angiographic measurement of radiographic contrast material kinetics for estimation of myocardial perfusion.

We studied the use of digital angiography for the quantification of regional myocardial perfusion in the dog using selective left coronary arterial injection of radiographic contrast material as a flow dilution indicator. We developed algorithms for generating time-intensity curves from regions of interest over the proximal coronary artery and the myocardium and for densitometric error correction by subtraction of the intensity curve over a small lead blocker before logarithmic transformation. The resultant myocardial time-density curves were analyzed for time from injection to peak concentration (TPC) and for exponential washout rate (k). A linear correlation was found between absolute coronary arterial blood flow and both k (slope = 0.13, r = .85) and 1/TPC (slope = 0.18, r = .85). Reproducibility of TPC and k for repeated studies was 11% and 16%. Induced hyperemia significantly improved the sensitivity to stenosis by increasing the average difference in TPC and k between regions served by normal and stenotic coronary arteries to 65% and 80%, respectively. By combining selective coronary arterial injection with the left lateral x-ray projection it was possible to avoid most overlap of regional perfusion beds in the dog. This study suggests that contrast dilution measurements made during digital coronary angiography provide a means for assessing the hemodynamic significance of stenoses and the efficacy of therapeutic interventions.

Angiography↗
PubMed1985

Digital quantification eliminates intraobserver and interobserver variability in the evaluation of coronary artery stenosis.

A leading problem with subjective interpretation of coronary angiography is high intraobserver and interobserver variability. Four experienced angiographers independently determined percent diameter narrowing of 36 stenoses using 3 methods: by subjective analysis of single-frame cine film images (film), by subjective analysis of digitized nonenhanced single-frame images (digital), and by using a semiautomated digital caliper quantification system (Corona). The reproducibility of interpretations was assessed by comparison of estimated intraclass correlation coefficients. Digital and Corona readings correlated well with subjective interpretation of film (r greater than 0.85 for both). In contrast to Corona, the angiographers systematically overestimated the magnitude of stenoses in the intermediate (50 to 75%) range. Corona markedly improved intraobserver (p less than 0.005) and interobserver (p less than 0.001) reproducibility. Corona less frequently misclassified individual observations than did film when categories of less than 50%, 50 to 75% and more than 75% diameter stenosis were used (3.7% vs 31.5%, p less than 0.001). Our results suggest that digitization of a coronary angiogram in a 512 X 512 matrix has no significant adverse effects on the perception and quantification of stenosis by angiographers. Additionally, automatic measurement of coronary stenosis has 2 major advantages: It is accurate compared with a group of experienced angiographers and for the practical purpose of clinical decision-making, it eliminates intraobserver and interobserver variability.

Angiography↗
PubMed1985

Fibrinolytic therapy of St. Jude valve thrombosis under guidance of digital cinefluoroscopy.

Fibrinolytic therapy is an alternative to urgent reoperation for patients with St. Jude prosthetic valve thrombosis, but requires an accurate method for repeated assessment of prosthetic function. Since the St. Jude valve is not well visualized by conventional cinefluoroscopy, digital subtraction techniques were developed that improved visualization of the value and allowed assessment of leaflet separation and velocity. A 74 year old woman with prosthetic valve thrombosis 5 years after St. Jude aortic valve placement had an opening angle of 58 degrees (normal range 10 to 13; n = 8) with a maximal opening velocity of 1.37 degrees/ms (normal range 2.46 to 2.93). The closing angle was 125 degrees (normal range 120 to 127) with a maximal closing velocity of 1.38 degrees/ms (normal range 2.24 to 3.60). The patient received 250,000 U of streptokinase intravenously, then 100,000 U/h for 72 hours. Improvement in auscultatory findings occurred at 12 hours; repeat digital cinefluoroscopy showed an opening angle of 20 degrees with a maximal velocity of 2.77 degrees/ms, and a closing angle of 126 degrees with a maximal velocity of 1.91 degrees/ms. Digital cinefluoroscopy 4 weeks after discharge on warfarin and dipyridamole therapy was unchanged. There have been no thromboembolic complications after 6 months of follow-up. Thus, digital cinefluoroscopy is a new noninvasive technique that permits accurate measurement of normal and abnormal St. Jude leaflet function. Intravenous streptokinase dissolution of prosthetic valve thrombosis under digital cinefluoroscopic guidance may be an acceptable alternative to emergency reoperation. The frequency and significance of residual subclinical leaflet dysfunction after fibrinolytic therapy and the indications for elective reoperation require further evaluation.

Aged↗