Cerebral hemodynamics in preterm infants during positional intervention measured with diffuse correlation spectroscopy and transcranial Doppler ultrasound.

Four very low birth weight, very premature infants were monitored during a 12 degrees postural elevation using diffuse correlation spectroscopy (DCS) to measure microvascular cerebral blood flow (CBF) and transcranial Doppler ultrasound (TCD) to measure macrovascular blood flow velocity in the middle cerebral artery. DCS data correlated significantly with peak systolic, end diastolic, and mean velocities measured by TCD (p(A) =0.036, 0.036, 0.047). Moreover, population averaged TCD and DCS data yielded no significant hemodynamic response to this postural change (p>0.05). We thus demonstrate feasibility of DCS in this population, we show correlation between absolute measures of blood flow from DCS and blood flow velocity from TCD, and we do not detect significant changes in CBF associated with a small postural change (12 degrees ) in these patients.

Comparative analysis of logistic regression and artificial neural network for computer-aided diagnosis of breast masses.

RATIONALE AND OBJECTIVE: To compare logistic regression and artificial neural network for computer-aided diagnosis on breast sonograms. MATERIALS AND METHODS: Ultrasound images of 24 malignant and 30 benign masses were analyzed quantitatively for margin sharpness, margin echogenicity, and angular variation in margin. These features and age of patients were used with two pattern classifiers, logistic regression, and an artificial neural network to differentiate between malignant and benign masses. The performance of two methods was compared by receiver operating characteristic (ROC) analysis. RESULTS: The area under the ROC curve Az (+/-SD) of the logistic regression analysis was 0.853 +/- 0.059 with 95% confidence limit (0.760-0.950). The area under the ROC curve of the artificial neural network analysis was 0.856 +/- 0.058 with 95% confidence limit (0.734-0.936). Although both the logistic regression and the artificial neural network had the same area under the ROC curve, the shapes of two curves were different. At 95% sensitivity, the artificial neural network had 76.5% specificity, whereas logistic regression had 64.7% specificity. CONCLUSION: There was no difference in performance between logistic regression and the artificial neural network as measured by the area under the ROC curve. However, at a fixed 95% sensitivity, the artificial neural network had higher (12%) specificity compared with logistic regression value.

Multigated contrast-enhanced power Doppler to measure blood flow in mice tumors.

This study evaluated an image-gating method using contrast-enhanced power Doppler ultrasound (US) to estimate blood perfusion in mice tumors. A mathematical model that compensates for the effect of bubble destruction by US pulses was used to determine contrast flow through an image plane. Multigated power Doppler images were obtained following contrast injection. Contrast flow index (CFI) was determined by measuring the area under the color level vs. time curve for each gating frequency. CFI was compared with true flow. The method was first evaluated using a flow phantom with variable flow rates, and then verified in a mouse model with implanted tumors. Color levels in Doppler images were modulated with gating frequency due to variable destruction of microbubbles by US pulses. CFI measured from the images correlated strongly with true flow in the flow phantom (r(2) = 0.87). The proposed method yielded reproducible CFI for mice tumors, suggesting that multigated contrast-enhanced power Doppler imaging may provide noninvasive measurement of tumor perfusion in mice.

Correlation between Doppler vascular density and PSA response to radiation therapy in patients with localized prostate carcinoma.

RATIONALE AND OBJECTIVES: The authors performed this study to ascertain whether there is a correlation between pretreatment Doppler vascular density (DVD) of the prostate and prostate-specific antigen (PSA) response following radiation therapy in prostate cancer patients. MATERIALS AND METHODS: Prior to radiation therapy, 14 patients with biopsy-proven carcinoma (of Gleason grades 2-7) were imaged with transrectal ultrasound in gray-scale, color Doppler, and power Doppler modes. The Doppler images were analyzed for mean DVD with the aid of a computer program. PSA levels were measured before therapy and every 3 months after therapy. The PSA measurements were fitted to an exponential to determine PSA halving time (T1/2). Correlations were made between T1/2 and the following pretherapy measurements: mean DVD, PSA level, prostate volume, and Gleason grade. RESULTS: Median follow-up time was 392 days. A linear correlation with regression coefficient (R) of 0.75-0.80 was observed between mean DVD and T1/2 for color Doppler and power Doppler imaging. In both imaging modes, each percentage increase in mean DVD led to an increase in T1/2 by 25 days. Pretherapy prostate volume, PSA level, and Gleason score did not correlate with T1/2. CONCLUSION: The pretreatment mean DVD correlates inversely with the rate of posttherapy decline in PSA in patients with prostate cancer. That is, pretreatment vascularity prognosticates postirradiation PSA response. The mechanism underlying this correlative relationship is not known.

Delta-projection imaging on contrast-enhanced ultrasound to quantify tumor microvasculature and perfusion.

RATIONALE AND OBJECTIVES: The aim of this study was to assess the Delta-projection image processing technique for visualizing tumor microvessels and for quantifying the area of tissue perfused by them on contrast-enhanced ultrasound images. MATERIALS AND METHODS: The Delta-projection algorithm was implemented to quantify perfusion by tracking the running maximum of the difference (Delta) between the contrast-enhanced ultrasound image sequence and a baseline image. Twenty-five mice with subcutaneous K1735 melanomas were first imaged with contrast-enhanced grayscale and then with minimum-exposure contrast-enhanced power Doppler (minexCPD) ultrasound. Delta-projection images were reconstructed from the grayscale images and then used to evaluate the evolution of tumor vascularity during the course of contrast enhancement. The extent of vascularity (ratio of the perfused area to the tumor area) for each tumor was determined quantitatively from Delta-projection images and compared to the extent of vascularity determined from contrast-enhanced power Doppler images. Delta-projection and minexCPD measurements were compared using linear regression analysis. RESULTS: Delta-projection was successfully performed in all 25 cases. The technique allowed the dynamic visualization of individual blood vessels as they filled in real time. Individual tumor blood vessels were distinctly visible during early image enhancement. Later, as an increasing number of blood vessels were filled with the contrast agent, clusters of vessels appeared as regions of perfusion, and the identification of individual vessels became difficult. Comparisons were made between the perfused area of tumors in Delta-projections and in minexCPD images. The Delta-projection perfusion measurements were correlated linearly with minexCPD. CONCLUSION: Delta-projection visualized tumor vessels and enabled the quantitative assessment of the tumor area perfused by the contrast agent.

Predicting PSA response of prostate cancer to radiation therapy with Doppler sonography.

OBJECTIVE: We report a prospective investigation of the correlation between pretreatment Doppler vascular density (DVD) of the entire prostate gland and subsequent prostate-specific antigen (PSA) response following external beam radiation therapy, for patients with low- or intermediate-risk prostate cancer. This report updates a previous report (Sehgal et al., Acad Radiol 2003;10:366) with longer patient follow-up and additional quantitative and clinically relevant end points. METHODS: Before radiation therapy, we imaged 12 patients with transrectal Doppler sonography and measured the mean DVD of the prostate for each. For analysis, patients were separated into 3 groups by low, intermediate, and high DVD. The mean DVD for each group was linearly correlated with mean values for time above a PSA threshold of 1.0 ng/ml, post-therapy plateau PSA, and nadir PSA. RESULTS: We previously observed that pretreatment mean DVD had a strong inverse correlation with initial rate of post-therapy decline in PSA. With substantially longer follow-up on the same cohort of patients (median, 52 months), we now observe that pretreatment mean DVD also correlates with post-therapy nadir PSA (R = 0.94) and with time above a PSA threshold of 1.0 ng/mL (R = 0.99). CONCLUSION: The results of the current study are consistent with our earlier suggestion that pretreatment measurement of DVD of the entire prostate gland may be a clinically useful prognostic indicator in early prostate cancer treated with radiation. However, additional data from larger numbers of patients are needed to draw firm conclusions.

A review of breast ultrasound.

Frequent advances in transducer design, electronics, computers, and signal processing have improved the quality of ultrasound images to the extent that sonography is now a major mode of imaging for the clinical diagnosis of breast cancer. Breast ultrasound is routinely used for differentiating cysts and solid nodules with high specificity. In combination with mammography, ultrasound is used to characterize solid masses as benign or malignant. There is growing interest in using Doppler ultrasound and contrast agents for measuring tumor blood flow and for imaging tumor vascularity. Ease of use and real-time imaging capability make breast ultrasound a method of choice for guiding breast biopsies and other interventional procedures. Breast ultrasound is used in many forms. B-mode is the most common form of imaging for the breast, although compound imaging and harmonic imaging are being increasingly applied to better visualize breast lesions and to reduce image artifacts. These developments, together with the formulation of a standardized lexicon of solid mass features, have improved the diagnostic performance of breast ultrasound. Several approaches that are currently being investigated to further improve performance include: (1) computer-aided-diagnosis; (2) the assessment of tumor vascularity and tumor blood flow with Doppler ultrasound and contrast agents; and (3) tissue elasticity imaging. In the future, ultrasound will play a greater role in differentiating benign from malignant masses and in the diagnosis of breast cancer.

Teaching medical students diagnostic sonography.

OBJECTIVE: The purpose of this pilot project was to train medical students in sonography. METHODS: Thirty-three medical students participated in a pilot sonography course, which included exposure to ultrasound physics, knobology of a compact ultrasound scanner, training in scanning and anatomy of the aorta and right kidney, and reading assignments in these areas. Pretraining and posttraining examinations were given in these areas to analyze the degree of knowledge gained by these methods. RESULTS: Nearly all of the medical students increased their basic knowledge of sonography and improved their scanning skills. The improvement was statistically significant in all areas. CONCLUSIONS: Training in sonography for medical students could be used as a foundation for later, more specialty-specific training to improve the overall medical sonography skills for all physicians.

Using sonography to examine adult patients at an academic medical center: have usage patterns changed with the expansion of managed care?

OBJECTIVE: This study was designed to determine whether significant changes have occurred in the utilization of sonography relative to more expensive cross-sectional imaging techniques in adult patients during a time of increasing reliance on managed care. MATERIALS AND METHODS: Use of sonography was compared with use of CT and MR imaging of the abdomen, pelvis, and retroperitoneum in adult patients in 1993 and 1998 at an academic medical center. Clinicians who requested the greatest number of examinations in both years were surveyed to assess their perception of changes in their practice patterns during the interim. RESULTS: Between 1993 and 1998, the use of sonography relative to the other cross-sectional imaging modalities decreased from 56% to 43% (p < or = 0.001). During the same time, CT use increased from 30% to 41% (p < or = 0.001), and MR imaging use increased from 14% to 16% (p < or = 0.001). Survey responses indicated that potential cost saving was not a major factor in physicians' decisions to use sonography rather than other cross-sectional imaging modalities. CONCLUSION: Sonographic utilization decreased during a 5-year period in which managed care provided an increasingly large proportion of overall reimbursement. Cost did not appear to be a major factor in selection of diagnostic tests. Differences over time in refering clinicians' perception of the relative usefulness of sonography, CT, and MR imaging may have contributed to the change in usage patterns.

Brachial artery: measurement of flow-mediated dilatation with cross-sectional US--technical validation.

Ultrasonographic examination of flow phantoms and the brachial artery of a healthy volunteer undergoing reactive hyperemia was performed. Images were analyzed with a user-guided automated boundary detection (UGABD) algorithm to extract boundaries and measure cross-sectional area. UGABD correctly detected pulsatile vasomotion and measured area within 5% of the true value. A comparison of UGABD versus manual tracing yielded linear correlation of 0.81-0.91. Peak vasodilatation measured in response to reactive hyperemia was 150 times greater in pixel count than that measured with longitudinal imaging. Cross-sectional imaging is more sensitive than longitudinal imaging for measuring flow-mediated dilatation of the brachial artery.

Color and power Doppler sonography in the diagnosis of prostate cancer: comparison between vascular density and total vascularity.

OBJECTIVE: Advances in color flow Doppler (CFD) and power Doppler imaging (PDI) have potential for prostate cancer diagnosis. Previous reports based on qualitative assessment suggest that hypervascularity increases likelihood of prostate cancer. Our objective was to compare 2 methods of vascularity assessment using PDI: total vascularity (TV) and vascular density (VD). The goal was to determine whether quantitative Doppler vascularity correlates with the likelihood of prostate cancer. Quantitative measurements were compared with subjective visual analysis of images. METHODS: Ninety patients before biopsy had gray scale sonography, CFD, and PDI. Histologic analysis showed adenocarcinoma, prostate intraepithelial neoplasia, benign prostatic hypertrophy/prostatitis, and benign findings. The CFD and PDI images were analyzed for vascularity by (1) integrating the number of blood vessels over an imaged area (TV) and (2) integrating the number of vessels over a unit area of tissue (VD). Images were also assessed visually. VD, TV, and visual assessment were compared with one another and histologic findings. RESULTS: Mean volume was not different. In each pathologic group, vascularity extent measured by TV and VD ranged from low to high. Disease groups did not exhibit a substantial difference in vascularity by either quantitative or qualitative analyses. Regionally, central gland TV was not significantly more vascular than peripheral gland TV except in benign prostatic hypertrophy. However, peripheral gland VD was 2.5 times greater than central gland VD. Seventy-one percent of the 31 focal hypoechoic lesions were hypervascular. Only 23% were carcinoma. CONCLUSIONS: Pathologic categories were not separable by apparent vascular measurement. All pathologic categories showed low, moderate, or high vascularity; thus vascular areas by themselves did not distinguish cancer types, nor did focal hypervascular hypoechoic areas increase the likelihood of cancer. These imaging techniques provided no further resolution of tumor discrimination over multiple biopsies of the prostate.

Impact of added biopsy areas on prostate cancer detection: preliminary analysis.

OBJECTIVE: To evaluate variations in prostate cancer detection relevant to the number and areas of biopsy cores. METHODS: Ninety patients with elevated prostate-specific antigen levels, abnormal physical examination findings, or both had ultrasound examinations plus biopsies. Forty-nine patients had 11 biopsies, and 41 patients had 6 biopsies. The numbers of cancers detected were compared on a patient-by-patient basis and by all biopsy sites grouped together. An analysis of the relationship between a positive gray scale sonographic finding and the presence of adenocarcinoma was done. RESULTS: On a patient-by-patient basis, 43% of patients who had 11 biopsies had adenocarcinoma. In patients who had 6 biopsies, 32% had adenocarcinoma. Thirty-eight percent of the additional cancers found in the 11-biopsy group were in 5 additional areas not sampled in the 6-biopsy group. Of the total of 539 biopsy specimens obtained in the 11-biopsy group, 56 (10%) had adenocarcinoma; 43% of these 56 were positive in the 5 additional areas not sampled in the 6-biopsy group. No statistical differences (P > .05) were found for mean age, mean prostate-specific antigen level, and mean volume in the groups with 11 and 6 biopsies. This indicated that the observed difference was not related to any of these factors. Similar pathologic data were found for patients with prostatic intraepithelial neoplasia. CONCLUSIONS: Our data indicate the added value of additional biopsy sites over the usual 6 biopsies to increase the yield of adenocarcinoma and prostatic intraepithelial neoplasia detected. The added biopsy sites of the central and midperipheral glands were areas where additional specimens positive for adenocarcinoma and prostatic intraepithelial neoplasia were obtained.

Computer-based margin analysis of breast sonography for differentiating malignant and benign masses.

OBJECTIVE: To evaluate the role of quantitative margin features in the computer-aided diagnosis of malignant and benign solid breast masses using sonographic imaging. METHODS: Sonographic images from 56 patients with 58 biopsy-proven masses were analyzed quantitatively for the following features: margin sharpness, margin echogenicity, and angular variation in margin. Of the 58 masses, 38 were benign and 20 were malignant. Each feature was evaluated individually and in combination with the others to determine its association with malignancy. The combination of features yielding the highest association with malignancy was analyzed by logistic regression to determine the probability of malignancy. The performance of the probability measurements was evaluated by receiver operating characteristic analysis using a round-robin technique. RESULTS: Margin sharpness, margin echogenicity, and angular variation in margin were significantly different for the malignant and benign masses (P < .03, 2-tailed Student t test). According to quantitative measures, tumor-tissue margins of the malignant masses were less distinct than for the benign masses. Although the mean size of the lesions for the two groups was the same, the mean age of the patients was statistically different (P = .000625). After logistic regression analysis, the individual features age, margin sharpness, margin echogenicity, and angular variation in margin were found to be associated with the probability of malignancy (P < .03). The area under the receiver operating characteristic curve +/- SD for the 3-feature logistic regression model combining age, margin echogenicity, and angular variation of margin was 0.87 +/- 0.05. CONCLUSIONS: The proposed quantitative margin features are robust and can reliably measure margin distinctiveness. These features combined with logistic regression analysis can be useful for computer-aided diagnosis of solid breast lesions.

Does use of a PACS increase the number of images per study? A case study in ultrasound.

The purpose of this study was to determine if the use of a picture archiving and communications system (PACS) in ultrasonography increased the number of images acquired per examination. The hypothesis that such an increase does occur was based on anecdotal information; this study sought to test the hypothesis. A random sample of all ultrasound examination types was drawn from the period 1998 through 1999. The ultrasound PACS in use (ACCESS; Kodak Health Information Systems, Dallas, TX) records the number of grayscale and color images saved as part of each study. Each examination in the sample was checked in the ultrasound PACS database,.and the number of grayscale and color images was recorded. The comparison film-based sample was drawn from the period 1994 through 1995. The number of examinations of each type selected was based on the overall statistics of the section; that is, the sample was designed to represent the approximate frequency with which the various examination types are done. For film-based image counts, the jackets were retrieved, and the number of grayscale and color images were counted. The number of images obtained per examination (for most examinations) in ultrasound increased with PACS use. This was more evident with some examination types (eg, pelvis). This result, however, has to be examined for possible systematic biases because ultrasound practice has changed over the time since the authors stopped using film routinely. The use of PACS in ultrasonography was not associated with an increase in the number of images per examination based solely on the use of PACS, with the exception of neonatal head studies. Increases in the number of images per study was otherwise associated with examinations for which changes in protocols resulted in the increased image counts.