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Biomedical subjects

R G Aarnink

Publications and source records attributed to R G Aarnink.

At least 19 recordsLinked to original sources
PubMed1999

Contrast-enhanced three-dimensional power Doppler angiography of the human prostate: correlation with biopsy outcome.

OBJECTIVES: To determine the feasibility of contrast-enhanced three-dimensional (3D) imaging of the prostatic vasculature using power Doppler imaging and to analyze whether semiquantitative judgments of 3D images with respect to symmetry and distribution of vascular structures correlated with biopsy outcome. METHODS: 3D power Doppler images were obtained before and after intravenous administration of 2.5 g Levovist. Subsequently, random and/or directed transrectal ultrasound (TRUS)-guided biopsies were performed. Vascular images were analyzed by two experts. Prostate vasculature was judged with respect to symmetry and vessel distribution using a (scale) grading system. RESULTS: Eighteen patients with a suspicion of prostate cancer either because of an elevated prostate-specific antigen (greater than 4.0 ng/mL; Tandem-R-assay) or an abnormal digital rectal examination were included in the study. Prostate cancer was detected in 13 patients. Vascular anatomy was judged abnormal in unenhanced images in 6 cases, of which 5 proved malignant. Enhanced images were considered suspicious for malignancy in 12 cases, including 1 benign and 11 malignant biopsy results. Sensitivity of enhanced images was 85% (specificity 80%) compared with 38% for unenhanced images (specificity 80%) and 77% for conventional gray-scale TRUS (specificity 60%). Of 6 patients who showed no B-mode abnormalities, vascular patterns were judged abnormal in 4 cases, of which 3 were malignant. CONCLUSIONS: Contrast-enhanced 3D power Doppler angiography is feasible in patients with suspicion of prostate cancer who are scheduled for prostate biopsies. The sensitivity of power Doppler 3D imaging for the detection of prostate malignancy increased from 38% (5 of 13) to 85% (11 of 13) after administration of intravascular microbubble contrast (Levovist), and specificity was found to be 80% (4 of 5) for both imaging modalities. Thus, the use of Levovist when combined with the power Doppler display mode and 3D image reconstruction offers a promising new research area that might prove useful in prostate cancer detection in the future.

Angiography↗
PubMed1999

Contrast angiosonography: a technology to improve Doppler ultrasound examinations of the prostate.

OBJECTIVES: A feasibility study to evaluate whether analysis techniques adapted from X-ray angiography can be used to analyze the transient enhancement of prostate blood flow patterns in color Doppler maps as obtained after administering ultrasound contrast agents. METHODS: Injections of ultrasound contrast agents were given to dogs and humans, and color Doppler blood flow patterns in fixed transverse sections through the prostate were recorded on video tape. Computer assistance of Doppler signals over time is used to evaluate the transient enhancement of flow patterns obtained with contrast-enhanced Doppler ultrasound. Results are compared to indicator dilution curve theory as used in, e.g., X-ray angiography. RESULTS: Administering a contrast agent to improve color Doppler evaluation of prostate blood flow resulted in clear enhancement of Doppler signal intensities without unwanted side effects. Using the computer, the perfused area of the prostate could be obtained quantitatively over time showing profiles of individual heartbeats. Averaging the perfused area over one heartbeat resulted in an indicator dilution curve, and correlation with dilution theory indicated the feasibility of applying wash-in and wash-out analysis of contrast agents in color Doppler images. CONCLUSION: Frame-by-frame interpretation by the computer indicated the feasibility of analyzing the transient enhancement of blood flow visibility in the Doppler image over time using techniques such as wash-in and wash-out time. This technology provides researchers in the field of ultrasound evaluation of the prostate the opportunity to apply a new diagnostic tool, contrast angiosonography, in their research. This method for analysis of prostatic blood flow can be helpful in any application that affects the blood supply of the prostate such as heat treatments and hormonal treatments.

Aged↗
PubMed1999

Feasibility of minimally invasive intrauterine fetal access in a monkey model.

PURPOSE: We evaluated new intervention techniques and surgical instruments in a fetal monkey model to determine improvements that would be useful for early intrauterine intervention. Our findings may be helpful in the future for treating select cases of severe prenatal obstructive uropathology. MATERIALS AND METHODS: In a series of experiments on 18 pregnant rhesus monkeys (Macaca mulatta) at mid trimester we assessed various endoscopic intra-amniotic access techniques as well as morbidity, mortality and possibilities for fetoscopy. RESULTS: In all 18 fetuses adequate fetoscopy was possible with no maternal mortality. Of the 18 pregnancies 14 went to term with no early or late postoperative complications. Technical improvements changed the intrauterine access technique from open placement of trocars to the use of the Seldinger technique, gun introduction of needles with small caliber sheets and small caliber introduction trocars, resulting in minimal amniotic membrane separation. Various rigid and flexible endoscopes were evaluated for fetoscopy and up to 3 cannulas were placed. No change in the fetal growth pattern was observed on postoperative ultrasound. Subsequent pregnancies occurred during this study period, and there were no acceptance problems of the newborns by the mothers. CONCLUSIONS: New techniques have led to improved intrauterine fetal access. Morbidity mainly depends on the disruption of amniotic membranes, which has an important preterm role. Adapted endoscopes and other instruments offer new possibilities for fetal diagnosis and therapy in the future. Our primate model seems to be suitable for evaluating these new techniques before they are used in a clinical setting.

Animals↗
PubMed1998

Edge detection in prostatic ultrasound images using integrated edge maps.

OBJECTIVE: We investigated an algorithm to detect grey level transitions with multiple scales of resolution to improve edge detection and localisation in ultrasound images of the prostate. INTRODUCTION: We had developed a non-analytical operator for prostate contour determination implemented with minimum and maximum filters and locate edges. We implemented a technique for improved determination of boundary parts in prostatic ultrasound images by adjusting the edge detection parameter to signal information. METHODS: First the influence of prefilter settings and edge detection parameters is investigated in a test image and a real ultrasound image. Then, local standard deviation is used to identify or fewer homogeneous regions that are filtered with course resolution, while areas with larger deviation that grey level transitions occur, which should be preserved using smaller filter sizes to improve edge localisation. RESULTS: Analysis of images with different filter sizes indicated that areas are merged for increasing filter sizes: less pronounced edges disappear or displace for larger filters. Two scales of resolution lead to an improved localisation of edges when smaller filter sizes are used in areas with an increased local standard deviation. CONCLUSIONS: This paper illustrates an edge detection method suitable as pre-processing step in interpretation of medical images. By adapting input parameters to signal information, object recognition can be applied in images from different imaging modalities. Also, disadvantages are discussed, resulting in a new application combining a localisation algorithm to find the initial contour and a delineation algorithm to improve the outlining of the resulting contour.

Algorithms↗
PubMed1998

Transrectal ultrasound of the prostate: innovations and future applications.

PURPOSE: We present a critical evaluation of the use of ultrasound for prostate disease examination in urological practice, and provide perspectives on ultrasound applications that may become important for the future evaluation of prostate problems. MATERIALS AND METHODS: Based on an evaluation of clinical data in cases suspicious for prostatic malignancy, we addressed the apparent shortcomings of transrectal ultrasound for accurately diagnosing prostate cancer. Future applications presented in the literature were noted. RESULTS: Evaluating the ultrasound data in cases suspicious for malignancy indicated that imaging has little advantage over digital rectal examination for detecting malignant areas. The new applications of ultrasound that hold great promise for use in the urology clinic include the injection of contrast agents to obtain information on blood supply, temperature estimation for the noninvasive assessment of temperature distributions during heat treatment and a therapeutic application for local treatment of prostate cancer. CONCLUSIONS: While differential diagnosis with ultrasound appears to result in disappointing sensitivity and specificity values, its use in volume measurement and biopsy guidance is unquestioned. The development of new applications may improve the clinical value of ultrasound in urological practice. The application of ultrasound contrast agents for the detection and clinical staging of prostate cancer is especially promising. Future research will indicate whether the promise evolves in clinical applications.

Animals↗
PubMed1997

The correlation between prostate volume, transition zone volume, transition zone index and clinical and urodynamic investigations in patients with lower urinary tract symptoms.

OBJECTIVE: To determine if, in patients with lower urinary tract symptoms (LUTS), measurement of the transition zone (TZ) of the prostate by transrectal ultrasonography (TRUS) and the ratio between the TZ volume and total prostate volume (TZ index) correlates better with clinical and urodynamic investigations than total prostate volume alone. PATIENTS AND METHODS: In total, 150 consecutive patients with LUTS underwent a standardized screening programme including the International Prostate Symptom Sore (IPSS), a physical examination, TRUS of the prostate and urodynamic investigations with pressure-flow studies. The total prostate volume and TZ volume were assessed from TRUS using the ellipsoid formula. Spearman's rank correlation coefficients were calculated between different prostate volume measurements and specific symptomatic and urodynamic variables. RESULTS: The relationships between specific IPSS symptoms, symptom scores and the prostate volume measurements were not statistically significant except for one domain, nocturia, that appeared to be statistically significantly correlated with the TZ index (r = 0.25). The correlations for free flow, pressure-flow variables and prostate volume measurements were stronger, but only moderate at best. The highest correlations were between TZ volume and the linear passive urethral resistance obstruction category, urethral resistance factor and detrusor pressure at maximum flow (r = 0.43, 0.44 and 0.40, respectively). The differences between the correlations of prostate volume and TZ index and these variables were small (r = 0.39, 0.38 and 0.37, respectively for prostate volume and r = 0.38, 0.40 and 0.33 respectively for TZ index). CONCLUSIONS: There were very small differences between the correlations of total prostate volume, TZ volume and TZ index, and clinical and pressure-flow variables. In the assessment of the last two, the estimation of the total prostate volume by TRUS was a reasonable way to obtain the required information about prostate size and measuring TZ volume and calculating TZ index was of limited additional value. Symptoms and bladder outlet obstruction were mainly determined by other factors than the prostate and, specifically, TZ volume. As earlier studies have indicated that including pressure-flow data in the pre-operative evaluation and selection of patients for interventional therapies may improve the overall clinical results, we think that prostate volume, TZ volume or symptoms alone should not be used as the main indication for deciding on the appropriate invasive treatment options.

Adult↗
PubMed1997

[Diagnosis of prostate cancer in urination disorders in urological practice: current status and future developments].

This paper presents the current diagnostics of patients with prostate related problems (lower urinary tract symptoms) who visit the urology clinic. The diagnostic triad for prostate cancer detection is presented, consisting of a serum Prostate-Specific Antigen test, a digital rectal examination to palpate the prostate, and transrectal ultrasound of the prostate to visualise internal structures and guide the urologist in taking biopsies. The results of the tests for a biopsied population of 232 patients illustrate the shortcomings of the individual tests in predicting the presence of a malignancy. Biopsies are needed to prove or rule out prostate cancer in case of a suspicion. Future developments in early detection of prostate cancer are directed to improve the clinical use of the current diagnostic triad, and to identify new diagnostic tools.

Aged↗
PubMed1996

Standardized assessment to enhance the diagnostic value of prostate volume; Part I: Morphometry in patients with lower urinary tract symptoms.

BACKGROUND: The diagnostic value of prostate volume results has been evaluated in patients with prostate problems of benign cause. METHODS: For 247 patients, automated volume results were compared to manual results of planimetric reference volume and of the classical ellipsoid formula. Also, transition zone volume was estimated and growth curves of the prostate and prostate dimensions over age were investigated. RESULTS: Application of automated volume determination gives accurate results compared to the reference volume (Pearson correlation, R = 0.938). The ellipsoid volume results were slightly less correlated (R = 0.921). Average growth of the entire prostate was 1.7% per year, for the transition zone the growth was 4.3%. Compared to growth rates for a community-based population, comparable growth rates were found for our group that had higher mean prostate volume. CONCLUSIONS: The results indicate that the age of onset of volume growth is the determining factor in developing benign prostate enlargement not a change in growth rate.

Adult↗
PubMed1996

Standardized assessment to enhance the diagnostic value of prostate volume; Part II: Correlation with prostate-specific antigen levels.

BACKGROUND: Standardized estimations of prostate volumes are used for interpretation of prostate specific antigen (PSA) levels. METHODS: In 243 patients with clinically benign diagnosis, automated and reference prostate volumes and transition zone volumes are correlated to PSA levels. Besides, growth curves of PSA level when aging are determined. RESULTS: The strongest correlation was found with multiple regression analysis between PSA and transition zone volume and rest volume (R = 0.854). Mean PSA density was 0.092 ng/mL2, its labelling quality for benign disease was 91% (threshold = 0.15 ng/mL2). An average growth factor for PSA levels of 2.9% per year was obtained. CONCLUSIONS: The contribution per unit tissue to PSA level was for the transition zone 1.9 times higher than for the rest volume. Average growth of PSA per year is in consonance with the increase in normal levels of age specific PSA ranges, although only weak correlations were found between PSA and age and PSA density and age.

Adult↗
PubMed1996

Construction and application of hierarchical decision tree for classification of ultrasonographic prostate images.

A non-parametric algorithm is described for the construction of a binary decision tree classifier. This tree is used to correlate textural features, computed from ultrasonographic prostate images, with the histopathology of the imaged tissue. The algorithm consists of two parts; growing and pruning. In the growing phase an optimal tree is grown, based on the concept of mutual information. After growing, the tree is pruned by an alternating interaction of two data sets. Moreover, the structure and performance of the constructed tree are compared to the results using a slightly modified corresponding growing and pruning algorithm. The modified algorithm provides better retrospective and prospective classification results than the original algorithm. The use of the tree for automated cancer detection in ultrasonographic prostate images results in retrospective and prospective accuracy of 77.9% and 72.3%, respectively. Using this tissue characterisation, a supporting tool is provided for the interpretation of transrectal ultrasonographic images.

Algorithms↗
PubMed1996

Endoscopic intrauterine fetal therapy: a monkey model.

OBJECTIVES: Prenatal ultrasonographic investigations have led to an increasing number of prenatally detected abnormalities, of which a large number involves the urogenital tract. This study was performed to evaluate if endoscopic intra-amniotic access is possible in primates. METHODS: In 10 midtrimester rhesus monkeys (Macaca mulatta), endoscopic intrauterine fetoscopy was performed with three access cannulas. Using a Seldinger technique, a vascular access system, and a pediatric laparoscopy set, intra-amniotic inspection was attempted. Fetal growth throughout pregnancy was monitored by ultrasonographic measurements of fetal biometry. RESULTS: Intrauterine access could successfully be achieved in 10 rhesus monkeys with three cannulas. After partial amniotic fluid exchange, adequate fetoscopy was always possible. Two monkeys aborted on the second and sixth postoperative days. Serial ultrasonographic investigations for fetal biometry showed no disturbance of the intrauterine growth patterns in the remaining 8 monkeys. CONCLUSIONS: We currently conclude that the rhesus monkey model for experimental intrauterine endoscopic surgery may be suitable for study of the developmental abnormalities of the genitourinary tract.

Animals↗
PubMed1996

Reproducibility of prostate volume measurements from transrectal ultrasonography by an automated and a manual technique.

OBJECTIVE: To assess the reproducibility of estimates of prostate volume determined by planimetry from transrectal ultrasonography (TRUS) images. MATERIALS AND METHODS: Two sequential sessions of images obtained by TRUS were obtained from 30 patients, with the ultrasound probe removed and inserted between the sessions. The stored images were outlined, both manually and by computer, and measurements of prostate volume obtained planimetrically. In addition, the ability of the urologist to accurately draw the contour was assessed by outlining predefined contours. RESULTS: The mean (SD) variability of manual outlining between sessions was 3.5 (3.4)%, within one session was 1.7 (1.3)% and of computer outlining between sessions was 4.3 (3.8%). Comparing the results of manual and computer outlining showed a mean (SD) variability of 7.5 (5.6)%, with larger values obtained from computer outlining. The mean (SD) variation in manually outlining predefined contours was 1.4 (1.4)%. CONCLUSIONS: The variability of computer outlining was slightly higher than expected theoretically. The within-session variability was higher than the variation caused by errors in outlining predefined contours, indicating that the interpretation of TRUS images differed with time. Automated determination of prostate volume can save time during clinical investigation and the variability is within the clinically acceptable range of 5%.

Aged↗
PubMed1996

Formula-derived prostate volume determination.

OBJECTIVES: Despite disadvantages such as time-consuming and tedious to the user, planimetric volumetry is considered to be the most accurate method for prostate volume determination. This study investigates the possibilities of formula-derived volume determination and reveals the best alternative to planimetric volumetry. METHODS: The prostate volume is calculated using prostatic dimensions (length, height and width) in four mathematical descriptions for prostate volume calculations. As reference, the planimetric results obtained with 4 mm step size were used. RESULTS: Compared to the results of planimetric volumetry obtained with 4-mm intersection distance, the best results for volume determination with mathematical calculation were obtained with a formula describing a spheroid volume using half the mean of width, height and length as radius. CONCLUSION: Although planimetric volumetry remains the most accurate method for prostate volume determination, the spheroid formula is the best alternative method for quick volume assessment with reasonable accuracy.

Humans↗
PubMed1995

Planimetric volumetry of the prostate: how accurate is it?

Planimetric volumetry is used in clinical practice when accurate volume determination of the prostate is needed. The prostate volume is determined by discretization of the 3D prostate shape. The are of the prostate is calculated in consecutive ultrasonographic cross-sections. This area is multiplied by the distance between the cross-sections and the total volume is determined by summation of all contributions. Besides the quality of the automated outlining, the accuracy of this method depends on this intersection distance and on the angle of the scan plane with the probe. Also, the location of the first cross-section is of influence. This paper describes the influences of these parameters on the accuracy of the volume determination using a simple prostate model. This theoretical influence is compared to clinical volume determinations using automated planimetric volumetry with different step sizes. From our data, it is concluded that a step size of 4 mm for planimetric prostate volume determination is a good compromise between investigation time and accuracy in a clinical setting.

Humans↗
PubMed1995

Computerized analysis of transrectal ultrasonography images in the detection of prostate carcinoma.

OBJECTIVE: To report on the use of automated image analysis in the interpretation of transrectal ultrasonographic images of the prostate. PATIENTS AND METHODS: During transrectal ultrasonography, images were recorded from biopsies performed in 127 patients. Subsequently in the image, the puncture place was marked and analysed. Analysis of the images was performed with the Automated Urologic Diagnostic Expert (AUDEX) system, consisting of a personal computer connected to the ultrasound machine. From the images collected, parameters can be calculated for image classification. The parameters obtained with this procedure were correlated with the histological result. RESULTS: Evaluation showed a sensitivity of 84.8% and specificity of 87.5%. The positive and negative predictive values, to predict prostate carcinoma, were 84.8% and 87.5%, respectively. CONCLUSION: Automated image analysis can help in the diagnosis of prostate carcinoma. In patients with non-palpable lesions or with poorly visualized tumours, image analysis is superior to the standard current diagnostic techniques.

Humans↗
PubMed1995

Automated analysis and interpretation of transrectal ultrasonography images in patients with prostatitis.

Transrectal ultrasound (TRUS) offers a valuable complement to digital rectal examination (DRE) in diagnosing prostate diseases. However, in case of prostatitis syndromes, contradictions are found with regard to characteristic ultrasound features in these patients. Therefore we sought for better imaging techniques. This paper describes a study on the automated analysis of ultrasonographic prostate images (AUDEX). With image processing, in the present study, tissue characterization is performed to predict the probability of the presence of inflammated prostate tissue. This technique already proved its validity in patients with prostate cancer. During prostate examinations, images were recorded with clear indication of the puncture position. Only patients with an unambiguously inflamed or noninflamed benign histologic result were included. Evaluation showed that a sensitivity of 90.6% and a specificity of 64.2% was reached. Finally, the prospective positive and negative predictive value for prostatitis was 50.0% and 94.6%, respectively. This means that AUDEX predicts the diagnosis 'prostatitis' in a large number of patients with no infection. In case of prostatitis, however, this prediction is almost always right.

Data Interpretation, Statistical↗
PubMed1995

Automated prostate volume determination with ultrasonographic imaging.

A method for automated determination of the prostate volume based on planimetric volumetry was developed to overcome subjectivity in prostate volume measurements using ultrasonography. An edge detection method is applied to locate the prostate boundary in sequential ultrasonographic images. During regular examinations, the volume was assessed automatically in 55 patients. The Pearson correlation coefficient of the automated volume compared to the reference prostate volume was 0.93. The estimated ratio of the automated volume to the reference volume was 0.92. This method overcomes the individual subjectivity when interpreting ultrasonographic images, and provides accurate and objective results for followup of benign prostatic hyperplasia treatments and for comparison of multicenter trials. Also, this method is a useful tool for objective determination of prostate specific antigen in proportion to the volume (prostate specific antigen density).

Aged↗