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Biomedical subjects

D J Rubens

Publications and source records attributed to D J Rubens.

At least 19 recordsLinked to original sources
PubMed2000

Three-dimensional sonoelastography: principles and practices.

Sonoelastography is an ultrasound imaging technique where low amplitude, low-frequency shear waves (less than 0.1 mm displacement and less than 1 kHz frequency) are propagated through internal organs, while real-time Doppler techniques are used to image the resulting vibration pattern. When a discrete hard inhomogeneity, such as a tumour, is present within a region of soft tissue, a decrease in the vibration amplitude will occur at its location. This forms the basis for tumour detection using sonoelastography. For three-dimensional (3D) imaging the acquisition of sequential tomographic slices using this technique, combined with image segmentation, enables the reconstruction, quantification and visualization of tumour volumes. Sonoelastography and magnetic resonance images (MRI) of a tissue phantom containing a hard isoechoic inclusion are compared to evaluate the accuracy of this method. The tumour delineation from sonoelastography was found to have good agreement with the tumour from MRI except for a bleeding at one of its ends. Although sonoelastography is still in an experimental phase, the principles behind this imaging modality are explained and some practical aspects of acquiring sonoelastography images are described. Results from a 3D sonoelastography reconstruction of a tissue mimicking phantom and an ex vivo whole prostate specimen are presented.

Elasticity↗
PubMed1999

Intraoperative optimized inverse planning for prostate brachytherapy: early experience.

PURPOSE: To demonstrate the feasibility of an intraoperative inverse planning technique with advanced optimization for prostate seed implantation. METHODS AND MATERIALS: We have implemented a method for optimized inverse planning of prostate seed implantation in the operating room (OR), based on the genetic algorithm (GA) driven Prostate Implant Planning Engine for Radiotherapy (PIPER). An integrated treatment planning system was deployed, which includes real-time ultrasound image acquisition, treatment volume segmentation, GA optimization, real-time decision making and sensitivity analysis, isodose and DVH evaluation, and virtual reality navigation and surgical guidance. Ten consecutive patients previously scheduled for implantation were included in the series. RESULTS: The feasibility of the technique was established by careful monitoring of each step in the OR and comparison with conventional preplanned implants. The median elapsed time for complete image capture, segmentation, GA optimization, and plan evaluation was 4, 10, 2.2, and 2 min, respectively. The dosimetric quality of the OR-based plan was shown to be equivalent to the corresponding preplan. CONCLUSION: An intraoperative optimized inverse planning technique was developed for prostate brachytherapy. The feasibility of the method was demonstrated through an early clinical experience.

Algorithms↗
PubMed1999

Automated treatment planning engine for prostate seed implant brachytherapy.

PURPOSE: To develop a computer-intelligent planning engine for automated treatment planning and optimization of ultrasound- and template-guided prostate seed implants. METHODS AND MATERIALS: The genetic algorithm was modified to reflect the 2D nature of the implantation template. A multi-objective decision scheme was used to rank competing solutions, taking into account dose uniformity and conformity to the planning target volume (PTV), dose-sparing of the urethra and the rectum, and the sensitivity of the resulting dosimetry to seed misplacement. Optimized treatment plans were evaluated using selected dosimetric quantifiers, dose-volume histogram (DVH), and sensitivity analysis based on simulated seed placement errors. These dosimetric planning components were integrated into the Prostate Implant Planning Engine for Radiotherapy (PIPER). RESULTS: PIPER has been used to produce a variety of plans for prostate seed implants. In general, maximization of the minimum peripheral dose (mPD) for given implanted total source strength tended to produce peripherally weighted seed patterns. Minimization of the urethral dose further reduced the loading in the central region of the PTV. Isodose conformity to the PTV was achieved when the set of objectives did not reflect seed positioning uncertainties; the corresponding optimal plan generally required fewer seeds and higher source strength per seed compared to the manual planning experience. When seed placement uncertainties were introduced into the set of treatment planning objectives, the optimal plan tended to reach a compromise between the preplanned outcome and the likelihood of retaining the preferred outcome after implantation. The reduction in the volatility of such seed configurations optimized under uncertainty was verified by sensitivity studies. CONCLUSION: An automated treatment planning engine incorporating real-time sensitivity analysis was found to be a useful tool in dosimetric planning for prostate brachytherapy.

Algorithms↗
PubMed1999

Calf sonography for detecting deep venous thrombosis in symptomatic patients: experience and review of the literature.

PURPOSE: We determined the accuracy of sonography in the detection of isolated calf deep venous thrombosis (DVT) and the rate of indeterminate ultrasound examinations in patients with physical signs or symptoms suggestive of DVT. METHODS: We reviewed the medical literature (MEDLINE) to determine the accuracy of sonography and the frequency of indeterminate studies in detecting isolated calf DVT in patients with physical signs or symptoms suggestive of DVT. A meta-analysis was used to derive summary measures of sensitivity, specificity, and accuracy from studies in which 5 or more isolated calf DVT were identified. Frequencies of indeterminate examinations were recorded for studies in which these data were provided, and we pooled these results with our own data for 196 patients. RESULTS: The meta-analysis revealed that sonography correctly identified isolated calf DVT in 49 of 53 extremities (sensitivity, 92.5%; 95% confidence interval, 81.8-97.9%) and correctly identified the absence of calf DVT in 157 of 159 extremities (specificity, 98.7%; 95% confidence interval, 95.5-99. 9%), yielding an accuracy of 97.2% (95% confidence interval, 93.9-99. 0%) for ultrasound examinations considered diagnostic. However, when evaluating our patient population and the literature, we found a substantial number of indeterminate studies (overall rate of 54.6% in 463 extremities), with a wide variation in the reported frequency of indeterminate studies (9.3-82.7%). CONCLUSIONS: Sonography is highly accurate in detecting isolated calf DVT in symptomatic patients, but indeterminate studies occur frequently, with a wide range of reported rates. Each ultrasound laboratory should evaluate its own rate of indeterminate studies.

Female↗
PubMed1999

Effect of angiotensin converting enzyme inhibition on the Doppler waveform in dogs with renal artery stenosis.

Our objective was to investigate whether the angiotensin converting enzyme inhibitor enalaprilat improves detection of hemodynamically significant renal artery stenoses in dogs. Renal artery stenoses of 50 to 99% were surgically created unilaterally in five dogs. Doppler ultrasonographic evaluation was performed at baseline (no stenosis), after creation of the stenosis, and after the administration of enalaprilat. The resistive index increased in the nonstenotic kidney (P < 0.01) but not in the stenotic kidney after administration of enalaprilat. The difference in resistive indices between nonstenotic and stenotic kidneys increased significantly (P < 0.05) after administration of enalaprilat. Measurement of the resistive index after administration of an angiotensin converting enzyme inhibitor in humans may improve the performance of Doppler ultrasonography in detecting hemodynamically significant renal artery stenoses.

Angiotensin-Converting Enzyme Inhibitors↗
PubMed1998

Extravisceral masses in the peritoneal cavity: sonographically guided biopsies in 52 patients.

OBJECTIVE: Our objective was to determine the effectiveness of sonographically guided biopsies of extravisceral masses (masses outside the solid organs) in the peritoneal cavity. MATERIALS AND METHODS: We retrospectively reviewed the results of sonographically guided biopsies of extravisceral masses found in the peritoneal cavity of 52 patients (age range, 25-90 years old; mean age, 52 years) from June 1990 to December 1996. Fifty-one patients underwent biopsy through the abdominal wall, and one patient underwent transvaginal biopsy. Sonographic guidance was obtained using 3.5- to 7.0-MHz vector probes. The size, depth, and sonographic characteristics of the mass and the type of biopsy (aspirate versus core) were determined for all lesions. Pathology reports and clinical courses were reviewed. RESULTS: Placement of the biopsy needle within the lesion was successful in all patients. The mean depth from skin surface to lesion was significantly less (p < .0001) when shown by sonography (2.4 cm) than when shown by CT (3.8 cm). Biopsy results were true-positive for malignancy in 37 patients (no false-positives), true-negative for benign masses in 10 patients, and false-negative for malignancy in three patients (sensitivity, 93%; specificity, 100%; accuracy, 94%). Nondiagnostic samples were obtained in two patients (4%). Treatment was based on diagnostic biopsy results in 43 patients (86%). CONCLUSION: Sonography is an effective alternative to CT in guiding biopsy of extravisceral masses in the peritoneal cavity.

Biopsy, Needle↗
PubMed1997

Renal sonography: can it be used more selectively in the setting of an elevated serum creatinine level?

The objectives of our study were to (1) assess the outcomes resulting from the use of sonography in patients referred to our institution's ultrasound laboratory for an elevated serum creatinine level and (2) determine relevant clinical parameters in these patients to better triage them for sonography. We retrospectively identified and determined outcomes of 60 patients (20 women, 40 men; mean age, 61 years; range, 33 to 100 years) referred for sonographic evaluation because of an increased serum creatinine level (> or = 1.3 mg/dL). Ultrasound findings (hydronephrosis, renal size, and echogenicity) were correlated with clinical outcomes. Twenty-one patients (35%) had hydronephrosis, with 14 of these patients confirmed to be obstructed and five not obstructed. Two were indeterminate for obstruction. Eight of 14 obstructed patients were successfully treated. All obstructed patients had a suggestive history for obstruction with at least one of the following: pelvic mass (n = 9), stone disease (n = 4), or flank pain (n = 1). Only 2 of 44 patients, who were not obstructed, had any of these parameters (statistically significant difference, P < 0.0001). Thirty of the patients, who were not obstructed, had more likely alternative causes for renal failure, with sonography having no effect on patient management. Renal size and echogenicity had little effect on patient management. Sonography was efficacious in guiding management in patients with a suggestive history for obstruction (eg, pelvic mass, stone disease, or flank pain) but not in most patients who had no suggestive history and other more likely causes for renal failure.

Adult↗
PubMed1997

Radiologic consultation: effect on inpatient diagnostic imaging evaluation in a teaching hospital.

RATIONALE AND OBJECTIVES: The authors evaluated radiologic consultation affecting resident physician ordering of relatively expensive imaging studies. METHODS: Requisitions (n = 180) for expensive imaging studies from three general medicine floors (two consultation floors, one control floor) were prospectively evaluated. Information on the requisitions was classified as appropriate, inappropriate, or undecided if insufficient information was provided. On the consultation floors, but not the control floor, the medical residents were contacted about all studies initially considered inappropriate or undecided before they were performed. RESULTS: Nine of 119 requisitions (7.6%) from the consultation floors were considered inappropriate. In three studies (2.5%) the imaging evaluation was modified as the result of the interaction with the radiologist. There was no significant difference in the total number of radiologic studies or percentage of the total that were expensive imaging studies when comparing the consultation floors with the control floor. CONCLUSION: Radiologic consultation on expensive imaging studies through routine review of requisitions did not significantly change their use by house staff.

Diagnostic Imaging↗
PubMed1997

Interobserver and intraobserver variation in determining intrarenal parameters by Doppler sonography.

OBJECTIVE: This study identified the extent of inter- and intraobserver variation in assessing intrarenal Doppler waveform parameters. SUBJECTS AND METHODS: Optimized Doppler waveforms from the interlobar arteries of five healthy volunteers were recorded. The waveforms were digitized for off-line evaluation by six observers. Using the same set of waveforms, the observers initially selected three of six waveforms for each subject on the basis of their preference for clinical usefulness. The observers then were directed to evaluate three previously picked waveforms. The systolic acceleration time (SAT) and the resistive index were calculated from each waveform. The observers also characterized the shape of each waveform according to four categories. RESULTS: Significant interobserver (p < .01) but not intraobserver variation occurred when measuring the SAT. Differences were caused by the observers' perceptions of waveform shapes (kappa = .12, p < .01) as well as the observers choosing different systolic starting points. No significant inter- or intraobserver variation occurred in measuring the resistive index. CONCLUSION: Much variability among and within laboratories can be expected when observers of Doppler waveforms use SAT to evaluate patients for renal artery stenosis.

Adult↗
PubMed1997

Sonographic guidance of mediastinal biopsy: an effective alternative to CT guidance.

OBJECTIVE: Our objective was to determine the diagnostic and cost efficacy of sonographically guided mediastinal biopsy as an alternative to CT-guided mediastinal biopsy and to review our biopsy triage experience in switching from CT to sonography. CONCLUSION: Sonography is as safe and accurate as CT and is 25% less costly than CT. Sonography proved particularly valuable for identifying vessels and perfused tissue and for permitting upright biopsy positions in dyspneic patients. When using our triage criteria, radiologists should find sonographically guided mediastinal biopsy to be an attractive alternative to CT-guided mediastinal biopsy in most patients.

Biopsy, Needle↗
PubMed1997

Effective ultrasonographically guided intervention for diagnosis of musculoskeletal lesions.

Current algorithms recommend computed tomography or fluoroscopic guidance rather than ultrasonography for musculoskeletal intervention. We analyzed our ultrasonographically guided experience to evaluate its efficacy. Forty-seven patients underwent needle aspirates or biopsies or both in 13 extremity and 34 axial locations for 12 inflammatory lesions, 23 soft tissue masses, and 12 lesions arising from bone. Four lesions were initially imaged by ultrasonography; the remaining lesions were identified by computed tomography (25) or magnetic resonance imaging (18). Forty-six samples were diagnostic; one needle aspirate of an inflammatory mass yielded no diagnostic material. No complications occurred. Ultrasonographically guided musculoskeletal aspiration and biopsy are diagnostic and effective throughout the body, and with appropriate lesion access, they should be considered as an alternative to computed tomographic-guided procedures.

Adolescent↗
PubMed1996

The prostate: decreasing cost-effectiveness of biopsy with advancing age.

RATIONALE AND OBJECTIVES: The purpose of this study was to determine the cost-effectiveness of prostate biopsy at different excess prostate-specific antigen (PSA) levels as a function of age. METHODS: Medical decision analysis was performed with standard software (SMLTREE) to determine marginal effectiveness in quality adjusted life years (QALYs) and marginal cost-effectiveness in dollars per QALY of immediate prostate biopsy at different excess PSA levels between 0 ng/mL and 20 ng/mL. The probability of clinically significant cancer with a positive biopsy (pD+Bx+) was assumed to decrease with age from 1.0 at age 50 to 0.2 at age 70. Costs were based on charges at our hospital and were considered over a 2-year time frame. RESULTS: With our base case assumptions there was a decrease in QALYs and an increase in costs doing an immediate prostate biopsy at all excess PSA levels between 0 ng/mL and 20 ng/mL, compared with not biopsying the prostate at > or = 70 years. Doubling pD+Bx+ from 0.2 to 0.4 in the 70-and-older age group resulted in a small increase in QALYs in biopsying the prostate at excess PSA levels between 0 ng/mL and 20 ng/mL. However, the marginal cost-effectiveness of prostate biopsy was very high, ranging from $275,000/QALY biopsying at an excess PSA level of 0 ng/mL to $68,000/QALY biopsying at an excess PSA level of 20 ng/mL. This compared with it being more effective and less costly to biopsy at all excess PSA levels > or = 0 ng/mL in 50-year old patients. CONCLUSION: Immediate prostate biopsy is not cost-effective and can be detrimental in patients > or = 70 years of age at all excess PSA levels between 0 ng/mL and 20 ng/mL.

Aged↗
PubMed1996

Clinical evaluation of prostate biopsy parameters: gland volume and elevated prostate-specific antigen level.

PURPOSE: To determine whether excess prostate-specific antigen (PSA) improves the accuracy of predicting positive biopsy results. MATERIALS AND METHODS: Results of prostate biopsy in 130 consecutive patients were correlated with transrectal ultrasound (TRUS) findings, digital rectal examination results, serum PSA level, and excess PSA (serum PSA level minus predicted PSA level [prostate volume x 0.12]), alone and in combination. Random sextant biopsy was performed in all patients, as well as directed biopsy of any suspicious lesion seen at TRUS. RESULTS: Excess PSA alone was most accurate in the prediction of positive biopsy results. Use of an excess PSA of > or = 0 ng/mL instead of a serum PSA level of > 4 ng/mL to initiate prostate biopsy increased the positive yield from 49% to 56% and accuracy from 51% to 62%, eliminating 21% of biopsies while maintaining sensitivity at 94% (vs 95% with serum PSA level). CONCLUSION: Use of only excess PSA of > or = 0 ng/mL to initiate prostate biopsy results in the best combination of sensitivity and specificity compared with the other standard parameters.

Aged↗
PubMed1995

Primary lymphoma of bone. Correlation of magnetic resonance imaging features with cytokine production by tumor cells.

BACKGROUND: Primary lymphoma of bone is a rare, aggressive neoplasm that can present with a large, soft-tissue mass despite minimal evidence of cortical destruction on plain radiographs. METHODS: High resolution magnetic resonance imaging (MRI) examinations of four patients with primary lymphoma of bone were reviewed retrospectively, and in each case intramedullary tumors demonstrated "penetrating channels" extending through the cortex. The MRI studies were correlated with the histopathologic assessment of the tumor for each patient. Immunohistochemistry was performed for immunophenotyping and for cytokine expression by tumor cells. The cytokines that were investigated were interleukin-1, interleukin-6, and tumor necrosis factor-alpha, molecules known to regulate osteoclastic activity. RESULTS: The linear cortical foci noted on MRI correlated with the histopathologic findings of tumor-associated cutting cones, in proximity to osteoclastic bone resorption. Immunohistochemical stains showed a B-cell phenotype for each tumor and positive immunoreactivity in tumor cells for cytokine mediators that stimulate osteoclastic activation. CONCLUSIONS: These findings indicate that the tumor cells in these cases produce soluble cytokine mediators that may regulate extensive osteoclastic activity. In primary lymphoma of bone, tumor activation of osteoclastic resorption, with production of tumor tunnels through the cortex, may represent one of the mechanisms by which lymphoma escapes the intramedullary space and forms large, soft-tissue masses without extensive cortical destruction.

Adult↗