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Biomedical subjects

D Rubens

Publications and source records attributed to D Rubens.

14 recordsLinked to original sources
PubMed1999

Ovarian cancer: comparison of observer performance for four methods of interpreting CT scans.

PURPOSE: To assess the effects of four interpretative methods on observers' mean sensitivity and specificity by using computed tomography (CT) of ovarian carcinoma as a model. MATERIALS AND METHODS: CT scans in 98 patients with ovarian carcinoma and 49 women who were disease free were retrospectively reviewed by four experienced blinded radiologists to compare single-observer reading, single-observer reading with an anatomic checklist, paired-observer reading (simultaneous double reading), and replicated reading (combination of two independent readings). Confidence level scoring was used to identify three possible disease forms in each patient: extranodal tumor, lymphadenopathy, and ascites. Patient conditions were then categorized as abnormal or normal. RESULTS: There were no significant improvements in sensitivity or specificity for classification of patient conditions as abnormal or normal when comparing single-observer interpretation with single-observer interpretation with a checklist or paired-observer interpretation. Although there was no significant improvement in the mean sensitivity (93% vs 94%) by using the replicated reading method, there was a statistically significant improvement in mean specificity (85% vs 79%) for the replicated readings compared with single-observer interpretations (P < .05). CONCLUSION: Diagnostic aids such as checklists and paired simultaneous readings did not lead to an improved mean observer performance for experienced readers. However, an increase in the mean specificity occurred with replicated readings.

Female↗
PubMed1998

Acoustic backscatter properties of the particle/bubble ultrasound contrast agent.

Bubble-based suspensions with diameters in the 1-5 microns range have been developed for use as ultrasound contrast agents. Bubbles of these dimensions have resonance frequencies in the diagnostic ultrasonic range, thus improving their backscatter enhancement capabilities. The durability of these bubbles in the blood stream has been found to be limited, providing impetus for a number of approaches to further stabilize them. One of the approaches has been the development of micrometer-size porous particles or 'nano-sponges' with properties suitable for the entrapment and stabilization of gas bubbles. However, the complex morphology and surface chemistry involved in the production of this type of agent makes it unfeasible to directly measure the volume of the entrained gas. A model based on acoustic scattering principles is proposed which indicates that only a small volume fraction of gas should be necessary to significantly enhance the echogenicity of this type of particle-based contrast agent. In the model, the effective scattering cross-section is evaluated as a function of the volume fraction of gas contained in the overall scatterer and the overall scatterer diameter. Initially, the volume fraction of gas is considered as a discrete entity of single bubble. Using common mixture rules, it is then shown that the gas can be considered to be distributed throughout the particle and still arrive at a result that is similar to that for a single, discrete volume of gas. The main contribution to the increased scattering cross-section is due to the compressibility difference between gas and water. The backscatter coefficient is computed as the product of the resulting differential scattering cross-section and the scatterer number density. This approach facilitates comparison with known backscatter coefficients of biological targets such as liver and blood. Simple experimental results are presented for comparison with the model, and the implications relevant to clinical use are suggested.

Animals↗
PubMed1998

The role of ultrasonography-guided fine-needle aspiration biopsy in the management of nonpalpable and palpable thyroid nodules.

The introduction of highly sensitive imaging techniques has made it possible to detect many nonpalpable thyroid nodules (non-PTN). We investigated the value of ultrasound-guided fine-needle aspiration biopsy (US-guided FNAB) as a diagnostic tool in the management of non-PTN as well as palpable thyroid nodules (PTN) that were considered difficult to aspirate without guidance. US-guided FNAB was performed on a total of 119 nodules (71 palpable and 48 nonpalpable) from 119 patients between 1992 and 1996. All available clinical and follow-up data were reviewed. Surgical follow-up was available in 24 cases. The patients included 100 females and 19 males ranging in age from 9 to 81 years (average, 51 years). FNA diagnoses (PTN versus non-PTN) included papillary carcinoma (12.7% [9/71] versus 4.2% [2/48], follicular neoplasm (16.9% [12/71] versus 0%), medullary carcinoma (1.4% [1/71] versus 0%), atypical cytology (5.6% [4/71] versus 2.1% [1/48], non-neoplastic thyroid (63.4% [45/71] versus 85.4% [41/48]) and unsatisfactory (0% versus 8.3% [4/48]). In 2 cases of occult papillary carcinoma, risk factors included radiation exposure (1 case) and a newly developed nodule during follow-up for hypothyroidism (1 case). Subsequent surgical follow-up (24 cases) confirmed the FNA findings, except for a case of Hürthle cell adenoma and 1 of Hashimoto's thyroiditis diagnosed as papillary carcinoma and follicular neoplasm, respectively. US-guided FNAB in most non-PTN are diagnosed as benign. For most patients with non-PTN and without any high-risk factors, a conservative approach such as clinical follow-up may be a more cost effective and logical approach. In contrast, US-guided FNAB is more useful in diagnosing biologically significant lesions in PTN that may be difficult to aspirate without guidance.

Adolescent↗
PubMed1998

Ultrasound surveillance for asymptomatic deep venous thrombosis after total joint replacement.

Prospective data on 202 consecutive patients who had a total of 123 total hip and ninety-four total knee arthroplasties were collected from two university medical centers. The findings of routine surveillance for deep venous thrombosis performed with ascending contrast venography were compared with those of surveillance with duplex ultrasonography complemented with color-flow Doppler imaging. All of the studies were performed between the third and seventh postoperative days. Of the 202 patients (342 extremities) who were examined, fifty-five (27 per cent) were found to have deep venous thrombosis; fifty-two (95 per cent) of the thrombi were in the calf and three (5 per cent) were in the proximal veins. All of the thrombi were clinically asymptomatic and all were nonocclusive, allowing passage of contrast medium around an intraluminal filling defect. Duplex ultrasonography with color-flow Doppler imaging correctly identified two of the three proximal thrombi and five of the fifty-two thrombi in the calf (sensitivity, 10 per cent). The sensitivity for the detection of thrombi in the calf was zero of sixteen at one of the institutions involved in the study and 14 per cent (five of thirty-six) at the other. There were two false-positive findings on ultrasonographic examination; one involved a proximal thrombus and one, a distal thrombus. We believe that the interinstitutional variability and insensitivity of duplex ultrasonography with color-flow Doppler imaging for the detection of asymptomatic deep venous thrombi in the calf after total joint replacement make it unreliable as a routine surveillance tool after total hip or knee arthroplasty.

Adult↗
PubMed1998

3D visual presentation of shoulder joint motion.

The 3D visual presentation of biodynamic events of human joints is a challenging task. Although the 3D reconstruction of high contrast structures from CT data has been widely explored, then there is much less experience in reconstructing the small low contrast soft tissue structures from inhomogeneous and sometimes noisy MR data. Further, there are no algorithms for tracking the motion of moving anatomic structures through MR data. We represent a comprehensive approach to 3D musculoskeletal imagery that addresses these challenges. Specific imaging protocols, segmentation algorithms and rendering techniques are developed and applied to render complex 3D musculoskeletal systems for their 4D visual presentation. Applications of our approach include analysis of rotational motion of the shoulder, the knee flexion, and other complex musculoskeletal motions, and the development of interactive virtual human joints.

Adult↗
PubMed1995

The cultural production of Bioterapia: psychic healing and the natural medicine movement in Slovakia.

Despite powerful opposition, natural medicine (NM) has achieved a toe-hold in the state-run biomedical system in the Slovak Republic. The physician-leader of the NM movement hopes to leverage his ministerial post as NM 'supreme expert' and his interlocking NM clinical and research facilities to achieve a complex, unified health care system under control of medical doctors. This health care model simultaneously reinforces biomedical hegemony and decenters classical medicine by substituting a bioenergetical paradigm. NM includes, among other diagnostic and healing modalities, acupuncture, herbal therapies, bee therapy, reflexology, iridology. However, its paradigmatic form is bioterapia, the focus of this paper. Bioterapia is a form of psychic healing or therapeutic touch. According to its practitioners, it is based on bioenergetic and information-processing principles. Conceptually, bioterapia unifies psyche, soma and energy dimensions of the human body and situates the human organism in an extended transpersonal social, physical and cosmological environment. Bioterapia is a scientized and medicalized reconstruction of a folk healing tradition whose appropriation simultaneously secularized and re-sacralized this tradition by re-locating its practice from lay healers to medical doctors, from the religious domain to the venerated scientific domain, from deviant science to normal science. The reconfiguration into bioterapia as part of the creation of an academic secular parapsychology in the former Soviet Bloc in the late 1960s, illustrates the use of the privileged discourse of science for a cultural production that seems to have both supported and subverted the regime.

Complementary Therapies↗
PubMed1991

Gadopentetate dimeglumine-enhanced chemical-shift MR imaging of the breast.

Standard T1-weighted MR images enhanced with gadopentetate dimeglumine show relatively minimal enhancement of breast lesions due to the high background signal from fat in the breast. Strongly enhancing lesions may become isointense relative to the fat signal and become invisible or indistinct after contrast administration. Fat-suppressed chemical-shift imaging (CSI) combined with administration of gadopentetate dimeglumine improves lesion detection and characterization in other areas of the body where a strong lipid signal is present. We evaluated this technique in the breast. Twenty patients with mammographic lesions were studied with standard unenhanced T1- and T2-weighted images and enhanced T1-weighted images, as well as with CSI before and after administration of gadopentetate dimeglumine. The series were ranked independently for border and matrix characteristics. The border was assessed for a smooth, irregular, or spiculated margin. The matrix or internal substance was evaluated for visibility and type of enhancement, homogeneous or inhomogeneous. The enhanced CSI images were superior to all other images in the depiction of border and matrix characteristics. Of 20 patients, a corresponding mass was detected on MR in 14. In two of the 14 patients, the lesion was seen only in the enhanced CSI images. Chemical-shift artifacts on enhanced T1-weighted images obscured border detail in several cases. Enhanced CSI improves visualization of breast lesions as compared with conventional MR imaging with or without enhancement. The enhanced CSI technique produces differential enhancement between glandular tissue and lesions while suppressing the signal from fat. This improves the visualization of border and matrix characteristics and depicts lesions that otherwise might be obscured.

Breast Neoplasms↗
PubMed1988

Stage IB cervical carcinoma: comparison of clinical, MR, and pathologic staging.

In patients with stage IB cervical carcinoma (carcinoma confined to the cervix), accurate staging is essential in order to determine the best treatment strategy--that is, whether to use surgery alone or surgery in combination with pre- or postsurgical radiation therapy. Currently, decisions regarding the management of patients are made on the basis of clinical staging that has an error rate of 34-39% (when surgical staging is used as the standard). To investigate the value of MR in staging patients with IB cervical cancer, we performed prospective MR examinations in 27 patients who had cervical carcinoma. Of these, 10 were clinically staged as having IB cervical carcinoma and underwent radical hysterectomy, providing specimens for pathologic correlation. In six of these 10 patients, the extent of disease had been underestimated during clinical examination under anesthesia. These six patients would have received radiation therapy before surgery had the MR information been used at the treatment-planning stage. MR imaging correlated better with surgical pathology than did clinical examination under anesthesia in determining the location and extent of tumor. MR imaging should be used in conjunction with clinical staging to determine appropriate therapy in patients with stage IB cervical carcinoma.

Adult↗
PubMed1986

Breast MR imaging with loop-gap resonators.

Breast images obtained at 1.5 T using a loop-gap resonator pair as both the excitation and detection device are presented. The efficiency of this approach is high, as judged by the low level of radio frequency (RF) power required to obtain a 90 degree pulse and the uniformity of the RF field within the resonator pair. A modification of the pair geometry provides for reasonable observation of the tissues through the chest wall and laterally to the axillae.

Breast Diseases↗
PubMed1986

Distal ureteral calculi: diagnosis by transrectal sonography.

Eight patients were studied by both transrectal sonography and excretory urography for the presence of distal ureteral calculi. The sonographic diagnosis was correct in 5 of 5 true positives and 3 of 3 true negatives. Urography was correct in 4 of 5 true positives and 2 of 3 true negatives. None of the sonograms and two of the urograms were considered equivocal. Transrectal sonography appears to be a useful adjunct for the diagnosis of distal ureteral calculi when excretory urography is equivocal or contraindicated.

Adult↗
PubMed1986

Sonographic examination of the abdominal aorta through the left flank: a prospective study.

Ultrasonographic evaluation of the abdominal aorta is most often done with the patient in the supine position. The right lateral decubitus position, which views the aorta through the left flank has, until now, been considered unsatisfactory for aortic evaluation. One hundred consecutive patients were prospectively examined for visualization of the aorta both through the left flank and the anterior abdomen. Twenty-one patients were then comparatively examined from the right coronal and left coronal approach. These studies showed that the aorta was clearly visualized using the left flank approach in the majority of patients (96 per cent). The combined approach yielded 99 per cent satisfactory visualization, and in a few select cases (13 per cent) the left flank was actually superior. The left flank approach was superior when directly compared with the right flank in 42 per cent of patients and comparable in 48 per cent. The right flank approach was superior in only 10 per cent.

Adult↗
PubMed1985

Postpartum renal vein thrombosis.

Renal vein thrombosis in adults is usually a complication of the nephrotic syndrome. Rarely, it has been reported in nonnephrotic women postpartum. The thrombosis may be a complication of the hypercoagulable state associated with both the nephrotic syndrome and pregnancy. Two postpartum patients with renal vein thrombosis and no prior history of renal disease are reported here. Neither patient had heavy proteinuria. In both cases, pyelonephritis was suspected clinically and the diagnosis of renal vein thrombosis was first suggested and confirmed by radiologic examination. Renal vein thrombosis should be considered in women presenting postpartum with flank pain.

Angiography↗