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Biomedical subjects

S Shahabi

Publications and source records attributed to S Shahabi.

36 records · Page 2Linked to original sources
PubMed1997

Complete hydatidiform mole and coexisting normal fetuses. A report of two cases with contrasting outcomes.

BACKGROUND: Multiple pregnancies consisting of a complete hydatidiform mole and coexisting fetuses are relatively rare but may become more common due to the increasing use of ovulation-induction agents. CASES: We report on a twin and a triplet pregnancy, conceived using clomiphene citrate, with contrasting outcomes. The twin pregnancy resulted in a term delivery of a healthy singleton and the triplet pregnancy in a termination at 17 weeks followed by the development of choriocarcinoma. CONCLUSION: The few cases available suggest that a subgroup of complete moles follows a more benign course and can be managed conservatively, allowing the pregnancy to go to term with appropriate follow-up, whereas other cases follow a more aggressive course. Larger case series are needed to develop definitive protocols.

Adult↗
PubMed1996

Effect of bonding agents on adhesion of composite resin following CO2 laser etching of dental enamel.

Etching of dental enamel using pulsed carbon dioxide (CO2) laser radiation has been shown to give acceptable bond strengths when hydrophobic enamel bonding resins are used between the lased surface and composite resin. There have been dramatic changes in the composition of bonding agents in recent years. The present laboratory study examined the influence of the bonding agent on the shear bond strength to laser- and acid-etched enamel. Two current generation bonding systems were used (Scotchbond Multipurpose and Optibond). Shear bond strengths in the order of 10 MPa were consistently obtained using laser etching at "optimal" parameters, in the absence of any other preparation of the natural enamel surface. Although there was a consistent trend for shear bond strengths to be greater with Optibond than for Scotchbond MP in both human and porcine test systems, this difference was only statistically significant with acid etching of nonpolished human enamel, and suboptimal laser etching of polished human enamel. Prior surface polishing increased the shear bond strength obtained with maleic acid etching and Scotchbond MP by more than 2-fold, and increased bond strength when Optibond was used following optimal laser etching. These results indicate that both the type of surface preparation and the choice of bonding agent can influence bond strengths to laser-etched and acid-etched enamel.

Acid Etching, Dental↗
PubMed1992

Sequential comparison of low dose rate and hyperfractionated high dose rate endobronchial radiation for malignant airway occlusion.

A pilot trial (S2) was conducted at the University of Wisconsin to determine the feasibility, efficacy, and toxicity of hyperfractionated high dose rate endobronchial radiation. To avoid multiple bronchoscopies, an optimized hyperfractionated schema was derived from the linear-quadratic model. Utilizing a single bronchoscopy, 31 patients with malignant airway occlusion received 4 Gy x 4 fractions over 2 days at 2 cm from source center using a high dose rate remote afterloader. Response and morbidity were compared to a previous trial (S1) in which 66 patients were treated with conventional low dose rate endobronchial radiation. Response was assessed by change in performance status, symptom resolution, percent of lifetime rendered symptom-free or improved, and radiographic reaeration. These parameters were highly comparable between the two groups. The mean ECOG performance status improved from 2.2 to 1.8 for S1 and 2.1 to 1.6 for S2; symptom improvement or resolution was noted in 78% for S1 and 79% for S2; lifetime rendered symptom-free or improved was 54% for S1 and 57% for S2; and the overall radiographic response rate was 78% for S1 and 85% for S2. The overall incidence of fistulae was 7/101. We conclude that endobronchial radiation is an effective and safe modality for palliation, and hyperfractionated high dose rate endobronchial radiation achieves responses similar to low dose rate endobronchial radiation with a similar complication rate.

Airway Obstruction↗
PubMed1992

High dose rate intracavitary brachytherapy for carcinoma of the cervix: the Madison system: II. Procedural and physical considerations.

The loss in therapeutic ratio accompanying a conversion from low dose-rate (LDR) to high dose-rate (HDR) intracavitary brachytherapy (ICR) requires increased attention to the precision and accuracy of dose distribution calculations and treatment delivery. While the HDR-ICR treatment unit allows better custom-tailored dose distributions compared to LDR, it also requires more attention to detail to achieve the distribution desired. Because the relative biological effectiveness of different isodose levels in a dose distribution varies with the absolute dose (as described in Part 1 of this article), the relative dose distribution used with LDR must be modified for HDR to produce the same expected biological effect. Because of the difference in the radiobiology and physical positioning, simply duplicating applications as performed with LDR misses opportunities for dose distribution improvement as well as opens possibilities for significant complications. Due to differences in positioning the applicator (e.g., retraction of the cervix low in the pelvis instead of packing the applicator high), traditional definitions of points of interest (such as point A) apply poorly with HDR-ICR, compelling new systems of dose specification. With HDR-ICR, irreparable mistakes can happen very quickly, and quality assurance for the treatment plan and calculated dwell times prove much more important than with LDR. Key features of the dose distribution and constant relationships involving doses and dwell times help screen planned treatments for mistakes. This paper details the procedural and physical consideration of the Madison system for HDR-ICR brachytherapy for carcinoma of the cervix.

Brachytherapy↗
PubMed1990

Effect of endobronchial radiation therapy on malignant bronchial obstruction.

We evaluated the effect of endobronchial radiation therapy in 52 patients with malignant airway occlusion. Fifty-five endobronchial applications of the radioisotope iridium 192 were carried out. Response was assessed by change in performance status, symptom resolution, duration of symptom relief, roentgenographic reaeration, pulmonary function tests, and postimplant bronchoscopy. Thirty-three patients showed at least a one-level improvement in performance status. Of a total of 166 symptoms present prior to therapy, 131 resolved or improved. Approximately 70 percent of a patient's lifetime was rendered symptom improved or symptom free. A roentgenographic reaeration response of 30/41 (73 percent) was achieved. The average FEV1 and FVC improved from 1.5 to 2.1 L and from 2.3 to 2.9 L, respectively. Posttherapy bronchoscopy was performed between one and two months following the implant in 15 patients who agreed to undergo the procedure. Eleven (73 percent) of 15 had complete tumor regression. Major long-term complications were noted in seven patients. Endobronchial radiation, therefore, appears to be a safe and effective technique to palliate malignant airway occlusion.

Aged↗
PubMed1989

Endobronchial irradiation for malignant airway obstruction.

An afterloading endobronchial irradiation (EBRT) technique using Iridium-192 (Ir-192), was piloted for malignant airway obstruction. Under bronchoscopic guidance, a catheter is threaded distal to the lesion. Orthogonal radiographs and computerized tomographic (CT) scans are obtained for dosimetry. Forty implants in 38 patients have been performed. Thirty-two patients had lung cancer; 23 had received prior irradiation and eight had prior chemotherapy. Eight patients underwent pre-endobronchial irradiation laser excision. Median implant duration was 50.5 hr; median dose at 1 and 2 cm from source center was 50 and 20 Gy, respectively. The procedure was well tolerated with four long-term complications (10.5%). Twelve of 38 patients are currently alive with a median survival of 5+ months and a range of 1 to 21+ months. Changes in performance status (PS), symptom resolution, radiographic demonstration of re-aeration of atelectatic lung, changes in pulmonary function (PFT), and post-endobronchial irradiation bronchoscopy were used to assess response. Seventy percent of the patients' remaining life was rendered symptom-free or improved. A 70% radiographic response was noted. Fourteen patients underwent post-endobronchial irradiation bronchoscopy with 12 complete responses. Endobronchial irradiation, therefore, appears to be a safe, effective technique to palliate malignant airway obstruction.

Airway Obstruction↗
PubMed1988

Treatment of probable subclinical liver metastases and gross pancreatic carcinoma with hepatic artery 5-fluorouracil infusion and radiation therapy.

Since subclinical hepatic metastases are frequently present at time of diagnosis of pancreatic carcinoma, any meaningful effort to improve survival must include 'prophylactic' liver therapy in addition to treatment of the pancreatic primary. We report the results of a prospective, unrandomized clinical trial of a 2-week liver and pancreas infusion (by hepatic artery) of 5-fluorouracil (5-FU) and pancreatic irradiation to 50-60 Gy, combined with prophylactic irradiation of the liver with approximately 20 Gy. Of 21 evaluable patients, 17 completed therapy without excessive toxicity and had a median survival of 50 weeks. Contrary to historical controls, the liver in our series was rarely the first site of failure (6%), suggesting that the combination of hepatic artery 5-fluorouracil and 20 Gy liver radiation may suppress subclinical (microscopic) liver metastases without significant hepato-toxicity. When radiation doses to the pancreas were increased above 50 Gy there was improvement in primary tumor control, although failure in the pancreatic bed remained the most common site of failure. Future clinical investigation of this form of combined therapy for eradication of micro-metastasis in the liver, combined with more aggressive local pancreatic therapy, would seem appropriate.

Adenocarcinoma↗
PubMed1987

An improved method for estimating the entrance exposure in diagnostic radiographic examinations.

There is currently a widespread consensus on the importance of monitoring patient radiation exposures during radiographic examinations. Diagnostic facilities under federal jurisdiction already legislate maximum patient exposure limits for various diagnostic radiologic examinations, while an increasing number of state legislatures have instituted such regulations. Compliance requires that institutions be capable of assessing each patient's entrance exposures. A method is proposed that would facilitate the acquisition of such patient exposure information in a relatively straightforward and accurate manner, requiring a minimum number of measurements and access to a suitable programmable calculator. A standardized set of exposure measurements obtained on an accurately calibrated three-phase radiographic unit has been fitted by an analytic function. The average accuracy of the fit between the limits of 40-140 kVp and 2.5- to 6.0-mm aluminum filtration was 0.3%. The concept of linear scaling was employed to allow the analytic function to accurately reproduce the exposure outputs of different radiographic units. Validation experiments on patients indicated that an overall accuracy of 10% can be expected when using well-calibrated radiographic equipment. The method described permits institutions to verify their compliance with federal and/or state regulations and to confirm that their radiation exposures are consistent with national averages.

Humans↗
PubMed1986

Imported cases of chloroquine-resistant falciparum malaria in Iran.

Six imported cases of chloroquine-resistant Falciparum malaria have been studied since October 1984. In five cases including two Iranian men, returned from India, two Afghan and one Bengalee immigrants came to Iran through Pakistan, recrudescence occurred following treatment with chloroquine. In these five cases resistance of P. falciparum to chloroquine was clinically (by the in vivo test) at R1 level in all patients. The resistance was also confirmed by the macro in vitro susceptibility test which was carried out in four of them. These five chloroquine-resistant cases were treated, one with Sulfadiazine-Pyrimethamine, three with Quinine-Sulfadiazine-Pyrimethamine and one with Sulfadoxine-Pyrimethamine (Fansidar) successfully. In the sixth case who was a Pakistani tourist the parasites showed resistance in the macro in vitro test, but apparently responded to chloroquine treatment in three days. It seems the resistance in this case was also at R1 level as other cases.

Adolescent↗
PubMedDate not supplied

Effective wedge angles for 6-MV wedges.

Measurements were undertaken with 30 degrees and 45 degrees large wedges on a 6-MV linac to determine the effective wedge angle for various combinations of open and wedged fields. The validity of Tatcher's equation, relating effective wedge angle to maximum dose weightings, was examined over a range of field sizes from 5 X 5 to 20 X 20 cm. An alternative equation involving only central axis quantities was also investigated. The results obtained from an analysis of point dose measurements indicate that, for these wedges, either equation yields sufficient accuracy for clinical purposes.

Animals↗
PubMedDate not supplied

On the cause of the variation in tissue-maximum ratio values with source-to-detector distance.

While tissue-maximum ratios (TMR) for 60cobalt treatment units have been shown to be independent of source-to-axis distance (SAD), high-energy photon beams demonstrate variations in their TMR as a function of SAD. Some authors have asserted that the distance dependence of the TMR stems from electron contamination in the beams, while others have suggested low-energy, scattered photons as the cause. Using a magnet to sweep contaminant electrons out of the photon treatment beam eliminates any variation in TMR with distance. Thus, electron contamination accounts for all of the distance dependence, and any low-energy, scattered photons behave indistinguishably like the high-energy photons.

Cobalt Radioisotopes↗
PubMedDate not supplied

Spontaneous rupture of a splenic artery aneurysm in pregnancy: report of two cases.

The spontaneous rupture of a splenic artery aneurysm during pregnancy is a rare but catastrophic event. Two cases are reported, both involving fetal death and one maternal death as well. A review of the literature covering this condition shows that mortality amongst pregnant women remains high at 75% with 95% fetal loss, which compares with a 25% mortality rate amongst non-pregnant women. Clinical presentation is often non-specific, with good haemodynamic compensation, followed by a rapid deterioration. The best investigation appears to be a diagnostic laparotomy. The discussion stresses the importance of early diagnosis faced with this serious condition, as well as the potential benefits of a prompt lower mid-line incision in terms of statistical survival for both mother and fetus.

Adult↗
PubMedDate not supplied

The role of chemotherapy and prophylactic bilateral oophorectomy in a case of colorectal adenocarcinoma with ovarian metastases.

A 66-year-old female presented with a large abdominal mass and accompanying systemic complaints of abdominal pain, constipation. and fever. On exploratory laparotomy, the mass was found to be a moderately differentiated adenocarcinoma of the sigmoid colon with metastasis to the left ovary. A primary colorectal carcinoma that has metastasized to the ovaries can be difficult to distinguish clinically from an advanced primary ovarian tumor. Histology and tumor markers are currently the most useful tools available in making an accurate diagnosis. If the nature of the primary tumor is uncertain and the initial response to chemotherapy is poor, the patient's prognosis will also he poor. Though controversy exists regarding the role of prophylactic bilateral oophorectomy during resection for primary colorectal cancer, later confusion can be avoided by performing this procedure when the colorectal carcinoma is first diagnosed. However the possibility of a concurrent primary ovarian tumor must not be overlooked.

Adenocarcinoma↗
PubMedDate not supplied

The role of laparoscopy in the diagnosis and treatment of peritoneal carcinomatosis: a case report.

A patient presented with deep venous thrombosis and an elevated CA-125 level, but normal pelvic ultrasound and abdominal and pelvic CT scans. Laparoscopy revealed diffuse carcinomatosis and a diagnosis of stage IIIc, poorly differentiated epithelial ovarian carcinoma was made. Laparoscopy may provide an alternative means of diagnosis when conventional imaging fails, and may facilitate the placement of catheters for subsequent intraperitoneal therapy.

Antineoplastic Agents↗
PubMedDate not supplied

Management of a ruptured basilar artery aneurysm during pregnancy.

A 36 year old woman who ruptured a basilar artery aneurysm at 38 weeks gestation in her second pregnancy was managed successfully by endovascular embolisation 36 hours after an emergency Caesarean section. The timing of treatment along with the obstetric, neurosurgical and anaesthetic aspects of this complex problem are discussed along with a review of the current literature on the subject.

Adult↗