Search PubMed⌕ Search

Biomedical subjects

A Sethi

Publications and source records attributed to A Sethi.

At least 37 records · Page 2Linked to original sources
PubMed2000

Improvement of tomographic intensity modulated radiotherapy dose distributions using periodic shifting of arc abutment regions.

Based on the study of treatment arc positioning versus target length, a method that allowed periodic shift of arc abutment regions through the course of intensity modulated radiotherapy (IMRT) was developed. In this method, two treatment plans were developed for the same tumor. The first plan contained the original target (Planning Target Volume as defined by radiation oncologist) and the second one contained a modified target. The modification of the original target consisted of simply increasing its length, adding a small extension to it, or creating a distant pseudo target. These modifications cause arc abutment regions in the second plan to be shifted relative to their positions in the first plan. Different methods of target modification were investigated because in some cases (for instance, when a critical structure might overlap with the target extension) a simple extension of the target would cause an unacceptable irradiation of the sensitive structures. The dose prescribed to the modified portion of the target varied from 10% to 100% of the original target dose. It was found that a clinically significant shift (> or =5 mm) in abutment region locations occurred when the dose prescribed to the extended portion of the target was > or =95% of the original target dose. On the other hand, the pseudo target required only approximately 10% to 20% of the original target dose to produce the same shift in arc positions. Results of the film dosimetry showed that when a single plan was used for the treatment delivery, the dose nonuniformity was 17% and 25% of the prescribed dose with 0.5 and 1 mm errors in couch indexing, respectively. The dose nonuniformity was reduced by at least half when two plans were used for IMRT delivery.

Dose-Response Relationship, Radiation↗
PubMed2000

The role of strategic attention deployment in development of self-regulation: predicting preschoolers' delay of gratification from mother-toddler interactions.

Toddlers' use of effective attention deployment strategies to cope with separation from the mother and with maternal behavior predicted the use of effective delay-of-gratification strategies at age 5, even though the contexts, measures, and manifest behaviors were different. Toddlers who used distraction strategies during a brief separation from the mother were able, at age 5, to delay immediate gratification longer for more valued rewards. Toddlers who explored at a distance from a controlling mother when she tried to engage the child also delayed longer and used more effective delay strategies at age 5, compared with toddlers who did not distance themselves. Toddlers whose mothers were not controlling showed the opposite pattern: Those who did not distance themselves from the mother's bids had longer preschool delay times and more effective strategies. Strategic attention deployment was shown to be an enduring self-regulatory skill visible in early development across domains, measures, and over time.

Adaptation, Psychological↗
PubMed2000

The lateral fixation screw in implant dentistry.

This clinical report presents a means of retaining implant supported superstructures using lateral fixation screws (Novadent). 244 lateral fixation screws have been used for the retention of a variety of restorations including single teeth, short span and full arch bridgework as well as overdenture bars. Over a period of observation of 4 years, the authors have found the restorations to have effective retention, ease of retrievability, good aesthetics and occlusal contours.

Dental Implants, Single-Tooth↗
PubMed1998

Calculation of depth dose and dose per monitor unit for irregularly shaped electron fields.

A new dosimetric quantity, the lateral build-up ratio (LBR), has been introduced to calculate depth dose distribution for any shaped field. Factors to account for change in incident fluence with collimation are applied separately. The LBR data for a small circular field are used to extract radial spread of the pencil beam, sigma(r), as a function of depth and energy. By using the relationship between LBR, sigma(r), energy and depth, a formalism is developed to calculate dose per monitor unit for any shaped field. Criteria for lateral scatter equilibrium are also developed which are useful in clinical dosimetry.

Algorithms↗
PubMed1996

Initial results of the Osteo Ti implant system in general dental practice.

It is the purpose of this paper to present the preliminary results of 370 consecutively placed Osieo-Ti implants. Two stage screw form endosseous implants ranging in length from 7mm to 20mm in one mm increments were used. Four diameters of implant 2.75mm, 3.00mm, 3.75mm and 4.50mm were used to engage the maximum available width of bone. The larger, 3.75mm and 4.50mm diameter, implants were made from commercially pure titanium and the two smaller diameter, 2.75mm and 3.00mm, implants were manufactured from titanium alloy. The overall success rate for 370 exposed functioning Osteo-Ti implants was 98.6%.

Alveolar Bone Loss↗
PubMed1995

Incorporation of diaphyseal sequestra in chronic haematogenous osteomyelitis.

Seventeen patients with haematogenous osteomyelitis and long diaphyseal sequestra are reported. Treatment was incision and drainage with antibiotics for at least 6 to 8 weeks, the limb being protected in plaster for a long time. The sequestra became incorporated in every case. Sequestrectomy should only be undertaken when successive radiographs show no reduction in size of the sequestrum and an increase in the amount of the involucrum.

Adolescent↗
PubMed1995

Surgical treatment of complete acromioclavicular dislocation using the coracoacromial ligament and coracoclavicular fixation: report of a technique in 14 patients.

Fourteen cases of a complete dislocation of the acromioclavicular joint were treated using a modified technique of surgical repair involving the transfer of the coracoacromial ligament to reconstruct the coracoclavicular ligaments and coracoclavicular fixation with a screw. In addition, the lateral 2 cm of the clavicle was removed and the coracoacromial ligament attached to the raw surface. Eleven patients underwent surgery < 2 weeks after injury, whereas three underwent surgery 6 months after the initial episode. Follow-up of 2-4 years showed excellent results in 12 and good in two cases. It is our recommendation that coracoclavicular ligament reconstruction should be supplemented with clavicular fixation to the coracoid to ensure acromioclavicular alignment.

Acromioclavicular Joint↗
PubMed1995

Inferior alveolar nerve repositioning in implant dentistry: a preliminary report.

The surgical repositioning of the inferior alveolar nerve facilitates the placement of implants in the posterior mandible. The entire height of the posterior mandible is made available and enables implants to be anchored in two cortical plates, improving the primary fixation and increasing the area of the bone-implant interface. The posterior mandible can thus be predictably treated with implants in those cases where posterior support is considered important for occlusal stability and masticatory efficiency. The rapid and total recovery of sensation to the lip following nerve repositioning renders the procedure more acceptable to both the patient and the clinician.

Bicuspid↗
PubMed1994

Restoration of the maxillary arch using implants, natural teeth and the Konus crown: a case study.

Restoring the maxillary arch by using a suprastructure retained by a Konus crown means that the patient can remove the crown for oral hygiene. This construction enables large embrasure spaces to be avoided without compromising phonetics, that is, without adversely affecting the patient's speech. It also enables the dental surgeon to monitor the tooth and implant abutments and the soft tissues around them. In this article we demonstrate successful restoration of the maxillary arch by the use of Konus crowns on a combination of implants and natural teeth.

Crowns↗
PubMed1994

Brain stem auditory evoked responses during the cold pressor test.

This study was conducted to determine changes, if any, in Brain stem auditory evoked responses (BAEP's) during the cold pressor test (CPT) in healthy human subjects. Thirteen subjects (age 18-25 yrs) were selected for the study. Their BAEP's were recorded using standardized technique employing 10-20 international electrode placement system and sound click stimuli of specified intensity, duration and frequency. The standard CPT was performed in the non-dominant hand and the BAEP's, heart rate and blood pressure were recorded before and during the CPT. The values of absolute peak latencies and amplitude of evoked responses were statistically analysed. The amplitude of wave V showed a significant increase (P < 0.05) during the CPT (0.47 +/- 0.203 and 0.37 +/- 0.174 mu v before and during CPT respectively). This could be due to interaction of activated central ascending monoaminergic pathways or nociceptive afferents with the midbrain auditory generator so as to increase it's activity.

Acoustic Stimulation↗
PubMed1994

Sensory nerve conduction during cold pressor response in humans.

A study was carried out to find the correlation, if any of autonomic responses and experimental pain induced during the cold pressor test (CPT) with the median nerve sensory conduction velocity (SCV). In 19 healthy subjects who volunteered for the study, the nondominant hand of each was subjected to the CPT and, pain parameters, heart rate, blood pressure and SCV were recorded. Dominant median nerve SCV was measured by orthodromic stimulation of the index finger and evoked responses were recorded at the wrist. In each subject, 32 evoked action potential responses were averaged to determine the SCV. Median nerve SCV of 57.8 +/- 5.2, 56.6 +/- 5.1, 57.0 +/- 5.2 and 57.8 +/- 5.1 m/sec were recorded before, during, immediately after and after ten minutes of the CPT, respectively. The SCV and the amplitude of the evoked response were significantly (P < 0.001 and P < 0.01 respectively) decreased during the CPT. A significant relationship (P < 0.05) was found between nerve conduction parameters and diastolic blood pressure recorded before the CPT. These findings suggest that sympathetic overactivity and/or cold induced pain interacts with sensory conduction in the contralateral median nerve so as to decrease its conduction velocity. There also exists a relationship between SCV and vasomotor mechanisms controlling peripheral resistance, and hence the diastolic pressure.

Adolescent↗
PubMed1993

Allograft in the treatment of benign cystic lesions of bone.

Seventeen patients with benign cystic osseous lesions were treated by curettage and grafting using allogenic decalcified bone. Human bones were partially decalcified using 0.6 N HCl and preserved in 90% ethanol in a deep freezer at -16 degrees C. The cystic lesions were: 5 cases of fibrous dysplasia, 4 aneurysmal bone cysts, 3 simple bone cysts, 2 giant-cell tumours, 1 chondromyxoid fibroma, 1 non-ossifying fibroma and 1 fibrous cortical defect. The bones involved were: femur, tibia, humerus, fibula and calcaneum. Infection was a complication in three patients. In two of these it did not interfere with healing, but in one it persisted for more than 1 year with partial resorption of the graft. The time to adequate incorporation of the graft varied from 6 to 9 months in children and 9 to 15 months in adults. The overall response compares favourably with that to allograft from more sophisticated bone banks.

Adolescent↗