Biomedical subjects

D Rajasekar

Publications and source records attributed to D Rajasekar.

9 recordsLinked to original sources

PubMed2004

Problems and uncertainties with multiple point A's during multiple high-dose-rate intracavitary brachytherapy in carcinoma of the cervix.

AIMS: This study evaluates the consequences of point A as a dose prescription point during multiple high-dose-rate (HDR) intracavitary brachytherapy (ICBT) in cancer cervix. MATERIALS AND METHODS: Fifty patients who had received teletherapy were randomised into two groups of 25 to receive three HDR ICBT fractions of 6 Gy each at point A with either a flexible Ralstron (Shimadzu Corporation, Japan) or rigid Rotterdam (Nucletron, Netherlands) applicator. The orthogonal radiographs of the 150 applications were evaluated for applicator geometry and point A co-ordinates. RESULTS: Irrespective of the nature and rigidity of the applicators, its various components exhibited a highly significant variation during multiple fractionated HDR ICBT. The Cartesian co-ordinates of point A (left and right) for the applicator geometry also showed significant variation during multiple HDR ICBT procedures. This resulted in an average shift of 9.5 mm (SD= +/-4.4) and 11.1 mm (SD= +/-6.4) in right point A, 10.2 mm (SD= +/-4.5) and 10.8 mm (SD= +/-6.6) in left point A for Ralstron and Rotterdam applicator, respectively, during the three HDR ICBT. Consequently, doses to both right and left point A's showed significant variation during multiple ICBT application and were independent of the applicator type. CONCLUSION: Applicator variation in the components and spatial position in the pelvis during multiple HDR ICBT results in multiple point A's irrespective of the nature of applicator, leading to uncertainty in the dose prescription. These uncertainties, which have a bearing on clinical end points, could be minimised by shifting from point-based dose prescription to image-based target localisation and treatment planning in ICBT.

Adult↗

PubMed2003

Multimodality image fusion in dose escalation studies of brain tumors.

This article examines the utility of integrating images from computed tomography (CT), magnetic resonance imaging (MRI), and single photon emission computed tomography (SPECT) for radiation treatment planning of brain tumors for dose escalation studies. The information obtained from these imaging modalities is complementary to each other and could provide anatomic (through CT and MRI) and metabolic (through SPECT) information of the target. This anato-metabolic target localization could be expected to facilitate precise radiation therapy planning for brain tumors by delineating the boundary between the tumor, edema, and the normal brain parenchyma and identify the viable tumor nidus with greater degree of certainty. This could in turn lead to minimize dose to the normal tissue and permit dose escalation to the region of interest. The utility of these anato-metabolic imaging modalities for defining the clinical target volumes along with planning target volumes for different phases of the radiation therapy is illustrated.

Adult↗

PubMed2002

Electron beam therapy at extended SSDs: an analysis of output correction factors for a Mitsubishi linear accelerator.

The effects of extended source-to-surface distance (SSD) on the electron beam dose profiles were evaluated for various electron beam energies--6, 9, 12, 15 and 20 MeV-and the accuracy of various output correction methods was analysed on a Mitsubishi linear accelerator using a radiation field analyser (RFA). The dose fall-off region of the central axis depth-dose curves was nearly independent for SSDs up to 120 cm where as in the build-up region, a marginal reduction of surface dose was observed, particularly for lower energies and for smaller field sizes. Effective SSDs and virtual source distances were evaluated for field sizes ranging from 5 x 5 to 15 x 15 cm2 for various energies. Curve fitting was done with the measured outputs with various equations and coefficients were evaluated. The accuracy of the derived output correction factors by effective SSD, virtual source distance and curve-fit methods was assessed by evaluating correlation coefficients between the calculated and the measured values. The correlation coefficient was best with the linear-quadratic equation followed by the effective SSD method and the virtual source method. The output correction based on the linear-quadratic equation showed the best estimate of electron beam output at extended SSDs with an accuracy well within +/- 1%. The rapid reduction of dose due to the applicator-scattered component at d(max) point with an extended SSD was significant for the 5 x 5 cm2 applicator and lower energies.

Algorithms↗

PubMed2000

Pill knowledge amongst oral contraceptive users in family planning clinics in Scotland: facts, myths and fantasies.

OBJECTIVES: To document the extent of understanding about the combined pill amongst oral contraceptive users in Scotland. METHOD: A questionnaire was distributed to 2700 pill users in Scottish family planning clinics prior to their consultation with a clinician for a repeat prescription. RESULTS: Knowledge was patchy and usually incomplete in any given area. CONCLUSION: Counselling and teaching about oral contraceptives are important parts of the clinical consultation; even if the user appears knowledgeable about their contraceptive method, there are likely to be some areas where their knowledge could be improved.

Contraceptives, Oral, Combined↗

PubMed1999

Nationwide audit of pill knowledge amongst family planning users in Scotland.

OBJECTIVES: The primary objective of this study was to estimate knowledge about oral contraceptives amongst oral contraceptive users within family planning clinics in Scotland and to ascertain if this was due to clinicians not attempting to convey certain information or to a lack of understanding of teaching. METHOD: This was a criterion-based audit using three separate questionnaires to estimate the agreement of senior staff with criteria set by a multi-disciplinary expert panel, actual routine clinical practice and user knowledge. RESULTS: Senior clinical staff within family planning clinics in Scotland agreed with 12 out of 15 criteria set by a multidisciplinary panel in over 85% of cases. For six out of 15 criteria, there was a discrepancy of more than 30% in what clinicians did in practice compared to what senior staff thought they ought to do. For a further two criteria, there was a deficiency of over 30% between the number of clients who understood the criteria and the number of clients the clinicians thought they had taught. Most importantly, these latter criteria included the rules for safe and effective pill taking. CONCLUSION: An improvement in user knowledge is required to achieve effective and reliable use of oral contraceptives. Methods of doing this, such as staff and client prompts, should be further explored.

Contraceptives, Oral, Combined↗

PubMed1999

Analysis of pill knowledge amongst oral contraceptive users in Scotland according to client characteristics.

OBJECTIVES: The primary objective of this study was to investigate the relationship between various client characteristics and knowledge of oral contraceptives amongst pill users. METHOD: This was a subanalysis of the data from the national audit of Scottish family planning clinics. RESULTS: There were significant differences in knowledge about many different criteria according to the characteristics of the client group. Low educational attainment, unemployment and more rural residence produced greater significant differences in contraception knowledge than social deprivation according to postcode (zipcode). Age and duration of use affected different criteria to varying degrees, but teenagers scored relatively poorly compared to the general population and knowledge did not significantly improve overall with duration of use. CONCLUSION: Client characteristics do affect levels of pill knowledge. Clinicians must reflect on how to communicate more effectively with all types of pill users. They should take the opportunity of clinic visits for repeat pill prescriptions to improve knowledge levels.

Adolescent↗

PubMed1998

Partial transmission block for optimization of anterior supraclavicular-posterior axillary boost in the radiation therapy of carcinoma breast.

Radiation therapy of breast often involves an anterior supraclavicular-axillary (SC-AX) portal to irradiate the supraclavicular and axillary contents. However, the fall-off of the dose in this region leads to an inhomogeneity that could result either during the use of a single anterior SC-AX field or even with the concomitant use of a posterior axillary boost. An attempt has been made to circumvent this inhomogeneity by the use of a partial transmission block that could be placed in the anterior SC-AX portal corresponding to the posterior axillary boost field. The details of the quantum of partial transmission block to be used for different axillary separations and the reference depths of the dose prescription has been evaluated and presented.

Axilla↗

PubMed1997

Urinary tract injuries during obstetric intervention.

A retrospective case record review of obstetric urinary tract injury in the Grampian region from 1976 to 1993 identified 16 cases of bladder injury (0.1 per 1000 deliveries, 1.4 per 1000 caesarean sections and four cases of ureteric injury (0.03 per 1000 deliveries, 0.27 per 1000 caesarean sections). Diagnosis of bladder injury was immediate, but of ureteric injury often delayed. Although the injury rates are lower than previously reported and previously reported risk factors not confirmed, this audit has resulted in guidelines for junior staff, compliance with which will be monitored, and every case of urinary tract injury will be reviewed.

Cesarean Section↗

PubMed1995

Induction of abortion with mifepristone (RU 486) and oral or vaginal misoprostol.

BACKGROUND: Medical termination of pregnancy can be successfully performed with a combination of mifepristone (RU 486) and a prostaglandin analogue. We conducted a prospective, randomized trial to compare oral with vaginal administration of the prostaglandin E1 analogue misoprostol for first-trimester abortion in women treated initially with mifepristone. METHODS: The study population consisted of 270 women seeking abortion within 63 days after the onset of amenorrhea. The dose of mifepristone was 600 mg, and the dose of misoprostol was 800 micrograms. The study had two primary end points: expulsion of the conceptus without the need for a surgical procedure, and abortion within four hours after the administration of misoprostol. RESULTS: Expulsion of the conceptus without the need for a surgical procedure occurred in 95 percent of the women who received misoprostol vaginally and in 87 percent of those who received it orally (P = 0.03). The rate of continued pregnancy was 7 percent with the oral regimen and 1 percent with the vaginal regimen (P = 0.01). Ninety-three percent of the women receiving misoprostol vaginally had abortions within four hours, as compared with only 78 percent of the women receiving the drug orally (P < 0.001). Vomiting and diarrhea were reported more frequently by the women who received oral misoprostol than by those who received vaginal misoprostol (P = 0.04 and P = 0.002, respectively). CONCLUSIONS: After the administration of mifepristone, vaginal administration of misoprostol is more effective and better tolerated than oral administration for the induction of first-trimester abortion.

Abortion, Induced↗