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Biomedical subjects

S A Naqvi

Publications and source records attributed to S A Naqvi.

At least 19 recordsLinked to original sources
PubMed2005

Accuracy of admitting diagnosis in acute surgical patients by non consultant hospital doctors.

The incidence of accurate diagnosis made by non-consultant hospital doctors (NCHDs) is unknown in acute surgical admissions. There is a common assumption that reliance is made on excessive and inappropriate investigations. The aim of study was to assess the accuracy of admitting diagnosis by the NCHDs and the appropriateness of radiological investigations ordered. Data were collected on 100 consecutive acute surgical admissions. A final diagnosis was made in all the patients. 79 patients had accurate initial diagnosis (NCHDs). 23 scans were performed which confirmed the initial diagnosis. Out of 21 initial inaccurate diagnoses, final diagnosis was made on repeated clinical examination in 10, on imaging alone in 5 and by endoscopy or surgery in the remaining 6 patients. 11 patients had scans and 7 were appropriate. We conclude that 79% of diagnoses made by NCHDs are the accurate final diagnoses. The utilization of diagnostic modalities especially radiological imaging is highly appropriate. Our study suggests that the physical presence of a consultant on site may not lead to significant improvement to the delivery of health care to the Irish population.

Adult↗
PubMed2005

Bullying of junior doctors prevails in Irish health system: a bitter reality.

Workplace bullying in health systems is a well known fact. It leads to not only breakdown in teamwork but also has significant affect on the individual's personal life. True prevalence of bullying in junior doctors working in Ireland is unknown. Our aim of study was to find out the prevalence of bullying in junior doctors working hospitals in south and western counties of Ireland and to assess its effects on the productivity of work and family life and to identify the common source of bullying. We carried out a questionnaire survey. A total of 950 questionnaires were sent. Response rate was 51%. Our sample is 15% of the target population of all the hospital junior doctors. 30% of the responders claimed to be subjected to one or more bullying behaviors. Doctors from European Union (EU) reported significantly less rate of bullying compares to non EU doctors. Our results are in line with the results of studies conducted in United Kingdom. This study shows the magnitude and source of the problem. We conclude that bullying is a common problem in Irish health system. Increased awareness and zero tolerance are required to eradicate bullying.

European Union↗
PubMed2003

Management of pediatric urolithiasis in Pakistan: experience with 1,440 children.

PURPOSE: We evaluated the efficacy and safety of different modalities for pediatric urolithiasis in a developing country in 2 eras, namely before and after the advent of minimally invasive surgery. MATERIALS AND METHODS: We retrospectively reviewed the records of 1,440 children younger than 14 years treated with various modalities during a 14-year period. From 1987 to 1995, 486 and 50 patients were treated with open surgery, and extracorporeal shock wave lithotripsy (ESWL, Dornier Medical Systems, Inc., Marietta, Georgia) and minimally invasive methods, respectively. Between 1996 and 2000, 518 and 386 children were treated with surgery and minimally invasive methods, respectively. RESULTS: Of the 1,440 children 795 (55.2%) had renal, 198 (13.8%) had ureteral and 447 (31%) had bladder calculi. Of the renal stones 556 (70%), 177 (22%) and 62 (7.8%) were treated with open surgery, ESWL and percutaneous nephrolithotomy, respectively. Of the ureteral calculi 85 (43%), 37 (18.6%) and 76 (38%) were managed by ESWL, ureterorenoscopy and open surgery, respectively. Of the bladder calculi 307 (68%), 77 (17.2%) and 63 (14%) were treated with open vesicolithotomy, transurethral pneumatic cystolithotripsy and ESWL, respectively. The renal stone clearance rate was 98% after open surgery, 84% after ESWL and 68% after percutaneous nephrolithotomy monotherapy at 3 months of followup. Similarly the ureteral stone-free rate was 54% after ESWL and 86.9% after ureterorenoscopy. Of the patients with bladder calculi 48% and 93% become stone-free after ESWL and transurethral pneumatic cystolithotripsy, respectively. CONCLUSIONS: The use of ESWL, percutaneous nephrolithotomy and ureterorenoscopy has resulted in treating a large number of children with a short hospital stay and early return to school. Open surgery is reserved only for complex stones.

Adolescent↗
PubMed2001

Heavy mining vehicle controls and skidding accidents.

This paper examines various control locations in heavy mining vehicles. Three trucks have been tested on a skid pad in both clockwise and anticlockwise directions. The skid lengths were measured after each trial. The primary focus of the study was the positioning of various controls and their relevance to various skid lengths. Some additional measures such as NASA-TLX scales were also used to make subjective evaluations. The results are presented in this paper. The findings clearly indicate the relevance of control locations to actual skid lengths. The poorly located controls resulted in greater skid lengths. This is an important finding as skid lengths are related to greater reaction times in a skidding situation and hence greater risk of accidents on relevant trucks. Such accidents can incur large repair bills for damaged equipment whereas more importantly, jeopardizing the life and safety of heavy mining vehicle drivers.

Accidents, Occupational↗
PubMed2001

Analysing collimator structure effects in head-scatter calculations for IMRT class fields using scatter raytracing.

The frequent blocking of the irradiated volume in intensity modulated radiation therapy (IMRT) makes the head-scatter fraction of the incident photon fluence more significant than that in conventional therapy with open fields. On the other hand. certain collimator configurations block scatter photons directed to a given observation point while allowing primary photons to be transmitted. The 'anomalous blocking' makes the primary field a poor indicator of the scatter fluence. Since large MU-to-cGy ratios in IMRT can magnify head-scatter uncertainties, it becomes necessary to accurately model both the effective scatter source and the collimator structure that limits the scatter reaching the irradiated volume. First we obtain a dual-source model, using a Taylor series expansion to derive the effective scatter source distribution from the data measured for the Elekta SL20 linac equipped with a multi-leaf collimator (MLC). Then, using a raytracing algorithm, we calculate the transmission of scatter rays from the effective scatter source plane to points in the patient plane. The method can account for the anomalous blocking of scatter by the MLC leaves and the backup diaphragms. For a variety of collimator settings tested, the calculations agree with measurements to an accuracy of 0.002psi10 x 10, where psi10 x 10 is the total (primary + scatter) photon fluence of an open 10 x 10 cm2 field for the same MU delivered. Although the significance of collimator structure in IMRT depends strongly on fields shapes employed for the delivery, potential cumulative errors on the order of a few per cent can be avoided in fluence calculations if the proposed method is used.

Algorithms↗
PubMed2001

Reducing loss in lateral charged-particle equilibrium due to air cavities present in x-ray irradiated media by using longitudinal magnetic fields.

The underdosing of lesions distal to air cavities, such as those found in upper respiratory passages, occurs due to the loss in lateral charged-particle equilibrium (CPE). The degree of underdosing worsens for smaller field sizes, resulting in more frequent recurrence of the cancer treated. Higher photon energies further aggravate the outcome by producing longer second build-up regions beyond the cavity. Besides underdosing, the larger lateral spread of secondary electron fluence in the air cavity produces diffuse dose distributions at the tissue-air interface for shaped or intensity modulated fields. These disequilibrium effects create undesirable deviations from the intended treatment. The clinical concern is further intensified by the failure of traditional treatment planning systems to even account for such defects. In this work, the use of longitudinal magnetic fields on the order of 0.5 T is proposed for alleviating lateral electronic disequilibrium due to the presence of air cavities in the irradiated volume. The magnetic field enforces lateral CPE by restricting the lateral range of electrons in the air cavity. The problem is studied in a simple water-air-water slab geometry using EGS4 Monte Carlo simulations for 6 MV photons. Electronic disequilibrium is evaluated for beams of various sizes, shapes and intensity distributions constructed by linear superposition of the dose distributions for 0.5 x 0.5 cm2 beamlets. Comparison is also made with 60Co irradiation. The results indicate that the lateral confinement of secondary electrons in the air cavity by sub-MRI strength longitudinal fields is effective in reducing deterioration of dose distributions near tissue-air interfaces. This can potentially reduce recurrence rates of cancers such as the larynx carcinoma.

Cobalt Radioisotopes↗
PubMed2001

Evaluating the effectiveness of a longitudinal magnetic field in reducing underdosing of the regions around upper respiratory cavities irradiated with photon beams--a Monte Carlo study.

The problem of underdosing lesions adjacent to upper respiratory cavities and a proposal to correct it are presented in this work. The EGS4 Monte Carlo code was used to simulate a 6 MV x-ray beam passing through a block of tissues with air cavities 2, 4, and 6 cm wide. The geometry used approximates the tracheal geometry used by previous researchers who investigated the underdosing phenomenon. A uniform longitudinal magnetic field of 0.5 T strength is used to reduce secondary electron outscatter caused by the presence of an air gap, and thus improving the dose at the distal surface of air cavities. We introduce the term "percent dose reduction" (PDR), which is defined as the difference between the dose after the air cavity and the dose at the same depth in soft-tissue phantom normalized to the dose in the tissue phantom, to quantify the reduction in dose after an air gap. We also introduce the term dose improvement ratio (DIR), which is defined as the dose ratio with magnetic field to the dose, at the same point, without magnetic field, to quantify the improvement in dose when the magnetic field is applied. For 2 x 2 x 20 cm3 and 4 x 4 x 20 cm3 air cavities irradiated by 2 x 2 cm2 beams, we found PDRs of 38% and 52%, respectively. This means that for these cavities, there is a 38% and a 52% reduction in dose at the cavity edge compared to the same dose in tissue at the same depth for each cavity. The dose improved by 30% (DIR= 1.3) and 87% (DIR= 1.87), respectively, when applying the magnetic field. The worst effect on dose at the distal side came from larger cavities irradiated with small fields. In these situations, the improvement in dose due to the presence of magnetic field was the largest. This article deals with "ideal" head and neck geometries with a uniform magnetic field. In a paper to follow we will use a CT-based phantom to study the effect in realistic geometries with the presence of a magnetic field from a Helmholtz coil pair.

Electrons↗
PubMed2001

Pericardial effusion as a cause of morbidity in patients on maintenance hemodialysis: is it preventable?

OBJECTIVE: Cardiovascular diseases are the cause for 45% mortality and 20% morbidity in hemodialysis (HD) patients. Pericardial effusion (PE) accounts for 03-04% of all deaths in HD patients as a result of tamponade, arrhythmias or heart failure. This study aims to find out the prevailance and precipitating factors for PE in hemodialysis patients. PATIENTS AND METHODS: Fifty-five patients were identified for echo-cardiographic assessment on the basis of signs and symptoms suggestive of PE i.e., hypotension during dialysis, dyspnea, globular heart in chest x-ray, raised JVP, soft heart sounds and low voltage ECG. A matched controlled group of 55 patients for age, sex, dialysis schedule, cause of ESRD and dialysis bath, was also studied echocardiographically. RESULTS: Pericardial Effusion was detected in 12 patients (10.9%), 10 (83.3%) were on 2/week and only two on 3/week dialysis. Of these 75% were non-compliant in fluid intake and 58.3% were irregular in treatment. The morbidity of PE in study group (18.2%) is significantly higher as compared to controls (3.6%) (P = < 0.05). No correlation was found between development of PE and high iPTH and low albumin levels. Ten patients with mild PE responded to vigorous dialysis. Two patients developed cardiac tamponade needing pericardiocentesis. CONCLUSION: We have identified 2/week dialysis (inadequate dialysis dose), acetate bath and fluid and dialysis non-compliance as factors contributing to development of PE in HD patients.

Adult↗
PubMed2000

High-energy microwave thermotherapy in patients in urinary retention.

PURPOSE: To study the outcome of high-energy transurethral microwave thermotherapy (TUMT) in patients with obstructive benign prostatic hyperplasia (BPH). PATIENT AND METHODS: Between September 1995 and March 1998, patients presenting with urinary retention secondary to BPH were recruited into the study. Their mean age was 67.2 years (range 50-85 years). The mean catheterization time prior to treatment was 3 months (range 15 days-1 year). Among the 200 patients treated during this period, 30 were high anesthesia risk (American Society of Anesthesiologists Class III/IV). The patients were treated in a single 1-hour session using high-energy (Prostatron 2.5) software, the range of energy transmitted being 111.9 to 214.2 kJ (mean 196.3 kJ). Symptoms were scored according to the International Prostatic Symptom Score (IPSS). The mean prostate volume subjected to TUMT was 59 cc (range 40-149.7 cc). The patients were followed every 3 months with measurements of peak flow rate, postvoiding residual urine volume estimation, and IPSS. RESULTS: Of the 200 patients, 33 were lost to follow-up, 155 were responsive (catheter free with physiologically acceptable peak flow rate), and 12 (7%) were nonresponsive. Only 4 patients (2%) experienced deterioration in their flow rates during the follow-up period of 2 years. They underwent transurethral resection. High-energy thermotherapy resulted in irritative voiding complaints in 80% of patients for 2 to 4 weeks. CONCLUSION: The initial results were encouraging, and the 2-year follow-up has shown appreciable sustainability in the treatment outcome, particularly in patients at high anesthesia risk.

Aged↗