Use of statistical checks as maintenance tools for TLD readers

Although the values of different parameters may remain within permissible limits during the operation of a thermoluminescent dosemeter (TLD) reader, certain effects can become apparent only when a long-term followup of these parameters is performed. In order to ensure an accurate and reliable operation of a TLD reader, the system characteristics must be monitored continuously. Long-term statistical checks of key system parameters may give a broader insight into the operational characteristics of the TLD reader and may help for proper maintenance of the system. The photomultipliers noise, the internal reference light source stability and the A to D reference voltage were found to be critical parameters, which have a major influence on the accuracy and stability of the system. A followup of these parameters for a period of about 10 y is presented, and some problems are seen to be reflected in the distributions.

On the reassessment of doses in TL-dosimetry by measuring the residual dose

Second readouts and the photo-transferred thermoluminscence (PTTL) method are sometimes used to reassess high doses. When using the common LiF:Mg,Ti, if the second readout is performed by a regular readout cycle of 13.3 s, its efficiency is low and the estimations cannot be obtained with acceptable accuracy for low doses in the 10-100 mSv range. By applying the PTTL method, the efficiency is much higher, but a high background is also present, deteriorating the quality of the reassessment. A simple and efficient method was studied, which consists of expanding the heating time to 30 s. Although the efficiency relative to a standard readout is improved by only a factor of 3, the low background enables to obtain results with the same uncertainty as the more complicated PTTL method. By applying region of integration discrimination, the errors can be further diminished.

On the reassessment of thermal neutron doses in TLD-100 by measuring the residual dose

By employing second readouts and the Phototransferred thermoluminescence (PTTL) method, high doses may be reassessed on the basis of residual dose information. It was shown in the past that for TLD-100, gamma doses can be reassessed by using a simple and efficient method, which consists of expanding the heating time to 30 s. In the present study, the 'extended time' method and the PTTL residual dose evaluations are used for reassessing thermal neutron doses when using TLD-100 crystals. Reassessment characteristics are presented for relatively low thermal neutron doses, in the range between approximately 1 and 18 mSv gamma dose equivalent.

Improved localization of a 'hot spot' in the lungs for an array of four HPGe detectors--the isotopic ratio effect

Considerable errors in the determination of radioactivity in lungs are caused by the usual assumption of homogeneous distribution, while actually the radioactive contamination can be distributed, and even in the form of a 'hot spot'. Modern lung counter systems use several HPGe detectors, and the ratio of the different count rates of the detectors can be used to locate a 'hot spot' and apply correction algorithms for activity calculation. In the present work it is shown that the variability of the isotopic composition of the uranium source has a major effect on the process of localization of the 'hot spot' in the lungs. A way to eliminate this effect is proposed by separate normalization of the count rates of each energy peak.

Optimisation of the readout parameters when evaluating thermal neutron doses by TL dosimetry with LiF:Mg,Ti

The location of the glow peaks depends on the heating rate. It takes some time until the crystal reaches the heater temperature, and this time lag has a direct effect on the shift of peaks towards higher temperatures. Some information on the high-temperature peaks may be lost if the readout conditions (mainly length of time) are not properly chosen. Step heating profiles to a varying final temperature between 300 degrees C and 125 degrees C were used to study the time dependence of the collected information in the glow curves of (6)LiF:Mg,Ti crystals, and the minimal heating time for evaluation of thermal neutron doses was determined.

Are national guidelines for total hip replacement in the UK reflected in practice?

INTRODUCTION

A cross-sectional study was performed to compare the practice of total hip replacement (THR) in the UK against national guidelines.

MATERIALS AND METHODS

A postal questionnaire was sent to all fellows of the British Orthopaedic Association.

RESULTS

Of the 1587 questionnaires sent out, 966 (60.9%) were returned. Of these, 706 (73.1%) were available for data collection and analysis.

CONCLUSIONS

Consensus was observed in several areas including the use of pre-admission clinics and modern cementing techniques. Facilities deemed necessary for THR surgery such as HDU/ITU back-up, ultra-clean air and dedicated orthopaedic wards are almost universally available. However, a lack of consensus is evident in many areas including the process of obtaining written consent, thrombo-embolic prophylaxis, duration of antibiotic prophylaxis, supervision of trainee surgeons and follow-up arrangements. The proliferation in the range of implants, particularly aimed at 'younger' patients, available to surgeons has once again been highlighted.

A comparative study of fuzzy classification methods on breast cancer data

In this paper, we examine the performance of four fuzzy rule generation methods on Wisconsin breast cancer data. The first method generates fuzzy if-then rules using the mean and the standard deviation of attribute values with 92.2% correct classification rate. The second approach generates fuzzy if-then rules using the histogram of attributes values with 86.7% correct classification rate. The third procedure generates fuzzy if-then rules with certainty of each attribute into homogeneous fuzzy sets with 99.73% correct classification rate. In the fourth approach, only overlapping areas are partitioned with 62.57% correct classification rate. The first two approaches generate a single fuzzy if-then rule for each class by specifying the membership function of each antecedent fuzzy set using the information about attribute values of training patterns. The other two approaches are based on fuzzy grids with homogeneous fuzzy partitions of each attribute. The performance of each approach is evaluated on breast cancer data sets. Simulation results show that the simple grid approach has a high classification rate of 99.73%.

There is more than one kind of myofibroblast: analysis of CD34 expression in benign, in situ, and invasive breast lesions

AIMS

Smooth muscle actin (SMA) positive myofibroblasts have been implicated in tumour invasion; however, acquisition of SMA is not limited to peritumorous fibroblasts and other changes in fibroblasts may be more specifically related to the malignant environment. CD34 is a sialomucin expressed by normal breast fibroblasts but lost in invasive carcinomas. The aim of this study was to establish the relation between CD34 and SMA expression in breast fibroblasts and to analyse whether loss of CD34 is specific for invasive disease.

METHODS

Immunohistochemistry for CD34 and SMA was performed on 135 cases including 10 normal, 10 fibroadenomas, 40 infiltrating ductal carcinomas, 55 cases of ductal carcinoma in situ (DCIS), and 20 radial scar/complex sclerosing lesions. The relation between staining pattern and histopathological features was recorded as positive, negative, or reduced.

RESULTS

Fibroblasts around all normal duct-lobule units and those showing epithelial hyperplasia were CD34 positive and mainly SMA negative. In fibroadenomas, fibroblasts retained CD34 but acquired SMA expression. In contrast, fibroblasts around invasive carcinoma were CD34 positive and SMA negative. In DCIS, loss of CD34 was significantly more frequent in high grade tumours than in low or intermediate grade ones (p < 0.001). The acquisition of SMA was seen more frequently than the loss of CD34, particularly in non-high grade DCIS. In all radial scars, fibroblasts were SMA positive but CD34 negative, and a similar pattern was seen in stromal cells in areas of fibrosis following core biopsy.

CONCLUSIONS

These results show that SMA positive myofibroblasts exhibit variable expression of CD34, indicating that these markers are not coordinately controlled. Loss of CD34 is strongly related to the malignant phenotype, in both invasive and preinvasive disease, but is not entirely specific because radial scar fibroblasts and fibroblasts in reactive fibrosis exhibit a similar phenotype. The functional relevance of altered CD34 expression is unclear but the very focal changes implicate local signalling mechanisms probably of epithelial origin.

Sensorineural hearing loss following acute bacterial meningitis in non-neonates

OBJECTIVE

Sensorineural hearing loss (SNHL) is an important sequelae of acute bacterial meningitis (ABM) in children. This study was undertaken to determine the incidence of SNHL following meningitis in non-neonates and its correlation with various factors.

METHODS

Children between the ages of 1 month and 12 years with ABM admitted in a teaching hospital over a period of 18 months were enrolled. Detailed history was taken, clinical examination performed and cerebrospinal fluid analyzed at commencement of therapy, 48 hours later and at the end of treatment. On discharge brainstem evoked response audiometry (BERA) was recorded. Data were analyzed using appropriate statistical tests.

RESULTS

Out of 32 children enrolled, 9 (28.1%) developed SNHL, bilateral in 21.9% and unilateral in 6.2%. Among hearing impaired subjects, 11.2% had mild while 44.4% each had moderate and profound hearing loss. Age, presence of vomiting, altered sensorium seizures and aminoglycoside usage were not significantly different in those with and without SNHL, but the total duration of fever was (p<0.05). There was significantly higher protein content and neutrophils in the second CSF sample of those with SNHL.

CONCLUSION

There is a greater than 50% probability of the child developing SNHL if neutrophil percentage in the second CSF is 80% or more. Since the overall risk of SNHL is significant in children with meningitis, it is recommended that BERA be recorded in all, so that early intervention may be possible.

Refractures in patients at least forty-five years old. a prospective analysis of twenty-two thousand and sixty patients

BACKGROUND

Individuals who sustain a low-energy fracture are at increased risk of sustaining a subsequent low-energy fracture. The incidence of these refractures may be reduced by secondary preventative measures, although justifying such interventions and evaluating their impact is difficult without substantive evidence of the severity of the refracture risk. The aim of this study was to quantify the risk of sustaining another fracture following a low-energy fracture compared with the risk in an age and sex-matched reference population.

METHODS

During the twelve-year period between January 1988 and December 1999, all inpatient and outpatient fracture-treatment events were prospectively audited in a trauma unit that is the sole source of fracture treatment for a well-defined local catchment population. During this time, 22,060 patients at least forty-five years of age who had sustained a total of 22,494 low-energy fractures of the hip, wrist, proximal part of the humerus, or ankle were identified. All refracture events were linked to the index fracture in the database during the twelve-year period. The incidence of refracture in the cohort of patients who had sustained a previous fracture was divided by the "background" incidence of index fractures within the same local population to obtain the relative risk of refracture. Person-years at-risk methodology was used to control for the effect of the expected increase in mortality with advancing age.

RESULTS

Within the cohort, 2913 patients (13.2%) subsequently sustained a total of 3024 refractures during the twelve-year period. Patients with a previous low-energy fracture had a relative risk of 3.89 of sustaining a subsequent low-energy fracture. The relative risk was significantly increased for both sexes, but it was greater for men (relative risk = 5.55) than it was for women (relative risk = 2.94). The relative risk was 5.23 in the youngest age cohort (patients between forty-five and forty-nine years of age), and it decreased with increasing age to 1.20 in the oldest cohort (patients at least eighty-five years of age).

CONCLUSIONS

Individuals who sustain a low-energy fracture between the ages of forty-five and eighty-four years have an increased relative risk of sustaining another low-energy fracture. This increased risk was greater when the index fracture occurred earlier in life; the risk decreased with advancing age. Secondary preventative measures designed to reduce the risk of refracture following a low-energy fracture are likely to have a greater impact on younger individuals.

Prognostic significance of intratumoural microvessel density (IMD) in resected pancreatic and ampullary cancers to standard histopathological variables and survival

AIM

Angiogenesis is required for tumour growth. Its evaluation, by intratumoural microvessel density (IMD), has prognostic significance in many solid tumours. There is controversy regarding its use in pancreatic cancer and little is known about its role in ampullary tumours. The aim is to study IMD as a prognostic marker in resected ductal adenocarcinomas of head of pancreas and cancers of the ampullary region.

METHODS

Forty-seven patients (23 pancreatic and 24 ampullary, mean age 62.0 years) surviving a potentially curative (R0/R1) resection were analysed. Paraffin-embedded sections of these tumours were immunohistochemically stained for CD-34 and IMD was determined (magnification x200). This was correlated with histopathological data and survival using Cox's multivariate analysis.

RESULTS

Mean survival for the pancreatic cancer group was 18.4 months (SE=2.7) and 81.2 months (SE=9.9) for the ampullary cancer group. In the pancreatic cancer group, IMD was found to have independent prognostic significance to survival on multivariate analysis (P=0.002, Hazard Ratio (HR) 13.60) along with microscopic resection margin involvement (P=0.003, HR 15.18). For ampullary cancers, IMD was higher in those with lymph node metastasis (P=0.02, Mann-Whitney U -test).

CONCLUSION

IMD in resected pancreatic cancers correlates with survival.

Assessment of faecal occult blood loss by qualitative and quantitative methods

BACKGROUND

Various methods exist for the assessment of faecal occult blood loss in a patient with suspected gastrointestinal blood loss.

METHODS

The present study examined the effectiveness and financial implications of a qualitative guaiac-based method (Haemoccult) of faecal occult blood detection and a quantitative measure of haeme-derived porphyrins (Hemoquant) in 184 patients who underwent assessment of faecal blood loss by both methods over a three year period during assessment of iron deficiency anaemia.

MAIN FINDINGS

At least one Haemoccult test was positive in 72.2% of patients while Hemoquant was suggestive of significant blood loss (> 2mg haemoglobin/g faeces) in 29.9%. Patients underwent a total of 324 further endoscopic or radiological investigations of which 76.5% demonstrated no abnormality. A diagnosis was reached in 60 patients (32.6%). A significant potential source of gastrointestinal bleeding was found in 48 patients (26.1%). Hemoquant achieved a sensitivity of 62.5% and a specificity of 81.6% while with Haemoccult it was 85.4% and 32.4%, respectively. Hemoquant was normal in 18 patients with significant gastrointestinal conditions including peptic ulcers and colonic polyps. While Haemoccult only missed 7 lesions, two of these were colonic cancers. The quantitative nature of the Hemoquant test gave little clue as to diagnosis.

CONCLUSION

Neither of the tests examined was ideal but Hemoquant had an overall better performance and further investigation of patients with evidence of blood loss from this test should be mandatory.

CSF beta-1 Globulin--a potential marker in differentiating multiple sclerosis and acute disseminated encephalomyelitis: a preliminary study

The exact diagnosis of demyelinating diseases is an enigma even in the best neurological centres. In the present study, the potential role of differential CSF proteins has been critically evaluated in differentiating multiple sclerosis (MS) and acute disseminated encephalomyelitis (ADEM). Cellulose acetate electrophoresis was carried out on CSF and serum samples of 14 MS patients, 23 ADEM patients and 30 controls. There was no statistically significant difference between serum electrophoresis of controls and MS patients. However, in case of CSF electrophoresis there was a statistically significant decrease in beta-1 fraction in 92.2% of MS patients (p=0.01). A comparison between serum electrophoresis of controls and ADEM patients indicated a statistically significant decrease in serum albumin in 87% patients and an increase of alpha-2 globulin in 73.9%. There was no statistically significant difference between CSF electrophoresis of controls and ADEM patients except for the prealbumin fraction which was raised in 60.9% of patients. No statistically significant difference was seen between the serum electrophoresis of ADEM and MS patients. However, on comparing CSF electrophoresis, it was seen that beta-1 fraction was significantly higher in ADEM patients (p<0.05). The predictive value of beta-1 fraction in differentiating MS and ADEM was then evaluated. The negative predictive value was 100% indicating that all samples with a beta-1 fraction of>6.5% cannot be diagnosed as MS. The significant decrease in beta-1 fraction in MS patients may prove to be an early indicator in differentiating between MS and ADEM patients.

Severe hyponatraemia: current concepts on pathogenesis and treatment

Severe hyponatraemia (serum sodium <120 mEq/L) is a serious electrolyte disorder associated with life-threatening neurological complications. It develops most often when the ability of the kidney to excrete free water is impaired. The initial adaptation of the brain to hyponatraemia includes loss of water, sodium, potassium and chloride into the cerebrospinal fluid and the late adaptation consists of the loss of organic osmolytes. Adaptation of the brain to hyponatraemia causes potential problems during therapy, as re-adaptation requires a considerably longer time. Rapid correction of hyponatraemia may lead to the development of the osmotic demyelination syndrome. Though the ideal treatment for severe hyponatraemia remains controversial, a consensus regarding therapeutic guidelines has emerged. The rate of correction and the type of infusate depend on the duration and cause of the hyponatraemia, clinical presentation, volume status, renal function and the serum potassium level. The prognosis of the osmotic demyelination syndrome is rather dismal although several therapeutic modalities have been tried.

Growth arrest lines and recurrent patellar dislocation: a new sign

The phenomenon of growth arrest lines has been widely described in the medical literature. They are usually found at the metaphysis of growing long bones and are the result of short periods of partial growth arrest. Recurrent dislocation of the patella is a well-recognised problem, particularly in adolescents. Several radiological features have been reported in association with patellar dislocation or instability. We have reported a hitherto undescribed radiological sign of patellar growth arrest lines on the skyline radiographs of two patients with this condition. The shape of the patella when symptoms were at their worst corresponded remarkably closely to the outline of the subsequent growth arrest line. We postulated that repeated dislocations adversely affect the process of normal maturation of the patella. With the resolution of symptoms, patella ossification resumes, leaving the telltale sign of previous injury in the form of a growth arrest line and an improvement in bone density once the patella has been stabilised and tracks normally.

Assessing an educational intervention to improve physician violence screening skills

OBJECTIVES

Health professionals play an integral role in assessing the risk of violence in their patients. However, there have been few evaluations of violence prevention education programs for health care personnel. The objective of this study was to evaluate the effects of a violence-screening education program on pediatric residents' and medical students' comfort level and skills in the identification and management of violence risks.

SETTING

Adolescent clinic of a tertiary care pediatric hospital.

PARTICIPANTS

Fifty-six second-year residents and third-year medical students assigned to a 4-week adolescent clinic rotation.

DESIGN

Randomized, controlled comparison study conducted over a 1-year period.

INTERVENTION

On alternate months, medical students and residents in the intervention group participated in a 3-hour workshop on violence prevention. The workshop included a didactic session with an overview of firearm, media, and sexual violence; a discussion of risk factors for adolescent violence; and training on the approach to the adolescent interview. Participants also discussed violence risks in the community with a panel of teen health educators, engaged in one-on-one role play with the youth educators, and received feedback on their violence screening skills. The control group received the standard ambulatory clinic manual with articles on violence prevention.

EVALUATION METHODS

All participants completed prerotation and postrotation questionnaires assessing their self-reported screening practices, as well as perceived importance and confidence in violence screening. Participants also interviewed and examined an adolescent standardized patient (SP) in the clinic. SPs completed evaluations on the content of the residents' and students' screening, their interpersonal skills, and their skill in the identification and management of the violence-related problem.

RESULTS

Over 12 months, 30 control and 26 intervention participants were recruited. There were no differences in prerotation questionnaire scores for intervention and control groups in screening practices, perceived importance and confidence in violence screening. Postrotation intervention participants reported more screening compared with controls on violence in school/neighborhood and fighting history. There was also greater perceived importance in asking about access/use of weapons and violence in school/neighborhood. Intervention participants also had improved performance compared with controls on SP evaluations of screening for violence, identification and management of the violence-related scenario, and interpersonal skills.

CONCLUSION

A violence prevention education program with teen health educators improved participants' self-reported violence questioning, as well as increased perceived comfort and importance in violence screening. Participants in the program also improved their identification and management of a standardized violence-related scenario presented in an adolescent clinic setting. adolescent violence, physician education, violence risk screening.

Toxic megacolon in a renal allograft recipient with cytomegalovirus colitis

We report a 35-year-old man, a renal allograft recipient, who presented with toxic megacolon. Segmental biopsies from the colon were consistent with cytomegalovirus colitis. Serum polymerase chain reaction for cytomegalovirus DNA confirmed the diagnosis. He was treated with ganciclovir but, though his abdominal condition improved initially, he worsened later and succumbed to his illness.