Radiation dose reduction in computer assisted navigation for functional endoscopic sinus surgery--cadaver head experiments and clinical implementation

OBJECTIVES

Computed tomography based navigation for endoscopic sinus surgery is inflationary used despite of major public concern about iatrogenic radiation induced cancer risk. Studies on dose reduction for CAS-CT are almost nonexistent. We validate the use of radiation dose reduced CAS-CT for clinically applied surface registration.

METHODS

Dose reduced CAS-CT of mineral salt fixed, human cadaver heads with 9.6, 6, 4, 2 and 1.1 mGy were compared with the reference dose at 65 mGy CTDI (CT-Dose Index). For each CT dose with different surface resolution, the precision of the soft touch registration was measured with target registration error (TRE). In a practical step, dose reduced protocols were tested for 12 months.

RESULTS

Using surface registration at highest and lowest doses, TRE did not differ significantly for registration accuracy. Protocols tested preserved technical registration accuracy and the pragmatics of dose reduction was limited only by different needs for picture quality of the individual surgeon, use for uncomplicated or revision surgery, and reserve for other unexpected factors (movement artifacts).

CONCLUSIONS

The accuracy of today’s surface registration technology was not the limit for dose reduction. It is the amount of diminished picture quality tolerated by the individual surgeon and the question of how much of the ever refined radiological picture resolution is necessary at all. For the majority of operations, consensus for a significant 6-fold radiation dose reduction from 65 mGy to 9.6 mGy CTDI could be realized illustrating a big potential for similar approaches in other institutions.

Radiation dose reduction in computer assisted navigation for functional endoscopic sinus surgery--cadaver head experiments and clinical implementation

OBJECTIVES

Computed tomography based navigation for endoscopic sinus surgery is inflationary used despite of major public concern about iatrogenic radiation induced cancer risk. Studies on dose reduction for CAS-CT are almost nonexistent. We validate the use of radiation dose reduced CAS-CT for clinically applied surface registration.

METHODS

Dose reduced CAS-CT of mineral salt fixed, human cadaver heads with 9.6, 6, 4, 2 and 1.1 mGy were compared with the reference dose at 65 mGy CTDI (CT-Dose Index). For each CT dose with different surface resolution, the precision of the soft touch registration was measured with target registration error (TRE). In a practical step, dose reduced protocols were tested for 12 months.

RESULTS

Using surface registration at highest and lowest doses, TRE did not differ significantly for registration accuracy. Protocols tested preserved technical registration accuracy and the pragmatics of dose reduction was limited only by different needs for picture quality of the individual surgeon, use for uncomplicated or revision surgery, and reserve for other unexpected factors (movement artifacts).

CONCLUSIONS

The accuracy of today’s surface registration technology was not the limit for dose reduction. It is the amount of diminished picture quality tolerated by the individual surgeon and the question of how much of the ever refined radiological picture resolution is necessary at all. For the majority of operations, consensus for a significant 6-fold radiation dose reduction from 65 mGy to 9.6 mGy CTDI could be realized illustrating a big potential for similar approaches in other institutions.

CT radiation dose for computer-assisted endoscopic sinus surgery: dose survey and determination of dose-reduction limits

BACKGROUND AND PURPOSE

Computer-assisted navigation is increasingly used in functional endoscopic sinus surgery (FESS) to prevent injury to vital structures, necessitating preparative CT and, thus, radiation exposure. The purpose of our study was to investigate currently used radiation doses for CT in computer-assisted navigation in sinus surgery (CAS-CT) and to assess minimal doses required.

MATERIALS AND METHODS

A questionnaire inquiring about dose parameters used for CAS-CT was sent to 30 radiologic institutions. The feasibility of low-dose registration was tested with a phantom. The influence of CAS-CT dose on technical accuracy and on the practical performance of 5 ear, nose, and throat (ENT) surgeons was evaluated with cadaver heads.

RESULTS

The questionnaire response rate was 63%. Variation between minimal and maximal dose used for CAS-CT was 18-fold. Phantom registration was possible with doses as low as 1.1 mGy. No dose dependence on technical accuracy was found. ENT surgeons were able to identify anatomic landmarks on scans with a dose as low as 3.1 mGy.

CONCLUSIONS

The vast dose difference between institutions mirrors different attitudes toward image quality and radiation-protection issues rather than being technically founded, and many patients undergo CAS-CT at higher doses than necessary. The only limit for dose reduction in CT for computer-assisted endoscopic sinus surgery is the ENT surgeon's ability to cope with impaired image quality, whereas there is no technically justified lower dose limit. We recommend, generally, doses used for the typical diagnostic low-dose sinus CT (120 kV/20-50 mAs). When no diagnostic image quality is needed, even a reduction down to a third is possible.

Which individuals with affective symptoms seek help? Results from the Zurich epidemiological study

OBJECTIVE

Several factors influence whether individuals with affective disorders seek help. The Zurich cohort study provides an opportunity to explore patient-based factors without confounding with problems of access. This study aims to identify features which predict help-seeking behaviour in symptomatic individuals and to explore failure of help seeking in those who did not.

METHOD

Characteristics of currently symptomatic 40-year-old individuals in a stratified epidemiological sample were tested against help-seeking behaviour using bivariate statistics and logistic regression. Individual predictors were identified and interaction effects tested.

RESULTS

Thirty-one per cent of the 364 subjects sought help in the preceding year. Past treatment and living alone were significantly associated with treatment. Total number of symptoms and several individual symptoms correlated with treatment in the bivariate analyses but regression analysis identified "unfounded self-reproach" and "hopelessness" interacting with social support to predict the best treatment.

CONCLUSION

Social support is strongly protective against needing help in the presence of distressing affective symptoms unless these symptoms become elaborated into conclusions about their meaning and prognostic significance.

[Antiaggregation: aspirin]

Many randomized trials have shown aspirin as an effective antiplatelet drug for the secondary prevention of cardiovascular events. The NNT (number needed to treat) to prevent 1 vascular event is about 25. The NNH (number needed to harm) inducing one cerebral bleeding is about 1'000, to provoke one severe extracerebral bleeding about 100-200. The primary prevention can be recommended only for high risk patients for cardiovascular events (annual risk of 1-1.5% or more), calculated on the basis of the Framingham data, the Sheffield tables or in analysis of U.S. Preventive Services Task Force. The mechanisms of action, interactions and the "aspirin-resistance" are briefly discussed.

[Vocational rehabilitation of the mentally ill - an evaluation of the Vocational Rehabilitation Center in Zurich, Switzerland]

OBJECTIVE

The aim of the Vocational Rehabilitation Center in Zurich (VRC) is to reintegrate mentally ill persons into the primary labour market, mainly by prevocational training followed by continuous professional support for employed individuals. The present study evaluated the impact of the VRC.

METHODS

The job and financial situation of 68 trained persons was assessed up to two years after the training. Additionally, their vocational history and sociodemographic data were analysed.

RESULTS

Before the training, only 9 % had a job, while two years after the course 42 % were employed in competitive jobs. On the other hand, using an ordinal scale, two years after the training, 78 % of the patients were found in a better job situation than before the course. Likewise, the financial situation of 52 % of the clients has improved within those two years. The strongest correlation with success was the intensity of support after the training.

CONCLUSIONS

The VCR is effective in training mentally ill patients for the primary job market. Continuous professional support is vital for ongoing success.

Closure of an open drug scene--a case register-based analysis of the impact on the demand for methadone maintenance treatment

AIMS

To assess the impact of the closure of an open drug scene on the demand for methadone maintenance treatment (MMT).

DESIGN

Interrupted time series analysis of case register-based data of all MMTs performed in the canton of Zurich (Switzerland) between June 16 1992 and July 7 1997.

SETTING

Five private and 14 state-controlled institutions as well as 330 general practitioners, 35 psychiatrists, and 79 other specialists offering outpatient MMT.

PARTICIPANTS

5210 opiate users with 9042 MMT episodes.

MEASUREMENTS

Monthly number of entries into MMT before, during and after the closure of the Letten scene in February 1995, MMT retention rates, participants' socio-demographic and drug-related data.

FINDINGS

ARIMA modelling revealed 68 (95% CI = 31-105; p < 0.001) additional MMT admissions due to the dispersion of the open drug scene without a decrease in MMT retention rates. Socio-demographic and drug-related characteristics of patients entering MMT in the month of the closure did not significantly differ from other admissions.

CONCLUSIONS

Law enforcement strategies to eliminate open drug scenes may increase the demand for MMT. Sufficient treatment facilities for opioid dependence should be provided when law enforcement activities against open drug scenes are planned.

Comparison of self-ratings and therapist ratings of outpatients' psychosocial status

In psychiatric treatment, differences between therapists' observer ratings and patients' self-ratings are well known. We studied these differences in a sample of chronically mentally ill outpatients. The results show that the patients rated their psychosocial status significantly better than their therapists. By means of multiple regression analysis, we designed a model to explain the specific differences. By placing more emphasis on leisure activities and less emphasis on addictive behavior, compliance, and psychopathology, therapists might predict global ratings given by patients more accurately. This model helps therapists obtain a better understanding of their patients.

Concomitant analysis of the epidermal growth factor receptor family in esophageal cancer: overexpression of epidermal growth factor receptor mRNA but not of c-erbB-2 and c-erbB-3

The epidermal growth factor receptor family consists of four closely related transmembrane receptors: epidermal growth factor receptor (EGF-R), c-erbB-2, c-erbB-3, and c-erbB-4. Overexpression of each receptor may lead to cell transformation and contributes to tumor progression in various malignancies. Although these factors have been analyzed in many cancers separately, little is known about their concomitant expression in esophageal cancer. Based on the finding that EGF-R and c-erbB-2 form highly active transmembranous heterodimers that enhance cell growth and proliferation, we used Northern blot analysis and immunohistochemistry to analyze the concomitant expression of EGF-R, c-erbB-2, and c-erbB-3 in tissue samples obtained from 39 patients undergoing esophagectomy for esophageal cancer. Northern blot analysis revealed a fourfold increase (p < 0.01) in EGF-R mRNA levels in the esophageal cancer samples in comparison with normal tissue samples. The c-erbB-2 receptor was only 1.25-fold elevated in the esophageal cancers, which failed to be statistically significant (p = 0.31). In contrast, c-erbB-3 mRNA levels were 3.5-fold lower (p < 0.01) in the esophageal cancers than in the normal tissues. Immunohistochemical analysis showed weak EGF-R, c-erbB-2, and c-erbB-3 immunostaining in the normal esophageal tissue. In esophageal cancer samples, immunoreactivity for EGF-R, c-erbB-2, and c-erbB-3 was mainly located in the cancer cells. Strong EGF-R, c-erbB-2, and c-erbB-3 immunoreactivity was present in 59%, 64%, and 64% of the esophageal cancer samples, respectively. In consecutive tissue sections, identical cancer cell clusters often exhibited these three closely related receptors simultaneously. However, correlation of the immunohistochemical findings with the clinicopathologic patient parameters revealed that the presence of EGF-R, c-erbB-2, or c-erbB-3 had no influence on patient survival (p > 0.05). In addition, the simultaneous presence of these receptors did not influence survival. Our findings indicate that in esophageal cancer the presence of EGF-R, c-erbB-2, and c-erbB-3 alone or in combination seems to have no major influence on patient prognosis and does not alter tumor growth behavior significantly.

[How quickly do the effects of sector division appear? The initial results of the companion research of the Zurich sector division project]

Dividing the delivery system of larger psychiatric hospitals into defined smaller catchment areas called sectors, implies a contribution to quality assurance. Continuous monitoring and evaluation of a period before and after this reorganisation, which took place in 1994 for the central region of Zürich (Psychiatric University Hospital), allows perception of expected and possible unexpected changes. All newly registered patients were recorded within a time span divided into five periods of six month five each, the last one covering the first six months after sectorisation. This design permits to answer the question as to how fast the intended changes after sectorisation occur, and also to control side effects. Results show that sectorisation resulted in a marked increase of registrations from the defined catchment area of each sector, and that the investigated institutions achieve attainment of the aim to effect a special selection of psychiatric patients characterised by considerable psycho-social deficits. The two sectors display differences in respect of socio-demographic characteristics of newly registered patients.

[Bladder and rectal infiltration by uterine carcinomas: the accuracy of CT and MRI compared to endoscopic procedures]

PURPOSE

To establish the value of computed tomography (CT) and magnetic resonance imaging (MRI) in predicting bladder and rectum involvement in uterine carcinoma.

MATERIAL AND METHODS

6 different imaging signs (focal obliteration of perivesical or perirectal fat planes, area and angle of contact between uterus and bladder or rectum, asymmetric bladder or rectum wall thickening, evidence of intraluminal masses, and signal intensity of bladder or rectum wall on T2-weighted or contrast-enhanced MR images) were analysed retrospectively in 129 patients who underwent 92 CT and/or 64 MRI examinations. The data were correlated with intraoperative findings and the results of cystoscopy and rectoscopy.

RESULTS

Asymmetric wall thickening, evidence of intraluminal masses and increased signal intensities of the bladder wall or rectum wall were valuable signs of infiltration (sensitivity 71-100%, specificity 91-96% and accuracy 89-97%). In 27 patients submitted to both imaging examinations MRI was somewhat superior compared to CT (p > 0.1) and yielded similar results as endoscopic procedures (accuracy of cystoscopy and rectoscopy of 90% and 94%, respectively).

CONCLUSION

CT and MRI allow to predict involvement of bladder or rectum wall in carcinoma of the uterus with a similar accuracy as endoscopic procedures.

[Assessment of parathyroid gland function: predictive value of a nomogram]

Recent developments in measurement of intact parathormone (PTH) has enabled to generate a nomogram for parathyroid function. Blood levels of PTH can thus be interpreted in relation to calcemia. Intact PTH and calcium were assayed in blood from 99 healthy subjects studied under fasting conditions; 26 subjects were also studied during hyper- and hypocalcemia, induced by calcium and EDTA infusions, respectively. Serum levels of intact PTH which had been obtained in 99 patients were then analysed retrospectively by comparison with the nomogram. Patients whose intact PTH levels lie above the normal zone of the nomogram produce too much PTH relative to the blood calcium level (hyperparathyroidism); those falling under the normal zone produce too little (hypoparathyroidism).

Effects of electrical stimulation of low-threshold muscle afferents on visual reaction time

Human subjects performed plantar flexions of the foot in visual reaction time (RT) situations. In the simple RT task, the same foot had to be moved during the whole session, in the choice RT task, the right or left foot was moved in a random sequence. Low-threshold muscle afferents which evoked a monosynaptic H reflex were electrically activated on both sides at various intervals after the onset of the light stimulus. In both RT situations. RT was shortened equally by the electrical stimulation. The intersensory facilitation in the choice RT task provided support for the preparation enhancement model, since the subjects could not react to the electrical stimulus alone.

Relation between the specific H reflex facilitation preceding a voluntary movement and movement parameters in man

In a reaction-time situation, the monosynaptic spinal reflex (H reflex) is facilitated before the onset of an electromyographic (e.m.g.) response. The aim of the present investigation was to study aspects of this facilitation. Human subjects were required to perform isometric plantarflexions of the foot in response to a visual stimulus. The movement was always on the same side in the simple reaction-time situation, and randomly with the right or left foot in the choice reaction-time situation. Stimuli to evoke H reflexes were applied bilaterally 40-400 ms after the onset of the visual stimulus. Pre-motor time, i.e. the interval between the onset of the visual stimulus and the e.m.g. response, and reaction time, i.e. the interval between the onset of the visual stimulus and the response on the torque recording, were computed. In both reaction-time situations, there was a significant facilitation of the ipsilateral H reflex 100-160 ms before e.m.g. onset and, in some subjects, a small facilitation of the contralateral H reflex. The specific facilitation, i.e. the difference between the facilitation on the ipsi- and contralateral side relative to the movement, was not significantly different on the right and left side. Pre-motor time was divided into the interval from the light onset until the onset of the specific facilitation, and the interval from the onset of the facilitation until the onset of the voluntary response. Both intervals increased, and the slope and the amplitude of the facilitation decreased with increasing pre-motor time and reaction time. The specificity of the H reflex facilitation in a choice reaction-time situation implies that the interval from light onset until the onset of the facilitation includes stimulus identification and response selection, and the interval from the onset of the facilitation until the e.m.g. response preparation of the motor system for the required movement. The present results suggest that the specific facilitation of the H reflex before a movement is caused by removal of presynaptic inhibition at I a terminals or by activation of interneurones intercalated in polysynaptic components of the H reflex rather than by a subthreshold activation of motoneurones.

Detection of reaction time by an adaptive filter based on the least squares fit

An adaptive filter based on the least squares fit between a template and individual records was developed. It has been applied to compute reaction times of a voluntary movement. Its performance was tested by comparing these reaction times with the latency of the EMG responses. Different properties of the least squares fit technique and Woody's filter technique (Woody 1967) are discussed.