Horizontal Line-of-Sight Turbulence Over Near-Ground Paths and Implications for Adaptive Optics Corrections in Laser Communications

Atmospheric turbulence over long horizontal paths perturbs phase and can also cause severe intensity scintillation in the pupil of an optical communications receiver, which limits the data rate over which intensity-based modulation schemes can operate. The feasibility of using low-order adaptive optics by applying phase-only corrections over horizontal propagation paths is investigated. A Shack-Hartmann wave-front sensor was built and data were gathered on paths 1 m above ground and between a 1- and 2.5-km range. Both intensity fluctuations and optical path fluctuation statistics were gathered within a single frame, and the wave-front reconstructor was modified to allow for scintillated data. The temporal power spectral density for various Zernike polynomial modes was used to determine the effects of the expected corrections by adaptive optics. The slopes of the inertial subrange of turbulence were found to be less than predicted by Kolmogorov theory with an infinite outer scale, and the distribution of variance explained by increasing order was also found to be different. Statistical analysis of these data in the 1-km range indicates that at communications wavelengths of 1.3 mum, a significant improvement in transmitted beam quality could be expected most of the time, to a performance of 10% Strehl ratio or better.

Real-time modal control implementation for adaptive optics

The electronics, computing hardware, and computing used to provide real-time modal control for a laser guide-star adaptive optics system are presented. This approach offers advantages in the control of unobserved modes, the elimination of unwanted modes (e.g., tip and tilt), and automatic handling of the case of low-resolution lens arrays. In our two-step modal implementation, the input vector of gradients is first decomposed into a Zernike polynomial mode by a least-squares estimate. The number of modes is assumed to be less than or equal to the number of actuators. The mode coefficients are then available for collection and analysis or for the application of modal weights. Thus the modal weights may be changed quickly without recalculating the full matrix. The control-loop integrators are at this point in the algorithm. To calculate the deformable-mirror drive signals, the mode coefficients are converted to the zonal signals by a matrix multiply. When the number of gradients measured is less than the number of actuators, the integration in the control loop will be done on the lower-resolution grid to avoid growth of unobserved modes. These low-resolution data will then be effectively interpolated to yield the deformable-mirror drive signals.

Radiation myelopathy following transplantation and radiotherapy for non-Hodgkin's lymphoma

BACKGROUND

Combined modality therapy with chemotherapy and radiotherapy has become increasingly popular in the management of solid malignancies. However, unexpected toxicities may arise from their interactions.

METHODS AND MATERIALS

We report the case of a young woman with a large mediastinal non-Hodgkin's lymphoma who underwent high-dose chemotherapy with autologous bone marrow transplantation and involved field radiotherapy, and who developed radiation myelopathy after a latent period of only 3 months. The spinal cord dose did not exceed 40.3 Gy in 22 fractions over 4.5 weeks, which is well within accepted tolerance limits. She had no other identifiable risk factors for radiation myelopathy, suggesting an adverse drug-radiation interaction as the most likely cause of her injury.

RESULTS AND CONCLUSIONS

This represents the first report of radiation myelopathy at accepted safe radiation doses following high-dose chemotherapy with autologous bone marrow transplantation, and we recommend caution in the choice of radiotherapeutic dose in this setting.

Symptom duration and delay in referral for palliative radiotherapy in cancer patients: a pilot study

OBJECTIVE

To estimate the frequency of delay in referral for palliative radiotherapy (PRT), and to identify factors associated with delay.

DESIGN

Prospective survey over three months in 1997.

SETTING

Radiotherapy department of a cancer centre in Melbourne, Victoria.

PARTICIPANTS

158 consecutive patients prescribed PRT in the lung, breast, urology and haematology units.

MAIN OUTCOME MEASURES

Duration of symptoms; incidence of "unreasonable" delay in referral; and incidence of negative clinical outcome associated with referral delay.

RESULTS

The median duration of symptoms before prescription of radiotherapy was four weeks. Thirty-eight patients (24%) were considered to have had an unreasonable delay in referral, with median symptom duration of 15 weeks, and median delay in referral of 12 weeks. Causes of delay were classified as "diagnostic uncertainty" (29%), "other treatment given" (18%), "patient related" (18%), "language difficulty" (3%), and "unexplained" (32%). Twenty-seven of these 38 patients (71%) had negative outcomes, including persistent pain, neurological deterioration and persistent respiratory symptoms.

CONCLUSIONS

These data suggest that delay in referral for PRT is not uncommon, has a variety of causes and can result in negative clinical outcomes. There appears to be a need for greater awareness of patients' symptoms and of the role of PRT among clinicians caring for patients with cancer.

Primary central nervous system lymphoma: age and performance status are more important than treatment modality

PURPOSE

To assess prognostic factors and treatment modalities of patients with primary central nervous system lymphoma (PCNSL) in terms of response rates, patterns of failure and overall survival.

METHODS AND MATERIALS

Sixty-two patients presenting with PCNSL between 1982 and 1994 at Peter MacCallum Cancer Institute with no evidence of human immunodeficiency virus infection were included in the study. Their median age was 60 years; World Health Organisation (WHO) performance status was > or = 2 in 85%. All patients were planned to receive whole brain irradiation; 7 also received spinal irradiation. The median planned dose to the target volume was 50.4 Gy. Twenty patients were planned to receive chemotherapy as well. Patients were followed up to June 20, 1995, giving a median follow-up for 14 surviving patients of 5.4 years, range 0.3 to 10.2 years.

RESULTS

The clinical response rate to treatment was 77% [95% confidence interval (CI) 65 to 87%]. The estimated median overall survival was 20.6 months (CI 12.4 to 33.4 months). On univariate analysis male gender, age <60 years, WHO performance status < or = 1, treatment to the target volume > or = 45 Gy, and treatment with additional chemotherapy, were associated with a significantly better overall survival (p < 0.05). On multivariate analysis only age and performance status remained significant prognostic variables. Relapse involved the central nervous system or cerebrospinal fluid (CSF) in all patients with known sites of relapse except three who had ocular relapse only. There was a low incidence of relapse in the initial brain site (23% of known cases) and a high incidence (50%) of CSF/spinal cord relapse. Of 48 deaths, 15 were related to initial or subsequent treatment.

CONCLUSIONS

Patient outcome is strongly influenced by age and performance status. Studies suggesting better survival for patients treated with chemoradiation may reflect patient selection rather than treatment variables. Optimal management remains to be defined. The high CSF/spinal relapse rate deserves particular attention.

Special aspects of severe head injury: recent developments

Trauma in general, and head injury in particular, is the most frequent cause of mortality and morbidity in those aged up to 45 years. Outcome from severe head injury depends on the nature and severity of the primary lesion, and the manifestations of secondary brain damage of extra- and intracranial origin. The most important sequela is cerebral ischaemia resulting from intracranial hypertension caused by, for example, traumatic brain swelling or intracranial haemorrhage and/or systemic complications, of which arterial hypotension is the most significant. Because treatment so far is limited in principle to general symptomatic measures, continuing improvements in patient management is required on a comprehensive basis. In this context, major efforts are being made all over the world, not only to assess the current efficacy of, for example, logistics, organization and patient management in severe head injury, but also towards development of a consensus aimed at standardizing management and treatment procedures. With regard to the predominant influence of secondary ischaemia of the brain, recent experimental and clinical pathophysiological studies focus on the quality of cerebral blood flow, including the intriguing phenomenon of post-traumatic vasospasm. Other research objectives are concerned with the role of cytokines, leucocyte-endothelial interactions and molecular genetics in severe head injury (e.g. illuminated by the emerging role of the apolipoprotein E gene). Finally, the formation of international organizations, the American and European Brain Injury Consortium, is noteworthy. Although their primary objective is the development of guidelines for clinical trials, future objectives are conceivably more far spread and influential. It can be hoped, therefore, that the unacceptably poor outcome from severe head injury until now can be improved. Moreover, alleged management discrepancies between up-to-date trauma centres and rural hospitals may be eliminated.

Salvage radiotherapy for Hodgkin's disease following chemotherapy failure

PURPOSE

This study aims to: 1) assess failure-free survival (FFS), overall survival (OS), and failure pattern after salvage radiotherapy (SRT) for patients with Hodgkin's disease (HD) who fail chemotherapy (CT); 2) identify patients suitable for SRT as an alternative to more aggressive salvage regimens.

METHODS AND MATERIALS

Between 1978 and 1992, 52 patients with relapsed/refractory HD following 26 CT received SRT at the Peter MacCallum Cancer Institute. Patient characteristics at diagnosis were: median age (range 12-63); male-31, female-21; Stage I-4, II-16, III-25, or IV-7. Prior to SRT 27 patients had received the equivalent of both MOPP and ABV(D). The duration of initial complete response (CR) from CT was greater than 12 months in 22 patients. SRT (dose 34-42 Gy) was given to active disease sites.

RESULTS

Five-year FFS and OS rates following SRT were 26 and 57%, respectively. Five-year FFS and OS rates of 36 and 75%, respectively, were achieved in patients who relapsed in supradiaphragmatic nodal sites without B symptoms; in a subset of patients with initial Stage I-II disease the FFS and OS rates were 50 and 86%, respectively. On multivariate analysis significant factors for FFS were B symptoms at the time of SRT (p = 0.003), extranodal involvement (p = 0.011) and histology (p = 0.018). For OS significant factors were B symptoms (p = 0.0007), age (p = 0.014) and number of prior CT regimens (p = 0.03).

CONCLUSION

The relatively poor results of SRT in terms of FFS justify the use of alternative salvage strategies for most patients with Hodgkin's disease who fail CT. However, SRT offers a low morbidity, potentially curative option for a subset of patients. Our data suggest that patients most suitable for SRT are those with relapse in supradiaphragmatic nodal sites and no B symptoms.

[Metabolic syndrome]

The metabolic syndrome consists of a cluster of metabolic diseases which often coexist: abdominal obesity, glucoseintolerance, diabetes mellitus type II, dyslipidemia, hypertension and impaired fibrinolysis. The common pathophysiologic link of these diseases in insulin resistance. All clinical disorders of the metabolic syndrome are risk factors for the vascular system. Since several diseases are present at the same time the risk for atherosclerotic complications such as coronary artery disease and apoplexy is potentiated. As a consequence the costs for direct and indirect health care are high. Besides a genetic predisposition the metabolic syndrome is mainly caused by the typical life style in industrialized countries with high energy and fat intake, physical inactivity, alcohol consumption, smoking, and stress. Therefore, prophylaxis and therapy imply the removal of these factors. In order to be successful experienced physicians and motivated patients are prerequisites. Even more affective than therapy is prophylaxis which is, however, not established in Germany. The metabolic syndrome is up to now not identified as a major health problem neither by the medical profession nor by health insurances and politicians. An effective therapy and prophylaxis would induce far-reaching changes in our health system and diminish health costs.

Atrial natriuretic peptide and plasma renin levels in assessment of mineralocorticoid replacement in Addison's disease

Assessment of mineralocorticoid replacement therapy in Addison's disease relies on clinical features and laboratory measurements, including plasma renin and potassium. Previous studies have questioned the value of measuring the plasma renin concentration (PRC), particularly in the setting of fludrocortisone overreplacement. The aim of this study was to evaluate the usefulness of plasma atrial natriuretic peptide (ANP) measurements as a marker of sodium and volume status in Addison's disease. Fourteen patients with Addison's disease receiving their usual glucocorticoid doses were placed on various doses of fludrocortisone (FC; 0 mg, 0.05 mg, 0.1 mg and 0.2 mg) in random order for four 2-week periods. At the end of each period, blood pressure and clinical symptoms were assessed, and blood was drawn for measurement of PRC and ANP levels. PRC was significantly elevated in patients receiving placebo (54.2 +/- 57.9 ng/mL x h) compared with PRC in those receiving baseline FC (24.7 +/- 42.4 ng/mL x h), 0.1 mg FC (15.2 +/- 25.9 ng/mL x h), and 0.2 mg FC (5.5 +/- 5.7 ng/mL x h). ANP levels were measured by either an extraction method (ANP(ext)) or directly from plasma (ANP(dir)). ANP(dir) was significantly elevated at 0.2 mg FC (87.1 +/- 20.1 pg/mL) compared with baseline (63.3 +/- 8.1 pg/mL), placebo (56.1 +/- 5.5 pg/mL), 0.05 mg FC (60.5 +/- 16.0 pg/mL), and 0.1 mg FC (65.4 +/- 13.7 pg/mL) values. ANP(ext) was elevated in patients receiving 0.2 mg FC (42.7 +/- 41.8 pg/mL) compared with that in patients receiving placebo (7.9 +/- 5.4 pg/mL), 0.05 mg FC (16.2 +/- 11.2 pg/mL), or 0.1 mg FC (19.7 +/- 11.1 pg/mL). Our data suggest that PRC is of value in determining mineralocorticoid underreplacement, whereas ANP is a more sensitive index of FC overreplacement. ANP levels may, therefore, be complementary to PRC in adjustment of mineralocorticoid doses in the upper dose range, where clinical symptoms and signs appear to be of little value.

Quality assurance by specification and achievement of goals in palliative cancer treatment

As the goals of palliative cancer treatments have not always been clearly specified, this paper describes how frequently the goals of palliative cancer treatment can be specified according to a given definition and how frequently those specified goals can be achieved. The clinical problems of 171 cancer patients were discussed in the Interdisciplinary Oncologic Conference (IOC) of the Cancer Centre University of Ulm (CCUU) and recommendations concerning further diagnostic treatments and/or therapy were provided. These recommendations had been documented and analysed retrospectively. The goals were classified as either cure or palliation or further investigation. If the goal was palliation, it was investigated whether or not the goal was specified as either alleviation of existing problems or prevention of impending problems. The achievement of the specified goals was assessed. Palliation was the goal of treatment in 119 (71%) of the 168 evaluable recommendations. In 83 of the 119 cases (70%), immediate treatment was recommended. The goal was specified in 57 (69%) of the 83 recommendations and could be realized in 24 of 57 specified cases (42%). Patients in this group survived longer (p < 0.01) than patients in whom the goals could not be achieved. Impending problems could be prevented more often (p = 0.001) in 14 out of 18 cases, while existing problems could be alleviated in only 10 out of 34 cases. It is concluded that specification of the goals of palliation is necessary because it is impossible to decide if a goal of treatment could be achieved or not unless the goal of treatment has been defined (as existing/impending problem). The prevention of impending problems could be investigated in prospectively controlled clinical trials.

[Non-pharmacological therapy of metabolic syndrome]

The metabolic syndrome usually goes along with abdominal obesity: diabetes type II, hypertension, dyslipidemia, and gout are often associated. The common characteristic is the resistance to insulin action. Reasons for the metabolic syndrome are--besides a genetic determination--overnutrition, physical inactivity, and alcohol consumption. Therefore, a causal therapy aims at the elimination of these factors. Consequently, the non-pharmacological therapy of the metabolic syndrome should be emphasized. The most important treatment is the reduction of body weight in the presence of obesity which is relevant for almost 90% of the patients. Body weight can rapidly be diminished by hypocaloric diets. Both, conventional reducing diets or formula diets may be used for weight reduction. Total fasting should not be performed for several reasons. For minor weight reduction or weight maintenance following a period of rapid weight loss with a hypocaloric diet, increased physical activity also lowers weight or prevents relapsing. Aims of therapeutical procedures are the elimination or amelioration of insulin resistance and subsequently the diseases of the metabolic syndrome. Both methods, reducing diet and physical training, act on various factors related to insulin resistance. For example, hypocaloric diets activate thyroxine kinase of the insulin receptor and reduce glucose and insulin in plasma. Physical training reduces not only insulin and glucose in plasma but also free fatty acids in addition and increases capillary density in skeletal muscle. Using the glucose clamp technique, diets and training are equally effective in improving glucose metabolism. Compared to these non-pharmacological methods drugs are less convincing. Since the non-pharmacological treatment implies behavioral changes with regard to nutrition, physical activity and alcohol consumption, simple instructions are not sufficient. Usually long-lasting changes in life style are necessary in order to achieve health improvement. Therefore, health care programs on individual or social basis are required in order to improve nutrition and increase physical activity. However, long-acting effects are difficult to achieve in adults; more promising is the prevention of insulin resistance.

Improvement of left ventricular morphology and function in obese subjects following a diet and exercise program

The aim of this work was to compare left ventricular performance during weight reduction induced by either physical training and diet or diet alone. Forty-three moderately obese subjects received a hypocaloric diet of 800 kcal/d for 4 weeks; 22 of them were also subjected to an exercise program. By means of echocardiography, left ventricular dimensions and systolic time intervals were determined. Heart rate and blood pressure were measured at rest and during exercise. The addition of physical training resulted in a more favourable change in weight loss (-8.3 vs -6.3 kg), heart rate (-14 vs -7 bpm), systolic (-17 vs -8 mm Hg), and diastolic (-11 vs -6 mm Hg) blood pressure. Left ventricular mass (LVM) was diminished more pronounced by combined therapy (-10.0%) as compared to diet alone (-4.7%). Changes in LVM were correlated with weight loss but not with alterations in heart rate and blood pressure. Fractional shortening and mean circumferential fiber shortening velocity did not improve significantly whereas the ratio of preejection period/left ventricular ejection time (PEPi/LVETi) was shortened in the diet and diet plus exercise group by -10.7 and -17.9%, respectively. It was concluded that exercise training in combination with a hypocaloric diet reduces left ventricular dimensions, LVM and PEPi/LVETi more distinctly than diet alone.

MEG localization of interictal epileptic focal activity and concomitant stereotactic radiosurgery. A non-invasive approach for patients with focal epilepsy

Two patients with complex partial epilepsy and tumour of the temporal lobe scheduled for gamma knife radiosurgery were evaluated pre- and postoperatively by multichannel magnetoencephalography (MEG). Centers of epileptic dipole activity found preoperatively disappeared after the focal irradiation as did the epileptic seizures. Thus, to combine stereotactic MEG and gamma knife radiosurgery seems to be a non-invasive alternative to the conventional neurosurgery in focal epilepsy.