Significant dose reduction using synchrotron radiation computed tomography: first clinical case and application to high resolution CT exams

Since the invention of Computed Tomography (CT), many technological advances emerged to improve the image sensitivity and resolution. However, no new source types were developed for clinical use. In this study, for the first time, coherent monochromatic X-rays from a synchrotron radiation source were used to acquire 3D CTs on patients. The aim of this work was to evaluate the clinical potential of the images acquired using Synchrotron Radiation CT (SRCT). SRCTs were acquired using monochromatic X-rays tuned at 80 keV (0.350 × 0.350 × 2 mm3 voxel size). A quantitative image quality comparison study was carried out on phantoms between a state of the art clinical CT and SRCT images. Dedicated iterative algorithms were developed to optimize the image quality and further reduce the delivered dose by a factor of 12 while keeping a better image quality than the one obtained with a clinical CT scanner. We finally show in this paper the very first SRCT results of one patient who received Synchrotron Radiotherapy in an ongoing clinical trial. This demonstrates the potential of the technique in terms of image quality improvement at a reduced radiation dose for inner ear visualization.

Synchrotron X-ray microtransections: a non invasive approach for epileptic seizures arising from eloquent cortical areas

Synchrotron-generated X-ray (SRX) microbeams deposit high radiation doses to submillimetric targets whilst minimizing irradiation of neighboring healthy tissue. We developed a new radiosurgical method which demonstrably transects cortical brain tissue without affecting adjacent regions. We made such image-guided SRX microtransections in the left somatosensory cortex in a rat model of generalized epilepsy using high radiation doses (820 Gy) in thin (200 μm) parallel slices of tissue. This procedure, targeting the brain volume from which seizures arose, altered the abnormal neuronal activities for at least 9 weeks, as evidenced by a decrease of seizure power and coherence between tissue slices in comparison to the contralateral cortex. The brain tissue located between transections stayed histologically normal, while the irradiated micro-slices remained devoid of myelin and neurons two months after irradiation. This pre-clinical proof of concept highlights the translational potential of non-invasive SRX transections for treating epilepsies that are not eligible for resective surgery.

Muscle fatty infiltration in rotator cuff tears: descriptive analysis of 1688 cases

INTRODUCTION

Fatty infiltration (FI) is an important prognosis factor in the anatomical and functional outcomes of rotator cuff repairs. The objective of this study was to analyze the natural history of muscle FI and better evaluate its onset and aggravation time frame.

MATERIAL AND METHODS

A total of 1688 medical charts of patients operated on for rotator cuff tear and with a preoperative CT arthrogram (82%) or an MRI (18%) were reviewed. Surgery was performed between 1988 and 2005. The FI of each muscle was assessed as minimal (in Goutallier's stages 0 and 1), intermediate (in stage 2), and severe (in stages 3 and 4). Regarding supraspinatus, we retained the mean FI observed in the sagittal, coronal, and axial planes; for the infraspinatus and the subscapularis, we retained the observed mean on two views at the upper and lower levels of the glenoid in the axial plane.

RESULTS

We found a statistically significant correlation (p<0.0005) between FI, the type of tendon lesion, and patient age for the supraspinatus, the infraspinatus, and the subscapularis. Statistically, the FI significantly increased (p<0.0005) with time elapsed for the supraspinatus and the infraspinatus but not significantly for the subscapularis. The mean time to tendon rupture observed for intermediate FI was three years for the supraspinatus and 2.5 years for the infraspinatus and the subscapularis when their tendons ruptured. The mean time observed to severe FI was five, four, and three years for the supraspinatus, the infraspinatus, and the subscapularis, respectively.

DISCUSSION AND CONCLUSION

The more extensive the lesion, the longer the time following rupture, and the older the patient is, the more severe the FI is. The objective of surgery is to intervene before intermediate FI sets in, which means irreversible functional loss.

LEVEL OF EVIDENCE

Level IV. Diagnostic Retrospective Study.

Monitoring of Dermanyssus gallinae in free-range poultry farms

Various methods for monitoring Dermanyssus gallinae infestations within free-range egg production units were compared. The study was carried out in five egg-producing free-range poultry buildings infested with D. gallinae. Each farm was divided into six zones (each zone including nest boxes, perches and duckboard) for placing two types of traps (corrugated cardboard and thick card traps) or examining dried droppings for presence of mites. Traps were removed 24 h later, placed into bags and mites were counted at the laboratory using binocular magnification. Droppings were also inspected by eye and mite numbers were estimated. All the methods used allowed us to detect mites although their efficacy differed. The number of mites collected was independent of the type of trap used. Examination of the droppings did not differentiate between buildings with differing mite populations. Placing traps in the nest boxes is a less reliable indicator than placing them on the perches. It appears that the most coherent method for evaluating the D. gallinae population within a free-range flock is to place thick card traps throughout the building, on perches favoured by birds.

[Psychophysiological factors in high intellectual potential: comparative study in children aged from 8 to 11 years old]

Factors of intellectual talent as well as physiological and psychological characteristics are little known. However, giftedness is now a social problem and the knowledge of precocity hallmarks should permit the diagnosis in order to undertake the adequate educational orientation of these children. From questionnaires given anonymously to parents, this work showed comparative results between a population of gifted children and a control one.

OBJECTIVES

The aim of this study was to present precocity hallmarks in the gifted population, following factorial analysis of socio-economic and familial parameters, as well as medical and psycho-physiological variables linked with the children's post-natal life.

POPULATION

Four hundred and twelve children aged eight to 11 years, from Lyon, have been used in the survey: 217 children (control group) were included after a random selection in schools, and 195 children (gifted group, IQ >130, Wechsler test) were enrolled after clinician's diagnoses in four medical departments.

RESULTS

Regression analysis allowed to draw relation between several factors and giftedness: abnormal pregnancy (CR =3.205, P =0.009), perinatal stress (CR =2.166, P =0.003), and presence of migraine (CR =3.169, P =0.001). Parents living together (married or not) (CR =2.100, P =0.080) with a good and superior level of learning (CR =5.464, P =0.0002) were also linked with giftedness.

CONCLUSION

Our results indicate that precocity hallmarks are multifactorial. These data confirm some socio-economic and medical physiological features correlated with giftedness, and suggest that psychological factors may bear on the etiology of intellectual talent. We focus on the hypothesis than early stress may play a role on central nervous system maturation in these children.

Effect of tidal volume on distribution of ventilation assessed by synchrotron radiation CT in rabbit

A respiration-gated synchrotron radiation computed tomography (SRCT) technique, which allows visualization and direct quantification of inhaled stable xenon gas, was used to study the effect of tidal volume (Vt) on regional lung ventilation. High-resolution maps (pixel size 0.35 x 0.35 mm) of local washin time constants (tau) and regional specific ventilation were obtained in five anesthetized, paralyzed, and mechanically ventilated rabbits in upright body position at the fourth, sixth, and eighth dorsal vertebral levels with a Vt from 4.9 +/- 0.3 to 7.9 +/- 0.4 ml/kg (means +/- SE). Increasing Vt without an increase in minute ventilation resulted in a proportional increase of mean specific ventilation up to 65% in all studied lung levels and reduced the scattering of washin tau values. The tau values had log-normal distributions. The results indicate that an increase in Vt decreases nonuniformity of intraregional ventilatory gas exchange. The findings suggest that (SRCT) provides a new quantitative tool with high spatial discrimination ability for assessment of changes in peripheral pulmonary gas distribution during mechanical ventilation.

Lack of cell death enhancement after irradiation with monochromatic synchrotron X rays at the K-shell edge of platinum incorporated in living SQ20B human cells as cis-diamminedichloroplatinum (II)

In this paper we describe the results of experiments using synchrotron radiation to trigger the Auger effect in living human cancer cells treated with a widely used chemotherapy drug: cis-diamminedichloroplatinum (II) (cisplatin). The experiments were carried out at the ID17 beamline of the European Synchrotron Radiation Facility, which produces a high-fluence monochromatic beam that is adjustable from 20 to 80 keV. Cisplatin was chosen as the carrier of platinum atoms in the cells because of its alkylating-like activity and the irradiation was done with monochromatic beams above and below the platinum K-shell edge (78.39 keV). Cell survival curves were comparable with those obtained for the same cells under conventional irradiation conditions. At a low dose of cisplatin (0.1 microM, 48 h), no difference was seen in survival when the cells were irradiated above and below the K-shell edge of platinum. Higher cisplatin concentrations were investigated to enhance the cellular platinum content. The results with 1 microM cisplatin for 12 h showed no difference when the cells were irradiated with beams above or below the platinum K-shell edge with the exception of the higher cell death resulting from drug toxicity. The intracellular content of platinum was significant, as measured macroscopically by inductively coupled plasma mass spectrometry. Its subcellular localization and particularly its presence in the cell nucleus were verified by microscopic synchrotron X-ray fluorescence. This was the first known attempt at K-shell edge photon activation of stable platinum in living cells with a platinum complex used for chemotherapy. Its evident toxicity in these cells leads us to put forth the hypothesis that cisplatin toxicity can mask the enhancement of cell death induced by the irradiation above the K-shell edge. However, K-shell edge photon activation of stable elements provides a powerful technique for the understanding of the biological effects of Auger processes. Further avenues of development are discussed.

Quantitative functional lung imaging with synchrotron radiation using inhaled xenon as contrast agent

Small airways play a key role in the distribution of ventilation and in the matching of ventilation to perfusion. The purpose of this study was to introduce an imaging method that allows measurement of regional lung ventilation and evaluation of the function of airways with a small diameter. The experiments were performed at the Medical Beamline of the European Synchrotron Radiation Facility. Monochromatic synchrotron radiation beams were used to obtain quantitative respiration-gated images of lungs and airways in two anaesthetized and mechanically ventilated rabbits using inhaled stable xenon (Xe) gas as a contrast agent. Two simultaneous images were acquired at two different energies, above and below the K-edge of Xe. Logarithmic subtraction of the two images yields absolute Xe concentrations. This technique is known as K-edge subtraction (KES) radiography. Two-dimensional planar and CT images were obtained showing spatial distribution of Xe concentrations within the airspaces, as well as the dynamics of filling with Xe. Bronchi down to 1 mm in diameter were visible both in the subtraction radiographs and in tomographic images. Absolute concentrations of Xe gas were calculated within the tube carrying the inhaled gas mixture, small and large bronchi, and lung tissue. Local time constants of ventilation with Xe were obtained by following the evolution of gas concentration in sequential computed tomography images. The results of this first animal study indicate that KES imaging of lungs with Xe gas as a contrast agent has great potential in studies of the distribution of ventilation within the lungs and of airway function, including airways with a small diameter.

Venous allografts preserved at 4 degrees C for infrainguinal bypass: long-term results from 170 procedures

From April 21, 1982 to December 31, 1997, we performed 170 infrainguinal bypass procedures using isolated (n = 35) or composite (n = 135) venous allografts preserved at 4 degrees C as a substitute for saphenous autografts in 146 patients. The mean age of the patient population was 74 years. The indication was critical lower limb ischemia in 71% of cases. Seventy-five percent of procedures were below the knee and 26% were infrapopliteal. Mean length and diameter were 19.5 +/- 0.5 cm and 4.8 +/- 0.5 mm, respectively. After December 8, 1993, a reinforcement net was placed over the graft to prevent expansion in 71% of cases. Primary and secondary 5-year patency, calculated according to the Kaplan-Meier method, were 33 +/- 6% and 43 +/- 6%, respectively. Factors correlated with secondary patency were studied using the log-rank test. Previous ipsilateral infrainguinal revascularization was associated with a 40% decrease in secondary patency at 2 years (71% vs. 31%). Patency at 5 years was correlated with the level of anastomosis (47% for low popliteal anastomosis vs. 30% for infrapopliteal anastomosis). The likelihood of stenosis or dilatation of the allograft was 8% and 29.5%, respectively, at 5 years. The 5-year limb salvage and survival rates were 84% and 57%, respectively. The encouraging results of this series suggest that venous allografts provide a useful alternative for infrainguinal bypass when autologous grafts or other more reliable conduits are unavailable.

First human transvenous coronary angiography at the European Synchrotron Radiation Facility

The first operation of the European Synchrotron Radiation Facility (ESRF) medical beamline is reported in this paper. The goal of the angiography project is to develop a reduced risk imaging technique, which can be used to follow up patients after coronary intervention. After the intravenous injection of a contrast agent (iodine) two images are produced with monochromatic beams, bracketing the iodine K-edge. The logarithmic subtraction of the two measurements results in an iodine enhanced image, which can be precisely quantified. A research protocol has been designed to evaluate the performances of this method in comparison with the conventional technique. Patients included in the protocol have previously undergone angioplasty. If a re-stenosis is suspected, the patient is imaged both at the ESRF and at the hospital with the conventional technique, within the next few days. This paper reports the results obtained with the first patients. To date, eight patients have been imaged and excellent image quality was obtained.

Research at the European Synchrotron Radiation Facility medical beamline

The application of synchrotron radiation in medical research has become a mature field of research at synchrotron facilities worldwide. In the relatively short time that synchrotrons have been available to the scientific community, their characteristic beams of UV and X-ray radiation have been applied to virtually all areas of medical science which use ionizing radiation. The ability to tune intense monochromatic beams over wide energy ranges differentiates these sources from standard clinical and research tools. At the European Synchrotron Radiation Facility (Grenoble, France), a major research facility is operational on an advanced wiggler radiation beamport, ID17. The beamport is designed to carry out a broad range of research ranging from cell radiation biology to in vivo human studies. Medical imaging programs at ID17 include transvenous coronary angiography, computed tomography, mammography and bronchography. In addition, a major research program on microbeam radiation therapy is progressing. This paper will present a very brief overview of the beamline and the imaging and therapy programs.

In vivo K-edge imaging with synchrotron radiation

We present in this paper two imaging techniques using contrast agents assessed with in vivo experiments. Both methods are based on the same physical principle, and were implemented at the European Synchrotron Radiation Facility medical beamline. The first one is intravenous coronary angiography using synchrotron radiation X-rays. This imaging technique has been planned for human studies in the near future. We describe the first experiments that were carried out with pigs at the ESRF. The second imaging mode is computed tomography using synchrotron radiation on rats bearing brain tumors. Owing to synchrotron radiation physical properties, these new imaging methods provide additional information compared to conventional techniques. After infusion of the contrast agent, it is possible to derive from the images the concentration of the contrast agent in the tumor area for the computed tomography and in any visible vessel for the angiography method.

Using thoracic helical CT to assess iodine concentration in a small volume of nonionic contrast medium during vascular opacification: a prospective study

OBJECTIVE

The goal of the study was to assess whether, using thoracic helical CT, diagnostic mediastinal and hilar vascular enhancement can be obtained with a small amount of nonionic contrast material (80 ml) injected at a relatively slow rate (2 ml/sec).

SUBJECTS AND METHODS

One hundred twenty patients (60 in their fourth decade of life and 60 in their seventh decade of life) referred for contrast-enhanced thoracic CT for malignancies or infections prospectively entered the study. They were randomly assigned to be given one of three iodine concentrations of a nonionic contrast material: 250 mg/ml (1250), 300 mg/ml (1300), and 350 mg/ml (1350). Two radiologists independently graded perivenous artifacts and arterial enhancement of mediastinal and hilar vessels on a 4-point scale: 1, poor; 2, fair; 3, good; and 4, excellent. Measurements of arterial attenuation values (quantitative assessment) were obtained on the aorta and pulmonary artery.

RESULTS

Mean scores were equal to or greater than 3 for all vessels only using 1350. The higher the iodine concentration was, the higher the mean score, but there was a statistically significant difference only between scores obtained with 1350 and those obtained with 1300 or 1250. Mean scores were higher for the patients in their seventh decade of life than those in their fourth decade; however, there was no statistically significant difference between scores of the two decade groups. We found a highly significant statistical relationship between scores and arterial attenuation values.

CONCLUSION

During contrast-enhanced helical CT examinations for general thoracic evaluations, good opacification of central vascular structures is obtained with a low volume of high iodine concentration nonionic contrast medium.

[Study by NMR of the modifications of brain lipid composition related to the tumor processes]

1H, 13C, 31P and 14N NMR spectroscopies were used to investigate the lipid composition of brain tumors (GL6 glioma) in rats, by comparison with controlateral hemispheres. Comparative indexes derived from NMR signal intensities were used to establish the statistical analysis. It was found that sterol metabolism and sphingolipid/glycerolipids ratio are significantly modified when a tumor is present.

AREVA: multicenter randomized comparison of low-dose versus standard-dose anticoagulation in patients with mechanical prosthetic heart valves

BACKGROUND

Moderate anticoagulation may be proposed to reduce the risk of hemorrhage for certain patients with a mechanical prosthesis, but the consequences for risk of thromboembolism are debated.

METHODS AND RESULTS

The purpose of the AREVA trial was to compare moderate oral anticoagulation (international normalized ratio [INR] of 2.0 to 3.0) with the usual regimen (INR of 3.0 to 4.5) after a single-valve replacement with a mechanical prosthesis, either Omnicarbon or St Jude. Patients included were between 18 and 75 years old, in sinus rhythm, and with a left atrial diameter < or = 50 mm on the time-motion echocardiogram. Patients were randomized for INR after surgery. From 1991 to 1994, 433 patients underwent valve replacement (aortic, 414; mitral, 19) with 353 St Jude and 80 Omnicarbon prostheses; 380 patients were randomized for INR: 188 for INR 2.0 to 3.0 and 192 for INR 3.0 to 4.5. Mean follow-up was 2.2 years (1 to 4 years). Analysis of 18001 INR samples showed that the mean of the median of INR was 2.74 +/- 0.35 in the 2.0 to 3.0 group and 3.21 +/- 0.33 in the 3.0 to 4.5 group (P < .0001). Thromboembolic events, as assessed from clinical data and CT brain scans, occurred in 10 patients in the 2.0 to 3.0 INR group and 9 patients in the 3.0 to 4.5 INR group (P = .78). Hemorrhagic events occurred in 34 patients in the 2.0 to 3.0 INR group and 56 patients in the 3.0 to 4.5 INR group (P < .01), with 13 and 19 major hemorrhagic events, respectively (P = .29).

CONCLUSIONS

In selected patients with mechanical prostheses, moderate anticoagulation prevents thromboembolic events as effectively as conventional anticoagulation and reduces the incidence of hemorrhagic events.

Education program for general practitioners on breast and cervical cancer screening: a randomized trial. PRE.SA.GF Collaborative Group

This study was aimed at evaluating the effects of an education program for general practitioners on their prescribing behaviour for cervical and breast cancer screening tests, and assessing the feasibility of general practitioners participation in screening programs. All three cytology laboratories and 19 of the 20 radiologists in one administrative region ("Haute-Savoie") in France agreed to participate. The 278 general practices in this region were randomly assigned to either the intervention group (a one-day seminar on screening for breast cancer and cervical cancer) or the control group (n for both = 139). The prescriptions of tests for the following year were noted from the laboratories' and radiologists' records. No significant differences were observed between the intervention group and the control group for the number of mammographies prescribed with a mean of 19.3 and 15.2 per practice, respectively. However, significantly more mammographies were prescribed in women aged over 50 by the intervention group (p = 0.038). Inversely, fewer smear tests were prescribed in the intervention group (mean per practice: 40.5 and 46.1, respectively). A significantly higher number of practices in the intervention group did not prescribe any smear tests (p = 0.007). This study suggests that it is possible to influence general practitioners' participation in screening programs, but that the messages should be carefully presented, since negative effects are possible.

Allogenic BMT in children: differential lymphocyte subset reconstitution according to the occurrence of acute GVHD

To acquire some biological markers associated with the occurrence of acute graft-versus-host disease (aGVHD) after allogeneic bone marrow transplant (BMT) in children, we have studied the lymphocyte subset reconstitution and the percentage of peripheral blood mononuclear cells bearing HLA-DR and HLA-DQ class II molecules. This study included 37 allogeneic BMT: either with (n = 17) or without (n = 20) aGVHD. Within 2 months after transplantation, we observed that patients with aGVHD had a unique mononuclear cell profile characterized by (i) a significant increase in the percentages of CD8bright+CD28- T cells (P = 0.05) and CD3+ T cells (P = 0.001), (ii) an important decrease in the percentage of CD56+ cells (P = 0.0001), and (iii) a decrease in the percentages of HLA-DQ+ and HLA-DR+ monocytes (P = 0.001) and HLA-DQ+ T lymphocytes (P = 0.0001), in comparison with patients without aGVHD. Moreover, statistical studies indicate that there was a positive correlation between CD8bright+CD28- and CD3+ T cells, whereas CD3+ T cells were negatively correlated to CD56+ cells. We did not find any statistical correlation between the percentages of HLA-DQ+ or HLA-DR+ cells and the percentages of these lymphocyte subsets. Therefore, in this study done in children, we suggest that patients with (i) less than 20% of DQ+ monocytes, (ii) less than 25% of CD56+ lymphocytes, and (iii) an enhanced percentage of CD8bright+CD28- T cells are strongly associated with aGVHD. Unfortunately, these biological markers of a GVHD may not precede the clinical manifestations of the disease.

[Rheumatoid metatarsals, original development of the first metatarsals]

Weight-bearing roentgenograms of 308 feet of rheumatoid arthritis patients were analyzed. Several angles were determined, including the metatarsus primus adductus angle (between the first and second metatarsals, > or = 10 degrees) and the forefoot spread angle (between the first and fifth metatarsals, > or = 30 degrees). Pes planus was diagnosed when the internal arch angle was equal to or greater than 130 degrees. Tarsal arthritis was defined as the presence of joint space narrowing. Varus of the first metatarsal was correlated with tarsal arthritis and pes planus but not with duration of the disease. Forefoot spread was correlated with duration of the disease and erosive metatarsal disease but not with involvement of the midfoot. These data demonstrate that orthopedic treatment should be initiated as soon as involvement of the first metatarsal is detected and should be directed at the hindfoot, midfoot, and first metatarsal whose deformations occur concomitantly.

Rheumatoid metatarsus. The original evolution of the first metatarsal

Three hundred and eight unselected rheumatoid feet underwent a weight-bearing X-ray examination. If the malformations of the forefoot studied here present a statistical association, the primus metatarsus adductus is closely connected with tarsal arthritis and flattened foot but does not depend on the duration of the disease. The spread forefoot is indeed related to the duration of the disease and the presence of a metatarsal erosion at the foot level, but is not affected by the lesions of the midfoot. It appears then that an early orthopaedic treatment should be prescribed, once the first signs of involvement of the first ray or pronounced pronation of the hindfoot are noticed; it must affect the hindfoot, the midfoot and the first ray which progress together.

[Idiopathic dilated cardiomyopathies in children. Development and prognostic factors]

This review is a retrospective study of the cases of 103 patients under 20 years of age with idiopathic dilated cardiomyopathy and represents the whole experience of the Department of Paediatric Cardiology of the Hospital of Cardiovascular Disease, Lyon, between January 1970 and December 1988. The aetiological investigations were constantly negative: hypertrophic, restrictive and secondary cardiomyopathies were excluded. The clinical, radiological, electrocardiographic and echocardiographic data of each patient was noted at the time of admission and at the end of the clinical course. There were many more infants in this series. The onset of the disease was usually sudden. All patients were given medical treatment. The study period ranged over 19 years. Forty one patients (39.8%) died mainly of terminal cardiac failure. Sixty two patients are still alive, of whom 39 are completely cured, 2 have undergone cardiac transplantation, and 21 have a variable degree of chronic invalidity. The six months survival was 77.5%; the 1 year survival was 70% and the 5 year survival was 60%. Over one third of deaths (36.6%) occurred during the first month, 56% during the first 3 months and 70% during the first year. A statistical analysis comparing the initial criteria to death by the chi 2 test revealed the following prognostic factors: age at presentation (32.9% of deaths in patients under 2 years of age compared to 56.6% in the group over 2 years of age, p less than 0.025) and a family history of myocardial disease. The other clinical, radiological and echocardiographic parameters had no predictive value in this series and it was not possible to identify potential candidates for cardiac transplantation.

Effects of dydrogesterone on hydroelectrolytic metabolism: a randomized double-blind study

To determine a possible influence on sodium balance or blood pressure of a normal treatment with dydrogesterone, a randomized cross-over double-blind study was performed on 22 healthy young women. Each woman had (in random order) 1 cycle of treatment with dydrogesterone (20 mg/day during the last 12 days of the menstrual cycle) and 1 with equivalent placebo. On days 15 and 27 of each cycle the following data were noted: weight, systolic (SBP) and diastolic (DBP) blood pressures (mean of 13 measurements during 1 hour), natriuresis, kaliuresis, plasma renin activity (PRA) and plasma aldosterone concentration (P ald). For each variable the difference between day 27 and day 15 was calculated. The comparison between progesterone and placebo influence was made on these differences. Neither for sodium balance nor for blood pressure were there any statistically significant differences between placebo and dydrogesterone. However, the confidence intervals of the difference were rather large. There is a need for a more extensive study to confirm the absence of influence of progesterone on sodium balance and blood pressure.

A graphical and statistical method for investigation of time series in chronobiology according to the cosinor procedure

The mathematical and statistical analysis of biological time series is complex. In view of the necessity to deal with non equidistant data to analyse biological variables, preference is often given to the "cosinor procedure". We propose here a graphical and statistical assistance program for single or multiple cosinor procedure applicable to time series in chronobiology. This program investigates whether a cosine function or a mixture of cosine functions describe the experimental data adequately. The computer program is illustrated on data which have been published in a preceding paper.

A computer program for determination of equilibrium constants and binding site concentrations in radioimmunoassay systems

We propose a method allowing the automatic determination of equilibrium constants and binding site concentrations for an immune serum composed of a series of homogeneous antibody subpopulations. It is then possible to decompose the 'Scatchard plot' in its straight components corresponding to each antibody subpopulation.

Treatment of radioimmunoassay data: a computer program for curvefitting and dose interpolation using orthogonal polynomials

We propose a method allowing the automatic exploitation of radioimmunoassay results. The standard curve is calculated according to two models; a linear model by Logit-Log transformation of data and another one using Fisher's orthogonal polynomials. The computer programs are written in FORTRAN IV.