Lung dose rate and interstitial pneumonitis in total body irradiation for bone marrow transplantation

The effect of dose rate to the lungs and development of interstitial pneumonitis (IP) was evaluated in 114 bone marrow transplant patients receiving fractionated total body irradiation (TBI) (1200 rads TD in 6 fractions twice daily over 3 days) as part of their pre-conditioning regimen. The tumour dose (TD) was calculated as the mean lung dose as previously described (1). A 6MV linear accelerator at a mid-line dose rate of 7.5 rads/minute was used between March 1981 and June 1985 and a Co-60 source at 5 rads/minute thereafter. This resulted in a range of dose rates to the lung of between 6.9 and 8.9 rads/minute and 2.9 and 6.5 rads/minute respectively. In the majority of patients the aetiology of IP was investigated by lung biopsy with histology and culture. There was no statistically significant difference in the incidence of IP over the two sets of dose rates. Our study suggests tat the incidence of IP using fractionated TBI is not influenced by dose rates below 8.9 rads per minute.     

DIURETIC RADIONUCLIDE RENOGRAPHY IN UPPER URINARY TRACT OBSTRUCTION

Diuretic renography using radioidine sodium hippurate and a frusemide stimulus was used to differentiate between obstructive and nonobstructive dilatation of the urinary tract. Information was recorded by a gamma camera on line to a computer. Sixty-seven uretero-renal units (URU) were studied in 33 patients with an average age of 9¹/₂ years. The diuretic renogram correctly indicated obstructions in 18 URU but gave false positive results in another five. Of these five, four had severely Impaired function. The renogram indicated nonobstruction in 49 URU, and gave false negative results in another two; of these two one patient had a duplex kidney with a poorly functioning ureteric segment and the other patient had gross reflux and megaureters. The diuretic renogram is useful in the investigation of equivocal upper urinary tract obstruction but may be unreliable in situations of inadequate renal function.     

The Heart Rate Response to Carotid Artery Massage in a Sample of Healthy Elderly People

Carotid artery massage was carried out in a cross-section of 95 healthy elderly subjects (51 men and 44 woman, mean age of 74 years) to assess the heart rate response and associated symptoms. These subjects were drawn from a larger group of randomly selected healthy elderly people living in Southampton. They had no history of myocardial infarction or stroke and were not taking any drugs that might enhance the carotid sinus reflex. A continuous distribution of response to carotid artery massage was seen with a median percent change in RR interval of 11.6% (IQR 22.9%); 66% had a percent change in RR interval of < 20%, 90% had a change of < 50%, and 9.5% a change of > 100%. Carotid sinus hypersensitivity (sinus arrest > 3 s) was found in 4 previously asymptomatic subjects; a prevalence of 4.2% (95% CI 1.2%–10.4%), and this was associated with dizziness in 2 of these 4 subjects. Dizziness also occurred in one other subject who had a change in RR interval of 178%, The definition of an abnormal carotid sinus reflex is arbitrary given the continuous RR interval response to carotid artery massage. In diagnosing carotid sinus syndrome, the RR interval response to carotid artery massage alone is not sufficient, as this maneuver must also reproduce the patient's presenting symptoms.     

A short protocol for muscle MRI in children with muscular dystrophies

The use of muscle magnetic resonance imaging in patients with muscular dystrophies or congenital myopathies has been limited. We describe the development of a short protocol to be used in young patients with neuromuscular disorders. The protocol includes transverse T1-weighted spin echo sequence images of thighs and calves. The total scanning time is less than 30 minutes, and can be easily applied to patients over the age of 4 years without any need for sedation. Although only the leg muscles are imaged, the images obtained can still help to identify specific patterns of muscle involvement and provide additional help in the differential diagnosis of muscle disorders with overlapping clinical features.     

SERUM FREE 1,25-DIHYDROXYVITAMIN D AND THE FREE 1,25-DIHYDROXYVITAMIN D INDEX DURING A LONGITUDINAL STUDY OF HUMAN PREGNANCY AND LACTATION

The changes in three different indices of 1,25-dihydroxyvitamin D (1,25(OH)2D) biological activity were studied longitudinally in 35 women during late pregnancy and lactation and in 26 control women. Measurements were made of maternal serum total 1,25(OH)2D and free 1,25(OH)2D concentration (by centrifugal ultrafiltration) and the free 1,25(OH)2D index (the molar ratio of total 1,25(OH)2D and vitamin D binding protein (DBP]. During late pregnancy total 1,25(OH)2D concentrations were significantly elevated when compared to controls, as were free 1,25(OH)2D and DBP concentrations and the free 1,25(OH)2D index. Serum total 1,25(OH)2D, free 1,25(OH)2D and DBP concentrations all fell dramatically during the first 2 weeks of lactation with total 1,25(OH)2D and free 1,25(OH)2D concentrations falling to levels below those of controls. During the course of lactation both total 1,25(OH)2D and free 1,25(OH)2D levels rose significantly although they were not different from controls at 18 weeks of lactation. In contrast, the free 1,25(OH)2D index fell during the first 2 weeks of lactation, but remained at this level, significantly lower than controls. Neither urinary calcium excretion nor dietary calcium intake correlated with total or free 1,25(OH)2D, DBP, or the free 1,25(OH)2D index. The disagreement in the results of free 1,25(OH)2D concentration and free 1,25(OH)2D index demonstrates that these two approaches to measuring biologically active 1,25(OH)2D are not equivalent. In attempting to account for the increased calcium requirements of human reproduction we conclude that in pregnancy any of the 1,25(OH)2D measurements may be appropriate. In lactation, however, either 1,25(OH)2D is not a major factor or 1,25(OH)2D biological activity is inadequately represented by any of the currently available methods.