Biomedical subjects
R Birch
Publications and source records attributed to R Birch.
Time-calorie displacement diet for weight control: a prospective evaluation of its adequacy for maintaining normal nutritional status.
An unsupplemented 1000 kcal (4186 kJ) diet emphasizing large quantities of unrefined complex carbohydrates was evaluated for nutritional adequacy in a 20-week weight-control program for obese adults. Assessment of nutritional status, routinely obtained upon admission, was repeated at approximately 10-week intervals on 26 patients who were losing weight while adhering to the dietary guidelines. At least one repeat assessment was obtained on all 26 patients: 13 had follow-up assessment at 10 weeks, three at 20 weeks, and ten at both 10 and 20 weeks. Weight loss averaged 0.7 kg/wk over an average of 15 weeks with a mean energy intake of 1020 kcal (4270 kJ), 55 percent of baseline. At each follow-up assessment mean skinfold thickness fell significantly whereas muscle mass was maintained according to arm muscle circumference and creatinine-height index. Mean blood levels of retinol, beta-carotene, folate, vitamin B12, ascorbic acid, thiamin, riboflavin, pyridoxine, iron, transferrin saturation and calcium excretion remained within normal limits throughout treatment. Ascorbic acid levels rose significantly. The results indicate that the experimental diet, without supplementation, can fulfil nutritional requirements while restricting energy intake for weight reduction.
The role of maintenance therapy in disseminated testicular cancer.
We concluded a prospective study of the value of maintenance therapy in disseminated testicular cancer after chemotherapy-induced complete remission or chemotherapy cytoreduction followed by surgical resection of residual teratoma. A group of 171 patients were randomized to treatment consisting of cisplatin, vinblastine, and bleomycin, or these drugs plus doxorubicin. There was no apparent difference between these two induction regimens. Complete remission was achieved in 113 patients (66 per cent), and 19 (11 per cent) were free of disease by surgical resection of residual tumor. Of the 171 who started, 113 were eligible to receive either maintenance doses of vinblastine (58 patients) or no further therapy (55 patients) after remission-induction therapy. There was a 9 per cent relapse rate during maintenance with vinblastine and a 7 per cent relapse rate with no maintenance therapy; the overall relapse rate was 8 per cent (nine of 113). Our data indicate that maintenance therapy is unnecessary in disseminated testicular cancer.
Unilateral outward-turning leg in infancy.
An unreported condition of the legs in infants was found in more than 130 children referred to one hospital from 1973-1979. One hundred of these children were studied. One leg, usually the right, lay in external rotation. Although there was no loss or restriction of movement at the hip joints, in most cases there was a difference in the arc of rotation. Eleven children also had mild hooking of the forefoot on the unaffected side. Hip radiographs were normal in all cases. Obstetric records were reviewed in 70 cases, but no relation was found between presenting position at birth and side of the affected limb. The condition resolved spontaneously in most of the children who were follow up. This condition may cause anxiety to parents and doctors but it seems to be a variant of normal with an excellent prognosis.
Importance of stratification in later stages of clinical trials.
An erroneous assumption is often made in clinical trials that once patients achieve a remission on an early phase of a study, then they can be randomized to various arms of later phases of that trial without stratifying for induction therapy, the contention being that complete remissions imply a homogeneous sample with respect to therapy already received. This short article shows that this is not the case because induction therapies may be equal with respect to the percentage of complete remissions achieved but may differ in overall proportion of patients actually cured. Examples of clinical trials with this flaw are presented. A statistical explanation of the problem, which illustrates specific methodological points, is included.
An anomalous flexor digitorum superficialis indicis muscle presenting as carpal tunnel syndrome.
The description is given of an anomalous muscle arising from the flexor digitorum superficialis indicis tendon distal to the transverse carpal ligament which presented as carpal tunnel syndrome.
Alternating non-cross-resistant drug combinations in the treatment of metastatic small-cell carcinoma of the lung.
In a randomized trial of the Southeastern Cancer Study Group, patients with metastatic small-cell lung carcinoma were treated with a combination of cyclophosphamide (500 mg/m2 I.V.), Adriamycin (50 mg/m2 I.V.), DTIC (250 mg/m2 I.V.), and vincristine (1 mg/m2 I.V.) every 4 weeks for three cycles. Complete and partial responders to this induction regimen were then randomized to receive either the same combination every 4 weeks for an additional six cycles versus a non-cross-resistant drug combination of BCNU (100 mg/m2 I.V.), procarbazine (100 mg/m2 p.o. daily x 10 days), methotrexate (25 mg/m2 I.V.), and vinblastine (5 mg/m2 I.V.) every 4 weeks for six cycles versus alternating treatments with the two regimens for a total of six cycles of therapy. Patients who were less than good responders received six cycles of the non-cross-resistant drug combination. Of 202 evaluable patients, 40% responded (complete + partial responses) to induction; the complete response rate for the whole group was low (14%). Patients randomized to the BPMV combination, or crossed over to it, failed to improve upon their response to induction. Patients who responded to induction had a median survival of 41 weeks versus 20.6 weeks for the nonresponders, p less than 0.001. Performance status greater than or equal to 60%, and absence of prior radiotherapy were associated with improved survival (30 and 31.5 weeks, respectively). The toxicity of these regimens was acceptable. Failure to improve on results of our earlier protocol were probably due to the long (weeks) interval between treatments, inclusion of a relatively inactive but toxic drug (DTIC) in the induction combination which limited doses of the more active agents, and the use of a non-cross-resistant drug regimen which was inactive.
Silicone rubber cuffs--a cause of nerve compression.
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Computation of bremsstrahlung X-ray spectra and comparison with spectra measured with a Ge(Li) detector.
A method of computing theoretical X-ray spectra in the range 30-150 kV is presented. The theoretical spectra are compared with constant potential, high resolution spectra from a tungsten target measured with a Ge(Li) detector, for a range of target angles, tube voltage and filtrations. Above 100 kV the spectra were also measured with a NaI detector but, as there was good agreement between the Ge(Li) and NaI detectors, only the former are presented. Spectra computed using Kramers' theory are also included for comparison, giving fairly good agreement at large target angles (30 degrees) but becoming gradually worse as the target angle decreased. Spectra may be computed by this method for any desired filtration, target angle, and tube voltage between 30 and 150 kV, in excellent agreement with the measured data.
The detection of criticality incidents with a gamma dose rate alarm employing an ionization chamber.
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Constancy of radiation output during diagnostic x-ray expousers.
Variation in X-ray output and quality during a diagnostic exposure can be undesirable and may result in unnecessary dose to the patient. When significant build-up or decay periods are present errors will arise if factors obtained under steady-state conditions are employed to estimate the exposure. These parameters must be taken into account when calibrating X-ray generators. A variable speed spinning film device and a spectrometry system have been used to measure the variations under fluoroscopic and radiographic conditions for a number of generators. Variations in output due to filament heating, voltage supply and rectification, cable capacity and target pitting have been demonstrated. At low fluoroscopic currents, large surges and long decays have been observed; the significance of these effects is considered.
A technique for measuring the variation of photon spectrum from X-ray generators over the mains voltage cycle.
The variation in current and accelerating voltage across an X-ray tube, that occurs over the mains voltage waveform cycle, produces changes in photon flux and spectrum shape. A knowledge of these changes is required to provide an understanding of the parameters affecting X-ray output. Variation in the photon flux will cause distortion of a measured 'mean' spectrum if the dead time of the spectrometry system employed varies over the waveform cycle. A system has been developed that enables the spectrometer to be synchronized to the mains voltage cycle so that variations in photon flux and the instantaneous spectra at selected parts of this cycle can be measured. The variation in photon flux is dependent upon the type of power supplies (both high and low tension). the tube current and the degree of filtration employed. Examples are given of the ripple of photon output due to the voltage and current ripple for a nominally constant potential generator and a half-wave rectified type. The way in which they interact to produce the measured variation is shown.
Surgery of the knee in children with spina bifida.
The achievement of independent mobility by children with spina bifida is often hampered by deformities of the knee joints. This report reviews the results of surgical treatment in 34 spina-bifida children with knee deformities. The surgical procedures are described and it is concluded that surgery is justified in a proportion of cases with fixed-knee deformities.
The spectrum and intensity of extra-focal (off-focus) radiation.
Conflicting results have been obtained by other workers for the quality of radiation originating outside the area of the focal spot on X-ray tubes. This extra-focal radiation results in poorer picture quality, especially in cases where grids are not being used. As part of an investigation to assess the importance in diagnostic radiology of the various factors affecting the output from X-ray tubes, the photon spectrum has been examined using a Ge(Li) detector. The measured spectra have been adjusted for the effect of the detector characteristics. Results show that the extra-focal radiation is softer than that from the focal spot and, for the X-ray generator measured, constitutes approximately 8% of the exposure at 100 kV with a total filtration equivalent to 2 mm of aluminium. The possibility of further collimation to reduce this component, thus improving picture quality, is considered.
Respirable dust content of subway air.
During the non-heating months of June, July and August of 1974, the total and respirable dust content at an underground station of the Newark City Subway System was determined. Higher particulate levels than obtained for ambient Newark air were observed. Additionally, Federal Ambient Primary Air Quality Standards for suspended particulate matter was exceeded in two instances. Qualitative elemental analysis of the particulate matter collected is also reported.
The Bender Gestalt test as an ineffective predictor of reading achievement.
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Determination of the hyperparameters of a prior probability model in survival analysis.
This paper outlines the mathematical theory required for eliciting the hyperparameters of a subjective conjugate distribution for the exponential survival model with censoring. The technique involves the quantification of expert knowledge based on determination by the expert of expected fractiles of a survival distribution in a particular clinical trial setting. Once the prior predictive distribution is determined and the fractiles elicited one can proceed, using iterative techniques, to solve for the hyperparameters. The restrictions and constraints of the hyperparameters as well as the fractiles are studied. The theory is then applied in a clinical trial setting.