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Biomedical subjects

W Jackson

Publications and source records attributed to W Jackson.

51 records · Page 3Linked to original sources
PubMed1975

Measurement of kilovoltage by the penetrameter - theoretical aspects.

The penetrameter method makes use of the attenuation in copper of a heavily filtered X-ray beam to predict the generating kVp. This is derived from the matching step or copper reference number (CRN) of a film density matching process in which a fast and slow screen combination is employed. In the present work, theoretical spectra resulting from chosen representative kV and mA wave-forms have been derived by computer analysis, assuming Kramers' expression for the bremsstrahlung emission from a thick target. The CRN appropriate to each spectrum has been found and its relation to kVp recorded. The uncertainty in the use of the penetrameter is expressed in terms of the spread of the CRN as a function of kVp and waveform. The computer predictions agree well with experiment, provided a fall in the fast-slow screen ratio with energy is postulated - a fall verified by separate experimental work in screen ratios. Since Kramers' expression relates only to bremsstrahlung radiation, the theoretical analysis has been extended to include the effects of K characteristic and extrafocal radiation. An expression has also been derived for the sensitivity of the penetrameter.

Computers↗
PubMedDate not supplied

Prednisone and piroxicam for treatment of primary Sjögren's syndrome.

Primary Sjögren's syndrome is a systemic autoimmune exocrinopathy characterized by a lymphoplasmacytic infiltrate and destruction of salivary and lacrimal glandular tissues. There is no widely accepted or effective systemic therapy for this disorder. The purpose of this 6-month randomized, double-blinded, placebo-controlled study was to examine the effects of prednisone (30 mg, alternate days), piroxicam (20 mg, daily), or placebo on the salivary, lacrimal and immunologic alterations of primary Sjögren's syndrome. Eight patients were enrolled in each group. Salivary and lacrimal function were assessed at entry and at the completion of treatment. Labial minor salivary gland tissue was obtained at these times and examined for intensity of infiltration (focus scores) and for the relative proportion of glandular elements. Serologic and subjective evaluations were done as well, and patients were monitored for therapy-related side effects. Neither active treatment led to significant improvement in salivary or lacrimal function, although prednisone improved salivary flow in selected patients and was associated with positive subjective responses. Prednisone also significantly decreased the serum total protein, IgG, IgA, and sedimentation rate and increased the white cell count. There were no significant alterations in either focus scores or the percentage of glandular component tissues of minor glands with either active treatment. This study demonstrated that 6 months of prednisone or piroxicam at the doses utilized failed to improve the histological or functional parameters of salivary and lacrimal glands in primary Sjögren's syndrome.

Adult↗