A philosophical approach to treatment machine maintenance and breakdown.

Planned preventative maintenance (PPM), quality control (QC) checks and breakdown all contribute to the down-time of a radiotherapy treatment machine. Low levels of machine availability are unacceptable both clinically and financially. Clinical data demonstrate that, for many tumours, interruptions to treatment will result in reduced local control.

Ultraviolet B radiation was increased at ground level in scotland during a period of ozone depletion.

The potentially harmful effects associated with stratospheric ozone depletion are widely acknowledged. As the ozone layer principally absorbs ultraviolet (UV) radiation of wavelengths below 290 nm, reductions in stratospheric ozone levels are likely to result in increased UVB at the earth's surface, with the risk of increased incidence of skin cancer. Measuring the sun's spectrum at ground level requires sophisticated and reliable spectral instruments.

Short communication: a system for remote monitoring of a hospital linear accelerator.

Linear accelerators are complex machines with many parameters affecting the quality of the treatment beam delivered. A high level of technical support is required but this can be difficult to achieve if the linear accelerator is at a centre distant from a medical physics department. This paper describes a solution to this problem whereby a newly installed linear accelerator at the Royal Shrewsbury Hospital is remotely monitored from the Royal Hospital, Wolverhampton.

UK nuclear medicine survey, 1992-93.

A postal survey of UK nuclear medicine departments was undertaken to collate information on equipment, numbers of procedures and staffing levels for the years 1992 and 1993. It was estimated that there are 235 sites undertaking nuclear medicine, the total number of procedures performed being some 490,000 in 1993 compared with 430,000 in 1989. Informal investigation suggests that the increase is due to greater usage of myocardial perfusion and lung ventilation/perfusion studies.

Ultraviolet and laser radiation safety.

Both ultraviolet radiation and laser radiation occupy pmt of the Spectrum designated "optical radiation". Thus, measurement techniques are similar and the same organs (eyes and skin) are at risk from accidental exposure. However, the equipment used to produce ultraviolet and laser radiation differs substantially and the harm caused by each type of radiation is also different.

Cine magnetic resonance imaging of pulsatile cerebrospinal fluid flow using CSPAMM.

Spatial modulation of magnetization (SPAMM) is a well established imaging technique which superimposes a tagging pattern on conventional magnetic resonance (MR) images, allowing movement to be visualized. A modification to the SPAMM technique, called complementary spatial modulation of magnetization (CSPAMM), which improves the contrast of the tagging pattern is explained. The application of CSPAMM to the visualization of pulsatile cerebrospinal fluid flow (CSF) using an 8 frame cardiac-gated cine sequence is described.

Fat suppressed magnetic resonance imaging at 0.5 T using binomial radiofrequency pulses.

Fat suppressed MR imaging can be achieved by selectively saturating lipid protons, just before applying a conventional spin-echo rf pulse sequence. The difference in the Larmor frequency between fat and water protons is only 3.5 ppm, so that the frequency response of the suppressing pulse, or pulses, has to be carefully designed.

Use of the linear quadratic model in order to accommodate a small reduction in the number of fractions of a standard radiotherapy treatment regime.

Use of the linear quadratic model is considered for reduction, by one or two fractions, of the number of fractions in a daily fractionated reference schedule while maintaining a continuous regime. The cases of maintaining late or early tumour reacting tissue are considered with the inclusion of time effects. The reduction of biologically effective dose (BED) to early-tumour type tissue is shown to be overestimated for both cases if time effects are not taken into account.

A cine-SPAMM sequence for NMR imaging of pulsatile cerebrospinal fluid flow.

The technical difficulties in designing a SPAMM sequence to image pulsatile cerebrospinal fluid (CSF) flow at different phases of the cardiac cycle are described. The criteria used to select the most appropriate order of binomial SPAMM sequence are outlined. Data collection times required to view both cephalad and caudad flow for all R-R intervals were considered.

Magnetic resonance imaging of pulsatile cerebrospinal fluid flow by spatial modulation of magnetization.

Various orders of binomial spatial modulation of magnetization sequences up to (1 4 6 4 1) have been tested to find the optimum sequence for clinical application. Stripe width, stripe sharpness and the tolerance of the sequences to radiofrequency non-linearity have been investigated. The (1 3 3 1) sequence was found to be a good compromise between competing design criteria, and its application to viewing pulsatile cerebrospinal fluid motion is described.

Application of the linear-quadratic model with incomplete repair to radionuclide directed therapy.

The linear-quadratic (LQ) model for fractionated external beam therapy has been modified by previous authors to include the effects due to an exponentially decaying dose rate. However, the LQ model has now been extended to include a general time varying dose rate profile, and the equations can be readily evaluated if an exponential radiation damage repair process is assumed. These equations are applicable to radionuclide directed therapy, including brachytherapy.

Application of radiobiological dosimetry to radionuclide directed therapy.

The standard linear quadratic model, which has been used to assess the radiobiological damage to tissue by external beam fractionated radiotherapy, has been extended to encompass a general continuous time varying dose rate protocol such as radionuclide therapy. If the radionuclide clearance from the tissue is purely exponential, the effect is readily calculated. Otherwise, the effect can be evaluated by numerical integration if the dose rate time-1 profile is known.

Dosimetric model for antibody targeted radionuclide therapy of tumor cells in cerebrospinal fluid.

Although encouraging results have been obtained using systemic radioimmunotherapy in the treatment of cancer, it is likely that regional applications may prove more effective. One such strategy is the treatment of central nervous system leukemia in children by intrathecal instillation of targeting or nontargeting beta particle emitting radionuclide carriers. The beta particle dosimetry of the spine is assessed, assuming that the spinal cord and the cerebrospinal fluid compartment can be adequately represented by a cylindrical annulus.

Simultaneous measurement of left ventricular function and perfusion.

A new radiopharmaceutical, methylisobutyl isonitrile (MIBI), has been developed as a technetium-99m-labelled alternative to thallium 201 for myocardial imaging. By virtue of the high specific activity of 99mTc, some 600 MBq may be administered as a 0.3 ml bolus, permitting the acquisition of a first-pass nuclear angiogram at rest and at peak exercise.

Computer linked apparatus for upper limb therapy: a new system of resistive exercise.

A need has been recognised for equipment that can be used to provide objective evaluation of exercise of the upper limb in occupational therapy while being motivational to the patient. The microcomputer was seen to be a suitable tool as part of a system that might satisfy this need. After consulting experienced hand therapists the criteria were established for equipment that would encourage and quantify exercise.

Initial blood pressure as a predictor of the response to antihypertensive therapy.

1. The relationship between fall in systolic blood pressure and initial systolic blood pressure has been investigated in 255 mixed normotensive and hypertensive subjects given placebo or one of five types of antihypertensive drug (ACE inhibitors, calcium antagonists, direct vasodilators, alpha-adrenoceptor blocker, beta-adrenoceptor blocker). 2.

Automated radiopharmaceutical dispensing.

An automated workstation, developed for clinical biochemistry, has been evaluated for potential use in preparing radiopharmaceuticals. It was found that substantial modifications, both hardware and software, would be required but the approach seemed feasible.

The effect of the vehicle formulation on the stratum corneum penetration characteristics of clobetasol 17-propionate in vivo.

The multiple skin surface biopsy technique to measure stratum corneum (SC) penetration characteristics in vivo has been more accurately quantified and used to provide information on the kinetics of transfer of a topical steroid through the SC. Radiolabelled clobetasol 17-propionate formulated in two different vehicles, consisting primarily of dibutyl adipate or of propylene glycol, was applied and the penetration characteristics compared. Using exponential expressions for radioactivity in skin surface biopsies as a function of SC depth, and total SC radioactivity as a function of time, a mathematical model was developed to calculate the rate of loss of steroid through superficial shedding and the rate of transfer of steroid from the SC into the epidermis.

The effect of baseline lesion mineral loss on in situ remineralization.

The effect of baseline lesion mineral loss on the remineralization of enamel lesions by a sodium fluoride dentifrice was studied in situ by means of an appliance carrying enamel sections. Artificial lesions of various sizes were created, by means of acidified gelatin, and were then mounted on the appliances of five volunteers. Each brushed twice daily for two min with a 1000 ppm F sodium fluoride dentifrice.

Total body potassium measurement--the effect of fallout from Chernobyl.

As a result of fallout from the nuclear accident at Chernobyl in April 1986, the caesium radioisotopes, 134Cs and 137Cs, have been detected in man. A minor consequence of this is that total body potassium (TBK) measurements obtained from the whole body activity of 40K, a naturally occurring radioisotope of potassium, can be overestimated because of gamma spectrum overlap between 134Cs and 40K. Whole-body activities for 134Cs and 40K were measured in 18 healthy adults (13 M, 5 F) in June/July, 1986, using a whole-body counter with NaI crystal scintillation detectors.