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The INTRABEAM 50 kV x-ray device can be used for intra-operative partial breast irradiation. Spherical applicators are added to the source probe to deliver a radially symmetric radiation dose. Dosimetric data for calculation of absorbed dose were measured for this unit and a superficial unit with a similar beam quality, as defined by half value layer (HVL). Chamber calibration factors, N(K), and chamber correction factors, k(ch), were determined based on HVL, according to the IPEMB code of practice and addendum. Depth doses were also measured using an ionization chamber and GafChromic EBT film. HVL was measured as 0.85-1.30 mm Al across the range of applicator sizes. Values for N(K) and k(ch) were found to be similar for the two units and all INTRABEAM applicator sizes. Therefore, calibration of ionization chambers, radiochromic film and other relative dosimeters could be performed on the superficial unit. This has the advantage of higher dose rates and lower dependence on small variations in detector positioning. Depth dose measurements performed using film also agreed with chamber values, published and manufacturer data, giving a simple and robust method for commissioning and regular quality assurance.

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Objectives: Therapeutic partial breast irradiation can be delivered intra-operatively using the Intrabeam 50 kVp compact X-ray device. Spherical applicators are added to the source to give an isotropic radiation dose. The low energy of this unit leads to rapid attenuation with distance, but dose rates are much greater than for diagnostic procedures. Methods: To investigate the shielding requirements for this unit, attenuation measurements were carried out with manufacturer-provided tungsten-rubber sheets, lead, plasterboard and bricks. A prospective environmental dose rate survey was also conducted in the designated theatre. Results: As a result of isotropic geometry, the scattered dose around shielding can be 1% of primary and thus often dominates measured dose rates compared with transmission. The absorbed dose rate of the unshielded source at 1 m was 11.6 mGy h 21 but this was reduced by 95% with the shielding sheets. Measured values for the common shielding materials were similar to reference data for the attenuation of a 50 kVp diagnostic X-ray beam. Two lead screens were constructed to shield operators remaining in the theatre and an air vent into a service corridor. A lead apron would also provide suitable attenuation, although a screen allows greater flexibility for treatment operators. With these measures, staff doses were reduced to negligible quantities. Survey measurements taken during patient treatments confirmed no additional measures were required, but the theatre should be a controlled area and access restricted.

Prospective evaluation of nerve conduction parameters in pediatric patients with diabetes should include both height (the most significant independent variable in latency analysis) and mean glycemic control (the most consistent variable in velocity analyses) as variables in the assessment of the natural history of evolving peripheral neuropathy.

These findings suggest that as early as 5-6 mo after diabetes diagnosis, and at a time frequently characterized by partial remission of IDDM, hyperglycemia has a role in the acute slowing of nerve conduction velocity. Other factors such as residual endogenous insulin production do not appear to influence these early changes.

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