| 摘要 |
<p>In radiotherapy use is made of apparatus of the type in which a chain of balls comprising radioactive balls and inert spacer balls is moved pneumatically to and from an applicator tube within the patient, the spacer balls are made of a material such as nylon which is softer and less dense than the radioactive balls, and is radiographically transparent. This reduces wear and tear on the radioactive balls and facilitates control of dosage and monitoring of the treatment. The balls are sorted after use by means of a radiation detector. The ball chain has a larger diameter end ball of ferromagnetic material, which blocks air flow through the applicator when correctly located therein, and whose position can be verified by an induction air coil. By assembling and storing the chain in a storage tube having two air inlets, respectively above and below the end ball, and choking the lower inlet, air may be selectively applied to the inlets to expel the chain from the storage tube either with its end ball for transport to the applicator tube, or without its end ball for sorting. Use of the lower inlet alone enables pressure retaining the chain in the applicator to be maintained only in the absence of send out air flow through the applicator tube, thus enabling malfunctions to be detected.</p> |
