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November 8, 2005

'IMRT Sensors' - a smart dose of medicine for cancer treatment

Topics: Medicine

IMRT, developed about 10-years ago, works by 'painting' small areas of different intensity radiation over the tumour. It involves the use of a servo-controlled device called a multi-leaf collimator, that has about eighty "moving fingers" that can "allow or stop" the radiation from the treatment machine reaching the patient. It's precise control allows a three dimensional pattern of dose to be scaled up. By painting the dose distribution in this manner, a high tumour-killing radiation dose is conformed to the tumour while an acceptably low and safe radiation dose goes to the surrounding tissues and vital organs. This is very different from conventional radiotherapy in which no such painting is done and the high dose can extend beyond the tumour and damage healthy tissue.

270302113856_4%20block%20IMRT%20photo.jpg
[IMRT 4 Block]

Intensity Modulated Radiotherapy (IMRT), is a radiation therapy for cancers that improves clinical outcomes by a providing more accurate targeting of tumours then with standard radiotherapy, and minimising the amount of radiation absorbed by healthy tissues. The good news about IMRT is that it results in patients only receiving a high radiation dose where they need it, thereby preserving healthy tissues. But like most good things in life, it doesn't come with a free lunch - there's a catch. It becomes increasingly more difficult to verify that patients are receiving the prescribed dose of radiation during the course of treatment, because of the complex computer simulations required by IMRT. There's a need to validate the simulations by verifying exactly how much radiation is reaching the patient, and where it's going, and up to now, that's been a problem.

Prostate IMRT.bmp
[Prostate IMRT]


But now INVORAD has come up with a solution by developing two sensors, a silicon diode and a p-channel metal-oxide semiconductor field-effect transistor (MOSFET), to solve the validation problem.

"Several features, such as miniature size, response to types of radiation involved in radiotherapy, compatibility with microprocessors that enables real-time read-out and low cost, make these semiconductor sensors eminently suitable for the intended application...

The diode sensor system is arranged in a series of modules containing 1069 individual diodes that can pick up incoming radiation.

"These diodes need to be very small and while there are commercial packaged diodes out there we needed diodes in bare die form with some novel properties so we developed the diodes ourselves, here at the Tyndall Institute," ...

The arrays are extremely accurate and can track radiation at micro-Gray resolution over millimetres of spatial resolution.

Read more ...

Posted by Richard at November 8, 2005 5:00 PM

While IMRT is becoming much more common in cancer treatment, there is another therapy that is still pretty slow coming out of the gate: Proton Therapy. Here in Houston, MD Anderson Cancer center is recognized globally as one of the premier cancer treatment centers. while Loma Linda has had Proton Therapy for nearly two decades (they started out at Lawrence Berkeley Laboratory using the old cyclotrons once used to separate uranium 235 for the manhattan project, since updated with new computerized controls.) we will not have one here for at least another year. this therapy promises to be even better than IMRT in protecting healthy tissue. However PT may suffer from a similar problem in accurately measuring the dosage since the energy delivery is not a "beam" like it is with x-rays but more like a "point source" not interacting virtually at all with tissue in between the device and the tumor. Would these technologies be applicable to PT?

Posted by: Rorschach Author Profile Page at November 9, 2005 3:58 PM



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