Review of related literature about computer radiation

This is a manuscript of the 3rd edition, a work in progress sponsored by the US National Science Foundation. The first edition was published by Third Millenium Books, Novato, California, in and as noted below, copyright was reassigned to the author upon breakup of that company. As to conditions for use, Dr. Grosch says "make sure it's as generous as possible.

Review of related literature about computer radiation

Aetna considers placement of fiducial markers medically necessary if the above criteria are met, and the radiation target is not clearly visible, and bony anatomy is not sufficient for adequate target alignment.

Aetna considers interfraction image guidance i. For purposes of this policy, to qualify as IMRT, radiation therapy requires highly sophisticated treatment planning utilizing numerous beamlets to generate dosimtery in accordance with assigned dose requirements to the tumor and organs at risk.

Fractionation

Intensity-modulated radiation therapy, also known as tomotherapy, is a type of stereotactic radiosurgery that delivers a highly conformal, 3D distribution of radiation doses.

This therapy allows for increased precision by the conforming of the radiation to the planned target site while significantly reducing the amount of radiation to surrounding healthy tissues.

IGRT is utilized to direct and guide the delivery of radiation to maximize accuracy and precision throughout treatment. Different techniques are utilized to control the radiation amount given during IMRT. The most common approach is the use of multileaf collimators MLCs.

These devices are attached to the linear accelerator. The leaves act as filters that block out certain areas. This Review of related literature about computer radiation utilizes custom made based on the 3D images and the treatment plan high density blocks to control the administration of the radiation.

The blocks are put into place, the patient is positioned and the radiation is delivered. Fiducial markers may be placed using CT, endoscopic or surgical guidance. In contrast to conventional trial-and-error approach, IMRT uses inverse planning automated optimizationcomputer-controlled radiation deposition, and normal tissue avoidance.

The delivery system combines 2 components: When IMRT is used for head and neck tumors, it allows for the treatment of multiple targets with different doses, while simultaneously minimizing radiation to uninvolved critical structures such as the major salivary glands e.

Collimator-based IMRT uses computers to modify the intensity of the beam across each individual field with the use of moving collimators. Conventional treatment with multi-leaf collimation MLC uses static positions of the collimator leaves whereas IMRT allows the dynamic motion of the various collimator leaves during each session of therapy.

Review of related literature about computer radiation

With compensator-based IMRT, a pre-shaped piece of material the compensator or modulator is used to modulate the beam. The amount of modulation of the beam is based on the thickness of material through which the beam is attenuated.

This modulation requires the fabrication and the manual insertion of the modulator into the tray mount of a linear accelerator. Intensity-modulated radiation therapy typically involves inverse treatment planning, although forward treatment planning has been used.

Forward treatment planning involves estimating the radiation delivery profile based on the number, directions and shape of the beams. In inverse treatment planning, the radiation oncologist and physicist determine the treatment target, the normal structures that should be protected, the required radiation dose for the tumor and the tolerated doses for the surrounding normal tissues; the computer then computes the beam profiles needed to yield those results.

The outlined objectives for radiation dose distribution are in prescribed dose volume histograms. The histograms are translated into beam configurations that will deliver tumor and normal tissue doses prescribed. A medical linear accelerator equipped with a dynamic MLC shapes the radiation beams wrapping around the tumor, conforming to its shape and delivers the radiation.

Intensity-modulated radiation therapy involves at least 5 separate ports. The beam angle or gantry position is what determines a port or entry point of the beam. Segments are part of the individual beam profile and there may be many per port or beam angle. The assessment found that current reports do no allow for a good comparison of relapse or survival data between IMRT and conventional techniques.

On the topic of patient safety, the assessment observed that total body irradiation is higher using IMRT and, in theory, may overall double the incidence of fatal secondary malignancies compared with standard external radiotherapy techniques.

The assessment noted that younger patients are especially at risk. The report also noted that large variations exist in total body irradiation between various IMRT techniques. Also use of daily radiation-based imaging for treatment set-up verification adds to the overall radiation exposure.

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CNS and Head and Neck Tumors Intensity-modulated radiation therapy may be indicated in CNS and head and neck tumors, due to the close proximity of critical structures in these anatomic regions.University of Alberta offers hundreds of undergraduate, graduate and continuing education programs and degrees.

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Review of related literature about computer radiation

Review of the related literature Use of cellular phone or mobile phone (MP) has increased exponentially as it became a part of the radiation emitted by these base stationsand their antennas. This is because, in contrast to mobile handsets, radiation by cell tower is emitted continuously and is more powerful at near byareas.

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Could Small Amounts of Radiation Be Good For You?