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Intensity Modulated Radiation Therapy (IMRT)
IMRT is the most technologically advanced treatment available
in external beam radiation therapy. It enables the Maddock Center
to control the dose distribution to increase the radiation
delivered to the tumor while lowering the amount of radiation
to adjacent radiosensitive tissues. IMRT is now the standard
of care in radiation treatment for cancer of the prostate and
cancers of the head and neck. Other sites that can benefit from
IMRT are pelvis, any tumor wrapped around critical organs or
tissues and certain types of breast cancer, particularly those
involving the left breast in patients who have received Adriamycin,
which is potentially cardiotoxic.
There are essentially three components of a successful IMRT
treatment plan:
- Tighter Margins (as compared with either conventional or
3-dimensional treatment planning). Because IMRT uses more fields
and many field segments (beams) to shape the radiation to the
exact contours of the tumor, we can shrink the margin of normal
tissue affected by the radiation. This means that nearby normal
tissues receive a lower dose of radiation, which in turn means
fewer side effects.
- Dose Escalation. Because the margins of IMRT are so tightly
controlled, we can actually increase the dose delivered to the
tumor itself, thereby reducing the risk of local recurrence.
- Tumor localization. Accurate daily
set ups are particularly important when treating cancer of the
prostate. Because the prostate can shift slightly within the
human body and because of the reduced margins of normal tissue,
it is important to accurately identify the position of the prostate
every day. The Maddock Center uses the award-winning ZMED
SonArray™ System to locate the prostate, bladder and
rectum relative to the isocenter of the accelerator. In fact,
the Maddock Center is the only facility in Rhode Island to use
the ZMED real-time ultrasound device for the utmost in clinical
accuracy. The 3D ultrasound images are then fused with the patient’s
CT images. The three axes of table movement are adjusted to
bring the prostate to the correct position for treatment. Unlike
implanted fiduciary markers, this system is non-invasive. For
cancers of the head and neck, we use custom molded masks and
immobilization devices.
For more information on IMRT and the technology and techniques
that make this advance in care feasible, please see Dr.
Maddock’s
recent article on IMRT in Medicine and Health, a publication
of the Rhode Island Medical Society.
Different field arrangements as defined by
the Multi Leaf Coordinator, a critical
component
of IMRT therapy.
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Therapies & Technologies at
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