Radiation Oncology

a report by

S t A g n e s H o s p i t a l , Ba l t imo re

Curing patients of cancer requires a constantcommitment on many levels in a healthcare system.To ensure top-notch patient treatment, St Agnes hasinvested in the latest technology available. Theradiation oncology group complements thissophisticated technology with university-levelleadership and experience. This site highlights thelatest and greatest in radiation therapies for thetreatment of all types of cancers, as well as the peoplebehind the equipment.

Adva n c e d Te c h n o l o g y i n C a n c e r C a r e

Improved cure rates for different types of cancers arethe result of advances in surgery, chemotherapy, andradiation therapy.A majority of cancer patients receiveradiation therapy as part of their overall course oftreatment. Radiation therapy may be in the form ofexternal beam irradiation, using powerful X-ray(electron, photon) machines called linear accelerators,or by placement of radioactive sources inside thetumor, a technique called brachytherapy.

Over the past decade, improvements in computersand networking, radiotherapy treatment planningsoftware, and medical imaging modalities –computerized tomography (CT), magnetic resonanceimaging (MRI), ultrasound (US), and positronemission tomography (PET) – have beenincorporated into radiotherapy practice.This has leadto the development of ‘image-guided radiotherapy’ –radiotherapy that uses cross-sectional images of thepatient’s internal anatomy to better target theradiation dose in the tumor while reducing theradiation exposure of healthy organs. Image guidanceleads to improved control of the tumor whilesimultaneously reducing the potential for acute sideeffects due to irradiation of healthy tissuesurrounding the tumor.

Advanced technologies are currently in use in the StAgnes Cancer Center that enable image-guidedradiotherapy treatments.These technologies representa continuum of advances allowing sophisticatedtreatments available only in select centers across the nation.

Im a g e - g u i d e d P ro s t a t e B r a c hy t h e r a py

Prostate cancer is the most commonly occurringcancer in men today, second only to lung cancer as acause of cancer-related death in men.The use of theprostate-specific antigen (PSA) test has lead to earlierdetection of prostate cancer, resulting in a greaternumber of candidates for ‘prostate brachytherapy’, orradioactive seed implantation.

Brachytherapy is the placing of rice-sized, radioactivepellets, or seeds, directly into the prostate usingneedles guided by realtime transrectal US imaging.The optimal number and location of the seeds aredetermined in the operating room by the oncologistusing specialized treatment planning software.Typically, rows of seeds are deposited uniformlythroughout the prostate so that the radiation cancover the entire gland. The metallic seeds emit low-energy radiation that is highly absorbed in theprostate gland close to the seed. With the correctplacement of seeds, a very high dose of radiation canbe given throughout the prostate gland with littleexposure of the healthy tissue and organs surroundingthe prostate. Radiation is gradually emitted from theseeds over a period of six to 12 months, after whichthey become completely inert and can safely remainin the prostate for the rest of the patient’s life. Theprocedure is well-tolerated by most men, withtypically no long-term side effects.

Im a g e - g u i d e d E x t e r n a l B e amRad i o t h e r a py

External beam radiotherapy is the most commonform of radiation treatment offered to cancerpatients. It consists of irradiating the tumor usinghigh energy X-rays and/or electrons using a machinecalled a medical linear accelerator. Most treatmentsconsist of multiple X-ray beams pointed at the tumorfrom different directions. This approach allows moreenergy to be absorbed in the tumor where the X-raybeams overlap, improving the potential forsimultaneously eradicating the tumor and sparinghealthy tissue.

Image-gu ided Rad io therapy – A Case S tudy

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DOI: 10.17925/OHR.2005.00.00.62

Delivering the future.

Stereotactic, IMRT, and 3D CRT in one system.

The Trilogy™ Stereotactic System opens a new chapter in the radiation therapy success story of increasing cancersurvival rates. As rapidly improving diagnostic techniquesdetect cancers earlier, Trilogy makes radiation therapy viableat earlier stages and for more types of disease.

Optimized for delivering higher doses to smaller areas overshorter time periods, the Trilogy system represents significantprogress toward turning cancer from a terminal disease into a chronic, manageable condition.

Practical as well as visionary, the Trilogy system provides acost-effective way for radiation oncology departments toexpand their treatment repertoire.

The Trilogy Stereotactic System. All in one. Best in one.

Inspiration, the Varian advantage

The Trilogy system is part of the Inspiration™

integrated oncology environment.

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Radiation Oncology

The medical linear accelerators used at the St AgnesCancer Center are the most advanced treatmentmachines available in the field today.These machineseach have two X-ray beam energies and four to fiveelectron beam energies. This variety of radiationbeams is clinically required to provide the mostflexibility in optimizing a patient’s treatment. Themachines also have multileaf collimators (computercontrolled radiation beam shaping devices thatminimize exposures to healthy tissues) and integratedrecord-and-verification systems (computer softwarethat monitors the treatment set-up and delivery toimprove treatment accuracy). One of the machines is outfitted with an electronic portal imager thatallows filmless imaging of the patient set-up prior to treatment.

I n t e g r a t e d S o f twa re

A sophisticated treatment planning system isnecessary to best utilize the capabilities of theseadvanced machines. St Agnes Cancer Center’s three-dimensional (3-D) treatment planning system iswidely recognized as the most advanced treatmentplanning software tool in the field of radiotherapytoday. The system is networked to a variety ofimaging systems on the campus, including CT, MRI,and PET. This allows the information from differenttypes of images to be used to better define the tumorvolume using a method called image fusion. It is thenpossible to combine information about tissuefunction using PET with anatomical informationfrom CT or MRI, a method currently underdevelopment in the Cancer Center by Dr RichardHudes, Director of Radiation Oncology, incollaboration with Dr Ethan Speigler, Director ofNuclear Medicine.

Enh a n c e d Ima g i n g C a p a b i l i t y

Most 3-D treatment planning utilizes CT imagesobtained in another area. Aside from the minorinconvenience to the patient, there are limitations to howa patient can be positioned for a treatment due to theopening, or bore, of a diagnostic CT scanner. Toovercome these issues, in 2002, the St Agnes CancerCenter acquired a state-of-the-art, large bore (85cm)

helical CT simulator.This was the first device of its kindin the greater Baltimore area, illustrating St Agnes’scommitment to advanced cancer care in this community.

T h e F u t u r e o f R a d i o t h e r a py

The different types of external beam treatments differmainly in the complexity of treatment planning andtreatment delivery. The most complex method ofimage-guided external beam radiotherapy is calledintensity modulated radiotherapy (IMRT). IMRTtreatments consist of irradiating the tumor from many(five to nine) beam directions using multiple (three to10) small field shapes per beam direction, in contrastto conventional radiotherapy treatment where onefield shape is used at each of the two to four beam

directions typically used. The primary advantage ofIMRT over conventional techniques is that it allowsexceptional flexibility in treating oddly shaped tumorvolumes while simultaneously avoiding healthytissues. IMRT has primarily been applied to tumorsof the brain.

• Advanced 3-D treatment planning software allowscomputer-automated optimization of thetreatment plan.

• IMRT-enabled computer-controlled treatmentunit with a multileaf collimator and electronicportal imager.

• IMRT-enabled record-and-verification system.

• Equipment for verifying the accuracy of thetreatment delivery.

• Network integration of the treatment planningsystem, CT simulator, and the treatment unit.

• Experienced staff to support the IMRT program.

In meeting these technical requirements, St AgnesHealthCare is demonstrating a substantial commit-ment to advancing the technical capabilities of thecenter to a level only available in select treatmentfacilities in the nation. ■

Over the past decade, improvements in computers and

networking, radiotherapy treatment planning software, and

medical imaging modalities … have been incorporated into

radiotherapy practice.

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