External Beam Radiation

External Beam Radiation

Can­cer treat­ment often re­quires a multi-dis­ci­pli­nary ap­proach, which in­cludes chemother­apy and ra­di­a­tion ther­apy. Every­one at Cen­tral Care Can­cer Cen­ter plays an im­por­tant role as an ac­tive team mem­ber. This team-ori­ented ap­proach is the key to en­sur­ing op­ti­mum pa­tient care.

Ex­ter­nal ra­di­a­tion is de­liv­ered by a ra­di­a­tion ther­a­pist using a ma­chine called a lin­ear ac­cel­er­a­tor. The treat­ment beam is only on for a mat­ter of sec­onds, al­though it is not mea­sured by time. The lin­ear ac­cel­er­a­tor runs on elec­tric­ity, so when the ma­chine is turned off there is no ra­di­a­tion in the treat­ment room.

Image-Guided Radiation Therapy (IGRT)

Pre­cise pa­tient po­si­tion­ing and real-time tumor mon­i­tor­ing are vital to ac­cu­rate treat­ment of de­fined areas while spar­ing sur­round­ing nor­mal tis­sues. The ad­vance­ment of con­for­mal ra­dio­ther­a­pies has been sup­ple­mented by im­age-guided ra­dio­ther­apy, or IGRT, en­abling clin­i­cians to com­pen­sate for the geo­met­ric un­cer­tain­ties in­her­ent in the treat­ment de­liv­ery process. Tu­mors can move, be­cause of breath­ing and other nat­u­rally oc­cur­ring processes within the body. IGRT al­lows physi­cians to lo­cate and track the tumor just prior to and dur­ing ra­di­a­tion treat­ment to en­hance the pre­ci­sion of the ra­di­a­tion beam and pro­tect healthy tis­sues, ul­ti­mately re­duc­ing side ef­fects and im­prov­ing out­comes.

Cen­tral Care Can­cer Cen­ter uti­lizes a di­verse set of imag­ing tools, such as kV and MV imag­ing with our elec­tronic por­tal im­ager, Cone Beam CT (CBCT), flu­o­roscopy, and res­pi­ra­tory gat­ing tech­nol­ogy. These tools make it pos­si­ble to deal with in­ter-frac­tion mo­tion (i.e., changes in tar­get po­si­tion due to setup error or nat­u­rally-oc­cur­ring changes in organ po­si­tion over time) and in­tra-frac­tion mo­tion (i.e., organ mo­tion dur­ing treat­ment, usu­ally due to res­pi­ra­tion or other phys­i­o­log­i­cal processes). Our ra­di­a­tion on­col­o­gists can then make im­me­di­ate tech­ni­cal ad­just­ments when a tumor moves out­side of a planned treat­ment range. As a re­sult, the ra­di­a­tion treat­ment is tar­geted pre­cisely to the tumor, help­ing to limit ra­di­a­tion ex­po­sure to healthy tis­sue and re­duce com­mon ra­di­a­tion side ef­fects.

The physi­cians can choose from a mul­ti­tude imag­ing tools for pa­tient repo­si­tion­ing based on bony anatomy, im­planted or ex­ter­nal fidu­cial mark­ers, soft tis­sue struc­tures, and/or res­pi­ra­tory gat­ing ver­i­fi­ca­tion. Im­ages are usu­ally ac­quired just after the pa­tient has been po­si­tioned for treat­ment, and then spe­cial match­ing soft­ware is used to com­pare the im­ages to ref­er­ence im­ages from the treat­ment plan. The sys­tem then cal­cu­lates a “shift” and sends in­struc­tions to the treat­ment couch, which moves to bring the tar­geted tumor into pre­cise align­ment for treat­ment. Pa­tient po­si­tion­ing is then ver­i­fied prior to treat­ment de­liv­ery. For some cases, tar­get po­si­tion­ing may occur dur­ing the treat­ment de­liv­ery as well.

Cen­tral Care Can­cer Cen­ter has de­vel­oped spe­cific pro­to­cols for IGRT based on na­tion­ally pub­lished guide­lines and ver­i­fied using a rig­or­ous in­ter­nal qual­ity as­sur­ance and peer re­view pro­gram. IGRT al­lows the treat­ment team to ob­tain high-res­o­lu­tion, three-di­men­sional im­ages to pin­point tumor sites, ad­just pa­tient po­si­tion­ing when nec­es­sary, and com­plete a treat­ment—all within the stan­dard treat­ment time slot of 15-20 min­utes. IGRT en­ables pin­point ac­cu­racy of treat­ment de­liv­ery by en­sur­ing re­pro­ducible, sta­ble and ac­cu­rate pa­tient po­si­tion­ing.

The pic­ture you ini­tially see is of a Var­ian Tril­ogy ma­chine with on-board imag­ing (OBI) and the setup CBCT im­ages of a pelvis field. The video shows the process of using the ac­quired CBCT and uti­liz­ing the ro­botic couch to re­motely po­si­tion a pa­tient for treat­ment. OBI with CBCT is just one of the many IGRT op­tions avail­able at Cen­tral Care Can­cer Cen­ter fa­cil­i­ties.

Intensity Modulated Radiation Therapy (IMRT)

In­ten­sity-mod­u­lated ra­di­a­tion ther­apy (IMRT) is an ad­vanced treat­ment method that uses com­puter-con­trolled lin­ear ac­cel­er­a­tors to de­liver high doses of ra­di­a­tion di­rectly to can­cer cells in a very tar­geted way, much more pre­cisely than is pos­si­ble with con­ven­tional ra­dio­ther­apy. IMRT en­ables an on­col­ogy team to di­rect and nar­rowly con­cen­trate po­tent doses of high-en­ergy X rays at a pa­tient’s tumor while min­i­miz­ing com­pli­ca­tions to sur­round­ing healthy tis­sue.

IMRT uses mul­ti­ple small ra­di­a­tion beams of vary­ing in­ten­si­ties to pre­cisely ir­ra­di­ate a tumor. This method in­volves vary­ing (or mod­u­lat­ing) the in­ten­sity of the ra­di­a­tion beam while si­mul­ta­ne­ously chang­ing the geo­met­ric pro­file of the de­liv­ery area so that the shape of the re­sult­ing dose de­liv­ery is tightly matched to the shape of the tumor. IMRT tar­gets a tumor with in­ten­sity-mod­u­lated beams de­liv­ered from mul­ti­ple an­gles. The area where the ra­di­a­tion beams in­ter­sect cre­ates a finely sculpted ra­di­a­tion cloud that en­velops and has the same shape as the tumor. The goal of IMRT is to con­form the ra­di­a­tion dose to avoid or re­duce ex­po­sure of healthy tis­sue and limit the side ef­fects of treat­ment.

Treat­ment plan­ning for IMRT is more com­plex than for con­ven­tional ra­di­a­tion ther­apy. The IMRT process starts with plan­ning im­ages, for ex­am­ple, com­puted to­mog­ra­phy (CT), mag­netic res­o­nance (MR) and/or positron emis­sion to­mog­ra­phy (PET) im­ages, of the pa­tient’s tumor and sur­round­ing anatomy. These im­ages are con­verted into a cus­tom three-di­men­sional model of the pa­tient’s in­ter­nal anatomy. A so­phis­ti­cated com­puter pro­gram is used to de­ter­mine the dose in­ten­sity pat­tern that will best con­form to the tumor shape, cre­at­ing a treat­ment plan based on tumor size, shape, and lo­ca­tion within the body, com­bined with the doc­tor’s dose pre­scrip­tion. Typ­i­cally, com­bi­na­tions of mul­ti­ple in­ten­sity-mod­u­lated fields com­ing from dif­fer­ent beam di­rec­tions pro­duce a cus­tom tai­lored ra­di­a­tion plan that max­i­mizes tumor dose while also min­i­miz­ing the dose to ad­ja­cent nor­mal tis­sues.

The equip­ment used to de­liver ra­di­a­tion treat­ment is called a med­ical lin­ear ac­cel­er­a­tor, which is equipped with a spe­cial beam-shap­ing de­vice called a multi-leaf col­li­ma­tor (MLCs). IMRT uti­lizes con­for­mal MLCs that can turn on or off dy­nam­i­cally chang­ing the field dur­ing dose de­liv­ery. The lin­ear ac­cel­er­a­tor ro­tates around the pa­tient to send beams from mul­ti­ple an­gles in order to give the tumor a high dose of ra­di­a­tion while pre­serv­ing im­por­tant healthy tis­sues.

The num­ber of IMRT treat­ments is typ­i­cally more than con­ven­tional ra­di­a­tion ther­apy be­cause of the highly con­for­mal beam which al­lows a higher dose to be de­liv­ered safely. Ac­tual treat­ment time for each ses­sion may be slightly longer than with con­ven­tional ra­di­a­tion ther­apy be­cause of the com­plex­ity of the treat­ment and the ad­di­tional qual­ity as­sur­ance checks and pre­ci­sion tar­get­ing.
His­tor­i­cally, the max­i­mum ra­di­a­tion dose that could be given to a tumor site has been re­stricted by the tol­er­ance and sen­si­tiv­ity of the sur­round­ing nearby healthy tis­sues. IMRT de­liv­ers higher doses of ra­di­a­tion di­rectly to tu­mors and can­cer cells, while sur­round­ing or­gans and tis­sues are pro­tected. The level of nor­mal tis­sue spar­ing achieved with IMRT is sig­nif­i­cant, re­sult­ing in fewer com­pli­ca­tions and side ef­fects.

IMRT of­fers very high-res­o­lu­tion de­liv­ery, giv­ing an on­col­ogy team the abil­ity to con­form the dose tightly to a small or ir­reg­u­larly shaped tar­get. Pre­ci­sion tar­get­ing is es­pe­cially im­por­tant when de­liv­er­ing dose around small or oddly shaped struc­tures such as the optic nerves or sali­vary glands. IMRT can more ef­fec­tively shape the dose around such crit­i­cal struc­tures, se­verely lim­it­ing or even elim­i­nat­ing un­nec­es­sary ex­po­sures to ra­di­a­tion dose.

IMRT dif­fers from con­ven­tional ra­di­a­tion ther­apy by em­ploy­ing com­plex soft­ware to plan a ther­a­peu­tic dose of ra­di­a­tion based on tumor di­men­sions and lo­ca­tion. IMRT de­liv­ers ra­di­a­tion in sculpted doses that ex­actly match the 3D shape of the tumor, ad­just­ing the in­ten­sity of the ra­di­a­tion beams across the tumor area with un­par­al­leled ac­cu­racy. Be­cause of its greater de­gree of ac­cu­racy, IMRT may be a treat­ment op­tion for re­cur­rent or per­sis­tent tu­mors after con­ven­tional doses have been de­liv­ered.
Be­cause the ratio of nor­mal tis­sue dose to tumor dose is re­duced to a min­i­mum with the IMRT ap­proach, higher and more ef­fec­tive ra­di­a­tion doses can safely be de­liv­ered to tu­mors with fewer side ef­fects com­pared with con­ven­tional ra­dio­ther­apy tech­niques. IMRT also has the po­ten­tial to re­duce treat­ment tox­i­c­ity, even when doses are not in­creased. The end re­sult is bet­ter tumor con­trol, less dam­age to healthy tis­sues and struc­tures in the treat­ment area, and a bet­ter qual­ity of life for the pa­tient.

The ini­tial pic­ture seen is a de­pic­tion of an IMRT plan of a pelvis con­structed using our Eclipse Treat­ment Plan­ning soft­ware. Eclipse soft­ware and IMRT tech­nol­ogy are two tools used by Cen­tral Care Can­cer Cen­ters to op­ti­mize your treat­ment out­comes.

Rapid Arc

Certain tumors are treated using Rapid Arc technology. The radiation is delivered in a circular pattern as the linear accelerator rotates around the patient’s body.

Respiratory Gating

Respiratory gating allows treatment to be given in sync with a patient’s breathing pattern. The radiation is delivered in small portions during a chosen portion of a normal breathing cycle. This allows maximum dose to a tumor volume that may be mobile during normal breathing.

Stereotactic Radiation Therapy (SRT)

Stereotactic Radiation Therapy (SRT)

SRT is used to de­liver ex­tremely high doses of ra­di­a­tion in a short amount of time. A dis­ease must meet very spe­cific cri­te­ria re­lated to tumor size, type, and lo­ca­tion, and a pa­tient must be able to fol­low care­ful in­struc­tions re­lated to po­si­tion­ing.

Stereotactic Body Radiation Therapy (SBRT)

Stereotactic treatments delivered to areas within the body but not the head.

Stereotactic Radiosurgery (SRS)

Stereotactic treatments delivered usually to a head or spine region, consisting of one very large dose of radiation delivered in one treatment.