Intensity Modulated Radiation Therapy (IMRT)
In intensity modulated radiation therapy (IMRT), very small beams, or beamlets, are aimed at a tumor from many angles.
IMRT permits the delivery of a high dose of radiation to the cancer while minimizing dose to other sensitive organs. Here multiple beams are all focused on the prostate. Each of these beams has a number of sub-beams or segments, and the intensity of each segment is varied according to the treatment plan.
During treatment, the radiation intensity of each beamlet is controlled, and the beam shape changes hundreds of times during each treatment. As a result, the radiation dose bends around important healthy tissues in a way that is impossible with other techniques. Because of the complexity of these motions, physicians use special high-speed computers, treatment-planning software, diagnostic imaging and patient-positioning devices to plan treatments and control the radiation dose during therapy.
For IMRT to be effective, the anatomical position of the tumor and surrounding healthy tissues must be accurately defined. Computed tomography (CT), positron emission tomography (PET) and magnetic resonance (MR) imaging provide the necessary three-dimensional anatomical information. It's also important to accurately position and immobilize the patient during treatment. This may be done with special head frames (if the head or brain is being treated), or with advanced imaging devices such as electronic portal imaging and scanning ultrasound, which provide daily information about the location of internal organs. Some organs, such as the prostate, move due to normal daily volume changes in the bladder and rectum. Gold seeds may be placed into the prostate to track prostate movement daily and ensure more precise targeting.
A device called a multileaf collimator adjusts the size and shape of the computer-determined radiation beams. The collimator, a computer-controlled mechanical device, consists of up to 120 individually adjusted metal leaves. These leaves move across the irradiated tissue while the beam is on, blocking out some areas and filtering others to vary the beam intensity and precisely distribute the radiation dosage
Radiation oncologists usually administer a regimen of IMRT treatments over four to eight weeks. The total dose of radiation and the number of treatments given depend on the size, location and type of cancer; the patient's general health; and other medical therapy the patient is receiving.
Additional Information
Multimodality Treament Versus Chemotherapy in Malignant Pleural Mesothelioma
Guntulu AK, Muzaffer Metintas, Husyin Yildirim, Hasan Batire, Cumhur Sivrikoz, Emine Dundar
Medical Faculty Department of Pathology Eskisehir, Turkey; Mammara University Medical Faculty Dep of Chest Surgery Instanbul, Turkey
For malignant mesothelioma (MPM) treatment, multimodality therapy is declared to be the best treatment. However, this multimodality therapy can only be applied to the chosen group of patients. More...
Pleural Intensity Modulated Radiation Therapy in Patients with Malignant Pleural Mesothelioma
Kenneth Rosenzweig, Benjamin Laser, Lee Krug, Ellen Yorke, Emily Levin, Valerie Rusch
Memorial Sloan-Kettering Cancer Center, USA
In patients with malignant pleural mesothelioma who are unable to undergo a pnuemonectomy, it is difficult to deliver tumoricidal doses to the pleura without significant toxicity. We have implemented a technique of using intensity-modulated radiotherapy to treat these patients. More...
Does Radiotherapy Add Anything to Extrapleural Pneumonectomy?
David Rice
Department of Thoracic Cardiovascular Surgery, The University of Texas, USAMalignant pleural mesothelioma remains a challenging disease from the surgical perspective. There is a rationale for using of radiation therapy. More...
Response to induction chemotherapy is the strongest predictor of survival in multicenter U.S. trial of trimodality therapy for resectable malignant pleural mesothelioma.
Lee Krug, Harvey Pass, Valerie Rusch, Hedy Kindler, David Sugarbaker, Kenneth Rosenzweig, Joseph Friedberg, Kathy Pisters, Coleman Obasaju, Nocholas Vogelzang
An aggressive surgical approach is frequently offered to fit patients with early stage mesothelioma, but the variable natural history makes it difficult to determine which patients are most likely to benefit. More...
Trimodality Treatment for MPM: The Heidelberg Experience
Has Hoffmann, Konstantina Storz, Thomas Muley, Helge Bischoff, Michael Thomas, Christian Thieke, Mark Munter, Philipp Schnabel, Felix Herth, Hendrick Dienemann
To investigate the combined modality treament with neoadjuvant chemotherapy followed by extrapleural pnuemonectomy and intensity modulated radiotherapy in patients with stage I-III malignant mesothelioma in a prospective study. More...
Compensator-based intensity-modulated radiation therapy for malignant pleural mesothelioma post extrapleural pneumonectomy. (10/29/08)
Javedan K, Stevens CW, Forster K.
Radiation Oncology,1 H. Lee Moffitt Cancer Center and Research Institute, Tampa, Florida, USA. khosrow.javedan@moffitt.orgTreatment plans for 4 right-sided and 1 left-sided MPM post-surgery cases were generated using a commercial treatment planning system, XIO/CMS (Computerized Medical Systems, St. Louis, MO). More…
Underestimation of low-dose radiation in treatment planning of intensity-modulated radiotherapy. (8/1/08)
Jang SY, Liu HH, Mohan R.
Department of Radiation Physics, The University of Texas M. D. Anderson Cancer Center, 1515 Holcombe Boulevard, Houston, TX 77030, USA.
PURPOSE: To investigate potential dose calculation errors in the low-dose regions and identify causes of such errors for intensity-modulated radiotherapy (IMRT). METHODS AND MATERIALS: The IMRT treatment plans of 23 patients with lung cancer and mesothelioma were reviewed. More…
Intensity-modulated radiotherapy for resected mesothelioma: the Duke experience. (7/15/08)
Miles EF, Larrier NA, Kelsey CR, Hubbs JL, Ma J, Yoo S, Marks LB.
Department of Radiation Oncology, Duke University Medical Center, Durham, NC 27710, USA. edward.miles@duke.edu
PURPOSE: To assess the safety and efficacy of intensity-modulated radiotherapy (IMRT) after extrapleural pneumonectomy for malignant pleural mesothelioma. METHODS AND MATERIALS: Thirteen patients underwent IMRT after extrapleural pneumonectomy between July 2005 and February 2007 at Duke University Medical Center. More…
Evaluating target coverage and normal tissue sparing in the adjuvant radiotherapy of malignant pleural mesothelioma: helical tomotherapy compared with step-and-shoot IMRT. (2/08)
Sterzing F, Sroka-Perez G, Schubert K, Münter MW, Thieke C, Huber P, Debus J, Herfarth KK.
Department of Radiation Oncology, University of Heidelberg, Germany. florian.sterzing@med.uni-heidelberg.de
PURPOSE: To evaluate the potential of helical tomotherapy in the adjuvant treatment of malignant pleural mesothelioma and compare target homogeneity, conformity and normal tissue dose with step-and-shoot intensity-modulated radiotherapy. METHODS AND MATERIALS: Ten patients with malignant pleural mesothelioma who had undergone neoadjuvant chemotherapy with cisplatin and permetrexed followed by extrapleural pneumonectomy (EPP) were treated in our department with 54 Gy to the hemithorax delivered by step-and-shoot IMRT. More…
Radiation To Healthy Lung Associated With Pulmonary-Related Death In Post EPP mesothelioma Patients (MD Anderson) (10/30/06)
A new study reveals that fatal pulmonary-related events following radiation therapy are associated with the amount of radiation received by the contralateral or healthy lung. More…