Intensity Modulated Radiation Therapy (IMRT) is a sophisticated approach to the planning and delivery of radiation therapy.  Unlike conventional techniques, IMRT utilizes sophisticated computerized optimization programs to generate treatment plans that highly conform the prescription dose to the shape of the tumor in 3-dimensions (3D), thereby reducing the volume of normal tissues irradiated. 

How is IMRT done?                                                                        

The key behind IMRT is the use of inverse planning. 

Unlike standard approaches, the target and normal tissues are first contoured on a planning computed tomography (CT) scan.

Example Contours in a Head and Neck Cancer Patient. Tumor (light blue), Target (red), left parotid (gold), right parotid (blue)

Computerized optimization programs are used to generate the intensity profile of each radiation beam (typically 7-9 are used).

During this process, beams are divided into small “beamlets” and the intensity of each beamlet is individually optimized to satisfy pre-determined planning goals.

Example Intensity Profile of an IMRT Beam. High intensity (red), moderate intensity (green), low intensity (yellow)

When cast into the patient, these modulated beams produce highly conformal treatment plans. Rapid dose gradients outside the target result in considerable sparing of nearby normal tissues. 

Such plans are almost always superior to conventional plans, particularly in patients with complex-shaped targets.

IMRT Plan in a Cervical Cancer Patient. Note how prescription isodose line (yellow) conforms to the target (green) and sparing the small bowel (orange) and bone marrow (red)

Facilitating the delivery of IMRT is a device known as a Multi-Leaf Collimator (MLC).  Positioning in the machine head, the MLC has leaves which move in and out of the beam’s path under computer control.

The longer the leaves are open, the higher the intensity; the longer they are closed, the lower the intensity.

Multi-Leaf Collimator (MLC)

Is IMRT Widely Available?_                                                           ____

Initially available at only a limited number of academic centers, IMRT has been quickly adopted by the Radiation Oncology community in recent years.

A Practice Survey in 2005 performed by Dr. Mundt found that nearly 75% of Radiation Oncologists in the United States were treating patients with IMRT. 

This was all the more remarkable given that his earlier 2003 Survey found that less than 1/3 of physicians were using it.

IMRT Adoption in the United States (Mell et al., 2005)

Is IMRT Beneficial to Patients?                                                      

IMRT is rapidly becoming standard practice in a wide number of tumors, particularly prostate and head/neck cancers.  Interest has also grown in other sites, notably cervical cancer, brain tumors and breast cancer.

IMRT has had a major impact on the quality and delivery of Radiation Therapy in this country and abroad.  There is a growing body of data demonstrating that IMRT planning is superior to conventional techniques in nearly all tumor sites. 

Moreover, clinical outcome data of patients treated with IMRT suggests that the dosimetric benefits may also translate to long-term reductions in toxicity.  This has best been demonstrated in head and neck cancers, where IMRT treatment reduces the risk of long-term xerostomia (dry mouth) (view paper).

In prostate cancer, higher doses of radiation are possible with IMRT resulting in excellent cure rates without increased complications (view paper). Promising outcome studies have also been reported using IMRT in brain tumors (view paper), breast cancer (view paper), gynecologic tumors (view paper) and pediatric cancers (view paper).

IMRT at UCSD                                                        

UCSD Clinicians and Physicists are experts in IMRT.  In fact, several UCSD faculty members are frequent invited speakers at national and international IMRT symposia (What’s New). 

Dr. Arno Mundt, the Chair of the Department, was a pioneer in the use of IMRT in gynecologic cancers. He is the co-Editor of the 1st international IMRT textbook IMRT: A Clinical Perspective.

This text brings together over 175 IMRT researchers at 42 institutions in 9 countries (USA, Canada, China, Japan, England, Belgium, Italy, Germany and Switzerland).

IMRT Publications by UCSD Researchers                                                                       

Mell LK, Kochanski JD, Roeske JC, Lengyel E, Mundt AJ. Dosimetric predictors of acute hematologic toxicity in cervical cancer patients treated with concurrent cisplatin and intensity-modulated pelvic radiotherapy. Int J Radiat Oncol Biol Phys 66:1356-1365, 2006

Aydogan B, Wang S, Smith B, Mundt AJ, Roeske JC. A dosimetric analysis of IMRT as an alternative to HDR brachytherapy in early endometrial cancer patients. Int J Radiat Oncol Biol Phys 2006;65:266-273

Kochanski JD, Mell LK, Roeske JC, Mundt AJ. IMRT in gynecologic malignancies: current status and future directions. Clin Adv Hem Oncol 4:379-386, 2006

Salama JK, Mundt AJ, Roeske JC, Mehta N. Preliminary outcome and toxicity report of extended field intensity modulated radiation therapy for gynecologic malignancies. Int J Radiat Oncol Biol Phys 65:1170-6, 2006

Daly ME, Lieskovsky Y, Pawlicki T, et al. Evaluation of patterns of failure and subjective salivary function in patients treated with IMRT for head and neck squamous cell carcinoma. Head Neck 2006 (in press)

Aydogan B, Mundt AJ, Roeske JC. Linac-based intensity modulated total marrow irradiation. Technol Cancer Res Treat 5:513-20, 2006

Mundt AJ, Mell LK, Roeske JC. IMRT Utilization. Adv Imaging Oncol Administrators July, 2005

Mell LK, Mundt AJ. Survey of IMRT use in the United States, 2004. Cancer 104:1296-1303, 2005

Montenegro CR, de Castro Neto AJ, Mundt AJ. Radioterapia de intensidade modulada pelvica. Câncer Hoje. A Oncologia baseada em Evidencias 3:10-11, 2005

Roeske JC, Lujan A, Reba RC, Penney BC, Yamada SD, Mundt AJ. Incorporation of SPECT bone marrow imaging in intensity modulated whole pelvic radiation therapy treatment planning for gynecologic malignancies. Radiother Oncol 77:11-7, 2005

Malik R, Oh JL, Roeske JC, Mundt AJ. Survey of resident education in intensity modulated radiation therapy. Technol Cancer Res Treat 4:303-10, 2005

Haslam JJ, Lujan AE, Mundt AJ, et al. Setup errors in patients treated with intensity modulated whole pelvic radiation therapy for gynecological malignancies. Med Dosim 30:36-42, 2005

Schomas DA, Milano MT, Roeske JC, Mell LK, Mundt AJ. IMRT and the Internet: evaluation of the content and quality of patient-oriented information. Cancer 101:412-20, 2004

Pawlicki T, Luxton G, Le QT, et al. Lens dose in MLC-based IMRT treatments of the head and neck. Int J Radiat Oncol BiolPhsy Biol Phys 59:293-9, 2004

Ma CM, Ding M, Li JS, Lee MC, Pawlicki T, et al. A comparative dosimetric study on tangential photon beams, IMRT and modulated electron radiotherapy (MERT) for breast cancer treatment. Phys Med Biol 48:909-24, 2003

Salama JK, Roeske JC, Mehta N, Mundt AJ. IMRT in gynecologic malignancies. Curr Treat Options Oncol 5:97-108, 2004

Roeske JC, Bonta D, Lujan AE, Mell LK, Yamada SD, Rotmensch J, Mundt AJ. A dosimetric analysis of acute gastrointestinal toxicity in women receiving intensity-modulated whole-pelvic radiation therapy. Radiother Oncol 2003;69:201-7, 2003

Lujan AE, Mundt AJ, Yamada SD, et al. IMRT as a means of reducing dose to bone marrow in gynecologic patients receiving whole pelvic radiotherapy. Int J Radiat Oncol Biol Phys 57:516-21, 2003

Mell LK, Roeske JC, Mundt AJ. Survey of IMRT use in the United States. Cancer 98:204-11, 2003

Mundt AJ, Mell LK, Roeske JC. Preliminary analysis of chronic gastrointestinal toxicity in patients with gynecologic malignancies treated with intensity modulated whole pelvic radiation therapy. Int J Radiat Oncol Biol Phys 56:1354-1360, 2003

Ma CM, Jiang SB, Pawlicki T, et al. A quality assurance phantom for IMRT dose verification. Phys Med Biol 48:561-72, 2003

Zygmanski P, Kung JH, Jiang SB et al. Dependence of cluence errors in dynamic IMRT on leaf-positional errors varying with time and leaf number. Med Phys 30:2736-49, 2003

Jiang SB, Pope C, Al Jarrah KM, et al. An experimental investigation on intra-fractional organ motion effects in lung IMRT. Phys Med Biol 48:1773-84, 2003

Mundt AJ, Roeske JC, Lujan AE. IMRT in gynecologic malignancies. Med Dosim 27:131-136, 2002

Mundt AJ. Intensity modulated radiation therapy- a revolution in cancer care. Men’s Total Health Digest 2:44, 2002           

Brixey C, Roeske JC, Lujan AE, Mundt AJ. Impact of intensity modulated whole pelvic radiation therapy on acute hematologic toxicity in women with gynecologic malignancies. Int J Radiat Oncol Biol Phys 54:1388-96, 2002

Bortfeld T, Jokivarski K, Goitein M, Kung J, Jiang SB. Effects of intra-fraction motion on IMRT dose delivery: statistical analysis and simulation. Phys Med Biol 47:297-302, 2002

Mundt AJ, Roeske JC. Can IMRT replace brachytherapy in the treatment of patients with cervical cancer? Brachytherapy 1:192-3, 2002

Mundt AJ, Lujan AE, Rotmensch J, Waggoner SE, et al. Intensity modulated whole pelvic radiation therapy in women with gynecologic malignancies. Int J Radiat Oncol Biol Phys 52:1330-7, 2002

Mundt AJ, Roeske JC, Lujan A, et al. Initial clinical experience using intensity modulated whole pelvic radiation therapy for gynecologic malignancies. Gynecol Oncol 82:456-63, 2001

Deng J, Pawlicki T, Chen Y, Li J, Jiang SB, et al. The MLC tongue-and-groove effect on IMRT dose distributions. Phys Med Biol 46:1039-60,. 2001

Pawlicki T, Ma CM. Monte Carlo simulation for MLC-based IMRT. Med Dosim 26:157-68, 2001

Roeske JC, Lujan A, Rotmensch J, Waggoner SE, Yamada D, Mundt AJ. Intensity modulated whole pelvic radiation therapy in patients with gynecological malignancies. Int J Radiat Oncol Biol Phys 48:1613-21, 2000

Lee MC, Jiang SB, Ma CM. Monte Carlo and experimental investigations of Multi0leaf collimated electron beams for modulated electron radiation therapy. Med Phys 27:2708-18, 2000

Ma CM, Pawlicki T, Jiang SB, Li J et al. Monte Carlo verification of IMRT dose distributions from a commercial treatment planning optimization system. Phys Med Biol 45:2483-95, 2000

Ma CM, Pawlicki T, Lee MC, Jiang SB et al. Energy and intensity-modulated electron beams for radiotherapy. Phys Med Biol 45:2293-311, 2000

Jiang SB, Ayyangar KM. On compensator design for photon beam intensity modulated conformal therapy. Med Phys 25:668-75, 1998