Novel Clinical Applications of IMRT
James S Welsh, MS, MD
Department of Human Oncology
University of Wisconsin, Madison
Linac
CT Couch
Ring
Gantry
CT
Detector
X-Ray Fan
Beam
Binary
Multileaf
Collimator
Binary MLC Leaves
Helical
Fan Beam
Helical
Scanning
X-Ray Beam
Binary MLC Leaves
Helical Fan Beam Delivery
Status June 2003
• MVCT scans obtained on 10 lung and 10 prostate cancer patients
• 9 dogs treated
• 10 human patients treated
• 9 palliative
• 1 definitive
MVCT of an Anesthetized Dog with a
Sinus Tumor Advantages of Helical
Tomotherapy
• CT component allows real-time imaging of patients to verify set-up and detect variations in positioning
• Relative Simplicity
• An optimal means of delivering co-planar therapy
• Adaptive Radiotherapy
• Conformal Avoidance
• Wide range of IMRT applications
Sinus
Tumor
Eroded
Bone

MVCT Before Our First Patient Treatment MVCT of a Lung Cancer Patient #1 at 3 cGy
Soft Tissue Window Lung Window
Target Volume
Lung
Tumor
MVCT of a Lung Cancer Patient # 2 at 3 cGy
Soft Tissue Window Lung Window
MVCT of a Prostate
Cancer Patient at 2.5 cGy
Prostate
Lung
Tumor
Advantages of Helical
Tomotherapy
• CT component allows real-time imaging of patient to verify set-up and detect variations in positioning
• Relative Simplicity
• An optimal means of delivering co-planar therapy
• Adaptive Radiotherapy
• Conformal Avoidance
95%
90%
50%
20%
Preliminary Tomotherapy
Planning

95%
90%
50%
20%
Preliminary Tomotherapy
Planning
15
10
5
25
20
0
3D plans
Tomotherapy
P1 P2
Tomotherapy decreases mean NTD (spinal cord)
Spinal cord NTDmean
P3
Patient
P4 P5 Mean
Conformal Avoidance
• Wide field XRT is frequently employed to target regional micrometastatic extension
• This regional disease extension is not precisely defined in terms of anatomic detail
• As a consequence, normal critical tissues are frequently irradiated and yield toxicities
• Conformal avoidance can “shield” these structures and improve the therapeutic index by decreasing these often permanent and debilitating NTCPs
– Salivary glands: Xerostomia/Dental hygiene/Osteonecrosis
– Oto-acoustic apparatus: Hearing/Balance
– Optic/Lacrimal tissues: Vision/Xerophthalmia/Corneal complications
Rationale for Conformal
Avoidance Radiotherapy
• The gross tumor volume (GTV) may not be clearly visible
• Uncertainty in defining the clinical target volume (CTV)
• The planning target volume (PTV) may be uncertain
• The target dose is limited by normal sensitive tissue
• Conformal avoidance is the ideal paradigm to treat suspected regional/nodal involvement
Conformal dose-distribution with tomotherapy
Continuum Between Conformal
Therapy and Conformal Avoidance
Know where tumor is and will not harm sensitive tissue
• Don’t really know where tumor is
• May miss part of target if overly conformal
• …..and still harm sensitive tissue

The Mantle
• Successfully used for many decades
• A classic example of the need to treat invisible microscopic regional disease
• Generally not easy to duplicate using conformal therapy
• A potential application of conformal avoidance IMRT
• Can reduce dose to Thyroid, Larynx, Heart,
Spinal cord thereby reducing complications
• Can reduce dose to breast in young women
(possibly) reducing risk of future breast cancer
Conformal Mantle Field
Subtotal/Total Lymphoid
Irradiation
• Inverted-Y
• Can be effectively duplicated using IMRT via linac or helical tomotherapy
• Significantly less dose to sensitive normal structures than older techniques is possible
Conformal Avoidance Radiotherapy for A Mantle Equivalent using
Helical Tomotherapy
Spine
Lungs
Regional field
Larynx
Mediastinal
L.axila node
R.axila node
The dose should be
Divided by 10

ROI slice 27
Dose Rate Cumulative Dose
50 %
80 %
90 %
Slice 31
50 %
80 %
90 %
Slice 36
50 %
80 %
90 %
Partial Breast Irradiation
• Good clinical results have been obtained using HDR brachytherapy
• Recent applications of partial breast irradiation using external beam approaches
• Visualization of target and immobilization of breast will be essential for success of this approach
Limited Field
Prone Breast
Limited Field
Prone Breast
Skin
Muscle
Lt Lung Rt Lung
PTV
GTV

IMRT for complicated tumor volumes
• IMRT can handle complicated tumor volumes using either a conformal therapy or conformal avoidance approach
• High conformality of isodose curves
– Lower doses to surrounding normal structures
– Higher dose to tumor volume
Skull Irradiation
Lt Eye
Rt Optic Nerve
PTV
Rt Eye
Chiasm
Lumbar Spine Treatment
Kidneys PTV
MVCT, Simple Contour, Plan & Treat Palliative Case: 30 Minutes Total
Setup ~3min
MVCT ~7min
Contour ~10min
Optimize ~5min
Delivery ~5min
Simple
Contour

Summary
• Conformal avoidance radiotherapy, the complement to conformal radiotherapy, focuses on avoiding dose to normal tissue
• IMRT, especially helical tomotherapy appears particularly well-suited for conformal avoidance
• Many innovative clinical procedures will evolve from conformal avoidance IMRT
Potential Clinical Applications of
Conformal Avoidance IMRT
• Improved irradiation of nodal chains using the conformal avoidance strategy
– Improved “Mantle” and “Inverted-Y”
– Para-aortic irradiation for GYN, GU and lymphoid malignancies
• Brain-sparing total scalp irradiation
– Scalp-sparing whole brain irradiation
• Pacemaker/defibrillator avoidance
• Bone marrow ablation while sparing visceral organs
• Craniospinal Irradiation
Potential Clinical Applications of
Conformal Avoidance IMRT
• Accelerated partial breast irradiation
• Complicated tumor volumes
– mesothelioma
• Extracranial stereotactic radiotherapy
• Widespread metastatic disease?
– Visible disease handled with radiotherapy
– Microscopic disease handled by chemotherapy
– “Intermediate” disease identified by PET and handled by IMRT