TREATMENT PLANNING PHOTONS & ELECTRONS

Karen P. Doppke 3/20/2007

Regions of Radiation Field Considered in Dose Calculations

DOSE TO A POINT IN TISSUE

Major Processes that Effect Dose in Tissue from Photon Beams

Inverse Square Law

Photon Attenuation

Photon Scatter

Dose Calculation Methods Used to Determine Dose at a Point in a Patient

Correction Based Methods

% Depth Dose Calculations

Tissue Maximum/Phantom Ratios

Tissue-Air Ratios

Model Based Methods

Pencil Beam Methods

Convolution Superposition

Monte Carlo Calculations

The General Form of Equation Used to Calculate Dose at Depth in the Patient

TPR (d, r, h) = Dose at Depth / Dose at Reference/Max

10 Mv X-ray Beam

Isodose Curves High Energy

Variation in Dose for Various Energy Beams

COMPARE MONTE CARLO DOSES IN LUNG

Comparison Dose Distribution 6 MV X-Rays

Conformal Planning Process

PATIENT DATA SET/SCT, MRI, PET

DEFINATION OF TARGET AND NORMAL TISSUES

PRESCRIPTION DOSE and FRACTIONATIONTOTAL DOSE TO VOLUMES DOSE TO NORMAL TISSUES

EXAMPLE OF A CONFORMAL PLAN

The prescription should include the total dose to the target volumes, the fractionation, a statement of the expansion of the GTV to the CTV and PTV.

The dose limits to the normal tissues that are near the site of treatment need to be defined.

ICRU 62

EXAMPLE OF TREATMENT VOLUMES

TREATMENT VOLUMES

GTVGTV

CTVCTV

ITVITV

PTVPTV

NORMAN TISSUES NEAR TREATMENT SITE

SPINAL CORD < ~45 Gy

LIVER <~25Gy/100%, 30Gy/35%, 35Gy/25%

KIDNEYS <~23Gy/66%

LUNG <~30Gy/40%, 60Gy/20%

HEART <~30Gy/100% LV, 45Gy/100% (atrium)

AP/PA OPPOSED FIELDS

DVH FOR TISSUES AP/PA

CTVPTVLiver

Lung RT Kidney RTHeart

FOUR FIELD PLAN AP/PA/RLAT/LLAT

DVH 4 FIELD PLAN

CTVPTVLiver

HeartKidney RTLung RT

5 FIELD PLANE AP/RA/RP/LP/LA

DVH 5 FIELD PLAN

CTVPTVLiverLung RTHeart Kidney RT

CTVLung RTKidney RT

Stereotactic Radiosurgery 1905: Introduction of stereotactic

equipment 1908: Mapping of brain in 3 planes 1918: First stereotactic frame for humans

in London 1940: Greatest strides in intracranial

applications began

Stereotactic Radiosurgery1982: Modified Linear Accelerator

Stereotactic RadiosurgerySRS Frame Placement

STEROTACTIC RADIATION THERAPY SRT

Fractionated Stereotactic Radiation Therapy

Fractionated Stereotactic Radiation Therapy(SRT) combines the target and dose localization characteristics of SRS with the biologic advantages of dose fractionization

STEROTACTIC RADIATION SURGERY SRS

Fractionated Stereotactic Radiation Therapy

Fractionated Stereotactic Radiation Therapy