HSC 3409-7-10

• History (Brief overview)• Treatment Delivery Equipment• Simulation Equipment

History

– Three aspects that paved the way to discovery of xrays:electricity, vacuums, image recording materials

– Discovery of x-rays by Wilhelm Roentgen 1895, received Nobel Prize in 1901

– Edison experimented with x-rays in 1896 (specifically fluoro), stopped experiments due to damage to colleague Clarence Daly (died in 1904 from radiation side effects)

– Becquerel discovered radioactivity in 1896– Marie Curie discovered radioactive elements (polonium and radium) in

1898– Radium was then used for the first documented cancer treatment in 1898– Soon replaced by Cobalt and Cesium in mid 1900’s– Linacs were developed in 1940

Isodose Curves

• Isodose lines- lines connecting points of equivalent relative radiation dose

• Isodose curve- plotted % depth dose at various points in the beam along the CAX and elsewhere

Isodose curve for a 6MV photon beam incident on a flat, homogenous medium

Isodose curves differ according to the surface they are incident upon

They also differ with different densities in tissues, such as air

Isodose curves for different energy beams

kV Treatment

• Kilovoltage characteristics– Superficial treatment– CAX dose and physical penumbra are based on beam

quality• Ex. the 50% line of a 200kv beam reaches deeper than the

50% line of a 100kv beam

• Low energy equipment– Grenz– Contact– Superficial– Orthovoltage

Grenz

•1928

•Low energy 10-15kV

•Superficial

•Inflammatory disorders, Herpes simplex

Contact

• 1934

•40-50kV

•Superficial

•Rectal cancer lower to middle third of rectum

Superficial• 1896

•50-150kV

•Superficial

• Skin no deeper than 5mm

Orthovoltage

•1923

•150-500 kV

•Skin, mouth, cervical CA

MV Treatment

• MV characteristics– Energy above 1MV– Skin sparing– Ability to treat deep tumors– γ-ray beams produces by Radionuclides are included if energy is above

1 MeV

• High energy equipment– Cyclotron– Van de Graaff generator– Betatron– Cobalt 60 unit– Linear accelerator

Cyclotron

•1928

•Charged particle accelerator

•Neutron and Proton production for clinical use

Van de Graff generator• 1937

•Electrons and X-rays

•Therapy 2MV

Betatron

•1941

•Electrons and X-rays

•Therapy 6 to more than 40Mev

Cobalt 60

• 1951• Radioactive

source• 1.17 MeV and

1.33 MeV

Linear Accelerator

• 1952• Electrons and X-rays• Can go as high as 35

MVCh.7 pg 143-146

SSD v SAD

SSD

• The distance from the source of radiation the patients skin

SAD

• The distance from the source of radiation to the axis of rotation of the treatment unit

Linac Components

• Drive stand– Klystron, Waveguide, Circulator, Cooling

System

• Gantry– Electron gun, accelerator structure, treatment

head

• Couch

Auxiliary components

• Control Console• Modulator cabinet• Computers

Linac accessories

• Block- usually made of cerrobend (50% bismuth, 26.7% lead, 13.3% tin, 10% cadmium)

• Wedge• MLC• Electron Cone• Compensator

MeVMV

HDR/LDR Units

• LDR- 40-200cGy/hour• HDR- 1200cGy/hour or 20cGy per min• Both utilize a source

– Iridium, Cesium, Cobalt, and Radium

• Require an Afterloader• Brain, esophagus, rectum, GYN, breast etc.

HDR advantages

• can be given on outpatient basis• Treatment time is short• Implant reproducibility is more

precise• Complete radiation protection

exists• no general anesthesia or bed

rest• Ability to treat large volume• Increased comfort level

Simulator Equipment

• YouTube - CT vs Traditional Sim - Simple Sim• What is simulation?• Conventional• CT • Additions to CT SIM

– MRI– PET

What is simulation?

• Assists in the treatment planning process • Original set-up technique is produced

– Supine– Prone– FF vs. HF

• Process: who would be involved in each?

Diagnosis Consultation Simulation Treatment Planning

Treatment

Conventional SimulationFig. 19-7

• Mimics treatment machine• Enables field delineation• Information is obtained using:

– Fluoroscopy– Radiographs– Physical measurements

CT Simulation

• Patient data is obtained using CT “slices”

• Cost effective for departments: multi-function

• May have a “virtual simulation” component

Conventional & CT sim order of events

• Conventional Sim:1. Field location2. Target defined3. Fields are shaped

• CT Sim:1. Target defined2. Fields are shaped

Additions to CT sim

• MRI• PET• Both of the above are able to be merged

with the CT to help delineate the tumor site as well as other “critical” structures

MRI

Utilized for soft tissue imaging

PET

Nuclear medicine technique which produces a three-dimensional image or picture of functional processes in the body