Test 3: Beam Shaping & Modifying Devices, Treatment Tech, R & V, Imaging in RT, Endocrine Cancers, and Bone Cancers

Ewing's Sarcoma: Field Borders

-2 cm margin around soft tissue -exclude 2 epiphyseal center -treat entire surgical scar -shape field to maintain lymph drainage

Stereoscopic Imaging

-2 images from different angles on the same point -ex. orthogonal films

Cone-Beam CT (CBCT)

-3D image -can be preformed on a linac with a KV source and flat-panel detector

Verification Imaging: Types

-EPID -port films using cassettes -in room CT scanner -KV cone-beam -MV cone-beam -Ultrasound

POP

-Hinge angle of 180 degrees -enter patient from 2 directions [AP/PA, Laterals, Obliques]

Pituitary Cancer: Critical Structures

-Lens: 10 Gy - cataract -Lacrimal gland: 26 Gy - dry eye -optic chiasm: 50 Gy - blindness -optic nerve: 50 Gy - blindness -brain stem: 50 Gy - necrosis -temporal lobe: 47 Gy - necrosis -spinal cord: 47 Gy - myelitis -ear: 30 Gy - acute serous otitis -ear: 55 Gy - chronic serous otitis

Backup System:

-MU -Time

Types of Treatment Techniques

-POP -Tangentials -4 Field/Box Technique -Wedge-Pair Technique -Arc Therapy

Emergency Procedures

-all departments will have an emergency plan to follow in case of machine malfunction or fire -always turn "beam-off" and get patient off the table [don't leave them there]

Conformal Therapy (IMRT)

-applies 3 dimensional localization of the tumor volume -6 or more fields -couch and gantry rotations

Beam Modifiers Examples

-bolus -wedges -virtual wedge -compensation filters -transmission filters

MLC Disadvantages

-can break easily -not as accurate for shaping of irregular fields

Advantages of EPID

-can verify the isocenter position and location of treatment field prior to treating -images can be viewed immediately online

Interlocks:

-closing doors -placement of proper beam modifiers -machine opération requirements -MU (with R&V) -Energy (with R&V) -pendant

Compensating Filter

-compensate for a sloped surface -(mostly for lung treatment) -[is the thing with little metal blocks of varying heights]

Wedges are used for:

-compensation for lack of tissue -eliminate hot and cold spots -create a more homogenous dose distribution -(Toe is smaller side, and Heel is larger end)

Room Prep before patient arrives

-confirm setup, F.S., gantry, collimator, and table positions -make sure lasers are visible -make sure table and accessories are cleaned after each patient, and new linens

Wedges

-cut at different angles -made of aluminum, lead, or plastic -labeled with machine, angle, and max field potential -computer coded for machine (will tell you if you put it in the wrong way)

R&V

-defines and records the patient's complete course of therapy

Beam Modifiers

-devices that change the shape of the treatment field or distribution of the radiation depth -modify the radiation dose across the treatment field

Custom Blocks Advantages

-divergent -more accurate -setup speed is faster (lighter)

Metastatic Bone Cancers: Field Borders

-encompass all involved areas -if patient had surgery, include ALL of fixation device

Pituitary Cancer: Field Borders

-encompass tumor and avoid critical structures -typically 5x5 or 6x6 field size

Totally Body Irradiation (TBI)

-entire body of the patient is treated -treated with arms down to lower the dose to the lungs -patient usually in fetal position -gantry at 90 or 270 degrees -treated POP -lead shield is placed to block critical structures in the head -TLDs used to check patient's midline doses

Application of bolus

-entire treatment area -over scars -superficial modes -areas of concern

Frequency of films

-films are taken in the first day of treatment and every 5th treatment to verify the actual treatment portal -if patient loses marks, film must be taken

Verification Imaging: Disadvantages

-films taken with linac usually have poor contrast, making landmarks hard to see -films are checked after treatment are given so no chance to correct that treatment -if films are taken and check before treatment, have to worry about patient movement while processing the film

Settings with tolerances

-gantry -collimator -table angle -MU -aperture settings -beam modifers -arc versus fixed treatment

Superficial

-goes no deeper than .5 cm -lead cut-outs used to treat superficial treatment ports -can be treated with electrons

Room Prep when patient arrives

-greets patient -identifies patient -verify site -have open communication -evaluate condition of the patient

Thyroid Cancer: Special Instructions

-head should be extended to avoid oral cavity -use immobilization for reproducibility -CT for treatment planning

Soft Tissue Sarcoma (STS): commonly met to

-hematogenous -lung (most common) -liver -other abdominal organs

Disadvantages of EPID

-high imaging dose (1-5 cGy) -low quality of image due to high energy (poor contrast, and bony anatomy hard to see)

Wedge Pair Technique

-hinge angle between 2 ports is decreased, which makes the dose increased -wedge added to improve the dose distribution

"Beam-Off"

-if treatment needs to be interrupted, turn off beam -emergency pendant (in gantry stand) may be needed to lower patient in the event the machine has been "shut down"

Thyroid Cancer: Field Borders

-include entire thyroid gland -neck -superior mediastinum

Pituitary Cancer: when to use Post-Op therapy

-incomplete resected invasive tumor -tumors demonstrating suprasellar extension with an associated visual field defect -large tumors in which the risk of attempted removal is relatively high -persistent hormal elevation after surgery

When Thyroid Cancer would be treated with XRT

-inoperable lesion -patient is physically unfit for surgery -superior vena cava syndrome -skeletal mets -residual disease involving trachea, larynx, or esophagus

Pituitary Cancer: Commonly Mets to

-invade sella turcia -neoplasms can invade sinuses, brain and 3rd ventricle -can met via CSF or vascular pathways [rare]

Pituitary Cancer: Special Instructions

-lead markers on canthus of eye -spare orbits by tucking chin

Bone Cancers: Other Information

-leave 1-3 cm strip of skin to avoid fibrosis and edema -spare joint farthest away from tumor

Multileaf Collimation (MLC)

-leaves of lead that close in on a field -made of tungsten -each leaf can be positioned independently -computer controlled

Chondrosarcoma

-low grade, doesn't tend to met -surgical resection is most common treatment (has radio-resistant qualities) -RT used when total resection cannot be made

Osteosarcoma: commonly met to

-lung -bone -liver -brain

Thyroid Cancer: Commonly Mets to

-lung -bone -liver -brain

Types of Beam Shaping Devices

-machine collimators (jaws) -custom blocks -standard blocks -multileaf collimation (MLCs)

Electronic Portal Imaging Device (EPID)

-method of improving treatment field accuracy and verification -used to check internal structures during entire treatment process

Arc Therapy

-multiple field technique -radiation is delivered as the gantry moves through its arc of rotation

Image-Guided Radiation Therapy (IGRT)

-newest technology -tracks changes in patient positioning due to variations -image patient every day

Brain-Lab ExacTrac

-not attached to linac -in the floor and ceiling -images are analyzed and couch corrections calculated

Fibrosarcoma

-not highly radio-sensitive -RT used for palliation

Custom Blocks Disadvantages

-not readily available -if wrong, you have to make a whole new one -expensive

Steps for Electron Block Cutting

-obtain DRR -template is used to form a mold -mold is made from cutting styrofoam -cerrobend is poured into the styrofoam -cerrobend hardens, and styrofoam is taken away

Metastatic Bone Cancers Cause

-pain -pathologic fractures -spinal cord compression -neurologic deficits -immobility -decrease in quality of life

EPID used to detect:

-patient movement during treatment -organ movement -patient positioning for breast and abdomen setups

Positioning of port films:

-perpendicular to the beam -maximize the SFD -radiopaque marker indicate the position of the port and central ray -graticule is used

Thyroid Cancer: CT Sim

-position patient supine -take diameter -position patient in head rest (head perfectly straight, extended neck) -construct thermoplastic mask -mark 3 reference points -but BBs on marks (for scan) -scan from apex of skull through mid-abdomen (including lungs) -after placement of reference points couch parameters, scanning limits and length scout are recorded -record all set up information

Thyroid Cancer: Conventional Sim

-position patient supine -take diameter -positition patient in registered head rest (perfectly straight, extended neck) -construct thermoplastic mask -set border according to physician -film both AP and lateral fields -mark 3 point setup -record ODI for all fields -take contour through CA if required

R&V: Electronic Medical Records

-prescribe treatments -create and edit plans -track doses -review reference images -record/monitor and evaluate patients health through out their course of tx -perform chart audits -scheduling -charging

Types of Bone Cancers

-primary -metastatic (more common in clinic)

Common sites of mets

-prostate -breast -lung (most common) -kidney -thyroid

MLC Advantages

-provides more flexibility than blocks -increases safety for patient and therapists

IGRT can track:

-respiratory motion -body movement -internal structure movement -weight loss -radiation-induced changes (tumor shrinkage)

Treatment Delivery

-review patient chart -prepare room -check patient ID, verify site -explain procedure -assist patient onto table, locate patient markings -raise couch, set appropriate SSD -align patient with lasers -set gantry and collimator angles -position blocks and conform with field light -position other beam modifying devices -inform patient you are leaving the room, but that you can see and hear them -monitor patient -set machine parameters and verify with R&V system -initiate "beam-on" -assist patient off table -complete patient's treatment chart -prepare room for next patient

Room Preparation

-room engineered around an isocenter -lasers projected from 3-4 points -standard and dim lighting is required in room

IMRT forms

-segmental MLC (SMLC) -dynamic MLC IMRT

Verification Imaging

-setup and portal verification imaging necessary -documents the actual treatment given by providing a visual confirmation of the planned treatment -identifying anatomy is vital for comparing on-board images with the DRR

Multiple Myeloma: common sites

-skull -vertebrae -ribs -pelvis

Dynamic MLC IMRT

-sliding window technique -leaves move through one beam on/off sequence -field-in-field technique: changed the beam shape during "beam-on" -commonly used for head and neck

Multiple Myeloma

-slow growing tumor -treatment: chemo and RT -RT for palliation of pain

Segmental MLC (SMLC)

-step and shoot -1st beam is delivered, then turned out and leaves are moved to a new position, and 2nd beam is delivered. this continues until all field are treated

Soft Tissue Sarcoma (STS) Treatments

-surgery -chemo -RT (pre-op or post-op)

Ewing's Sarcoma: Treatment

-surgery (main option) -RT -chemo (chemo-sensitive) -combo is most effective

Pituitary Cancer: Immobilization

-thermoplastic mask -bite block -intraoral stents

4 Field/Box Technique

-treat deep seated tumors (pelvis, abdomen) -usually arranged 90 degrees from each other -usually requires blocks for shaping fields

Giant Cell Tumor

-treated locally, doesn't tend to metastasize -surgery is common

Sterotatic Radiation Therapy (SRT)

-use of high-energy photon beam with multiple ports of entry convergent on the target volume -designed to deliver a high dose of radiation to the target utilizing either a single dose of small number of fx (as many as 5)

Treating with Electrons

-used to treat superficial areas -provides rapid dose build up followed by rapid fall-out -collimation is needed to decreases the scatter from the electrons

Tangentials

-used to treat superficial volumes (breast and ribs) -can be POP

Record and Verify Systems

-verify actual treatment being delivered -computer assisted set-up -records patient date -allows for data transfer from sim and treatment planning -assist in quality assurance

Lead Standard Block Advantages

-very dense -absorbs radiation

Lead Standard Block Disadvantages

-very high melting point -high boiling point -toxic and a carcinogen

Thyroid Cancer: Critical Structures

-vocal chords: 45 Gy -thyroid: 45 Gy -esophagus: 55 Gy -spinal cord: 45-47 Gy

Metastatic Bone Cancers

-what will see most of -not curable -treatment is for palliation

Patient Transfers

-wheelchair? stretcher? -O2 tubes, catheters -use proper body mechanics

Double exposed port film

1st part: -set F.S. -put blocks in our engage MLCs -expose film -take blocks out 2nd part: -open field size -make another exposure with the field size opened [No blocks]

Pituitary Cancer: Alignment

3 point set up

Thyroid Cancer: Alignment

3 point set up

Metastatic Bone Cancers: Dose

30 Gy in 10 fx

Multiple Myeloma: Doses

30 Gy in 10/15 treatments

Chondrosarcoma: Doses

40-55 Gy up to 70 Gy (for unresectable tumors)

Giant Cell Tumor: Doses

45-55 Gy for 5/6 weeks

Ewing's Sarcoma: Doses

55-60 Gy

Thyroid Cancer: Dose

6000-7000 cGy [180-200 cGy per fx]

Fibrosarcoma: Doses

66-70 Gy with shrinking field technique

Thyroid Cancer: Beam Arrangement

AP/PA to 45 Gy Obliques to 65 Gy

Malignant Fibrous Histiocytoma (MFH): Doses

EBRT: 46-66 Gy IORT single fx: 15-30 Gy

Malfunctions or Discrepancies in treatment must be recorded and reported

Malfunctions or Discrepancies in treatment must be recorded and reported

Standard Blocks

NOT divergent

Osteosarcoma: Doses

Preop: 35 Gy in 10 fx; 46 Gy in 23 fx (POP fields) Postop: -64-68 Gy for high risk areas -70 Gy for un-resectable tumors

Soft Tissue Sarcoma (STS): Dose

Preop: 50 Gy, with boost -Brachy: 12-20 Gy [3 days are resection] -IORT: 10-16 Gy [immediately after tumor removal] Postop: 45 Gy [negative margins] -EBRT & Brachy: 16-20 Gy [positive margins]

Pituitary Cancer: Beam Arrangement

RT/LT lateral with vertex field (couch at 90 degrees, beam is directed superiorly from top of the head), arc, IMRT, IGRT

Most Common Endocrine Cancer

Thyroid

Radioactive Iodine

Used to treat: -inoperable primary tumors -thyroid capsular invasion -thyroid ablation -post-op residual disease -cervical or mediastinal nodes -mets

Bolus: Skin Sparing-Effect

bolus thickness equal to the dmax dose of the energy being used will eliminate the skin-sparing effect of the mega-voltage beams

Malignant Fibrous Histiocytoma (MFH)

complete local excision is best chance for relapse-fete survival

Bone Cancers: Critical Structures

dependent on where the cancer is in the body

Pituitary Cancer: Dose

depends on department

Responsiveness of Thyroid Cancers

depends on histology

Transmission Filters

designed to allow the transmission of a predetermined percentage of the treatment beam to a portion of a treatment field and may be used throughout the course of treatment

Wedges:

designed to change the able of the isodose curve relative to the beam at a specified depth

Beam Shaping Devices

devices that produce the shape of the beam

Common sites for bone sarcomas

growth plates -distal femur and proximal tibia most common because they have large growth plates

KV Imaging

has more info about soft tissue and bony anatomy -on linac at right angles to the treatment beam (on board imaging)

Metastatic Spine: Field Borders

include 1 vertebrae above infected vertebrae, and 1 vertebrae below

Pituitary Gland

lies in sella turcica

Custom Blocks

made of lead of cerrobend

Thyroid Cancer: Lymph Drainage

mets to regional lymph nodes through lymphatic channels

Thyroid: Types and Treatment

radioactive iodine is used to treat papillary, mixed papillary-follicuclar and follicular cancers

Pituitary Cancer: Treatment Position

supine chin tucked

Thyroid Cancer: Treatment Position

supine, arms by side or with arm stretcher

Osteosarcoma Treatments

surgery and chemo -are chemo-sensitive and radio-resistant -RT used in patients that cannot have surgery

Pituitary Cancer: treatment techniques

surgery plays a significant role in treatment and controls 70-90% of tumors

Osteosarcoma: Field Borders

surgical scar must be included in field

Half Value Layer (thickness) [HVL]

the amount of material required to reduce the intensity of a beam by 50% -cannot have more than 5% transmission through a block

Monitor Units

the time the treatment machine is on in order to deliver a prescribed dose -effected by beam energy, distance from source of radiation, field size

Thyroid Cancer: Immobilization

thermoplastic mask with head rest to extend chin

Bolus

tissue equivalent material that conforms to the treatment surface without air gaps

Metastatic Bone Cancers: Treatment

treat to improve quality of life -relieving pain -decrease need for narcotic meds -maintaining ambulation

Virtual Wedges

use a moving straight edged collimator to create the same isodose curves as that produced using a physical wedge -delivers a range of dose over the treatment field

IGRT

used to image the patient right before treatment

Metastatic Bone Cancers: Beam Arrangement

varies depending on area, typically AP/PA