Dosi

HIFU

(high intensity focused ultrasound) (sometimes FUS or HIFUS) is a highly precise medical procedure using high-intensity focused ultrasound to heat and destroy pathogenic tissue rapidly. It is one modality of therapeutic ultrasound, and although it induces hyperthermia it should not be confused with this technique which heats much less rapidly and to much lower therapeutic temperatures (generally < 45°C).

disadvantages of HDR systems

- uncertainty in biological effectiveness - Potential for accidental high exposures - potential for serious errors - Increased staff commitment

Stereotactic Radiotherapy Doses

-Brain < 2cm (Single Fraction) - 2000 cGy / Fx -Brain >2cm 600 cGy X 3Fx - 1800 cGy Total

Daily QA for the HDR Afterloader

-Electrical interlocks at entrance to room -Source exposure indicator lights on the after loader, control console, and in the facility -Viewing and intercom systems -Emergency response equipment -Radiation monitors to indicate source position -Timer accuracy -Clock (date and time) in unit's computer -Decayed source activity in unit's computer

Tandem and Ring

-HIGH DOSE RATE procedure -Typical Dose Regimen is 600 cGy per fraction X 5 Fractions for a total dose of 3000 cGy -Pt is CT Simmed with T+R in and plan is done 1st fraction and then we try to position exactly the same for other 4 fractions. - has a pair shape

Eye Plaque Brachytherapy

-Intraocular melanoma is the most common eye tumor. -An eye plaque, loaded with Iodine 125 seeds, is applied externally to the scleral (outer) surface over the tumor base. The number of seeds to be used is related to the size of the plaque, and ranges from 7 to 24 for plaque diameters of 12-20 mm. The typical activity used is 0.5-5 mCi per seed so as to achieve treatment dose rates of 0.5-1.25 Gy/h, with a prescription dose of 100 Gy delivered in 5-12 consecutivedays. Palladium-103 can be used for plaque radiation therapy of most choroidal melanomas. Studies have shown that low-energy iodine-125 plaques have largely replaced cobalt-60 and ruthenium-106 for plaque radiation therapy

Tandem and Ovoids

-LOW DOSE RATE Procedure -Typical Regimen: 2000 cGy per fraction X 2 fractions for a total of 4000 cGy (with typical 4500 cGy 4-Field box pelvis External Beam. -Needs to be broken up into 2 fractions because we typically need 72 hours to delvier dose -Cesium 137 Capsules deliver dose through the Tandem and Ovoids.

Advantages of TBI

-No sanctuary sites for irradiation -No metabolism or clearance needed -All areas of the body receive the "same" dose

SIR Spheres Precautions

-No travel on public transport, including air travel, lasting more than 2 hours for 1 week. -Avoid crowded public places for 1 week. -Do not sleep in the same bed as your partner for 1 week. -No contact with children or pregnant women for 1 week. -Adult visitors may approach the patient for periods of a few minutes at a time, but for prolonged periods they should stay more than 2 meters (6 feet) away for 1 week.

Technical Criterion for PERMANENT IMPLANT PATIENT SELECTION

-Prostate size •≥ 20 cc •≤ 60 cc

Rationale for Stereotactic Radiotherapy

-Reduces risk of healthy brain and cranial nerve damage -Allows for treatment in critical areas (e.g., retina, brain stem, chiasm) -Allows for safe treatment of large lesions (> 3-5 cm.)

Fractionated TBI

-Today, TBI is fractionated. -Total doses range from 800 to 1400 cGy, administered over 3 to 5 days, 2 to 3 fractions per day -Dose rates range from 5 to 40 cGy/min, typically 15-25 cGy/min -Tissue compensation and shielding of critical structures varies

Endobronchs

-Used primarily to palliate symptoms such as hemoptysis, cough, and dyspnea that are caused by endobronchial malignancy. -Involves delivering 3 to 10 Gy/fraction over minutes and repeating this fraction every 1 to 2 weeks for 2 to 4 sessions. -Frequently used in those who either are not candidates for or have failed other therapy, such as surgery or external beam radiation. -The goals of EB are to deliver therapeutic irradiation to the tumor and to minimize normal airway injury.

mammosite

-Uses the HDR Afterloader -Typical Dose Regimen of 340 cGy per fraction in 10 fractions for a total dose of 3400 cGy. -Treatment point is 1 cm Past the Balloon -Outpatient Procedure

Pre-treatment Quality Assurance for SRS

-Verification of the collimator alignment with the nominal isocenter of the linac - most important. -Transfer accurately the treatment planning parameters into the controller system and frame system. -Patient repositioning with the localizer system

TBI

-form of radiotherapy used primarily as part of the preparative regimen for hematopoietic stem cell (or bone marrow) transplantation. -involves irradiation of the entire body, though in modern practice the lungs are often partially shielded to lower the risk of radiation-induced lung injury. -in the setting of bone marrow transplantation serves to destroy or suppress the recipient's immune system, preventing immunologic rejection of transplanted donor bone marrow or blood stem cells. - Additionally, high doses of total body irradiation can eradicate residual cancer cells in the transplant recipient, increasing the likelihood that the transplant will be successful.

Low dose rate

.4- 2 Gy/h

Doses of total body irradiation used in bone marrow transplantation typically range from

10 to >12 Gy -At these doses, total body irradiation both destroys the patient's bone marrow (allowing donor marrow to engraft) and kills residual cancer cells. -Non-myeloablative bone marrow transplantation uses lower doses of total body irradiation, typically about 2 Gy, which do not destroy the host bone marrow but do suppress the host immune system sufficiently to promote donor engraftment.

prescription for prostate realtime implant

14,500 cGy

Medium dose rate

2-12 Gy/h

5 ALA

5-Aminolevulinic acid (ALA) is a photosensitizer used in photodynamic therapy (PDT) because it causes preferential accumulation of protoporphyrin IX (PpIX) in tumor cells, where it forms singlet oxygen upon light irradiation and kills the tumor cells.

Treatment Doses to Prostate Plan Targets Prostate Doses for a Typical Radiation Treatment Plan

6800 cGy ("Centigray" or Rads) in 34 Fractions (Treatments) to Prostate Bed 8000 cGy in 40 Fractions 7020 cGy in 26 Fractions ("Hypo Fractionated")

high dose rate

>12G/h

Disadvantages of TBI

Acute side effects -Nausea and vomiting, alopecia, diarrhea, low grade fever, mucositis, pancytopenia Intermediate side effects -Intersititial pneumonitis, veno-occlusive disease, nephrotoxicity Potential late side effects -restrictive lung disease, hypothyroidism, chronic renal failure, sterility, cataracts, growth retardation, potential neurologic toxicity that may occur with irradiation

SIR Spheres how it works

After injection into the artery supplying blood to the tumors, the spheres are trapped in the tumor's vascular bed, where they destroy the tumor cells by delivering the beta radiation. The radiation is targeted and contained within the patient's body and after 14 days the majority of the radiation effect has occurred. SIR-Spheres microspheres are considered a regional treatment as the radiation is directed to the liver and does not affect other organs in the body.

How HIFU Works

As an acoustic wave propagates through the tissue, part of it is absorbed and converted to heat. With focused beams, a very small focus can be achieved deep in tissues. When hot enough, the tissue is thermally coagulated. By focusing at more than one place or by scanning the focus, a volume can be thermally ablated This technology can achieve precise ablation of diseased tissue, therefore being called HIFU surgery. Because it destroys the diseased tissue non-invasively, it is also known as "Non-invasive HIFU surgery". Anesthesia is not required. The treatment can be combined with radiotherapy or chemotherapy. HIFU has been successfully applied in treatment of cancer to destroy solid tumors of the bone, brain, breast, liver, pancreas, rectum, kidney, testes, prostate

Total Body Irradiation Primary Application is a Preparatory Regime for

Bone Marrow Transplantation (BMT)

True of False- In prostate seed loading, the most common technique is to place the needles inside the center of the prostate (hopefully close to the urethra to treat the cells close to the urethra) in order to keep the center of the prostate hot.

False

True or False - HDR requires less shielding than LDR sources and is often less complicated than LDR.

False

True or False - Low Dose Rate = >12 Gy / Hr and High Dose Rate = 2 Gy / Hr.

False

True or False - The preferred radioactive source for Tandem and Ovoids is Plutonium 238.

False

CHRONIC TOXICITY- PERMANENT IMPLANT

GU Cystitis/Urethritis Urethral Stricture GI Rectal Ulceration Rectal Bleeding

ACUTE TOXICITY- PERMANENT IMPLANT

GU `Nocturia `Dysuria GI `Proctitis Surgical `Bleeding `Infection `Perineal Soreness `Headache From Spinal Anesthesia

PERMANENT IMPLANT DOSIMETRY

Homogenous- seeds evenly spaced throughout prostate Peripheral- seeds placed along periphery of prostate Modified Peripheral- most seeds placed along edge of prostate, some placed centrally around urethra

Radio Dynamic Therapy

Light used here is the Cherenkov radiation generated by high-energy x-ray beams in the patient's body -Tumors preferentially absorb 5-ALA, thereby allowing radiation from the Microtron to hone in on the area in question. -Radiodynamtherapy uses targeted radiation to activate a drug given to the patient hours before treatment, thereby damaging the targeted tumor.

What brachytherapy procedure treats with a dose regimen of 340 cGy x 10 Fractions to a total dose of 3400 cGy as an outpatient procedure?

Mammosite

PROSTATE SEED PLANNING

PRE PLANNING -PLAN OFF OF CT/MRI REAL TIME PLANNING -PLAN OFF OF TRANSRECTAL ULTRASOUND IN THE OR

For a tandem and ovoid treatment, the isodose distribution resembles a: a)avocado b)strawberry c)pear d)jackfruit e) coconut

Pear

Types of Brachytherapy

Permanent "Seed" Implants Temporary implants

Temporary implants-

Placement of needles into the prostate through which a radioactive source delivers the radiation dose. the source and needles are removed after the treatment is given

Permanent "Seed" Implants-

Placement of non-removable radioactive seeds (I-125 or Pd-103) in the prostate

PERMANENT IMPLANT PATIENT SELECTION

Pre-treatment PSA ≤ 10 ng/ml Gleason score 6 Clinical T stage T1c and T2a Able to Tolerate Anesthesia

INTRA-OPERATIVE REAL-TIME PLAN pros and cons

Pros Less invasive- one procedure/one prep No reproducibility issues Cons More time in OR

PRE-PLAN pros and cons

Pros Prepared in advance Save time in OR Cons Difficult to reproduce patient position More invasive for patient 2 rectal ultrasound procedures 2 catheters 2 bowel preps

For planar implants, the system that delivers a uniform distribution of source strength, accepting a non-uniform delivery of dose is the

Quinby

Low Dose Rate (LDR) Brachytherapy

Radiation dose < 1 Gy/hour

High Dose Rate (HDR) Brachytherapy

Radiation dose > 1-2 Gy/minute

Radiosensitizers

Radiosensitizers are radiation effect enhancers of reactive oxygen species (ROS), DNA damage response modifiers, as well as agents that alter tumor microenvironment, etc. A radiosensitizer is an agent that makes tumor cells more sensitive to radiation therapy. It is sometimes also known as a radiation sensitizer or radio-enhancer.

Sir Spheres meaning

S elective I nternal R adiation

Planar Implants

Sarcomas Floor of Mouth Breast Pelvic Sidewalls

What is Stereotactic Irradiation?

Stereotactic irradiation is the term used to describe a focal irradiation technique that delivers a prescribed dose of radiation to stereotactically localized lesions. Stereotactically localized lesions make use of a three-dimensional coordinates system to locate small targets inside the body and to then treat them with radiation.

HDR Vaginal Cylinder

The usual daily dose is either 400 cGy / Fx or 700 cGy / Fx with a total of 3 Fractions.

Gamma Knife

There are 201 Cobalt sources of radiation. They go through the skull and into the brain separately. Each beam is too weak to harm normal tissue. The beams come together in the problem area. Together they are strong enough to destroy, shrink or stop the growth of the tumor or abnormality.

SIR Spheres

These microscopic radioactive beads, deliver radiation directly to the tumor site while sparing surrounding tissue. SIR-Spheres microspheres are tiny polymer beads that are loaded with yttrium-90, a radioisotope that emits pure beta radiation. Yttrium-90 has a "half life" of about 2 ½ days. The radiation from yttrium-90 is largely confined to a tissue depth of 2 - 3 mm.

Phototherapy Applications

Treatment of melanoma skin cancers Treatment of Acne vulgaris

T/F The primary advantage with brachytherapy is the fact that the sources are located within the tumor volume, thus minimizing the amount of normal tissue the radiation has to travel through to reach its target.

True

True false - Due to prostatic swelling immediately following a seed implant, the dose coverage to the prostate would appear cold.

True

True or False - A patient will come back an average of three weeks for post implant dosiemtry because the prostate will have no swelling and the coverage will be more accurate to evaluate the implant.

True

True or False - For endobronchs, the patient is filmed with a catheter and "dummy sources" which indicate the possible "dwell positions" for the physicist to use in planning

True

True or False - HDR is a quicker treatment with no radiation exposure to staff.

True

True or False - High Dose Rate brachy therapy delivers 1-2 Gy to the treated volume in just a few minutes.

True

True or False - In order to be eligible for an implant, the patient's prostate size must be between 20cc to 60 cc in volume.

True

True or False - In regards to prostate seed implants and HDR prostate procedures, if the procedure is HIGH dose rate it is delivered at greater than1-2 Gy per minute and if it is Low Dose Rate it is delivered less than 1 Gy per hour.

True

True or False - In regards to tandem and ovoid planning, the system that uses "Point A" and "Point B' is called the Manchester System.

True

True or False - In spite of all the precautions and even with the best of skill, seeds are not always placed at their exact planned locations.

True

True or False - The most common sources used in prostate seed implants are Iodine 125 and Palladium 103.

True

True or False - The patient must be imaged and the implant must be analyzed immediately post implant to ensure the implant is optimal before the patient is discharged.

True

True or False - The reason Brachy Sources are usually encapsulated is to ensure containment of the radioactive material and sometimes to act as a filter of unwanted radiation.

True

True or False - The source that is used for most HDR procedures is Iridium 192.

True

LDR vs. HDR Brachytherapy

`HDR is a quicker treatment with no radiation exposure to staff. `HDR is a outpatient procedure, as opposed to LDR which often requires extended stays in the hospital (Tandem & Ovoids) `HDR requires more shielding than LDR sources. `HDR is often more complicated than LDR. `HDR sources usually have a shorter half-life and need to be replaced more often (Co 60, Ir 192 vs. Cs 137) - More expensive.

Why is the Brachytherapy Source Encapsulated?

`To ensure containment of the radioactive material and sometimes to act as a filter of unwanted radiation. `Brachytherapy sources are usually sealed so that the radioactive material is contained fully encapsulated within a protective capsule. This capsule is designed to prevent leakage or escape of the radioactive source and it makes the source rigid. Furthermore, for photon emitting sources, the capsule can serve the purpose of absorbing alpha and beta rays produced through the source decay.

Brachytherapy

also known as internal radiotherapy, sealed source radiotherapy, curietherapy or endocurietherapy.

Manchester System

characterized by four dose points: point A, Point B, bladder point and rectum point. Point A is 2cm sup and 2cm lat point B is 2cm sup and 5 cm lat

Patterson-Parker dosimetry

deliver a uniform dose sources are distributed non-uniformly

Tomotherapy

literally "slice" therapy, is a form of cancer radiation therapy that combines the precision of a CT (computerized tomography) scan with the potency of radiation treatment to selectively destroy cancerous tumors while minimizing damage to surrounding tissue.

SpaceOAR

significantly decreases Rectal Dose during Prostatic Radiation Treatments

intracavitary

source are placed into a body cavity

intravascular

sources are brought intravascularly into a lesion or near a lesion

Intraoperative

sources are brought surgically into or near the tumor volume

Interstitial

sources are implanted into the tumor volume

intraluminal

sources are inserted into a lumen

Surface plaque

sources are loaded into a plaque which is brought into contact with a skin surface lesion

"Dose Painting"

the ability, through the use of the IMRT planning algorithm, to specifically place, or "paint" different doses to specific areas via a single course of treatment.

Quimby system

uniform distribution of source strength, accepting a non-uniform delivery of dose.

Ir192

very small source can provide a very high dose rate (HDR) short half-life of 74 days

Phototherapy

•A two-stage treatment that combines light energy with a drug (photosensitizer) •It is designed to destroy cancerous and precancerous cells after light activation. light excites the photosensitizers

proton therapy

•Cyclotrons can be used to treat cancer. Ion beams from cyclotrons can be used, as in proton therapy, to penetrate the body and kill tumors by radiation damage, while minimizing damage to healthy tissue along their path. •Cyclotron beams can be used to bombard other atoms to produce short-lived positron-emitting isotopes suitable for PET imaging The protons deposit nearly all of their energy at the end of their path, at a point called the Bragg peak. Tissue upstream receive only a small dose and those to the sides and behind the target receive virtually none. By implementing a scattering technique, a spread-out Bragg peak is obtained. By doing this, several depths of the target tissue volume will be precisely treated.

Microtron RaceTrack Microtron LA45-PET

•High energy up to 45 MeV • High radiation precision • Energy level is adjustable