Physics Chapter 15

Front 1

Define brachytherapy

Back 1

radiotherapy in which the source of irradiation is placed close to the surface of the body or within a body cavity.

Front 2

List the different types of brachy applications: (4 of them)

Back 2

-intracavitary
-intrastitial
-endovascular
-topical

Front 3

Ra-226 Half-life

Back 3

1600 years

Front 4

Rn-222

Back 4

3.83 days

Front 5

Co-60

Back 5

5.26 years

Front 6

Cs-137

Back 6

30 years

Front 7

Ir-192

Back 7

73.8 days

Front 8

Au-198

Back 8

2.7 days

Front 9

I-125

Back 9

59.4 days

Front 10

Pd-103

Back 10

17 days

Front 11

Explain the decay of Radium.
(for real... )

Back 11

*PHOTON EMITTING*
-is a product of U-238
-Alpha decays into radon gas
-Ends at stable Pb-206

Front 12

How are radium sources specified?

Back 12

1. active length
2. physical length
3. activity or strength of source
4. filtration

Front 13

Define active length

Back 13

the distance between the ends of the radioactive material

Front 14

Define physical length

Back 14

the distance between the actual ends of the source

Front 15

What are three types of radium needles used for implants?

Back 15

1. uniform linear activity
2. higher activity at one end (Indian club)
3. high activity at both ends (dumbbell)

Front 16

Advantages of Cs-137 over Radium?

Back 16

-Cs-137 requires less shielding
-Cs-137 is less hazardous in the microsphere form.

Front 17

Advantage of Co-60 as a brachy source?

Back 17

-High specificity: allows fabrication of small sources required for some special applications

Front 18

Disadvantage of Co-60 as brachy source?

Back 18

-more expensive than Cs-137
-has a short half life (5.26 years), so it necessitates more frequent replacement and a complex inventory system.

Front 19

What is the form that Ir-192 is fabricated in?

Back 19

-thin flexible wires that can be cut to desired lengths.

Front 20

What are the uses for Ir-192?

Back 20

used as:
-seed ribbons
-wires
*both used for afterloading technique

Front 21

What form is Au-198 fabricated in?

Back 21

-seeds or "grains"

Front 22

What is Au-198 used for?

Back 22

-interstitial implants

Front 23

Advantages of I-125 (over radon and Au-198)?

Back 23

-long half-life (59.4 days): this is convenient for storage
-low photon energy: which requires less shielding

Front 24

What is I-125 used for?

Back 24

-wide use for permanent implants in radiation therapy.

Front 25

What are the units for the source strength for any radionuclide?

Back 25

-millicuries (mCi)

Front 26

What are the objectives for treatment planning in implant dosimetry? (there are 2)

Back 26

1. determine the distribution and type of radiation sources to provide optimum dose distribution
2. provide a complete dose distribution in the irradiated volume

Front 27

Define the Paterson-Parker distribution rules for planar implants
(there are 4, and they are long)

Back 27

1. the ratio b/w the amount of radium in the periphery and the amount of radium over the area itself depends on the size of the implant (yeah, whatever.)
2. The spacing of the needles should not be more than 1 cm from each other or from the crossing ends.
3. If the ends of the implant are uncrossed, the effective area of dose uniformity is reduced. THEREFORE, the area is reduced by 10% for each uncrossed end for table-reading purposes.
4. In the case of multiple implants planes, the radium should be arranged as in rules 1-3, and the planes should be parallel to eachother.

Front 28

Define the Paterson-Parker distribution rules for volume implants
(there are only 3 this time, motherlicker.)

Back 28

1. the total amount of radium is divided into eight parts and distributed as follows for the various shapes.
-cylinder is composed of belt, 4 parts; core, 2 parts; and each end, 1 part.
-sphere is composed of shell, 6 parts, and core, 2 parts.
-cuboid is composed of each side, 1 part; each end, 1 part, and core, 2 parts.
2. The needles should be spaced as uniformly as possible, not more than 1 cm apart.
-There should be at least 8 needles in the belt and 4 in the core.
3. If the ends of the volume implant are uncrossed, 7.5% is deducted from the volume for the crossed end for table-reading purposes.

Front 29

Describe the use of orthogonal radiographs in localization of individual sources in brachy

Back 29

p. 340
sorry, its a paragraph of nonsense.

Front 30

Describe the Quimby System of interstitial implantation:

Back 30

-characterized by a UNIFORM distribution of sources of EQUAL LINEAR ACTIVITY.
-results in a NONUNIFORM dose distribution, higher in the central region of tx.

Front 31

Describe the Stereo-shift method for source localization

Back 31

taking two radiographs of the same view but the patient or the xray tube is shifted a certain distance b/w the two exposures.
-this means the z coordinates can be derived (... i knew that)

Front 32

Which one is better: stereo-shift method or orthogonals?

Back 32

Orthogonals has better accuracy.

Front 33

Explain the use of surface models:

Back 33

-used to treat small superficial areas.
-such as the: ear or lip
-distance between the source on the outside of the mold to the skin surface is usually 0.5 to 1.0 cm.

Front 34

Describe interstitial brachy
(also on p.342; its long as well)

Back 34

-radioactive sources are fabricated in the form of needles, wires or seeds
-can be inserted directly into the tissue.

Front 35

Name the two types of interstitial implants:

Back 35

1. temporary
2. permanent

Front 36

Describe the manchester system of brachytherapy:
-how many points are there and what are they?
- what is the duration of the implant based upon?

Back 36

-one of the oldest and most extensively used systems in the WORLD
-characterized by doses to 4 points: A, B, bladder point, rectum point.
- based on the dose rate calculated at point A.

Front 37

Advantages of Afterloading:
6 of 'em, NAME THE FIRST 3

Back 37

1. the major advantage is the elimination or reduction of exposure to medical personnel.
2. Well-designed systems can provide the capability of optimizing dose distributions beyond what is possible with manual afterloading.
3. Treatment techniques can be made more consistent and reproducible.

Front 38

Name the other 3 advantages of afterloading

Back 38

4. In LDR remote afterloading, sources can be retracted into shielded position to allow better patient care under normal as well as emergency conditions.
5. HDR remote afterloading permits treatment on an outpatient basis, using multiple fraction regimens.
6. HDR remote afterloading is suited for treating large patient populations that would otherwise require prolonged hospitalization if treated by LDR brachy.