June 28, 2010
Types of Brachytherapy
As brachytherapy is dependant on source placement, intensity of radiation and duration, it can be categorized as per each of these factors.
Classification of Brachytherapy: Source Placement
A radiation source can be placed in two ways:
- Interstitially
- In contact
In interstitial placement, the radiation source is placed directly in the target tissue of the site for e.g the breast or prostate.
Whereas in case of ‘in contact’ brachytherapy, the radiation source is placed next to the affected tissue. It could be:
- An intracavity placement such as in uterus, cervix or vagina
- An intraluminal placement such as in oesophagus or tracea
- A Surface placement such as in the skin
- An intravascular placement for coronary in-stent restenosis
Classification of Brachytherapy: Dose Rate
Dose rate refers to the intensity of radiation delivered to the affected area and its surrounding. It is expressed in Grays per hour, denoted by Gy/h. Brachytherapy, on the basis of dose rate can be classified into three categories:
- Low rate brachytherapy
- Medium rate brachytherapy
- High rate brachytherapy
Low-dose brachytherapy uses radiation sources that emit a rate of up to 2 Gy/h. This type of brachytherapy is used for oral cavity, prostate, sarcomas and oropharynx cancer. These treatments are occasionally followed by pulsed dose rate brachytherapy, which simulates the effectiveness of the low dose.
Medium dose brachytherapy has radiation dose rate ranging between 2 Gy/h and 12 Gy/h. High dose rate exceeds 12 Gy/h and is used in tumors of cervix tumors, lungs, oesophagus, breasts, cervix and prostate.
Classification of Brachytherapy: Duration
Brachytherapy on the basis of duration of dose can be classified in two ways:
- Permanent brachytherapy
- Temporary brachytherapy
Permanent brachytherapy is administered by implanting radiation sources directly into affected areas. It is most commonly used for prostate cancer.
Temporary brachytherapy is administered for a set duration, usually for a few minutes or hours. The duration of brachytherapy depends on the dose and source placement. Usually in case of low doses, the duration ranges up to 24 hours whereas is as short as few minutes in case of high dose brachytherapy.
In case of permanent insertions, the ‘seed’ is left in the body to exhaust itself over the time and become inactive. The inactive seed can be taken out later if desired, or else it does nothing harmful or inconvenient.
Dr. Robert Kuske
