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Medical uses of radiations
Transcript of Medical uses of radiations
X-Ray computed Tomography
* the external radiation hazard, both in terms
of instantaneous dose(amount, distance shielding)
rates and doses averaged (time and cumilative).
*the risks of radioactive contamination.
Radiation Protection in Nuclear Medicine:
* control of access to the area;
* calibration and tests of equipment
* initial and continuing training of the staff
* Patient records
* Strict procedure for waste managing
* special procedures that need to be followed
to restrict exposure workers and patients.
The amount of radiation used in most procedures
is very small and the benefits greatly outweigh
the risk of harm.
What is it?
* It is the medical use of high ionizing radiation
* High-powered X-rays particles, or radioactive seeds to kill cancer cells
* Cancer cells multiply faster than normal cells in the body, it prevents cancer cells from growing and dividing, this leads to cell death.
It is used to:
fight many types of cancer
• Shrink a tumor as much as possible before surgery
• Help prevent the cancer from coming back after surgery
• Treat cancers that cannot be removed with surgery
The amount of radiation used in photon radiation therapy is measured in gray (Gy),
The dose variates depending on the type and stage of cancer being treated. For curative cases, for example, the typical dose for a solid brain tumor ranges from 60 to 80 Gy,
Advantages and disadvantages
: * It doesn’t spread throughout all the body.
* Precisely delivered to one particular location
* No damage to healthy cells, just the surrounding area.
Effectiveness against Localized Tumors
* Destroys cancer cells that divide quickly
* Helps to stop the spread of cancer at the tumor site and cancer spreading on the body
* After a surgery, it destroys remaining cancer cells around the tumor.
1) Acute side effects
2) Long term side effects
They occur months to years after treatment, generally limited to the area that has been treated.
Cancer: Potential cause of cancer– usually less than 1/1000. It may occurs 20 – 30 years following treatment,
Presented after re-treatment. Cumulative effects from this process should not be confused with long-term effects—when short-term effects have disappeared and long-term effects are sub clinical, re-irradiation can still be problematic.
• Effects on reproduction
• Effects on pituitary system
3) Cumulative side effects
Limited Effectiveness against Metastasized Cancers
* Delivers cancer-killing doses of radiation at the tumor site, it doesn't travel throughout the body to destroy cancer cells that have spread.
Radiation accident (Risks): * Acute exposure
* Cumulative over-exposure
* Prolonged exposure
Radio therapy Risks
It refers to the exposition to large doses in one time
In Europe, fractionation for adults is
1.8 to 2 Gy
Calculus of acute exposure radiation toxicity : (see excel)
Effects of acute exposure:
Lethal acute exposure:
The effects of acute exposure vary with the dose, examples:
10 Sv - Risk of death within days or weeks
100 mSv - Risk of cancer later in life (5 in 1000)
All radioactive exposures that an organism receives from the first to the last exposure to x-rays.
Fractionation regimes can variate depending the therapy center and between doctors.
Europe: 1.8-2 Gy per day, five times at week.
No. of Fractions:
= D (Gy) = 60 =
Df (Gy) 2
total effective dose and (ex: 60)
fractionated dose. (ex: 2)
No of fractions per week
What is it ?
X-Ray sensors (detectors)
Detectors / Sensors
Rotation of both source and sensors
Diagnostic tool and guide for interventional procedures
The radiations in the form of x-rays used in computed tomography scans are energetic enough to directly and indirectly damage DNA.
DNA damage can be repaired by cellular repair mechanisms
Such damage to the DNA occasionally leads to cancers (lung, breast, thyroid, stomach, leukemia)
Allows to :
- control its functioning
- to detect not visible anomalies which can be detected by other examinations.
If the product concentration is very high in a precise place, it can be a disease sign : for example a tumor
To do scintigraphy for a specific organ we need:
- A radioelement
- In certain cases: help of a vector molecule
What is it ?
- Administration of a tiny quantity of radioactive product
- Active vision of the organ and not only its structure
Calculation of gamma rays ejection fraction
There are a three factors that control the amount, or dose, of radiation received from a source. Radiation exposure can be managed by a combination of these factors:
Exposure over the time of the session of the radiotherapy, it is expressed on minutes
In an early stage of cancer cervix with an exposure rate at
(this rate is based on the linear-quadratic model and clinical experience.)
ER= 14 Gy/h
Df= 1.8 Gy
So if we have:
14Gy – 60 min
The session should last
1.8 Gy -7.7 min
= 8 min.
(Cross multiplication rule)
What is it?
Drugs + Radioisotopes
3 treatment ways
How to use?
Case study- Bone metastases
Metastases are the major cause of death from cancer.
There is many types, but the most common is external beam radiotherapy
Move of patient along its axis (from head to feet)
effective radiation dose
distance from the source
effective radiation dose
a mass of absorbing material placed around radiative source or around the object to protect.
Alternative to X-Ray computed tomography
magnetic resonance imaging
for visualizing subcutaneous structures
X-ray computed tomography
Nuclear medicine is the use of unsealed radioactive sources in diagnosis, therapy and biomedical research.
ASTRO (American Society for Radiation Oncology) has launched a safety initiative called Target Safely that, among other things, aims to record errors nationwide so that doctors can learn from each and every mistake and prevent them from happening
There are rigorous procedures in place to minimize the risk of accidental overexposure of radiation therapy to patients.
1985-1897 Therac-25 was responsible for 6 accdiends, patients were given up 100x the intended dose; 2 people killed directly by the radiation overdoses.
2005- 2010, a hospital in Missouri overexposed during a five-year period because new radiation equipment had been set up incorrectly
Given in vein - into the blood circulation
+ 1 bone, better than External beam radiation therapy
The agents differ in terms of efficacy;
duration of pain palliation; tumoricidal effects;
ability to repeat treatments;
toxicity, and expense.
Bone metastases are caused by Prostate and Breast cancer.
lower blood cell counts
risk of infection
risk of bruising or bleeding
white blood cells
Transfer of cancer cells
Control of organ functioning or to detect anomalies not visible by other examinations
- Model the image (of whole body or organ)
-Control organ functioning
-Detect anomalies non visible by other exam