Types of error during treatment verification

we are all aware that there is some possibility that errors might occur in everything that we do. so here are the types of error that can occur during treatment verification .

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Types of error in treatment verification

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BEAM MODIFICATION DEVICES

Prezi : beam modification devices

you can check out some informations on beam modification devices by clicking the link above. it is on Prezi format created by us or simply view it straight from below. Enjoy !

Particle Beam Therapy

Introduction :

Cyclotron and Synchrotron are type of particle accelerator . Cyclotron is an apparatus in which charged atomic and subatomic particles are accelerated by an alternating electric field while following an outward spiral or circular path in a magnetic field. Synchrotron a cyclotron in which the magnetic field strength increases with the energy of the particles to keep their orbital radius constant .

Following are the compare and contrast between Cyclotron and Synchotron : 

Cyclotron	Synchrotron
1.       Use an increasingly strong magnetic field to control the paths of particle
2.       Used to accelerate charged elementary particles or ions to higher energies
3.       Basic part v  A source of elementary particles or ions v  A tube pumped to a partial vacuum in which the particles can travel freely v  Some means of speeding up the particles
Constant magnetic field and constant frequency electric field	Varying electric and magnetic field
A cylindrical or spherical chamber	A torus shaped tube
Its curve becomes larger	A constant radius circle
250MeV	6.84TeV

Image source : Google.com

Wave guide: Standing Wave

A waveguide is a special form of transmission line consisting of a hollow, metal tube.

Source: http://www.allaboutcircuits.com/

Wave guides conduct microwave energy at lower loss than coaxial cables.

Only for signals of extremely high frequency, the wavelength approaches the cross-sectional dimensions of the waveguide.

Below such frequencies, waveguides are useless as electrical transmission lines.

Waveguides may be thought of as conduits for electromagnetic energy, the waveguide itself acting as nothing more than a “director” of the energy rather than as a signal conductor in the normal sense of the word.

All transmission lines function as conduits of electromagnetic energy when transporting pulses or high-frequency waves, directing the waves as the banks of a river direct a tidal wave.

Waveguides are single-conductor elements; the propagation of electrical energy down a waveguide is of a very different nature than the propagation of electrical energy down a two-conductor transmission line.

Standing Wave

 Formation:

A standing wave pattern is a vibration pattern created within a medium when the vibrational frequency of the source causes reflected waves from one end of the medium to interfere with incident waves from the source.

Important part of the condition for this constructive interference for stretched strings is the fact that the waves change phase upon reflection from a fixed end.

Only created within the medium at specific frequencies of vibration.

These standing wave modes arise from the combination of reflection and interference such that the reflected waves interfere constructively with the incident waves.

Source: http://hyperphysics.phy-astr.gsu.edu/

Standing wave used in medicine.

Have advantages at low energies.

However, it is insufficient because it tries to combine two components that are out of phase.

TOMOTHERAPY

A few weeks ago, our lecturer gave a task about ‘Tomotherapy’ to our group.We are supposed to explain what is tomotherapy, its function, advantages and disadvantages of tomotherapy compared to normal radiation therapy.

TOMOTHERAPY

What?

   -   Radiation treatment for cancer.

-             -   3-D Imaging of target tissue.

-             -  Helical delivary pattern.

-             -   Intensity Modulation Radiotherapy (IMRT)

  - Multileaf Collimator (MLC)

  -   Radiation concentrates on moving target tissue.

There are 2 type :-

     1)      Serial (NOMOS corp) : The delivary of multiple fan beams with discrete table increments between each axial gantry arc.

     2)      Helical (Tomotherapy Inc.) : Continous synchronized gantry and table motion. From the patient’s point of view, the source describes a helical trajectory.

This is the diagram that showing the component presence in the tomotherapy machine.

Source : google

How it works?

A short 6 MV linac is collimated by jaws and a binary multileaf collimator. The treatment head rotates on a gantry in the x/z plane while a patient is continuously translated through the bore of the machine in the y-direction – the therapy analogue of spiral CT.

Function

       1)      For cancer treatment – Since there are presence of linac. The treatment is given slice by slice while normal radiation therapy is not.

Linac?

A linear accelerator (LINAC) customizes high energy x-rays to conform to a tumor’s shape and destroy cancer cells while sparing surrounding normal tissue. It features several built-in safety measures to ensure that it will not deliver a higher dose than prescribed and is routinely checked by the medical physicist to ensure it is working properly.

        2)      By presence of CT Scan, it will :-

-          Take image to check the location of tomour before give treatment to the patient so that the tumour is not mislocated if there is weight loss of patient.

-          If there are high difference of patient’s weight, patient maybe need to another treatment planning.

-          CT will show the 3D image and showing slice by slice of body part.

Advantage & Disadvantage

Advantage	Disadvantage
1)    Delivers radiationfrom all 360◦of the axial plane.	1)      Delivary is exclusively coplanar, currently nonplanar fields cannot be deliver.
2)      3D imaging is integral to treatment alignment.	2)      Expensive
3)      Excellent image quality.
4)      Binary collimator and helical delivary to enable highly conformal and precise treatment.
5)      Fully integrated system- easy to use.

ICRU : ICRU 83

Several days ago, our lecturer asked us to find out what ICRU stands for and what does it means. Then, we were given a task on ICRU 83. So today, we would like to share with you some informations about ICRU and focus on ICRU 83.

What is ICRU ?

ICRU stands for International Commission on Radiation Units and Measurements. it has principal objective on the development of internationally acceptable recommendations regarding :

1. Quantities and units of radiation and radioactivity.
2. Procedures that is suitable for the measurements and applications of these quantities in clinical radiology and radiobiology.
3. physical data needed in the application of these procedures, the use of which tends to assure uniformity in reporting.

source : google

ICRU 83

ICRU 83 : Prescribing, Recording and Reporting Photon-Beam Intensity-Modulated Radiation Therapy (IMRT)

source : google

This ICRU Report are closely related to the previous ICRU Reports 50, 62,71 &78.
It emphasize on :

1. Gross Tumour Volume (GTV)
2. Clinical Target Volume (CTV)
3. Planning Target Volume (PTV)
4. Organ at Risk (OAR)
5. Planning organ-at-risk Volume (PRV)
6. Internal Target Volume (ITV)
7. Treated Volume (TV)
8. Remaining Volume at Risk (RVR) 

As a summary, this report discusses on :

1. For malignant tumour, CTV should always be associated with the GTV .
2. the use of dose-volume histograms(DVHs) for the specification of absorbed dose is inherent to the treatment modality
3. Describes optimization techniques, which can control the compromise of absorbed-dose homogeneity in the PTV with dose reduction in the PRV.
4. Designate the sets of treatment goals as the "planning aims" to differentiate them from the "prescription" .
5. Recommendations concerning absorbed-dose reporting evolve from previous ICRU recommendations while attempting to retain a relationship with the previous recommendations.
6. Recommends that the median absorbed dose, specified by D50% should be reported as it is considered to correspond best with the previously defined dose at the ICRU references point.
7. Recommends that in low gradient situation , define as a relative change of absorbed dose that is less than 20% per cm in any direction, that 85% of target volume absorbed dose samples should be within 5%

More info on ICRU , U can visit this link below : 

download icru-83

icru 83 journal 

icru
icru 62
icru 50

icru official website 

CT SCAN : Advantages and Disadvantages

Advantages of CT Scan

• Rapid acquisition of images.
• A wealth of of clear and specific information.
• A view of a large portion of the body. 
• Better detail compared with ultrasonography.
• Relatively compared with MRI scanning.
• Most system can be scanned. (eg : Brain to Leg) 

Disadvantages of CT Scan

•  Required breath holding where patient cannot manage.
• Artefact is common. (Eg : metal clips)
• CT Scan of the brain can be affected by bone nearby.
• High doses of radiation are involved in CT Scanning - chest CT scan is equivalent to 350 chest x-rays ; CT abdomen to 400 chest x-rays and CT pulmonary angiography 750 chest x-rays.
• There is also a risk of childhood cancer and leukemia in mothers who have imaging during pregnancy. However, some of the studies are small and difficult to interpret due to confounding factors. Imaging to aid potentially fatal conditions during pregnancy should not be withheld.