ozgehan onay radiotheraphy technician estro school field shaping matching
TRANSCRIPT
![Page 1: Ozgehan onay radiotheraphy technician estro school field shaping matching](https://reader030.vdocuments.net/reader030/viewer/2022032503/55c017dcbb61eb685e8b46d1/html5/thumbnails/1.jpg)
![Page 2: Ozgehan onay radiotheraphy technician estro school field shaping matching](https://reader030.vdocuments.net/reader030/viewer/2022032503/55c017dcbb61eb685e8b46d1/html5/thumbnails/2.jpg)
MSc. Phy. Özgehan ONAY
Cerrahpasa Medical Faculty 8-9 May 2015, İSTANBUL
SIDE EFFECTS Nasopharyngeal Carcinoma
in Radiotherapy and Patient Care
Issues in Field Shaping and
Field Matching
![Page 3: Ozgehan onay radiotheraphy technician estro school field shaping matching](https://reader030.vdocuments.net/reader030/viewer/2022032503/55c017dcbb61eb685e8b46d1/html5/thumbnails/3.jpg)
Goal of Field Shaping
• Basic goal of radiotherapy treatment is the irradiation of a target volume while minimizing the amount of radiation absorbed in healthy tissue.
• Shaping the beam is an important way of minimizing the absorbed dose in healthy tissue and critical structures.
![Page 4: Ozgehan onay radiotheraphy technician estro school field shaping matching](https://reader030.vdocuments.net/reader030/viewer/2022032503/55c017dcbb61eb685e8b46d1/html5/thumbnails/4.jpg)
Field Shaping in NSF
• 1950 conformal radiotheraphy -shielding blocks
• 1960-1969 pair of lead cylinders suspended by gravity defined a different field aperture at each orientation.
• 1959 patent for a Multileaf Collimator (MLC)
• 1960 custom blocks
• 1985 MLC required features of such a device
• 1988 Inverse Planning
• 1992 "micro-size" MLC with 40 non-focused leaves projecting to a width of just 1.7 mm at isocentre has also been engineered for stereotactic linac-based radiotherapy
• 1993 Studies have shown that the MLC can be an
effective block replacement and also save time
![Page 5: Ozgehan onay radiotheraphy technician estro school field shaping matching](https://reader030.vdocuments.net/reader030/viewer/2022032503/55c017dcbb61eb685e8b46d1/html5/thumbnails/5.jpg)
Field Blocking and Shaping devices
Shielding blocks.
Custom blocks.
Asymmetric Collimator.
Multileaf Collimators.
![Page 6: Ozgehan onay radiotheraphy technician estro school field shaping matching](https://reader030.vdocuments.net/reader030/viewer/2022032503/55c017dcbb61eb685e8b46d1/html5/thumbnails/6.jpg)
Shielding Blocks
• Common use
• Provide by concern
• Determine shape and size before theratment
• Density 11,36 g/cm3, melting point 327 0C
• Geometrical and dosimetrical useless
• Divergent problem
![Page 7: Ozgehan onay radiotheraphy technician estro school field shaping matching](https://reader030.vdocuments.net/reader030/viewer/2022032503/55c017dcbb61eb685e8b46d1/html5/thumbnails/7.jpg)
Shielding Blocks
• As far as possible eliminate the radiation dose at some special parts of zone at which beam is directed.
• Shielding is achieved more easily with high energy radiation than low energy due to low scattering in high energies
![Page 8: Ozgehan onay radiotheraphy technician estro school field shaping matching](https://reader030.vdocuments.net/reader030/viewer/2022032503/55c017dcbb61eb685e8b46d1/html5/thumbnails/8.jpg)
Shielding Blocks
Beam Quality
• 1.0 mm Al HVL
• 2.0 mm Al HVL
• 3.0 mm Al HVL
• 1.0 mm Cu HVL
• 2.0 mm Cu HVL
• 3.0 mm Cu HVL
• 137 Cs
• 60Co
• 4 MV
• 6 MV
• 10 MV
• 25 MV
Pb Thickness
• 0.2 cm
• 0.3 cm
• 0.4 cm
• 1 cm
• 2 cm
• 2.5 cm
• 3 cm
• 5 cm
• 6 cm
• 6.5 mm
• 7 cm
• 7 cm
A primary beam transmission of 5% through the block is considered acceptable
![Page 9: Ozgehan onay radiotheraphy technician estro school field shaping matching](https://reader030.vdocuments.net/reader030/viewer/2022032503/55c017dcbb61eb685e8b46d1/html5/thumbnails/9.jpg)
Custom Blocks
• LIPOWITZ metal
• Commercial name Cerroband (% 50 Bismuth, % 26,7 Lead, % 13,3 Stannic, % 10 Cadmium)
• Density 9.4 gr/cm3
• It melts at 70 c and can be easily cast to any shape
• At room temperature it is harder than lead
• In Megavoltage range of photon beams the most commonly used thickness is 7.5 cm
• Divergent adjustment
Bi
Pb
Sn
Cd
![Page 10: Ozgehan onay radiotheraphy technician estro school field shaping matching](https://reader030.vdocuments.net/reader030/viewer/2022032503/55c017dcbb61eb685e8b46d1/html5/thumbnails/10.jpg)
Custom Blocks
Cm Cm
![Page 11: Ozgehan onay radiotheraphy technician estro school field shaping matching](https://reader030.vdocuments.net/reader030/viewer/2022032503/55c017dcbb61eb685e8b46d1/html5/thumbnails/11.jpg)
MLC
• Made of Tungsten
• Density 17-18.5 gr/cm3
• Leaf transmission %2,
• Interleaf transmission %3,
• Jaw transmission %1
![Page 12: Ozgehan onay radiotheraphy technician estro school field shaping matching](https://reader030.vdocuments.net/reader030/viewer/2022032503/55c017dcbb61eb685e8b46d1/html5/thumbnails/12.jpg)
![Page 13: Ozgehan onay radiotheraphy technician estro school field shaping matching](https://reader030.vdocuments.net/reader030/viewer/2022032503/55c017dcbb61eb685e8b46d1/html5/thumbnails/13.jpg)
![Page 14: Ozgehan onay radiotheraphy technician estro school field shaping matching](https://reader030.vdocuments.net/reader030/viewer/2022032503/55c017dcbb61eb685e8b46d1/html5/thumbnails/14.jpg)
MLC
• Reducing productive effort
• Easy to use
• Reliability
• Financial gain
• Time consuming
• Data transfer
• Methodical and safe work space
• Aplicability of high level treatment techniques
• Tangent to the field edge
![Page 15: Ozgehan onay radiotheraphy technician estro school field shaping matching](https://reader030.vdocuments.net/reader030/viewer/2022032503/55c017dcbb61eb685e8b46d1/html5/thumbnails/15.jpg)
Adjacent Fields
• X-ray beam is DIVERGENT
• Adjacent beams will meet at a region because of divergent
• Divergence causes hot spots (overdose) at depths and cold areas (underdose) near the surface
• Dose HETROGENIETY
• A field-matching methods must be verified by actual isodose distributions before it is adopted for general clinical use.
• For NSF treatment you must choose the more sophisticated and accurate methods.
• Management of the clinical case.
![Page 16: Ozgehan onay radiotheraphy technician estro school field shaping matching](https://reader030.vdocuments.net/reader030/viewer/2022032503/55c017dcbb61eb685e8b46d1/html5/thumbnails/16.jpg)
Adjacent Fields
• Double junction
• Dynamic junction
• GAP
• Divergent adjustment method
• Asimmetric collimator- half beam method
![Page 17: Ozgehan onay radiotheraphy technician estro school field shaping matching](https://reader030.vdocuments.net/reader030/viewer/2022032503/55c017dcbb61eb685e8b46d1/html5/thumbnails/17.jpg)
Double Junction
![Page 18: Ozgehan onay radiotheraphy technician estro school field shaping matching](https://reader030.vdocuments.net/reader030/viewer/2022032503/55c017dcbb61eb685e8b46d1/html5/thumbnails/18.jpg)
Dynamic Junction
![Page 19: Ozgehan onay radiotheraphy technician estro school field shaping matching](https://reader030.vdocuments.net/reader030/viewer/2022032503/55c017dcbb61eb685e8b46d1/html5/thumbnails/19.jpg)
• Fields on the same surface.
Fields separated at the skin surface. The junction point is at
a depth where dose is uniform across the junction
• Fields on orthogonal surfaces
Two principal methods:
1- Split field method (Half-beam block).
2- Collimator and table rotation.
Adjacent Fields - Divergent Adjustment Method
![Page 20: Ozgehan onay radiotheraphy technician estro school field shaping matching](https://reader030.vdocuments.net/reader030/viewer/2022032503/55c017dcbb61eb685e8b46d1/html5/thumbnails/20.jpg)
Adjacent Fields - Divergent Adjustment Method
![Page 21: Ozgehan onay radiotheraphy technician estro school field shaping matching](https://reader030.vdocuments.net/reader030/viewer/2022032503/55c017dcbb61eb685e8b46d1/html5/thumbnails/21.jpg)
Collimator Angle Couch Rotation
Adjacent Fields - Divergent Adjustment Method
![Page 22: Ozgehan onay radiotheraphy technician estro school field shaping matching](https://reader030.vdocuments.net/reader030/viewer/2022032503/55c017dcbb61eb685e8b46d1/html5/thumbnails/22.jpg)
Adjacent Fields - GAP
• An arrangement in which the central axes of the adjacent fields are orthogonal • A geometrical method of field separation with
S=1/2 L ( d/SSD) d is the depth of field junction
![Page 23: Ozgehan onay radiotheraphy technician estro school field shaping matching](https://reader030.vdocuments.net/reader030/viewer/2022032503/55c017dcbb61eb685e8b46d1/html5/thumbnails/23.jpg)
Adjacent Fields - GAP
• Electron- photon combination field. • 3 phase • Sparing ms
![Page 24: Ozgehan onay radiotheraphy technician estro school field shaping matching](https://reader030.vdocuments.net/reader030/viewer/2022032503/55c017dcbb61eb685e8b46d1/html5/thumbnails/24.jpg)
Asymmetric Collimator
• Conventional collimator jaws are used for shaping a rectangular treatment field;
but, as usually treatment volume is not rectangular, additional shaping is required.
• Asymmetric fields are sometimes used to block off a part of the field without changing the position of the isocenter.
• Although blocking is often used to generate irregular field shapes, rectangular
blocking can be easily done by independently movable collimators, or jaws. This feature is very convenient when matching fields or beam splitting.
• The beam is blocked off at the central axis to remove divergence. Whereas half-beam
blocks have been used as beam splitters in the past, this can now be done simply by moving in the independent jaws.
• Most modern machines are equipped with independently movable jaws. Some machines have one independent jaw, others have two independent pairs, and some have all four jaws as independent.
• Operationally, the independent jaw option is interlocked to avoid errors in the setting
of symmetric fields, in which case the opposite jaws open or close symmetrically
![Page 25: Ozgehan onay radiotheraphy technician estro school field shaping matching](https://reader030.vdocuments.net/reader030/viewer/2022032503/55c017dcbb61eb685e8b46d1/html5/thumbnails/25.jpg)
Adjacent Fields - Half Beam Method
Half-beam blocking gives rise to tilting of the isodose curves toward the blocked edge. This effect is due to missing electron and photon scatter from the blocked part of the field into the open part of the field
![Page 26: Ozgehan onay radiotheraphy technician estro school field shaping matching](https://reader030.vdocuments.net/reader030/viewer/2022032503/55c017dcbb61eb685e8b46d1/html5/thumbnails/26.jpg)
Adjacent Fields – Asymmetric Collimators
![Page 27: Ozgehan onay radiotheraphy technician estro school field shaping matching](https://reader030.vdocuments.net/reader030/viewer/2022032503/55c017dcbb61eb685e8b46d1/html5/thumbnails/27.jpg)
Adjacent Fields - Asymmetric Jaw
![Page 28: Ozgehan onay radiotheraphy technician estro school field shaping matching](https://reader030.vdocuments.net/reader030/viewer/2022032503/55c017dcbb61eb685e8b46d1/html5/thumbnails/28.jpg)
Adjacent Fields - Asymmetric Jaw
![Page 29: Ozgehan onay radiotheraphy technician estro school field shaping matching](https://reader030.vdocuments.net/reader030/viewer/2022032503/55c017dcbb61eb685e8b46d1/html5/thumbnails/29.jpg)
Conclusion
• What we have what we can
• Clinic acceptance
• Sparing OAR is the most important key
• Improving knowledge
• Keep up with technology
• İnnovative
![Page 30: Ozgehan onay radiotheraphy technician estro school field shaping matching](https://reader030.vdocuments.net/reader030/viewer/2022032503/55c017dcbb61eb685e8b46d1/html5/thumbnails/30.jpg)
THANK YOU