Treatment Planning Test 3(Most important things to learn)
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The abdomen is defined as ....?
the portion of the body that lies between the thorax and the pelvis and contains the peritoneal cavity
Generally speaking, the kidney tolerance to irradiation in the adult is _____cGy in ______cGy per fxs?
2000 cGy in 180-200 cGy per fraction
The most common site of pancreatic tumors is the _____of the pancreas?
Wilms' tumor is a tumor originating in the ____?
Neuroblastoma is a tumor most often originating in the____________?
sympathetic nervous system
When pelvic irradiation is delivered in an obese patient in the supine position, the concern is that....?
Uncertainty of dose due to variations in patient thickness would be caused when attempts were made to eliminate skin folds
To reduce the volume of small bowel within the treatment field, the patient's position should be...?
prone on a belly board
The primary purpose of a testicular shield is to...?
reduce the amount of internal scattered dose in the testes
Of gyn tumors treated with XRT, the most common is..?
squamous cell carcinoma of the cervix
The depth of the inguinal lymph nodes can vary from _____-______cm depending on the patient's size.
(remember it is the 2 worst ages for your kids!)
The 10 year survival for patient's with all stages of Hodgkin's disease is approximately ____%?
The patient position for treatment of a mantle field in Hodgkin's disease is usually...?
supine, chin extended, arms raised above head
It is important to align the patient with the saggital laser alignment line every day becuase
If it is not, then the field is rotated with respect to the patient's body
Tattoos made on the patient's skin indicating irradiated areas can ....
- shift due to:
- weight changes
The advantage of intraoperative radiation therapy is that it provides....?
- 1)superior normal tissue sparing
- 2) improved precision
High and Low dose total body irradiation is used when...?
- 1)preparing patients for a bone marrow transplant
- 2)treatment of CHRONIC LYMPHOCYTIC LEUKEMIA (CLL)
120-200 cGy/fx 1200 cGy
The most common position for patients receiving total skin electron irradiation is...?
Standing with legs spread and arms raised
The main goal of radiation therapy in patients with bone mets is..?
- Reduce pain
- Prevent fractures
In patients treated for a spinal cord compression, the treatment field should include...?
approximately 2 vertebral bodies in each direction beyond the demonstrable disease
- 1) right lobe of liver
- 2)left lobe of liver
- 7)right kidney
- 8)left kidney
- 9)right adrenal
- 10)left adrenal
- 12)hepatic duct
- *13)common bile duct
- *14)pancreatic duct
- *15) ampulla of vater
- 17)right ureter
- 18)left ureter
What is DICOM?
The Digital Imaging and Communications in Medicine (DICOM)Standard specifies a non-proprietary data interchange protocol, digital image format, and file structure for biomedical images and image-related information.
- *SOURCE_J Am Med Inform Assoc. 1997 May-Jun; 4(3): 199–212. PMCID: PMC61235Understanding and Using DICOM, the Data Interchange Standard for
- Biomedical ImagingW. Dean Bidgood, Jr., MD, MS, Steven C. Horii, MD, Fred W. Prio
- r, PhD, and Donald E. Van Syckle
- DICOM which stands for "Digital Imaging and
- Communication in Medicine " is a document
- which defines a method of communication for the various equipment of digital medical imaging devices/softwares ("modalities").
- This standard is now in use by the majority of medical imaging hardware manufacturers.
- It represents a progress in that it makes it possible to predict the interconnection of
- various imaging modalities, through a Document of Conformity or "
- Conformance Statement " emitted
- for each machine/software following this standard.Thus, the standard makes it possible for the equipment to communicate
- remotely through a network or a media (disk or tapes ). By ensuring the compatibility of
- the equipment and by eliminating proprietary formats.
What is TD 5/5?
The dose that would likely cause 5% of an exposed population to realize an adverse later effect in 5 years following exposure
What is the most common intracranial tumor?
Metastatic disease from a primary tumor, (elsewhere in the body)[W&L]
TD 5/5:Spinal Cord?
What is an off axis point?
It is any point which is not at the CAX and t least 1 cm from the edge of the field. It is useful for determining dosage at a point in order to determine if it is being underdosed or overdosed. The off axis point is used to determine the off axis ratio.(OAR)
What is the OAR?
The off axis ratio is defined as the ratio of the percentage depth dose at a point away from the central axis to the percentage depth dose at the central axis of the beam at the same depth.
OAR = PDD at off axis point/PDD at CAX
SOURCE: Technical Basis of Radiation Therapy: Practical Clinical Applications edited by Seymour H. Levitt, James A. Purdy, Carlos A. Perez, Philip Poortmans (pg 162)
*Gives the variation in dose across the field
Most important things to remember about CT, MRI, and PET
- 1)Computed Tomography(CT) is an imaging technique which irradiates the patient with a highly collimated polychromatic beam of energy
- from 20-140 keV.
- 2)Magnetic resonance imaging (MRI) is a technique that uses a powerful magnetic field and pulsating radio waves to create detailed images of the organs and tissues within your body.1
- 3)A CT works well for imaging bony structures while an MRI is best suited for imaging soft tissue.2
- 4)Positron Emission Tomography (PET) is a technique for imaging chemical or physiologic processes in the body.
- 5)The most commonly used PET cancer imaging agent is fluoro-2-deoxy-D-glucose.
- 6)It is used for imaging cancer because it has a chemical structure similar to glucose which
- cancer cells metabolize at a higher rate than normal cells.
- 1 http://www.mayoclinic.com/health/mri/MY00227
- 2 http://www.wdhospital.co/body.cfm?id=397
What is the TD5/5 of the salivary gland?
50 Gy [W&L]
What is a DRR?
- A digitally reconstructed radiograph is based on acquired CT information. They are images that render a beam's eye view display of the treatment field anatomy and areas of treatment interest. These images resemble conventional radiographs.
- SOURCE: W&L pg.943
What are wax covered eye shields protect..?
"corn with(con) eyelashes"
What is the dose for TBI?
1200cgy/120-200 cGY fx-
TBI fields are large:_____x_____, and a beam spoiler is used to ________. The ______are blocked.
TBI fields are large:40x40, and a beam spoiler is used to increase the dose to superficial tissues. The lungs are blocked.
Whole abdominal irradiation is used primarily to treat_____and ____cancer.
Thrombocytopenia is low_____and occurs at doses of _____?
Kidney's receive ___-_____% from scatter.
Kidney's receive 10-15% from scatter.
Which kind of block allows for a more certain % of attenuation, a transmission or full block?
What ARRT, RT.(T) stand for?
American Registry of Radiologic Technologists, Registered Technologist(Radiation Therapy)
Can we deliver high doses to the abdomen?
NO, due to the tolerance of organs in the vicinity of the treatment field.
The prognosis for pancreatic cancer is good. True or False?
False-the prognosis is dismal
A single field PA spine treatment
with 1800 cGy in 10 fractions. The field
size is 20x20 and the depth of the spinal cord is 5 cm. Calculate the MUs for
each fraction. (Use class handout for #s)
180/(.879)(1.055)=194.1= 194 MU
- D=5 f.s.=20x20
- dose=180 cGy
- of 5, f.s=20x20) =87.9(.879)
Calculate MUs for a 3-field pancreas. The
gantry angles are as follows: AP(0), Right Lateral(270), Left Lateral(90). The
lateral fields have 15 degree wedges(WF=.912). The AP field is weighted 60%,The Llat is weighted 20%. The Rlat is weighted 20%. Each fraction receives 200
cGy. The AP field has an SSD of 95 and
has a field size of 10x10, The right lat has an SSD=85 and a field size of 5x5,
The left lat SSD=92 and field size of 7x9. The tray factor is .934.
- AP field
- dose= 200x .60=120
- tray factor= .934
- NO WEDGE
- TMR(depth = 5,f.s.=10x10)= .928
40/(.602)(.980)(.912)(.934)=79.6= 80 MU
- RT LAT field
- dose=200 x .20=40
- wedge factor=.912
- tray factor=.934
- TMR(d=15, f.s.=5x5)=.602
(Right Lat Field)
40/(.829)(1.01)(.912)(.934)=56.08= 56 MU
- Left Lat Field
- f.s.=7x9 2(2x9)/7+9=7.9= 8x8(E sq)
- dose= 200 x .20= 40wedge factor= .912
- tray factor= .934
- TMR(fs=8x8, d=8) = .829
- OF=(fs=8x8)= 1.01
(Left Lat Field)
- TMR OF
- Depth of
- 5x5=.809 .980
- 6x6=.816 .990
- 7x7=.822 1.00
- 8x8=.829 1.01
- 9x9=.835 1.02
- 10x10= .842 1.032
(each step of TMR)
(each step of OF)
Calculate the the MUs for POP wedged obliques with Gantry angles of 290 and 170. The dose per fraction is 180 cGy. The RAO is weighted
60% and the LPO is weighted 40%. The RAO has a field size of 10x10 and an SSD
of 95. The LPO has a field size of 15x15 and an SSD of 90. Wedge factors are:
15 wedge= .934, 30 wedge= .920, 45 wedge= .912, 60 wedge= .901, The tray factor =.788
- Finding wedge angle:
- Hinge angle = 290-170=120
- wedge angle= 180-120(hinge angle)/2=30
- So we use the 30 wedge=.920
- Dose=180 x .60=108
- TMR(d=5, f.s=10x10)=.928
- WF(30 wedge)=.920
72/(.804)(1.071)(.920)(.788)=115.3= 115 MU LPO Field
- 156 MU RAO field
- Dose =180 x .40=72
- TMR(d=10. f.s.=15x15)=.804
- WF(30 wedge)=.920
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