Treatment planning Ch. 10

  1. The most common of all intracranial malignancies is
    metastatic disease

    *remember to be careful how this question is asked... If it asks what is the most common PRIMARY brain tumor the answer would be GLIOMAS
  2. A stereotactic frame is intended for use in(single/multiple) fraction treatments.
    single fraction

    • Image Upload 1
    • Leksell stereotactic frame
  3. When adjacent fields are matched, it is more important to
    Match the fields precisely during a GIVEN treatment than reproduce the LOCATION

    *In other words, the fields might move slighty but they always need to be MATCHED PRECISELY
  4. To appreciate the position of the eyes relative to the beam
    A radiopaque marker is placed on the lateral canthus of each eye

    Image Upload 2
  5. Dose heterogeneities within the brain when parallel opposed fields are used
    are increased when lower energy photon beam is used

    *However, when higher energy beams are used then the lateral aspect of the brain is compromised
  6. The vertex field is difficult to treat because
    there is no way to obtain a port film

    *couch is kicked 90 degree(along with gantry)make it possible to have beam vertex(come in through top of head) but then there is no place to put port film(and flat panel can not be raised into table or in the middle of the body)
  7. To minimize the beam divergence into the eye on the opposite side, when treating a brain through opposed lateral fields
    the beam is centered on the lateral canthus of the eye

    *Block for anterior portion of eye, beam anlged posteriorly
  8. When the entire spinal axis must be treated, the patient's posterior surface should be as flat as possible in order to
    make the dose more uniform
  9. Lateral brain fields and a posterior spinal field are matched by
    • rotating the collimator and rotating  the couch when treating lateral fields
    • Image Upload 3

    *Image Upload 4
  10. To trace the tumor volume onto a lateral sim film, a sagittally reconstructed CT or MRI image of the patient's head
    CANNOT be used because they may not represent the midsaggital plane
  11. When a 3-field technique(vertex and opposed lateral) is used to treat pituitary lesion
    Wedges are used in the lateral fields
  12. When  6-MV photon beam is used in a 180 degree arc technique to treat a pituitary lesion
    a wedge is used a reversed midway in the arc
  13. The disadvantage of a vertex field is that
    it often exits in the pharynx and spinal cord

    *also inability to take port film
  14. Field gaps are often shifted 2-3 times during a course of treatment to
    • to reduce the risk of overdosage in the spinal cord
    • Image Upload 5

    *Clinical Endocrine Oncology edited by Ian D. Hay, John A. H. Wass
  15. When the lateral cranial fields are treated and the couch is turned to facilitate the gap with the posterior spinal field then the SSD becomes(shorter/longer)in the ________spine segment when both lateral fields are treated.
    • the cervical spine section SSD becomes SHORTER
    • *
    • Image Upload 6

    *Leibel and Phillips Textbook of Radiation Oncology: Expert Consult By Richard Hoppe, Theodore L. Phillips, Mack Roach III
  16. The typical CSI setup, to avoid having the caudal margin of the lateral brain fields diverge into the cephalad aspect of the posterior spinal fields, the foot of the couch is turned
    In towards the collimator

    Image Upload 7
  17. To determine depth of the spinal cord
    Measure the depth on a lateral radiograph with a lead wire over spine
  18. Of all childhood tumors, medullablastoma represents____%
  19. Symptoms or myelopathy are (reversible/irreversible)
Card Set
Treatment planning Ch. 10
Treatment planning Ch. 10(Bentel)