Transcript Slackers Radiation Oncology Fact Stack

Slackers Radiation Oncology Fact
Stack
Mike Ori
Disclaimer
• These represent my understanding of the subject
and have not been vetted or reviewed by faculty.
Use at your own peril.
• I can’t type so below are common missing letters
you may need to supply
• erl
• I didn’t use greek letters because they are a pain
to cut and paste in.
• What are the five stages of cancer diagnosis
and therapy
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Screening
Diagnosis
Staging
Therapy
Follow-up
• What is the most successful use of radiology
for screening
• Mammography
• What is one area where radiology techniques
have not been successful in screening
• Ultrasound screening of the prostate
• Explain the role of contrast kinetics in MRI
• Wash-in and wash-out times help differentiate
benign and malignant
• Normal tissue tends to have slower wash-in
and wash-out kinetics than tumor.
• What is a sestamibi scan
• Use of 99mTc-sestamibi to identify areas of
angiogenesis and tumor.
• Compare sestamibi scans to MRI
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Uses ionizing radiation
Not as available as MR
Faster
Cheaper
• What is octreotide scanning
• A somatostatin-like compound that can
interact wit somatostatin receptors on the
surface of cells. Some types of cancer (neuroendocrine mostly) are notable for such
receptors.
• Compare octreotide scanning to MRI/CT
• Sometimes shows mets when other
modalities don’t
• Poorer anatomic localization than other
modalities
• Can be used to indicate treatment with
yttrium 90-octrotide
• What is MRI spectroscopy
• The use of the MRI machine to perform
spectroscopic analysis of tissue to look for
marker compounds that indicate growth or
abnormal metabolism.
• Rarely used capability due to reimbursement
• What radiographic techniques can be used to
stage cancer
• CT
– The workhorse
• PET
– Especially when combine with CT
• MRI
– Increasing in use. Dominant in some areas
• Radionucleotide bone scans
– For skeletal mets
• Ultrasound
– Rarely
• How does PET scanning work
• Fluoro-D-Glucose is injected into the body.
Hot spots appear in any tissue actively
metabolizing glucose. This includes tumors
but also inflammed and regnerating areas.
• For what cancers is PET scanning approved
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Non-small cell lung cancer
Colorectal cancer
Melanoma
Lymphoma
Head and neck cancer (not thyroid or CNS)
Esophageal
Cervical
Breast monitoring and restaging
Thyroid restaging
• Explain radionucleotide bone scans
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99mTC-methylene
diphosphonate is injected
into the body and incorporated into
hydroxyapatite in the bone by osteoblasts.
Thus areas of bone growth are visible.
• Needs follow-up anatomic imaging
• What is the role of radioactive iodine in the
treatment of thyroid neoplasia
• RAI is used post surgery to destroy remaining
thyroid tissue.
• What is image guided therapy
• The use of radiology techniques in the
performance of treatment
• Intra arterial chemo catheter
• Embolization
– Simple
– Chemo
• Alcohol ablation/cryotherapy
• RF ablation
• Focused ultrasound
• What is RECIST
• Response evaluation criteria in solid tumors is
an heuristic used to quantify the change in a
solid tumor over time.
– CR = complete response
– PR = partial response, 30% decrease
– PD = progressive disease, 20% increase
– SD = stable disease
• What type of radiation is used in radiotherapy
• Ionizing radiation such as x-rays, gamma rays,
electrons, protons
• What device produces the radiation used
most predominantly in the US
• The linear accelerator or linac
• How many linacs can fit on the head of a pin?
• None.
• Differentiate teletherapy from brachytherapy
• Teletherapy uses a radiation beam generated
by source remote to the patient. This is your
classic sci-fi death ray.
• Brachytherapy places an intrinsically
radioactive substance in close approximation
to the target tissue.
• What is linear energy transfer
• The amount of energy transferred per unit
length of track
• What is the bragg peak
• The point of maximum energy release along a
track.
• Differentiate directly ionizing from indirectly
ionizing radiation
• Directly ionizing radiation has sufficient
energy to directly disrupt the atomic structure
of DNA. Protons.
• Indirectly ionizing radiation creates free
radicals that damage DNA. X-rays.
• What is the primary method of cell killing
caused by radiation
• Double stand DNA breaks that are improperly
repaired.
• Why are oxygenated cells more susceptible to
radiation than are hypoxic cells
• The ionizing process generates free electrons
which are taken up by oxygen to generate
oxygen radicals which attack DNA. In hypoxic
conditions, less oxygen is available to generate
free radicals.
• Which phase of the cell cycle is sensitive to
radiation? Which is resistant?
• G1/M are sensitive
• S is resistant
• What factors influence the survival of a
radiated cell?
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Position in the mitotic cycle
Molecular checkpoint activation
Hypoxia
Repopulation
• Describe how a 50Gy dose of radiation is
delivered to patients
• The dose is usually fractionated into multiple
doses of ~2Gy. These are then delivered over
the course of many days until the total
prescription is delivered.
• Describe image modulated radiation therapy
• IMRT uses a multi-leaf collimator shape a
radiation beam to limit exposure of adjacent
structures.
• List several benign diseases for which
radiotherapy can be prescribed
• Omas of the CNS
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Schwanoma
Chordoma
Meningioma
Pituitary adenoma
AVM
Trigeminal neuralgia
Pterygium
Heterotopic ossification
Trigeminal neuralgia