slackers radiation oncology fact stack mike ori. disclaimer these represent my understanding of the...
Post on 15-Jan-2016
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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
• e r l• 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
• 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
• 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 (neuro-endocrine 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
• 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
• 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?
• 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– Schwanoma– Chordoma– Meningioma– Pituitary adenoma
• AVM• Trigeminal neuralgia• Pterygium• Heterotopic ossification• Trigeminal neuralgia