MEDICAL PHYSICS ABR PART 1 QUESTIONS WITH COMPLETE ANSWERS

What is the PDD for a Co-60 beam at 10cm depth?


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55%




Flair density weighted image description (2)

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1. removes fluid signal <br>
2. CSF + water are dark




Co-60 HVL Pb


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1cm




mm Lead to shield electrons, as function of energy&nbsp;


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E (MeV) / 2&nbsp;




earths inherent magnetic field strength&nbsp;


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6.5 x 10^-5T




What is the occupational limit for 1 year?


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, 50 mSv




What is the speed of sound in bone?


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3500 m/s




Dose vs. Kerma on PDD curve:&nbsp;<br>1. what is greater when&nbsp;<br>2. what
kind of equilibrium is needed&nbsp;&nbsp;


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"1. before Dmax, KERMA &gt; Dose.&nbsp;<br>&nbsp; &nbsp; &nbsp;After
Dmax, Dose &gt; KERMA&nbsp;<br>2. Transient CPE, happens after DMAX.
At Dmax CPE exists and Dose = KERMA<br><img src=""paste-
74ec93126779b13a9cfd184b0a68d22d820b5c8e.jpg""><br>All terms for
KERMA are collisional KERMA&nbsp;<br><br><img src=""paste-
5ade8988ea3b38f975f79d6b3b4739e1e1a115fc.jpg"">"




What is the PDD for a 18X beam at a 10cm depth?


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80%

, What are the brachytherapy medical events? (5)


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1. wrong patient
2. wrong site
3. wrong nuclide
4. total dose off by 20%
5. fraction off by 50%




define accuracy in ROC terms&nbsp;


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"-fraction of cases correctly diagnosed&nbsp;<br><br><img src=""paste-
711e2b64e7f7849deb09954d9d598cf682cb7e80.jpg"">"




"What is the CT # for air?"


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-1000




What is R50?


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