Focal Spot (Actual & Effective), Field Size and Line Focus Principle | Radiology Physics Course #12

[@asnutigst2845]

KZbin need to allow more likes for this kind of lecture😁 thank you!

[@radiologytutorials]

😆 Thank you Asnu!

[@ahntrjmpr]

The value of your efforts on your channel and in this overwhelmingly interesting series cannot be understated! Thank you! Cheers from a veterinary and PhD student in the USA.

[@theexplorer7578]

please make video on physics behind memography covering the tomosynthesis along with the alignment of all component with all dimensions also plz

[@melissanations6005]

I start emphasis of basic machine operator tomorrow evening. Prepping myself. I will have to brush up on my math. I never took trig in hs though. I didn't just finish Medical Assistant and had to do basic fractions and division and multiplication for dosing. It wasn't too complicated. Wish me luck 😊

[@fazaltahir4216]

Superb explanation, thank a lot 👏

[@caiyu538]

Great lecture. Excellent teacher.

[@radiologytutorials]

Thank you Cai 🙂

[@vjdarestodream347]

Your lectures are much appreciated, trying to prepare for my part 1s. Is there a way in modulating the volume difference between your video segments and the advertisements ? Your video volume is much softer than the ads especially for the anatomy ones. If there’s a paid way to avoid advertisements that would be also great.

[@YouGottaFeelYourLine]

There’s a way. It’s called KZbin premium

[@sumathiaruleeswaran8]

admiring ur teaching skill sir. excellent teaching . tnx a ton

[@radiologytutorials]

Thanks Sumathi 😊

[@lucashuss9075]

Thank you!

[@Abkklp]

Very great explanation

[@radiologytutorials]

Glad you think so! 🙂

[@babasahebkolhal5100]

Awesome Lecture

[@radiologytutorials]

Thank you!

[@petraguse2883]

Hi Michael, thank you for the excellent tutorials! I was reading about the heat bloom effect increasing focal spot size when taking multiple exposures in quick succession. Is this ever a practical problem rather than a theoretical problem now that more practices are using DR and can rapidly take images? Thank you!

[@usamaawan4165]

Excellent

[@radiologytutorials]

Thank you Usama!

[@samals9280]

Appreciate your explanation and your face thanks alot 🙏🏻

[@radiologytutorials]

My pleasure!

[@davnoloca7138]

Well done

[@radiologytutorials]

Thank you!

[@ismailabdullahi3831]

Thank you sir

[@radiologytutorials]

I'm so glad! Thank you for your support 🥰

[@alvicdavecaballero5280]

Good day! How can you select filament size? which parameter control this? Thanks in advance

[@freedaforbearance7272]

Tomorrow is my class test and you are cute- the only two motivation have for studying. Thanks for reading this comment. 😉

[@radiologytutorials]

Haha, thanks Freeda 😅 hope the test went well!

[@jugaljames9829]

Hi if we reduce the anode angle we get a increased tube rating right ? For the same effective focal spot decreasing the anode angle increases the tube rating right( by the formula)

[@jugaljames9829]

Also if we change the anode angle does it affect the actual focal spot size? The actual focal spot depends on the filament size and not anode angle right?

[@UK_hotspot]

Yeah I also got the same question. Micheal can you please clarify? @5:59 part of the talk you are saying increased anode angle make the anode can tolarate more heat. As this question has asked, for a given effective focal spot, anode angle should decrease for enhanced tube loading right?

[@abdovitamins6331]

Nice and easy explanation, very beneficial. But I am a little bit confused about the impact of using larger anode angle on actual focal spot size as mentioned in Farr's physics( page 59) as follow: The target angle θ is the angle between the central ray of the X-ray beam and the target face. The steeper the target angle (i.e. the smaller the angle θ), the greater is the foreshortening. The target angle is generally between 7 and 20º. For a target at 18º with an effective focal spot of 1 x1 mm2 , the actual focal spot would be 3.2 x1 mm2 , whereas for a target at 12º the actual focal spot could be increased to 4.8 x 1 mm2 to produce the same effective focus spot. The tube loading in the latter tube could be increased by 50% for the same effective focal spot size. How actual focal spot size increases with a steeper angle? Any explanation please?!

[@radiologytutorials]

Thank you! Reading this comment whilst I’m out the house so don’t have Farrs on me. What they are saying in this example is in order to create the SAME effective focal spot you can have a larger actual focal spot on the smaller anode angle. Therefore, you can ‘spread out’ your bombarding electron beam over a larger area whilst maintaining the same effecting focal spot (ie no increase in geometric blurring - a whole video on this to come) this allows better heat loading in the anode as the same number of electrons are spread over a larger actual focal spot. I hope that makes sense. If the actual focal spot size remained the same the larger anode angle would create a larger effective focal spot size. This example in farrs is keeping the effective focal spot the same and changing the actual focal spot.

[@abdovitamins6331]

@@radiologytutorials thanks a lot for your response but I am afraid you miss understood me! What I mean It does not make sense that ( using a steeper angle would increase the actual focus spot size) according to what is mentioned in Farr's physics, I assume the opposite is true, using a steeper angle would decrease the actual focus spot whilest using larger angle would increase actual focus spot! Sorry for long commentsbut I am suffering understanding this point more than one year ago!

[@radiologytutorials]

I understood 👍🏼 You are exactly correct. A steeper anode angle reduces actual focal spot size. What Farrs is saying is in order to keep the same effective focal spot size we need to increase the size of the actual focal spot on steeper anode angles (can do this by changing filament size or strength of focussing cup).

[@abdovitamins6331]

@@radiologytutorials now you understand me, and I find your answer a little bit convincing but in this case, should not a larger area of the target material surface be covered by the increased size of the newly actual focus spot size? Consequently the effective focal spot size would be increased?!

[@radiologytutorials]

This is the point of the example in Farrs. Because a steeper anode angle creates a smaller effective focal spot size, we need to increase the actual focal spot size on the steep anode in order to keep the effective focal spot (between the large and small anode angles) the same.

[@DOCJS89]

increasing anode angle increases the actual focal spot size ?

[@radiologytutorials]

Yes. Ever so slightly. Think of Pythagoras’ law.

[@bharti19rajput]

M like why he is soooooo handsome m not listening just seeing him👀

[@doremonkafan]

please speech clearly i dont understand what you say