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radioactiveradley · 3 months ago

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Can you tell us anything about how CT can be used to find small foreign bodies that may not have a density massively dissimilar from the body they're lodged in? The specific example in this case: Dog is going for a CT to look for a potential cat claw tip lodged in the face that is causing repeated abscesses.

Oooh! That's an interesting one.

TL;DR: there will probably be goo around the claw. We can see goo. If there is no goo and the claw is lodged in soft tissue, the amount of radiation attenuated by the claw and the soft tissue will be distinct enough for us to see. If the claw is lodged in bone and has a similar density, we will still be able to see it, but we will have to modulate the way we read the images, which will cause no extra dose to your poor doggo!

First off, we'll look for any anomalies in the surrounding tissue. Soft tissue might fully envelop a foreign object, but we still expect to see some sort of reaction - i.e., a granuloma, which can either absorb some organic foreign bodies (very freaky! very cool! you can 'eat' splinters that get stuck under your skin!) or encyst them in a capsule-like shield to cut them off from the rest of the body.

All my pictures are gonna be of humans because I know 0 about doggy CT... sorry...

Image courtesy of radiopedia

So, in the above pic, the arrows point to a surgical clip that went walkabout in the body, and wound up encapsulated! How cool is that!

But generally speaking... If the claw is lodged in soft tissue, it will be easy to spot.

The way CT works is, we see how much radiation can penetrate through each separate point within the person/pooch who's lying in the scanner's central bore. These different penetration levels are mapped onto a scale to describe radiodensity, known as the Hounsfield scale, with '0' being water, '-1000' being air, and '+1000' typically being bone.

The gathered values are then composited using greyscale (and. a very funky process that I do NOT have time to get into here but ask me about sinogram tomography later) to create images across three dimensions, with fluid being middling grey (depending on its content), air being black, and bone being white.

So, the claw will show up clearly as a different density to soft tissue, especially if it's surrounded by oedema. It should appear significantly brighter (attenuates more radiation) while the oedema will be darker (attenuates less radiation).

However, if the claw is lodged in bone and there happens to be minimal oedema and no telltale damage to the periosteum (the membranous sheathe around the bone) ... we would have to use a funky technique called windowing!

Image courtesy of radiopedia

Here's an example of windowing, using a human head. As you can see, the 'bone window' completely blocks out all soft tissue detail in the brain, but shows a lot more detail - i.e., trabecular patterns and mastoid cells! - within the bone.

Basically, there can be almost infinite Hounsfield units, depending on what you want to look at (if you're looking at, like, titanium, we'll be talking a RIDICULOUSLY HIGH Hounsfield number!) But the human eye can only see approximately

Image courtesy of a basic bitch google search

This is where windowing comes in! We can choose a certain point within the Hounsfield scale at which to generate a new image, focusing on one particular type of material. This is what makes CT so versatile!

If the claw is a subtly different density to the bone, it may not show up on a regular CT image. But by using a 'bony window' that selects a span of Hounsfield units to look at, right up towards the +1000 end of the scale, we can focus on the bone in far more detail, cutting out all extraneous soft tissue. This should give us a good idea of what's going on!

As a fun extra fact - windowing will not up the radiation dose to your poor pooch in any way. In CT, all we need to do is take a single 'picture', which compiles all the radiodensity info about our patient (be they bipedal or otherwise). We can then play around in 'post-production', so to speak, to our heart's content, producing different variations on the same image using windowing! Very nifty trick. :)

I hope that somewhere amidst my extensive rambling, I answered your question! And I hope that doggo gets better soon!

#radiography #radiology #ct scan #medblr #medicine #studyblr

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faofinn · 1 year ago

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22. Terms of Endearment/Nicknames

Part 2 to a fic we wrote for our very own MediwhumpMay! Enjoy

Part 1 | Part 2

What he didn’t miss, though, was the familiar face of one of his amazing colleagues leaning over him. “Hey, Fao. Didn’t expect to see you back here so soon, thought we sent you home? Don’t worry, we’ve got you now. Only the best for one of our own. I’ve got some pain relief for you here - oxy, don’t panic, I know what you can’t have - because that paracetamol isn’t going to be doing a lot for you, I’ll bet. Then we’ll get you checked out, get you to CT, and go from there. Sound like a plan?”

He sighed in relief. “Yeah, thanks.”

There was a moment of quiet, the nurses' conversations stopping. "For the love of God, please tell me this isn't Fao."

Fao sighed. “I wish it wasn’t?”

"Fuck this. I'm done." Finn muttered. "I'm done, I've had enough of this shift. I'm done."

“Finn!” Fao called out, but it wasn’t like he could go after his brother. Fuck’s sake.

He took a moment outside the bay to compose himself, swearing under his breath at every deity he knew. With a heavy sigh, he returned to Fao's side.

"You know when I call you dickhead and that's just your nickname? I bloody mean it this time." He squeezed Fao's hand, stretching to press a kiss to his forehead, brushing the damp hair away. "You're gonna be okay, yeah? I promise."

Fao managed a weak smile, still soaked to the skin and freezing cold. “Nicknames ‘ave gotta come from somewhere.”

"You don't need to live up to them, though."

“Mm, sometimes. Not my fault.”

"I'm sure. Where's the pain at the moment? Still bad?"

“Mm. Getting better?”

"That's good. Did you pass out?"

“No, don’t think so.”

"You sure? You've got a bruise coming up on your forehead, and you're talking like you're concussed."

“Pretty sure I hit my head, but I don’t remember blacking out. Feel concussed.”

"You're gonna be." He sighed. "I can't treat, you know that. The cons is coming, he won't be long."

“Yeah. Is nice jus’ having you.”

"I'll call mum in a sec, too. She can come and be with you." He paused. "You feel absolutely frozen. Have we got a temp yet? Not reading? Why didn't anyone say? Can someone get the bear hugger, please?"

“Mum’s gonna kill me.” He mumbled, as they set up the bear hugger to try and get some warmth back into Fao. It worked, and he definitely felt more comfortable with the warm air on him.

"I don't blame her."

“Wasn’t my fault.” He protested.

"I know."

He shifted uncomfortably, feeling suddenly overwhelmed. “‘M sorry.”

"Hey, hey, no. No sorry."

“Mm, still.”

"Just hold on for me."

“Yeah. The person I hit?”

"What about them?"

“They okay?”

"I'm sure they will be."

“Find out?”

"You're my priority."

“Please? ’m fine.”

"No, Fao. You're the priority."

He huffed. “Fine. When’s CT? I want to sit up.”

"As soon as we can."

“Ugh.”

"Don't ugh me."

“Can if I want to.”

"I'll tell mum." Finn threatened.

“She’ll be on my side, ‘m hurt.”

"She won't."

“Might.”

Finn softened. "Do you want me to get Hars?"

“Shit. I was supposed to be home hours ago.”

"Yeah, he'll be worried sick."

“I left late too. Can I call him?”

"You'll have to use my phone."

Fao realised then he didn’t know where his was. Probably still in his car. Hars would be going mad. “Yeah, I can do that.”

Finn dug round in his pockets, finally finding his phone. Harrison had already messaged him, and Finn said a silent apology to the other man as he rang, passing the phone to Fao. He balanced it by the blocks, loud enough for him to hear.

Fao practically held his breath as it rang, waiting for Harrison to pick up, probably crazy with worry.

“Hars? It’s me.” Fao got out, as he heard it pick up.

"Where are you? What's going on? Why's Finn ringing me? Are you okay?" His voice wavered. "Please tell me you're okay."

“‘M okay, ‘m okay. Finn’s with me. I, uh, I crashed the car, I’m in ED.”

Harrison was silent, the phone failing from his hand. He'd known something was wrong, he'd just felt it, and he was right. This wasn't fair.

Fao heard the phone clatter, and he winced. “Hars? Tomcat?”

Fao's voice snapped him back to reality. "I'm on my way. I'll be as quick as I can."

“‘M okay, I swear. A bit concussed but…”

He swallowed past the lump in his throat. "You're alive, we can deal with anything else."

“Yeah. Waiting on CT now, but not so bad. Drive safe?”

"I will. Do you need anything?" He'd already grabbed his Eeyore from the bed.

Even concussed, Fao knew he wasn’t getting discharged that evening. “Uh, clothes and toiletries?”

"Yeah, I've got the hospital bag."

“That’s all I need. That and you.”

"I won't be long, promise." He said, fighting with the keys to lock the door.

“Don’t rush, be safe.” He mumbled. “Weather is shit.”

"Yeah, yeah, I'll be careful."

“Thank you. Love you.”

"Love you too, Wolfie."

“Sorry I didn’t call sooner.”

"It's okay, it's okay. You called me."

“Always.”

He turned the keys in the ignition. "Thank you."

“I’ll let you drive, yeah?”

"I've got you on speaker, but if you need to go."

“Nothin’ is happening quick.” Fao grumbled.

"We're doing our best." Finn shot back.

Fao shot him a look. “Shit service here.”

"Don't be mean to us." Harrison managed to laugh down the phone.

Fao managed a grin. “‘Cause you’re not working.”

"Oh, is that why?"

“Yeah.” He mumbled, fidgeting with his other foot, still uncomfortable.

"Be nice to Finn."

“I am really. He’s good.”

"He's doing surprisingly well." Finn called to Harrison. "I'm not in charge or treating, but I'm gonna ultrasound your abdo while we wait. I'm not having anything happen because of the delays."

“Mm, ‘Kay.” He mumbled, knowing full well he didn’t have a choice. He just wanted this all to be over, or at least the scan done so he could sit up and get out of the blocks. It was so uncomfortable and he couldn’t stand staring at the ceiling.

"You're doing really well." Finn praised gently. "I know it's shit."

“Yeah.”

"Let me know if it hurts."

“Mm. Is not good.”

"No? It's hurting?"

“A bit.” He admitted. The painkillers he’d had had helped, but it was still painful. Everything was.

"When I'm scanning? Or just your leg?"

“Both? It’s sore.”

"Alright, I'm sorry." He said softly. "Can we get some more pain medication please?"

“Thanks.” Fao mumbled, feeling pathetic.

Finn hummed, distracted. "You're gonna be okay."

Fao frowned at him. “‘M fine.”

"Yeah, exactly."

“Consultant soon?”

"Yeah, he's on his way."

“Okay.”

Finn looked past the screen to the nurse. "Can you just chase them for me? Did we have an estimate for gensurg or ortho?"

Fao whined. “Gensurg? No.”

"Uh, I'm not sure."

"Page them again. Tell them they've got two fucking traumas waiting." He grumbled, unlike Finn.

“Finn.” Fao reached up for his brother.

"What? Lie still, Fao, I'm nearly done."

“Gensurg? Talk to me.”

"Just give me a minute. Try lie still."

Fao made a frustrated noise. It was late, he was exhausted and sore, and now his brother wouldn’t tell him what was going on. It wasn’t fair.

"Just a minute." He repeated. "Nearly there."

The pain meds they’d given him were starting to kick in a bit now, serving mostly just to make him spaced. It was still uncomfortable where Finn was pressing, but the pain in his leg was more bearable. He wanted to see what was going on, but he couldn’t, and trying to look around just made him dizzy.

“Fine.”

Finn took a few more minutes, struggling to see what he wanted. He was convinced there was a lac, but it didn't seem enough to rush to surgery. That, and his pressure was maintaining. He gave a heavy sigh.

"Can we get a space in x-ray?" He asked the nurse, shooting them a smile before moving back to Fao. "Hey, dickhead."

The nurse nodded. “Of course, I’ll speak to them. I just chased CT, they said there was just one more before him.”

Fao looked up at his brother. “Finished poking me now?”

"Reasonably."

“And? What was the scan like?”

He sighed. "You've got free fluid in your abdomen. I don't know if you'll need surgery for that."

“Fuck, no.”

"You're concussed. You don't have the capacity to make those decisions."

“My capacity isn’t that impaired.” He grumbled. “But I’m not refusing. I jus’ want to talk it through. All you’ve done is talk over me.”

Finn softened. "I was just trying to see what you'd done. I didn't want to miss something and tell you lies. Your leg…your leg is probably going to need surgery too, but you've got reasonable response in the foot, so it's not top of the list.

He hummed. If he was honest, he’d sort of been expecting that answer for the leg. It hadn’t looked great even in the ambulance. “I know, an’ US is hard, but… it’s shit when I can’t see anything and all ‘m getting is half the story.”

"I'm sorry for talking over you. It's hard because you know the words we throw about, and - no offense - you're not quite in the right state to understand how we're using them right now. I didn't want to say anything you'd take the wrong way and kick off."

Fao knew that really, but being able to understand it meant that it was easy to take off the wrong way regardless. He nodded, biting his lip. “Yeah. It’s hard though.”

"I know. I'm sorry."

“It’s shit.” He grumbled. “I had a shit shift, too.”

"Yeah?"

“Didn’t leave until nearly ten.” He huffed. “Wanted my bed."

"That's shit. "

“Yeah. And now I’m here.”

"Now you've got me to put up with."

He managed a smile. “Yeah.”

"Fucking shit trade."

“Exactly.”

"You're not supposed to agree with me!" Finn protested in good nature.

“Yeah, whatever.”

"Alright. How's that pain now?"

“Bit better.”

"That's good."

“Yeah.”

"Just let us know, yeah?"

“I will.” Fao murmured. “Will you find Hars when he gets here? Look after him?”

"He's an adult, Fao."

“And?”

"And I'll keep an eye out for him."

Fao reached for his brother’s hand. “Thank you.”

Finn took it, squeezing gently. "Always."

Not long after that, porters arrived to take Fao to CT. He really didn’t want to let go of Finn’s hand, but knew he didn’t have much of a choice, biting his lip as he let go. The consultant had arrived by then, and pulled Finn aside gently.

“You’ve done great, do you want to step back now, let us take over?”

Finn’s anxiety had flared and reached levels he didn’t realise he had. He folded his arms roughly, his jaw set to make him feel stronger than he felt.

"Am I going to have to leave him?"

“No, you don’t have to leave him. Just maybe take a step back from treating him. I’ll give you the rest of your shift off.”

"You'll have to find cover." Finn murmured distractedly.

“Let me worry about that.”

"Are you sure?"

“Yeah, of course. He’s your brother, we’ll cope.”

Finn sighed. "Thank you."

“Go on, you can go with him to imaging. Is Harrison coming in?”

"Can I go in with him?" He asked hopefully.

“That’ll be up to them, but you can certainly go with him and ask.”

Relief flooded his features. "Thank you."

“Go on, go and catch up to him.”

"Thank you." He said again, rushing after them.

They’d been quick to get things set up, awaiting Fao. They’d expected Finn to be there, but hadn’t seen him yet, and so carried on, chatting away to Fao as they did. He did his best to reply, slightly hazy from the meds and the exhaustion. With everything ready, they moved to transfer him across.

Fao knew full well it was going to hurt, it wasn’t exactly the first time he’d done this, and pressed his lips together, trying to think of something else. It didn’t go well, though, as halfway between the trolley and the scanner he slipped, the slide sheet under him ripping and totally giving out under him. Of course there wasn’t anything he could do about it, and everything hit the bed of the scanner with a clatter, including him. His bad leg took the brunt of it and he couldn’t help but swear, the string of profanity a mix of English and Irish. It was a burst of pain that made his vision blur and his head spin.

Finn had just pushed the door open as everything went sideways. He froze in the doorway, the nausea immediately overwhelming as it felt like the earth dropped from below his feet. He was frozen in place despite his brother’s outburst of pain, despite wanting to be by his side holding his hand and helping him. Even from across the room, he knew it was bad, beyond bad. Fao had already broken his leg, they knew that, but suddenly there was bone sticking through the skin, and blood everywhere from his pulled IV. He couldn't breathe. This wasn’t happening. This wasn’t real.

Fao hadn’t seen Finn, the angles just not quite right. What he did know was that the pain in his leg wasn’t getting any better, and there was blood everywhere where his cannula had been ripped out. The swearing stopped, trailing off as the initial shock died down. He felt sick to his stomach, though, his mouth dry with fear.

“What the fuck jus’ happened?”

"We're going to get you sorted, I'm just going to get the consultant."

Fao whined, trying to exhale slowly and control his breathing, the pain just getting worse and worse. “Fuck.”

The consultant was quick to arrive, pushing past Finn. It didn't look good, not in the slightest, and he pursed his lips. "What the fuck happened?"

“I don’t know.” Fao mumbled.

“I’m not sure.” One of the staff murmured. “Everything just slipped, I think the slide sheet went.”

"I need someone to page ortho yesterday, and I need as much fucking pain relief as we can get." He snapped.

“He’ll need a new cannula in.”

Fao could feel the blood running down his arm, tickling as it went, and he sighed. It had been a hard enough stick the first time, and now things were ten times worse. All he wanted was more pain relief.

"You're fucking kidding me." He groaned. "Let's get some penthrox then, someone get a line in.”

“I’m a really bad stick.” Fao said, doing his best to focus on the consultant.

He shot Fao a smile. "I was warned. We're going to get you sorted, I promise. We'll get that leg immobilised further, but I'm going to get you some sedation too, make it a bit easier for you."

“It’s bad, isn’t it?” Fao asked. Whilst he couldn’t see, he could certainly tell.

"It's not great."

“Fuck’s sake.”

"The surgery is going to have to be done tonight now."

“Where’s Finn?”

"He's…he's just sorting some stuff out." Fao didn’t need to know where his brother really was.

Fao frowned. That seemed fully like an excuse, but he didn’t have the thought processing power to work out what was really going on. “Hars?”

"I'm sure he's here."

“Can I see him?”

"Let me go see, yeah?"

“Thank you.” He said, forcing himself to take another deep breath and closing his eyes.

The voices outside were familiar, and more than just Finn and the nurses. He headed out to find Harrison, unsure how he was actually supposed to explain what had just happened.

Thankfully Harrison wasn’t hard to find, outside talking to a rather pale and worried looking Finn. The consultant cleared his throat, heading over to them.

“Hi, you two."

"Can you tell me what the fuck is happening?"

He managed a wry smile. “I’ll do my best. How much have you been told? Why don’t we find somewhere to sit down and talk?”

He shot a look at Finn. "He's not been much use, which means it's bad."

“It’s a lot to take in.” The consultant said carefully, glancing at Finn. “I’m sure you know earlier this evening Fao was involved in a collision on his way home from work. He’s appeared a bit concussed, and we’re concerned about a fracture to his right tib fib, as well as potential internal injuries to his abdomen.”

"It's now a fucking open fracture." Finn managed, arms folded tightly.

The consultant winced. “Yeah, which was what I was getting to. Obviously we wanted a CT, which we’re still going to get. However it looks like there was an incident during the transfer across; I wasn’t there, unfortunately, but, well, there’s no good way to really say this. Essentially he was dropped during the transfer and as a result that fracture is now open. I’m sorry.”

"What the fuck." Harrison muttered to himself. "So, the plan now? Can I go and see him before you get started? "

The consultant nodded. “Plan is get this CT done, then straight to x-ray so we get a better idea of what we’re looking at. Then ortho will be down to see him, but likely he’ll be in theatre tonight. He’s asked for you, so you can go and see him now if you’re quick.”

"Right." He nodded, chewing on his lip. "Look after Finn, will you?"

“Of course. Come on, Finn. We’ll go and get a cuppa.”

Finn nodded slowly. "O-okay."

He put a gentle hand on Finn’s arm, shepherding him away to the staff room, to let Harrison in to see his boyfriend. One of the HCAs looked up as Harrion came in, smiling. “Oh, Dr Cunningham.”

"It's just Harrison." He said softly, moving to Fao's side. "Hey, I'm here."

“Tomcat.” Fao reached out for him, relieved he was there.

"I've got you." He grabbed onto Fao's hand, gripping it tight. "You're gonna be okay."

He hummed, feeling the effects of the meds they’d topped him up with. “They fucked up.” He said, but he was grinning. “Oops.”

"You're in a better mood than Finn is."

Fao frowned. “Is he ‘kay?”

"He's stressed, saw the whole thing, so it's taking a bit of a toll on him. He's gone for coffee with the consultant."

“Oh. ‘m fine.”

"Your leg got a bit more broken."

“Hurt like fuck.”

"It's open now. "

“Oops.”

"Oops is right."

“An… an accident.”

"Yeah, but you're okay." He stroked the hair he could. "You're okay."

“Mm. Scan soon.” He mumbled, looking around. “Finn was fussin’.”

"Yeah, soon."

“Bleeding.”

"From your iv you pulled out."He said softly.

He frowned. “I didn’t pull it.” He protested. “But not jus’ that. Inside, Finn said.”

"Ah, yeah. That's why they're wanting the scan."

“Mm. Was prodding me.”

"He's a dick, isn't he?"

“He is.” Fao agreed. “Am I still bleeding?” He asked, trying to see his arm.

"Ah, ah. Lie still." Harrison said softly. "They've sorted it."

“Oh, okay.”

"Just relax."

“Yeah, relax.” Fao grumbled.

"Don't grumble at me, Wolfie. I didn't do it."

“Hard to relax.”

"I know it is."

“Sorry.”

"Don't be."

He hummed. “Hate this.”

"I know."

“Can you stay?”

"I'd like to see them try and move me."

Fao managed a smile. “Good.” Then he paused. “How bad is it? Be honest.”

"It's not great. You've had worse, you've had a lot worse."

“The bar is kinda low with that one.”

"That's not my fault."

“No. The opposite.” Fao mumbled. “Can I get a hug?”

Harrison leaned over awkwardly, pressing a kiss to Fao's forehead as he did so. "Better?"

Fao smiled. “Much.”

"Good."

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