Possible aspiration, do we need CT scan?

My dog is a 65lb blackmouth cur/shepherd mix. On 7/26 he was jumping around chasing a lizard, sniffing around deeply, and got a few little red cactus hair/spikes about 1/3cm long stuck in his nose which I pulled out. I am concerned he aspirated a few of these tiny cactus needles. Within about 48-72 hours he lost his appetite and I noticed him breathing shallow and rapid at rest. 8/1 I took him to urgent care and he had a 104.3 fever. His x-rays show pulmonary nodules. He also tested positive for valley fever antibodies, but his titer was only around a 1 and he does not have a cough. Today he is on fluconazole and 3 different antibiotics. He lost 2lbs by 8/16 and still had a 103.8 fever, but now that I am giving him entyce he is eating well, without diarrhea or vomiting. If we assume he aspirated little cactus needles, and got a fever a few days later, how long would it take for him to either show recovery with antibiotics OR take a serious turn for the worse? The vet has suggested CT scan and ultrasound guided needle to get samples. This is scheduled next week on 8/23. Since he has remained alert, and is now eating again, I am torn about whether to continue with such dangerous procedures (anesthesia for the CT scan and the needle into his lungs). If he should have taken a serious turn for the better (or worse) it hasn't happened yet and I'm hopeful he will get better on his own with time. My instinct/thoughts right now is that after almost 3 weeks, if he was going to pass away or get serious complications it would have happened by now. I'm thinking about canceling the anesthesia and waiting it out with keeping the antibiotics as long as he keeps eating well and he stays happy to go on short walks. It doesn't seem like his life is in danger, but I worry that if I wait he might decline rapidly and it could be too late.  Can someone give me insight into the typical progression from aspiration until getting better on his own vs really serious issues? Any other thoughts are welcome too. Money is not the concern, it's whether or not these diagnostics are really necessary to put him through.

Hello and I'm sorry that this happened to your loved one.  I have never heard of this happening and could therefore not give you an idea of timescales.  In the UK we have various social media networks, specialists and toxicology services, and I wonder whether your vet could use something similar across the veterinary networks or case reports to find someone who has experience of this, in order to figure out what to expect.  Sometimes cases are reported in 'the literature,' and your vet might be able to search for this.  My concern would be that while any infection may be controllable, I don't know how the needles are going to behave physically and unless someone can be found who does know, there are two options.  One is the predicable but very sad route of euthanasia: the other would be to try their best - to uncertain outcome - and write a case report for the next vet to see a case like this, to refer to.   I am sorry not to tell you anything that you don't already know.  You don't mention whether these cactus needles are native where you are, but speaking to vets where they are native might be useful; there are various veterinary social media networks where vets discuss interesting cases, for example.   Finally, no-one wants their pet to be an 'interesting case' and we wish you all the best in getting it solved.  I would be fascinated to know how this case ends up.

Regarding the CT, a good question for vets is 'What will the results of the CT scan change?'  If it is likely to make a big difference, then I always think (money aside, as you said) that it is worth doing.