Actually prednisone is an awful drug for side-affects - unless you have to take it, don’t.
In a nutshell, advancements in computing power. I was able to reconstruct almost exactly the same type images from a 1/2mm-thick slice(s) spiral-CT scan very easily. Its what the Trauma depnded upon quite often. NOt dificult at all once you understtand the software and where to place cursor(s) to select areas-of-interest.
As an example, one patient that is memorable came in with her face literally blown off by a shotgun blast. Her husband was allegedly cleaning weapon in another room and accidentally shot her. Eyebrows were raised by all medical persons as therre were clear 'burn marks all over her cranium/shulder(s), etc. It was a close-rance hit - but guess what? Shooter was son of a high-level LEO from the area. She would live, but needed serious reconstruction of facial structures remaining to live a as=normal-as-possible life once she healed enough.
I was tasked to do a high-detail #-D recon scan of her head so that a ‘plastic composite’ face could be nade for her (think of the relatively new 3-D printers). The data I got was sent to the place that makes such ‘models’ for ‘implanting’ and allow skin-grafting and other necessary stuff to have a ‘base’ to grow upon. I still have the images of her somewhere in a box in my closet, fwiw. I collected ‘amazing’ exams over the years to show friends, etc, though I removed all patient data from any films I took home.
Most of the imaging modalities have come a LONG ways in last decade, mostly due to computing power and improvements data transfer, plus much better detectors for the modalities of imaging used. Heck, when I started my carrer, there were a few places still using the manual hand-processing! Nowadays, there are many places that are purely digital and its rare for them to ever have a need to ‘develop’ a film - CD’s are used for portability, otherwise data is stored in ‘memory’ somewhere locally.
This is truly the most informative and eloquent explanation I’ve ever read of how MRI’s work on a molecular level.
And thanks to **Ionizer **also for his extremely informative posts!
And just to give a little more clarity on MRI’s : if/when a person has an actual MRI scan, the differing ‘sounds’/clickings/rate of such audibles are different ‘kicks’ by radio waves (and associated electronic relays used to alter the emissinons of the return signal(s)) to help differentiate the near-similar tissues. Sometimes, its just a steady slow ‘hum’ sound, and other times its a periodic and repeated thumping/buzzing/booming sound - each measuring the signal(s) returned from such various molecules within the patient. There are patterns of signal called T1, T2, FLAIR, etc that are common to show different tissues with resultant great contrast of appearance of the various soft tissues. Top of my head, I forget which sequences show cerebral fluid(s) either dark black or bright white - its like the opposite of each other by visual comparison of imagery, so to speak, and each sounds (to patient) different.
That is why there is almost always various portions/sequences to an exam of particular area of interest - differentiation by measuring response to differing level of signal returned by various known alterations of the ‘kick to molecules’ by using varying ways of altering the non-kicked molecules out of ‘spin-stability’, so to speak. Each type of pulse of radio-wave gives unique return signal. Just for those who might wonder why an exam takes so long sometimes - gotta use various patterns of ‘kicks’ to delineate various but near-the-same densities of molecules. This link goes into more detail for those interested, fwiw.
It’s true that the radiation load is much higher than a single x-ray, but in the grand scheme of radiation exposure, a single CT scan isn’t all that much. A single, whole body CT scan gives you about 10 mSv. Radiation workers are allowed up to 50 mSv in a year, and no cancer increase has been detected at exposures less than 100 mSv (which isn’t to say that it doesn’t increase the risk, but the increase is pretty small, and you’d have to look at a whole lot of people to see it). In truth, the financial cost of a CT scan is a much larger burden than the radiation risk.
Echoing Francis Vaughn and Ionizer, in the brain CT and MRI are often complementary.
CT is faster and is effective at finding most things that need to be dealt with urgently. It is widely avaiable on a 24 hour basis. It is also somewhat less expensive. This is a great first test for patients who present to the emergency room.
MRI is a significantly lengthier exam. It shows brain tissues marvelously well and even very small and early strokes can be easily seen. It is also more sensitive to injected intravenous contrast. This is especially true for the facial nerve. The major role for MRI in a case of “Bell’s palsy” is to better make sure that it is not caused by one of several other conditions which could cause similar symptoms. While MRI is being done in eemergency room cases with increasing frequency, it is not so readily available, and it is often reserved for relatively special circumstances.
To add to what Ionizer describes.
The noise in an MRI scanner is the sound of he gradient coils. The main magnet of a scanner is seriously powerful, and it is the filed it imposes on the system that defines the frequency that the hydrogen nuclei (protons) resonate at. The big invention that allowed MRI scanners to be produced was realising that if the field strength was varied slightly across the subject, different regions would have different frequencies, and thus is was possible to determine the response of a small volume, or indeed many small volumes. In order to impose a varying field, a set of electromagnets are wound around a cylinder sitting inside the tunnel of the main magnet - essentially forming the tunnel the patient sits in. When these coils are energised they react against the main magnetic field - in much the same manner as a loudspeaker’s voice coil does. So as the gradient coils are energised, and the current through them varied in order to create the various required changes to the magnetic field strength, they make noise, sometimes a lot of noise.
The difference in time taken between CT and MRI is interesting.
An X-ray CT scanner is pretty much limited in speed by the mechanical design. The system has to swing the X-ray tube (and power supply) plus all the detectors around the patient. Helical scanners
keep going around and around to build a 3-D volume. Modern machines shrink the entire thing, and can make scans remarkably quickly.
MRI scanners are limited by the physics of the MRI process. Once a proton is hit with an RF pulse it will emit RF energy, and will slowly relax back to equilibrium with its surroundings. The time it takes to do this varies with the precise surroundings of the proton and the magnetic field strength. Such relaxation times are what T1 and T2 measure. You can’t hurry these times up. So if you want an image you get to wait for the protons to give up their secrets in their own time.
Hey Biggirl, how are you doing now? Hope they decided for sure no stroke and that the Bell’s Palsy will resolve soon (although I guess soon is too much to hope for). Anyhow let us know what’s going on.
Actually, not totally correct, but close enough for the most part. Just got home from taking ma-in-law to the Trauma Center I worked at (non-trauma, fwiw) and I went back to see who was working there now for ol’ times’s sake. An old buddy of mine showed me the software upgrades done and how the data through-put had increased dramatically (software related, per se), and the hardware was the same exact stuff I had used. 16-slice helical was standard in my days for get-scan-ASAP; Images MUCH more detailed and 3-D/multiplane recons popped up literally five or six times faster.
I have been told by multiple GE engineers/repairers (and viewed internals of scanner head-unit myself) that its around, at that time, about two thousand pounds (well-balanced, of course) that spin around the person as a scan is done. The unit is spinning constantly whether or not a single-slice-per-rotation -v- ‘spiral’ scan is done so tube/decetors do not stop whatsoever until scan parameters are finished. Spiral scans have a continuous movement of table (which patient is on) as directed by Tech doing scan while a single slice (like a simple cranial CT for subdurals, etc) have the tabletop ‘step’ in defined increments (per defining paln per Tech and what is wanted azs output data, according to area of interest.
It was kinda cool to see once again marks upon the scanner that he and I had made when its location was moved from one building to another - we dated the move on hard-to-find area of scanner head-unit we made for posterity. Gave me a warm feeling knowing that ol’ unit was doing its job admirably with very little down-time for repair/upgrade/replacement 
Certainly, there are somehat better units overall, but medically-speaking, not really needed for Dx’ing tiniest of details affecting a patient’s outcome in serious-emergency situations. The images OP showed were definitely possible possible a decade ago, IME, as I personally did such images for a Orthos, Neuros, Trauma Surgeons headed straight to surgery to plug bleeds, etc. A Tech just needed to learn how to provide the necessary paraneters for 'puter to deal with, and quickly as lives DID depend on it
Any Tech with above-average skill-set could so without more than a few minutes of how-to shown to them. If it was worth having more details, I know the person who is Director of Trauma would make it happen, no doubt whatsoever It was not infrequent that my CT suite became an OR if conditions warranted. There was another near-similar CT-unit about 30’ from the other as back-up, just in case. It was not as fast at recons, but could do same imaging nonetheless. Slower data handling was only bottlenecj with that unit – so used mainly for CT-guided biosiies or routine head/belly scans. Not up to Trauma-level
Yeah, I was ignoring the computational issues any only comparing the fundamental limits of the physics of the systems. Software, and the computers it runs on has made a massive difference over they years. The first CT scanner I remember was a GE, installed in about 1981. It used a Data General Nova, with an attached FPS floating point accelerator - all installed in a separate room. Reconstruction times were not exactly quick, and the computer had to run into the night to catch up on the day’s work. First MRI scanner was a Siemens unit, and it used a VAX 11-730. That at least was simply under a bench. Not quick either, but MRI processing was less compute intensive than CT.
I think the point I was trying to make was - even in the face of infinite compute, there are fundamental limits to the speed of obtaining images, and for MRI these are deeply welded into the physics. For a given signal to noise ratio, voxel size and imaged volume, the physics defines the time the examination will take, no matter what. With X-rays the signal to noise ratio is much more under the control of the designer, and modern detectors have very high quantum efficiencies, so images are very fast to obtain. I will admit I didn’t realise the software was still limiting reporting times. Then again, I live is world of very high performance compute, and probably have unrealistic expectations of the amount of compute power being thrown at problems.
Neither a CT nor an MRI are useful ways to diagnose Bell’s palsy. By definition, Bell’s palsy is a dysfunction of the 7th cranial nerve. The cause for this dysfunction is unknown. Because it is not a structural cause (at least, not anything structural that we can see with imaging studies), neither CT nor MRI, nor any other imaging study show findings related to Bell’s palsy.
The diagnosis is made by a physical exam, which shows that the paralysis of the face is from dysfunction of a peripheral nerve and not a central (brain) lesion. The muscles of the upper part of the face (forehead, e.g.) are controlled by both sides of the brain, but the lower part only gets signals from one side of the brain (the opposite side).
Therefore if a patient has weakness involving the entire half of the face, the problem is a peripheral facial nerve dysfunction (and most likely, Bell’s in particular); if just the lower half of the face has weakness, it is more likely to be an upper motor neuron lesion (think brain–I am simplifying a few concepts here).
When we can’t find a good reason for a peripheral 7th nerve dysfunction, we call it Bell’s palsy. This has a typical presentation and is basically a clinical diagnosis of excusion: (“Not a stroke; it’s a lower motor weakness…not zoster…” etc. etc.)
The reason for imaging studies is that we want to make sure we are not wrong about the physical exam and presentation. So we are ruling out other things such as problem in the brain. Imaging studies can look for lesions that disrupt the area of the brain which controls the motor movements of the face–essentially the place where the signals that end up in the facial nerve start.
Without boring you with a long and detailed difference between MRI and CT in this context, I would say that if the clinical diagnosis of Bell’s is wrong and the problem is central instead of peripheral, an MRI would be better at finding multiple sclerosis or some sort of low-grade tumor (astrocytoma, e.g.) while a CT would be better for finding a small hemorrhage (particulary given time constraints around hemorrhages). If you decide to be a really good clinical case and have some teeny bizarre lesion in the brainstem, then maybe MRI gets the nod there as well.
This being the Dope and all, just a reminder that I am putting pages of clinical medicine into a paragraph.
What you probably have is Bell’s, and the real reason for either the CT or the MRI is that in our medical system we like to spend money, and we have money to spend. Further, our tolerance for error is close to zero. Win win for all except those who try to control health care costs. 
Francis Vaughan : when I worte my last post, I was agitated from a bad ER experience that ma-in-law was put through by several Nurses and how they treated my blind wife. The House Supervisor got a scathing call after my post, fwiw, because the Nurses said wife was NOT blind and it was up to her to remove her mother from exam room out to car - waaaay against policy/employment ‘rules’. The converation(sO I recorded during the event are damning to the ER staff, and House Super was shocked, etc, etc… My point being is that I meant no offense if any came across 
I only intend to show what the Tech(s) can do nowadays. The machines themselves are near the limit of performance of physical parts, IIUC, but software/processing can still be made faster and more detail-oriented. However, the cost(s) of upgrading the proprietary sofware is huge. One software ‘upgrade’ a GE repair-guy/engineer told me about cost at least $100,00+! Many, many Admins/Directors-of-Depts cannot justify such expenditures when they already have more than enough detail(s) for damn-sure Dx’s, so its kind of a cost-v-benefit thing in medical field, IME. My old employer spent the money on the unit I used for around 4 years (about 10 years ago) due to increasing throughput of multiple Trrauma patients (think MVA with 4 persons ejected (no seatbelt, etc) so that the patients could be Dx’d faster and into OR MUCH faster. I literally, on numerous occasions, had Trauma Director breathing down my neck to get her the images faster, so hospital owners listened to her reason(s), and followed her demand for getting the images NOW, instead of waiting up to 5 minutes for films to hang in the patients OR to guide the surgical approach. It cost much less than getting another whole unit and having another Tech on duty to increase Trauma rate-of-scan in near-overwhelming circumstances. The absolute last thing Director wanted was to place Trauma Center on divert due to inability to deal with the number of incoming Traumas (or in-patient serious stuff that needed to be done between Trauma-scans). The money was spent on upgrade as Trauma Director madea valid case, plus she was AWESOME at getting things she wanted for patient benefit. Tough as hell, she is, but also had reason on her side that rested upon the ‘mission’ she was tasked to perform. Rarely was she denied anythng when she showed how somethin would be better than what was on hand, trust me. Huge respect for her, and she helped make decision for me when I entered that Center after dieing. Her face made me feel I was in the exact place for my best chance(s) of full-recovery - which is how things turned out. Last night, my former co-worker (we covered three different buildings on campus, and one of us always had to be within a minute or two of receiving a patient to place upon CT table and get scan spun-up and done. There, apparently, have been two CT-software upgrades since I left, and performance improved quite notably despite the exact same physical unit being used.
Chief Pedant : I second everything you speak of about Bell’s from inaging point of view. I can only think of a few scans done for Bell’s, and that was because patient had other Sx’s that were needed to make sure it was only Bell’s. CT scan for Bell’s is hardly ever used, IME. Just totally agreeing with you is all - many Docs were refused their scan-order by Radiologist as unecessary and they cited the ALARA principle which we Radiology folk lived by. I have locked horns more than I can remember, gotten called to Admin(s) to explain the why of my stubborness to do what an ignorant Doc was furious about.
Not once was I ‘overruled’ and had full backing of all the attending/resident physicians that were on-board with risk-v-benefit of ionizing a person, fwiw. The more common denials of doing a scan tended to be newbie-residents demanding CT instead of ultrasound, particularly with minor-age patients (and females especially). Another risk-v-benefit thing, of course.
Thanks to all for going into more detail than I give/gave - just showing what happens in an Imaging dept that has patient safety/risk-of-future bad-things from being ionized (by the the scanner) on its agenda.
[QUOTE=Ionizer]
… many Docs were refused their scan-order by Radiologist as unecessary and they cited the ALARA principle which we Radiology folk lived by.
[/QUOTE]
As a patient, I appreciate this. Many years ago, I had a dentist that wanted to do some weird 3D or whatever set of X-rays on my TMJ. He called my HMO, confirmed they could do the imaging and set an appointment. When I arrived at the hospital a week or so later, there was a gaggle of radiology and med students waiting to witness what was sure to be an unusual afternoon. The radiologist pretty much said “He wants to do what? Let me call him…” After making it sound like the dentist was trying to blast my bones away with x-rays, a much more ordinary CT exam was scheduled.
Another aside… Do you know much about how the mechanical aspects of making CT and MRI units mobile? They seem like they could be easily put out of alignment, needing time-consuming re-setting and calibration after each trip, but my neurosurgeon’s practice owns a mobile MRI that gets driven from one office to another almost daily, so in practice it can’t be much harder than parking and plugging it into electricity and the practice’s LAN. Are these devices really more robust than they appear, or does my doc just have a really good pit crew?
Got passwords : I scanned in numerous semi-trailers with both CT or MRI units. The units themselves are rather heavy and not prone to shift easily, and QC images/calib’s are done prior to any scan. I rarely had to do anything to get in-spec, and these were units driven throughout Idaho/Montana area, often down bumpier gravelled roads.
I was told by one of the drivers (who had wife accompany most of time to share driving hours for longer trips) that extra bracing was under the trailer’s chassis and shock absorbing stuff was within floor where unit was mounted within trailer. The trailer was specially ‘adapted’ for such use, not an off-the-shelf item for such use.
Plus, MRI’s essentially have no moving parts (other than loud electrical relays that turn on/off/adjust the radio emissions during scan) like CT’s, which are carefully balanced and held in place internally by surprisingly large mounts/bolts, etc. Some units spin more than two tons of lead, power supplies, shielding/collimating parts around a patient during scan and no vibration is felt on outer ‘shell’ of unit during normal operation parameters. You can hear the hum of the rotation, but not feel it, for the most part.
As a general rule, it is ALWAYS wise to ask if the radiologist agrees with an outside physician’s order for any higher-level exposure exam. Its wise to ask if there is an alternative imaging method that does not cause physical harm to provide info requeted. If the Tech balks, ask for the Director or Admin as it is unwise to totally trust a non-Registered by ARRT person that exam is appropriate. More often than not, outside Docs ignorance wants them to order something they have read about or whatever, even if there is a safer-to-patient alternative that gives same diagnosis for treatment(s). Like using Ultrasound to try and visualize appendix or gall bldder, etc than to ionize/risk future health than to go straight to a high-level of rads to body parts ALARA is the rule-of-thumb for any responsible Imaging Dept. Feel free to ask the Tech if the exam is ALARA for ionizing radiation - ignorant ones will have no idea of what you ask. If so, run to another imaging place/hospital, etc that gives a darn about patient safety.
An example : one ‘outside’ Doc that always sent his patients to a certain place I worked always ordered a full head 3-D recon’d exam for ruling out a fracture of nasal bones. Two simple X-ray images would answer that inquiry, but Doc wanted the ‘fancy’ stuff to show patient. Radiologist overruled the Rx from outside Doc EVERY time, and finally called that outside Doc to say he was not ever to request such an exam without supporting documentation for the request or Rad would go after him regarding patient safety. Some of the folk that outside Doc sent were young females who are the most-sensitive to ionizations - and he was totally unaware of such things. Did not care, either.
When I left the profession, it was becoming less common, overall, to automatically (by a ‘standing order’) do a head CT for the smallest of bumps to head. Amount of energy absorbed from injury to skull/face should be taken into consideration as well as age/sex of patient. American College of Radiology put out a number of studies showing overuse and also gave recommendations in limiting use of ‘standing order’ scans in not-too-distant past, fwiw, and I hope that smaller hospitals/clinic follow the guidelines better nowadays.
I can recall at least two older patients who died of rad-related deaths. They were all chronically ill in gastic funtion, and various Docs over the years had done many, many multi-film exams repeatedly. IIRC, one of them had 17 film-folders where the average chronic-ill patient had only two or three typically. The attempts at Dx’ing them actually killed them outright! These examples were around 15-20 years ago, and much has been done to address such overuse of high-exposure exams, particularly by better oversight from Radiologists taking firmer control of what happens in their Dept.
HTH