Radiopaedia Blog : Radiologist

A recent research publication in PLoS ONE has described a new 3T MRI sign of Parkinson disease known as the 'absent swallow tail sign'. The discovery, which has the potential to revolutionise the diagnosis of this important disease, uses axial high resolution susceptibility weighted imaging (SWI) to assess the structure of the substantia nigra within the midbrain. 

In healthy individuals, a linear or comma shaped region within the substantia nigra known as nigrosome-1 returns high SWI signal. This nigrosome is bordered anteriorly, laterally and medially by low signal structures which produce a distinct likeness to the split tail of a swallow (Figure 1, Figure 1A - healthy subject).  

In Parkinson disease, the high SWI signal within nigrosome-1 is lost and the normal 'swallow tail sign' cannot be identified (Figure 1B - Parkinson disease). The researchers found that absence of the swallow tail sign had a diagnostic accuracy of greater than 90% for Parkinson disease.

You can read more in the original publication here. As always, please let us know your thoughts in the comments section. Do you think this diagnostic sign is going to translate into clinical practice? Should high resolution SWI imaging of the midbrain be standard in the MRI assessment of Parkinson disease? 

Dr Andrew Dixon is a Radiologist at the Alfred Hospital in Melbourne, Australia. He is a managing editor for and has interests in neuroradiology and the use of technology and social media to disseminate medical knowledge. 

Reference: Schwarz ST, Afzal M, Morgan PS et-al. The 'swallow tail' appearance of the healthy nigrosome - a new accurate test of Parkinson's disease: a case-control and retrospective cross-sectional MRI study at 3T. PLoS ONE. 2014;9 (4): e93814. Image adapted under creative commons license 3.0.

Thyroid cancer incidence has almost tripled since 1975 and yet mortality has remained stable, according to a new analysis reported in JAMA Otolaryngology - Head & Neck Surgery. The authors have suggested there exists an 'epidemic of diagnosis' rather than disease. And it would appear that detection of small, indolent, papillary thyroid cancers is probably to blame.

This latest research adds further weight to calls for improved reporting of incidental thyroid nodules on CT and MRI by radiologists. It is hoped that new guidelines, such as the Duke 3-Tiered System recently blogged about by Dr Jenny Hoang, can help ensure that radiologists take an evidence based approach to thyroid nodules.

Related post: Reporting of incidental thyroid nodules on CT and MRI

Cheating is one of the most important skills a radiology trainee needs to master. Not only can a good cheat hide your incompetence, but sometimes it may even bring glory!

1. The Crystal Ball 

There are times when you're reporting a chest x-ray that the patient has already gone on to have a CT. When this occurs, you'd be crazy not to use it! If the CT shows a mass then you should report that sucker on your film with all the confidence of a hero. If the CT is normal then spit out a standard report and move on. 

Key features: hero potential, zero risk to patient 

2. Ultimate balling 

This is a more advanced version of crystal balling that involves the use of future cervical spine or abdominal CT to find apical or basal chest lesions. One of the great benefits of ulti-balling is that there is little chance of anyone ever calling you out on the cheat. Recently it has become popular for radiologists to tally their ulti-ball successes as a form of competitive cheating among co-workers. 

Key features: extreme hero potential, an emerging competitive sport

3. The Status Quo

If the film you're reporting looks the same as the previous one, and that one was reported by someone far more experienced than you, then just say the same thing as them. The chance of you genuinely spotting something that they missed is very low, but the chance of you creating a fake abnormality is high. 

The status quo cheat also comes with free indemnity cover. If it is discovered in the future that you missed something on the film, the fact that someone more experienced also missed it will mean that they cop the major blame instead of you.

Key features: commonly applicable, free indemnity

4. The Sneaky Show

If there's no previous or subsequent imaging for you to cheat off, then it may be time for a sneaky show. Find a colleague more experienced than you and make up some excuse to get them to look at your screen. "How do I invert the contrast again?". A radiologist's natural instinct will be to point out any abnormality they see, to which you will simply reply "Yes, I know that". If they say nothing then be careful; this cheat is prone to false negatives. 

Key features: sneaky epinephrine rush, competence protected   

5. Rolling the Temp

A nice little fallback option for those chest radiographs you're not quite sure about. Find an experienced but unsuspecting radiologist who is only working temporarily within your department and pounce. Show them the case, ask them directly for their thoughts and then pass those off as your own. It doesn't matter if they end up thinking you are incompetent; temps are largely insignificant in the ultimate landscape of your radiology career. 

If it is later discovered that you missed something on the film then you have yourself the perfect scapegoat.  "Yes, I thought at the time that was a rib metastasis but I showed it to the short radiologist with bad teeth when he worked here and he assured me it was normal. I should've backed my own interpretation." 

Key features: controlled exposure of your incompetence, scapegoaty goodness


Disclaimer: This post is intended as entertainment only and should not be acted upon. Neither the author nor will be held responsible for any lawsuits, premature termination of employment, loss of income or ill-tempered temp related injuries resulting from the use of these cheats. 


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