Radiopaedia Blog

When reporting follow-up studies the usual practice is to compare to the most recent previous study. Although generally this is a safe thing to do, with increased frequency of follow up exams in many disciplines, one runs the risk of not detecting subtle growth. If this occurs repeatedly then a tumor that may have significantly increased over time will have a series of reports all of which state “no change”.

As an example (Fig 1) look at 4 studies in a patient with a partially excised low grade glioma. Each study (A to D) is approximately 6 months apart. Note how hard it is to discern a change between adjacent pairs.

We simply cannot reliably detect subtle change. How much is below our change threshold will depend on many factors, such as the size and shape of the lesion, scan parameters and partial volume effect, slice position and patient position etc… Regardless, there is an amount below which we simply won’t be convinced that any actual change has taken place. This is obvious if you consider what would happen if you were to scan a patient every day. Even the fasted growing mass would look unaltered on sequential scans.

So what is the solution?

Look at older scans and consider what you expect the biological behavior of the process you are looking at to be; the more indolent the process the longer interval you need between scan pairs to detect change.

In the same patient as before, see how easy it is to see that there has been change when comparing scans 2 years apart (Fig 2).


My practice when assessing gliomas for example, is to look at the most recent scan, and then at the oldest valid comparison; one which does not have intervening surgery, and is not in the  immediate postoperative period.

You are then left with three possible outcomes from such a comparison:

  1. change is obvious even when just compared to the most recent scan
  2. no change when compared to the recent scan but some change when compared to the oldest scan
  3. no change when compared to both the recent and oldest scan

In the setting of obvious change, there is no problem, and in fact there is no need to look at older scans.

If there is, however, no change compared to the recent study but change is evident when compared to the older scan, I usually pull up a few of the intervening scans, to try and assess whether growth is gradual, or something has changed in the behavior of this tumor, suggesting dedifferentiation into a higher grade. After all a tumor that had been stable for years but suddenly starts to grow needs, at the very least, closer follow-up and probably also needs to be considered for a change in management. My conclusion then reflects this distinction; e.g. “Although there is little discernable change when compared to the most recent study, when compared to multiple previous studies dating back 4 years, slow steady growth is evident.”

Only if there is no change when compared to the most recent scan, and no change when compared to the oldest scan does my conclusion read “Stable”, and then I append the time period over which I am claiming no change to have occurred; e.g. “Stable, with no appreciable growth over the past 24 months”.

This approach is valid to all comparison studies, regardless of system or underlying pathology. I hope this approach is useful to you, and will stop you from merely concluding with “stable”.

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9th Jan 2014 21:28 UTC

New features

We start the new year with a few small features / improvements, before we get stuck into some bigger feature sets. 

Ability to delete your own cases

Until now, users have been unable to delete thier own cases, which is crazy but was legacy of when we only had a few cases instead of over 16,000! 

Go to 'view mode' from 'quiz mode'

This is mostly one for editors. When viewing a case in quiz mode I often find myself wanting to pop into view mode, so that I can edit the case. Now you can. Just click the case ID at the bottom of the screen. 

Donation page added to footer

For those of you who want to help us out we have made our donation page available in the footer.  

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Each month I will collate some of the feedback we get from our users and post it on this blog. It is always rewarding to hear that what we are building is important and appreciated. If you have feedback or a story of how helps you, please send it to [email protected]


"Excellent job ,knowledge should be free, so everyone can have it to help patients ,especially for 3rd word where materials are insufficient and sources are poor. Great job" - A. L. 


"Awesome resource! Invaluable in preparation for my exams! Thanks" - Dr Allan G


"Well done for the good job so far" - Anonymous 


"[The] marvelous work done by Frank and his team. Congrats guys, keep it up. I have replaced my pubmed bookmark with radiopaedia." - Dr Colin C (via facebook) 


"Keep doing such a good job. The best."  Anonymous 


"Congratulations for the excellent work developing radiopaedia." - Dr Ricardo G - Portugal


"Please accept my grateful thanks" - M



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Stroke is the leading cause of disability in adults around the world. One of the major causes is atrial fibrillation (AF) and our aging population is contributing to an epidemic of AF. Anticoagulation therapy is highly effective stroke prevention for AF patients and there have been major changes to the therapeutics options available with the introduction of novel oral anticoagulants "NOACs".

In some ways the novel anticoagulants are simpler than warfarin - no regular INR monitoring, fixed dose, less food and drug interactions etc. However, like any new drugs there are unfamiliar issues. Despite the lack of INR monitoring, regular clinical monitoring and assessment of creatinine clearance is critical as they all have significant renal excretion. There are p-glycoprotein and other interactions to watch out for. Management of these anticoagulants around the time of invasive procedures is clearly an important area and the "safe" time off drug varies with renal function and the risk level of the procedure. Even recognizing that a patient is taking one of these new drugs can be an issue as most hospital protocols ask about warfarin but not dabigatran/Pradaxa, rivaroxaban/Xarelto and apixaban/Eliquis!

The management of bleeding complications remains a challenging area as no specific antidote is yet on the market and traditional factor replacement therapies have not been proven to work. The side effect profile does vary across the agents (eg dyspepsia with dabigatran) and there are drug-specific issues around the use of dosing aids and crushing tablets. AnticoagAF provides detailed information on the use of each of these novel anticoagulants with specific guidance on perioperative and bleeding management based on currently available guidelines and will be regularly updated as new information comes to light.

AnticoagAF, a simple but comprehensive  iOS app developed by the Royal Melbourne Hospital Neuroscience Foundation is the prefect reference for clinicians who are considering what and when to prescribe and how to manage specific situations like surgery, bleeding and stroke thrombolysis. 

AnticoagAF app is now available on iTunes for $1.99

Currently the app is only avialble on iOS, although an Android version may be available in future. Profits form the sale of this app go to the RMH Neuroscience Foundation supporting continuing stroke research.

This is a guest post from Dr Bruce Campbell, who authored the app, and who is a collegue and friend at Royal Melboure Hospital. 


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3rd Dec 2013 23:55 UTC


This man was caught body packing 500g of cocaine while entering Switzerland. The street value of his rectum, sigmoid and descending colon was around US$40,000.  

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