Radiopaedia Blog

More than 25% of Radiopaedia.org Reference Articles have been reviewed by a dedicated group of editors over the past two weeks. The first in an ongoing iterative process of reviewing style guide errors aiming to improve radiology reference articles, which are used by thousands of users every day. 

Managing editor Dr Jeremy Jones (United Kingdom) led a global team of volunteer editors consisting of subeditors Dr Prashant Mudgal and Dr Aditya Shetty, site editor Dr Ayush Goel (all of India), anatomy section editor Dr Tim Luijkx (The Netherlands) and fellow managing editor Dr Henry Knipe (Australia). The team reviewed more than 1800 articles in just two weeks, making thousands and thousands of changes.

"We want to create the biggest and most complete radiology resource on the planet. However, with a growing number of contributors updating our 7000+ articles, it is a huge challenge to be consistent. With a team like this who have spent hours of their time finding and fixing stylistic errors, we have got one step closer to our goal. Now we can concentrate on adding more awesome content!" said Jeremy. 

This is the first step in making Radiopaedia.org more consistent, readable and the best radiology resource. For more information on getting involved read the related blog post here.

Dr Henry Knipe is a radiology registrar at The Royal Melbourne Hospital in Australia, and is managing editor responsible for content development at Radiopaedia.org. Twitter: @DrHenryK.

NB: Opinions expressed are those of the author alone, and are not those of his employer nor of Radiopaedia.org. 

Radiopaedia.org is an open-source radiology education resource - this means that it is written by volunteer contributors from all around the world. 

Often it appears a daunting step to go from reader to contributor, but getting involved is very easy and there is a friendly editorial board, who can help guide you through the process. 

Just hit the edit button

See a spelling mistake that needs fixing or want to add a practical point? Just hit the edit button and make the necessary changes! Edits don't have to be large and even the smallest edit helps. 

Want more?

If you've had a little taste and want to contribute something more substantial, then have a look through the style guide and standard article structure and get stuck in revising an existing article or start an entirely new one.

Radiopaedia.org's editors always have projects on the go and are more than willing to help out any contributor. Just contact one of the editors, shoot through an email to the editorial group or you can contact Henry Knipe, managing editor for content development. 

Dr Henry Knipe is a radiology registrar at The Royal Melbourne Hospital in Australia, and is managing editor responsible for content development at Radiopaedia.org. Twitter: @DrHenryK.

NB: Opinions expressed are those of the author alone, and are not those of his employer, or of Radiopaedia.org. 

Our urogenital editor, Dr Ian Bickle, outlines his five favorite cases from Radiopaedia.org and explains why they give him a buzz.

5. Pagetoid perfection

Case: Paget disease with blade of glass sign

This case from managing editor and Radiopaedia legend Dr Andrew Dixon is explosive. It is the complete case, illustrating an uncommon sign with four modalities and rounded off with annotated images for the user. Beautifully structured and accompanied by just the right amount of text, it’s a taste of educational fairy-dust.

4. Illustrating duplex dilatation

Case: The Weigert-Meyer rule (illustration)

Radiology is largely about images, both acquisition and interpretation, but some concepts really come to life with an illustration.  This case of a key concept in uroradiology is ignited with this awesome illustration of a duplex kidney by our Musculoskeletal section editor (and site illustrator) Dr Matt Skalski. This is one of many of his contributions, which can be viewed on his profile page.

3. A fist full of questions

Case: Rectal foreign body - the spleen tickler

Perhaps predictable, but it’s the thoughts this kind of image conjures up in one’s mind and sensorium, that just never leave you. Why? How? Where? Is life that bad... or good?
What did his face look like? What did the A&E doctor’s face look like? Oh, and when you are having a bad day yourself... it always helps to have a smile and a laugh.

2. Modern imaging at its best

Case: Ethmoidal aneurysmal bone secondary to an ossifying fibroma

Apologises for including one of my own cases. I use this as it represents what I love about radiology to a T. The detective side of the speciality, investigating the case with all the powers of a modern imaging department. The value of reviewing previous imaging (not done enough), the multi-disciplinary discussion (not done enough), admiring the expertise of clinical colleagues surgical skills (not done enough) and the cosmetic perfection in seeing the patient post surgically.  

1. Historical beauty

Case: Drooping lily sign of duplex collecting system

Everyone likes a classic (dare I say an Aunt Minnie!). Single images that signify a unifying diagnosis. A rare entity, but well described. Fluroscopy is often considered untrendy in contemporary radiology and being less than fashionable myself, I especially like this quirky case. This drooping lily image also has something artistic about it – proving a radiologist can be in touch with their other side.

Ian Bickle is our urogenital section editor and a consultant radiologist at RIPAS Hospital in the south east Asian Sultanate of Brunei.  He has a long-standing interest in medical education.

In recent years 4D-CT has emerged as a useful imaging technique in the work-up of patients with primary hyperparathyroidism to allow sensitive detection and localization of parathyroid adenomas and parathyroid hyperplasia.  

What is 4D-CT?

4D-CT includes image sets in three planes (axial, coronal, sagittal) from the angle of mandible to the mediastinum (1). The “fourth” dimension of 4D-CT is the perfusion information derived from multiple contrast phases. It is most commonly performed with three phases: non-contrast, arterial, and delayed phase imaging (1, 2). 

Findings of adenoma or hyperplasia

An oval shaped enhancing mass with low attenuation on non-contrast phase relative to thyroid, greatest attenuation in the arterial phase, and rapid washout of contrast in the delayed phase. There are variations in enhancement patterns and helpful morphological findings such as the polar vessel (1, 3, 4).

Do I really need all those imaging phases?

At least 3 phases are required because:

1. Only 19% of parathyroid lesions are higher attenuation than thyroid on arterial phase. Other lesions (such as the imaging example here) could be missed without delayed and non-contrast phases (5).  
2. 23% of adenomas have the similar enhancement to the thyroid on both arterial and delayed phase and could be missed without the non-contrast imaging (5).  

How does 4D-CT compare to scintigraphy and ultrasound?

Several studies have found superior sensitivity of 4D-CT over scintigraphy in the workup of primary hyperparathyroidism.

Other advantages:

1. Difficult subgroups - 4D-CT is superior for subgroups of patients with small lesions, lesions in ectopic sites and multigland disease (2, 7, 8). 
2. Surgical planning - 4D-CT assists with surgical planning by providing high-resolution images in multiple planes. The size of the adenoma, polar vessel to the adenoma and surrounding structures are better seen on CT than other modalities. These are all important information for planning minimally invasive surgery.
3. Grading diagnostic confidence – Rather than just stating a study is positive or negative, a combination of imaging findings allows radiologists to provide an estimation of degree of diagnostic confidence (1, 3-5). Diagnostic confidence has become increasingly important in pre-operative planning for minimally invasive parathyroidectomy, in which all four parathyroid glands are not visualized intra-operatively.  High diagnostic confidence on 4D CT may also obviate the need for additional imaging, thereby reducing the cost of diagnostic evaluation. 
4. Cost-effective – Two studies using decision models have shown that the use of 4D-CT as a second line investigation after traditional modalities fail to localize the lesion is more cost-effective than other imaging protocols (single modality or combination of ultrasound and scintigraphy) (9, 10). This finding is due to the fact that improved localization allows minimally invasive surgery to be performed which is a less costly treatment than bilateral neck exploration and failed surgery. 

What about the risk from radiation exposure?

4D-CT has higher radiation dose than scintigraphy, but patients who develop primary hyperparathyroidism have a mean age in the 5th and 6th decades of life and have a lower risk for stochastic effects from radiation exposure (11, 12). A study comparing radiation dose from 4D-CT to scintigraphy found the effective dose was 28 mSv for 4DCT compared to 12 mSv for scintigraphy (13). However, in the exposed standard patient (female of 55 years age), the increase in lifetime incidence of cancer over baseline cancer risk was extremely small at 0.52% for 4DCT and 0.19% for scintigraphy. Given both studies cause negligible increases in lifetime risk of cancer, clinicians should not allow concern for radiation-induced cancer influence decisions regarding workup in older patients.

Dr Jenny Hoang, MBBS FRANZCR Associate Professor of Radiology and Radiation Oncology at Duke University Medical Center in Durham NC, United States of America. Dr Hoang has particular expertise in the area of parathyroid imaging and has produced several published and in press papers related to this topic. Connect with her via twitter @JennyKHoang.

REFERENCES

1.    Hoang JK, Sung WK, Bahl M, Phillips CD. How to Perform Parathyroid 4D CT: Tips and Traps for Technique and Interpretation. Radiology. 2014;270(1):15-24.

2.    Rodgers SE, Hunter GJ, Hamberg LM, Schellingerhout D, Doherty DB, Ayers GD, Shapiro SE, Edeiken BS, Truong MT, Evans DB, Lee JE, Perrier ND. Improved preoperative planning for directed parathyroidectomy with 4-dimensional computed tomography. Surgery. 2006;140(6):932-40; discussion 40-1.

3.    Bahl M, Muzaffar M, Vij G, Sosa JA, Choudhury KR, Hoang JK. Prevalence of the polar vessel sign in parathyroid adenomas on the arterial phase of 4D CT. AJNR American journal of neuroradiology. 2014;35(3):578-81.

4.    Bahl M, Sepahdari A, Sosa JA, Hoang JK. Parathyroid Adenomas and Hyperplasia on 4DCT: Different Enhancement Patterns Illustrate Importance of Multiple Phases. Under review. 2014.

5.    Bahl M, Sepahdari A, Sosa JA, Hoang JK. Parathyroid Adenomas and Hyperplasia on 4D CT: Grading System for Degree of Confidence. RSNA Oral Scientific Presentation. 2014.

6.    Eichhorn-Wharry LI, Carlin AM, Talpos GB. Mild hypercalcemia: an indication to select 4-dimensional computed tomography scan for preoperative localization of parathyroid adenomas. American journal of surgery. 2011;201(3):334-8; discussion 8.

7.    Galvin P, Oldan J, Bahl M, Sosa JA, Hoang JK. Discordant Parathyroid 4DCT and Scintigraphy Results: What Factors Contribute to Missed Parathyroid Lesions? Oral scientific presentation at ASNR Montreal 2014. Under review for publication.  Oral Scientific presentation at the American Society of Neuroradiology Scientific Meeting. Montreal, Canada 2014.

8.    Kukar M, Platz TA, Schaffner TJ, Elmarzouky R, Groman A, Kumar S, Abdelhalim A, Cance WG. The Use of Modified Four-Dimensional Computed Tomography in Patients with Primary Hyperparathyroidism: An Argument for the Abandonment of Routine Sestamibi Single-Positron Emission Computed Tomography (SPECT). Ann Surg Oncol. 2014.

9.    Wang TS, Cheung K, Farrokhyar F, Roman SA, Sosa JA. Would scan, but which scan? A cost-utility analysis to optimize preoperative imaging for primary hyperparathyroidism. Surgery. 2011;150(6):1286-94.

10.    Lubitz CC, Stephen AE, Hodin RA, Pandharipande P. Preoperative localization strategies for primary hyperparathyroidism: an economic analysis. Ann Surg Oncol. 2012;19(13):4202-9.

11.    Yeh MW, Ituarte PH, Zhou HC, Nishimoto S, Liu IL, Harari A, Haigh PI, Adams AL. Incidence and prevalence of primary hyperparathyroidism in a racially mixed population. J Clin Endocrinol Metab. 2013;98(3):1122-9.

12.    Wermers RA, Khosla S, Atkinson EJ, Achenbach SJ, Oberg AL, Grant CS, Melton LJ, 3rd. Incidence of primary hyperparathyroidism in Rochester, Minnesota, 1993-2001: an update on the changing epidemiology of the disease. J Bone Miner Res. 2006;21(1):171-7.

13.    Hoang JK, Reiman RE, Nguyen GB, Januzis N, Chin BB, Lowry C, Yoshizumi TT. Lifetime Attributable Risk of Cancer from Radiation Exposure During Parathyroid Imaging: Comparison of 4DCT and Parathyroid Scintigraphy. In press. AJR 2015.

A quick tiny itsy bitsy little feature which was actually a pain, but necessary on our way to a better stack experience. 

Now, if you do not set a stack key image, the default slice chosen for the series thumbnail will be the middle image rather than the first image. This of course makes much more sense, as rarely is the first image representative. 

This same middle image will be the start position for stack viewing in Quiz Mode, and soon the same will occur in case view. 

We have also gone back and set the middle image as key for each stack which had not had a key image set; all 16,175 cases !  But don't worry.. if you have previously set another image as the key image, we didn't touch that, so all should be good. 

Thanks, and happy case creation. 

Frank