This recently published Encyclopedia of Diagnostic Imaging is an impressive and comprehensive reference work that comes both in the traditional print form (two volumes, almost 2000 pages combined) and online. This review discusses the print edition.
This is not a traditional textbook on radiology, but one that attempts to cover all the major aspects of diagnostic imaging by providing roughly 4000 entries in alphabetical order. It targets general radiologists as well as residents, radiographers and even laypersons interested in medical imaging. As one browses through the volumes, the state-of-art character that was aimed for becomes quickly evident. I found extensive coverage of many topics and had to stop browsing to either start reading selected articles or at least appreciate the wide selection of excellent images that are presented, ranging from conventional x-ray studies and angiography to CT and MRI, including nuclear medicine scans and ultrasound as well. The quality of the images and their careful selection are definite strengths of the work. Although the title and the preface suggest that interventional procedures are not covered, this is not true, and excursions on interventional treatment options are found in many entries, for example regarding the interventional treatment of hepatocellular carcinoma and aneurysms.

According to the editor, Prof. Baert, who was also editor of European Radiology during the past years, a special focus has been put on topics related to molecular imaging, magnetic resonance imaging, and contrast media. Nevertheless, many topics deal with MDCT, not only regarding contrast media (in terms of safety, adverse effects and administration protocols), but also – and especially – regarding clinical applications.
Due to the fact that in any encyclopedic work the keyword index is missing, the biggest drawback of an encyclopedia that presents topics in alphabetical order is the potential difficulty in finding items if you do not know how they were indexed. For example, in this volume set, I looked for “CT coronary angiography” but found no direct entry. Thus, I looked under “Heart” and then “Coronary arteries”, where I found “Coronary artery disease” with a reference to “Ischemic heart disease – CT”. More leafing through pages and finally I found the entry on CT coronary angiography. The search was worthwhile, because I found four excellent pages covering, among other things, criteria for eligibility, aspects of CT technology, CT diagnostic performance, clinical applications, an excursion to plaque imaging, limitations of the method, a selection of references, a flow chart depicting a proposed diagnostic algorithm, and four sets of appealing figures with CT angiograms and corresponding conventional coronary angiograms.

In another search, I looked for “CTC” and was cross-referenced to “Computed tomographic colonography”. There, I read seven lines: “CTC is a novel imaging modality for the evaluation of the colonic mucosa in which thin sectional spiral CT provides high resolution two-dimensional (2D) axial images; CT datasets are edited off-line in order to produce multiplanar reconstructions (coronal and sagittal images) as well as three-dimensional (3D) modelling, including endoscopic-like views”. There was one cross-reference to “Neoplasms, benign, large bowel” . This is a reasonable explanation of CTC in my opinion, although somewhat short. I went on to “Neoplasms, benign, large bowel” and found four excellent pages, mainly dealing with colonic polyps, histopathology, clinical presentation, imaging, and diagnosis. The imaging section focuses on CT colonography, but it includes double-contrast barium enema (DCBE) as well as MR colonography. Four figures show representations of polyps as seen on DCBE, axial CT, CTC, and endoscopy.

Entries like CT, MDCT and MSCT are not dealt with as extensively as one could expect or in comparison to other imaging modalities covered in the Encyclopedia. Under “MDCT”, for instance, there is a cross-reference to “Multidetector computed tomography” and this technique is explained in only about 10 lines: “New generation of CT scanners where a 2D array of detector elements replaces the linear array detector elements used in typical conventional and helical CT scanners. The two-dimensional detector array allows acquisition of multiple scans simultaneously and greatly increases the speed of CT image acquisition. With MDCT thin collimation and thus the acquisition of near isotropic imaging of the urinary tract is possible. Isotropic datasets are the basis of high quality multiplanar reformations and 3D reconstructions of the organs including virtual cystoscopic views.”. There was only one cross-reference to “Neoplasms, bladder”.
I also looked up some topics related to MRI. Having recently read a clinical stroke MR examination, I started with diffusion-weighted MRI (DWI). I found the entry “Diffusion-weighted MR imaging” right away (seven lines): “Diffusion weighted MR imaging is a technique in which phase-defocusing and phase-refocusing gradients are used to evaluate the rate of microscopic water diffusion within tissues. With the evolution of echoplanar imaging with a preparation pulse that is sensitive to diffusion, high-speed imaging has become possible, thus reducing the motion artifacts during image acquisition.” There were two cross-references: “Lymphadenopathies, head and neck” and “ Neoplasms, salivary glands.” The explanation is technically correct, but there is unfortunately no mention of stroke – the most important indication for DWI – in either the text or the references.
Next, I looked up renal angiomyolipoma because I had just read a clinical case in which this pathology was diagnosed. I tried “Renal angiomyolipoma”: no entry. I checked “Angiomyolipoma”: no text, but a reference to “Lipomatous neoplasms, hepatic”. I thought there might be an entry under “ Lipomatous neoplasms, renal”, but no. I tried “Kidney tumors” (no entry), but then I found “Kidney cancer”, pointing to “Carcinoma, renal cell”. Then, I tried “Neoplasms, kidney”: no entry, but there was an entry for “Neoplasms, kidney, childhood” that dealt with nephroblastoma. I gave up at this point.
As far as cross-linking is concerned, I found a somewhat random selection to have been made. For example, under “Computed tomography”, after a brief definition, there is only one reference to “ Ischemic heart disease, CT” but no reference to the other major applications of CT.

Besides the issue of occasional difficulty in finding entries, which is – again – inherent to any encyclopedia, another issue with encyclopedias in general is the length of text dedicated to each topic. I understand that it is impossible to be perfectly right with this – and it depends very much on the reader’s expertise and on his or her individual interest in any given topic. Still, it seems strange to me that in my search on MRI, I saw that diffusion-weighted imaging occupied less than one-eighth of a page while “Diffusion-tensor MRI” had twice the coverage, “ Direct imaging” (i.e. targeted imaging) covered more than 2 pages, and “DISH” (diffuse idiopathic skeletal hyperostosis) had more than 3 pages of text and images.
Despite the difficulties I encountered in using this work, I really enjoyed reading the up to date coverage on many “hot” topics as well as on common pathologies, and especially appreciated the extensive contrast media sections. The quality of the figures, images, and tables is outstanding, as is the quality of the presentations of many clinically important topics. The joy of browsing these excellent articles is somewhat hampered by the inadequate cross-references. I do hope that these imperfections can be soon dealt with in the online edition and, as soon as possible, also in future print editions. Nevertheless, I anticipate that I will be using these two volumes many times in the future during my routine work.