Douglas Green

Dual-Energy Liver CT: Effect of Monochromatic Imaging on Lesion Detection, Conspicuity, and Contrast-to-Noise Ratio of Hypervascular Lesions on Late Arterial Phase

OBJECTIVEnThe purpose of this study was to evaluate the effect of use of dual-energy CT monochromatic imaging in the late hepatic arterial phase on hyperenhancing focal lesion detection and lesion conspicuity.nnnSUBJECTS AND METHODSnThis prospective study included 72 patients imaged with a single-source dual-energy CT scanner. Late arterial phase imaging was performed with dual energies of 140 and 80 kVp, and the portal venous and delayed phases were performed with a single energy of 120 kVp. Two deidentified image sets were created: set A consisted of 77-keV images only, and set B consisted of 40-, 50-, 70-, and 77-keV images and iodine-based contrast material decomposition images. Two independent reviewers identified hypervascular lesions and subjectively scored lesion conspicuity. Contrast-to-noise ratios were calculated, and radiation dose (volume CT dose index) was recorded.nnnRESULTSnThe 128 lesions identified had a mean size of 1.7 ± 1.4 cm. There was no difference in lesion detection between the two reviewers or the two image sets. The contrast-to-noise ratio at 50 keV was 72% greater than that at 77 keV (p < 0.0001). Subjective conspicuity was statistically greatest at 50 keV (p < 0.0001). There was no statistical difference in mean volume CT dose index between the dual-energy (12.8 mGy) and the two single-energy (14.4 and 14.2 mGy) phases.nnnCONCLUSIONnViewing dual-energy CT images may result in the greatest subjective lesion conspicuity and measured contrast-to-noise ratio at 50 keV with equal detection of hyperenhancing liver lesions compared with viewing 77-keV images alone. In addition, the radiation doses of dual-energy CT may be similar to those of single-energy CT.

Ferumoxytol in clinical practice: Implications for MRI

Ferumoxytol is an iron‐containing parenteral treatment for iron deficiency anemia that was recently approved by the Food and Drug Administration. The iron is in the form of a superparamagnetic iron oxide that causes T1, T2, and T2* shortening on magnetic resonance imaging (MRI). Furthermore, the drug has a long intravascular half‐life of 14–15 hours; a standard dose can affect MRI for days to months. We describe a case in which a patient underwent contrast‐enhanced MRI of the liver 2 days after receiving a dose of ferumoxytol, which was unknown to the radiology team. The blood pool and soft tissues were hyperintense on T1‐weighted images, concealing enhancement from the gadolinium‐based contrast agent that was administered during the exam and rendering the exam nondiagnostic. Radiologists must be aware of this potential effect in screening patients for MRI and interpreting exams. J. Magn. Reson. Imaging 2013;37:1476–1479.

Prospectively ECG gated CT pulmonary angiography versus helical ungated CT pulmonary angiography: impact on cardiac related motion artifacts and patient radiation dose.

OBJECTIVEnTo compare prospectively ECG gated CT pulmonary angiography (CTPA) with routine helical ungated CTPA for cardiac related motion artifacts and patient radiation dose.nnnSUBJECTS AND METHODSnTwenty patients with signs and symptoms suspicious for pulmonary embolism and who had a heart rate below 85 were scanned with prospectively ECG gated CTPA. These gated exams were matched for several clinical parameters to exams from twenty similar clinical patients scanned with routine ungated helical CTPA. Three blinded independent reviewers subjectively evaluated all exams for overall pulmonary artery enhancement and for several cardiac motion related artifacts, including vessel blurring, intravascular shading, and double line. Reviewers also measured pulmonary artery intravascular density and image noise. Patient radiation dose for each technique was compared. Fourteen clinical prospectively ECG gated CTPA exams from a second institution were evaluated for the same parameters.nnnRESULTSnProspectively ECG gated CTPA resulted in significantly decreased motion-related image artifact scores in lung segments adjacent to the heart compared to ungated CTPA. Measured image noise was not significantly different between the two types of CTPA exams. Effective dose was 28% less for prospectively ECG gated CTPA (4.9 mSv versus 6.8 mSv, p=0.02). Similar results were found in the prospectively ECG gated exams from the second institution.nnnCONCLUSIONnCompared to routine helical ungated CTPA, prospectively ECG gated CTPA may result in less cardiac related motion artifact in lung segments adjacent to the heart and significantly less patient radiation dose.

Noncontrast Functional MRI of the Kidneys

Functional magnetic resonance imaging (fMRI) techniques enable noninvasive assessment of renal function. Diffusion-weighted imaging, diffusion tensor imaging, blood oxygen level–dependent MRI, magnetic resonance elastography, and arterial spin labeling are some of the emerging techniques that have potential to investigate renal function without the use of exogenous gadolinium contrast. This article discusses the principles of these techniques, as well as their possible applications and limitations. This will introduce the readers to these novel imaging tools, which appear to have promising futures.

Negative ECG-Gated Cardiac CT in Patients With Low-to-Moderate Risk Chest Pain in the Emergency Department: 1-Year Follow-Up

OBJECTIVEnThe purpose of this article is to determine the frequency of adverse cardiac events during the year following a negative cardiac CT angiogram in a population of patients presenting to the emergency department with low-to-moderate risk chest pain.nnnSUBJECTS AND METHODSnEighty-one consecutive patients who had standard of care evaluation for low-to-moderate risk chest pain in the emergency department were enrolled and consented to have a cardiac CT angiogram added to their workup and to have follow-up for 1 year. Eleven patients were excluded, six because their cardiac CT examinations were unsuccessful, four because of a positive cardiac CT angiogram result, and one was lost to follow-up. Seventy patients with negative cardiac CT angiographic results (< 50% stenosis) were included and were interviewed in detail at 3, 6, and 12 months about intervening cardiac events, diagnostic testing, and therapy. Electronic medical records were also reviewed at each time point.nnnRESULTSnNone of the 70 patients reported an adverse cardiac event over the 12-month follow-up period. At 1 year, the cause of chest pain was unknown in 49 patients, gastrointestinal in nine patients, anxiety in seven patients, musculoskeletal in three patients, and other in two patients. Three of four patients with 50% or greater stenosis on their cardiac CT had subsequent cardiac catheterization and stent placement.nnnCONCLUSIONnIn patients with low-to-moderate risk chest pain evaluated in the emergency department, adverse cardiac events may be rare during the 12 months following a negative cardiac CT angiogram.

Irreversible electroporation of a liver metastasis

A 70 year old Caucasian man with a history of recently resected moderately-differentiated invasive adenocarcinoma of the colon presented with a 1.8 cm focal liver lesion in segment V (white arrow in Figs. a and b) newly diagnosed at MRI. No other metastatic lesions were detected at PET-CT. After discussing treatment options including resection and ablation, a decision was made to proceed with ablation of this single metastasis. An MRI performed the day after the procedure demonstrates a large area of ablation at the site of the metastasis before contrast administration (white arrow in Fig. c). The ablated area demonstrated no contrast enhancement and was surrounded by an enhancing rim after contrast medium administration (white arrow in Figs. d and e), this findings are consistent with successful metastatic lesion ablation. In Figs. 1d and 1e (black arrow), a contrast-filled vessel is clearly identified crossing the area of ablation. The vessel is not seen before contrast medium administration (black arrow in Fig. c). Irreversible electroporation causes an area of necrosis/apoptosis demonstrating no enhancement on post-contrast images (Figs. d and e) (1–3). While peripheral enhancement surrounding a zone of necrosis has been reported following chemoembolization, the significance of the post-IRE MRI changes has not been adequately studied (Figs. 1d and 1e), in this case the peripheral enhancing area demonstrates high signal intensity on diffusion weighted images (Fig. 1f) (1–3). Thirty days later, in the area of ablation, there has been complete radiological liver parenchyma regeneration (Fig. g), and only a mild perfusion abnormality is noted, the vessel spared by IRE is still patent. Metastatic colorectal carcinoma to the liver is common and treatment of single focal metastatic lesions may be achieved with multiple techniques such as surgical resection, radiofrequency ablation, cryoablation, highly focused ultrasound, microwave ablation and irreversible electroporation (IRE) (1). Each of these techniques has its specifics indications, benefits and risks. Stemming from its non-thermal nature, irreversible electroporation has the peculiar characteristic of ablating cells while sparing structural elements of the biliary ducts and vessels (1, 2). IRE consists of targeted delivery of electrical pulses to modify cell membrane permeability, either temporarily or permanently, depending on the electric field magnitude, pulse duration, and number of pulses applied (1, 2). IRE causes tissue necrosis and apoptosis through the formation of nanometer-scale pores in the cell membrane (1, 2). MRI characteristics of treated lesions have been described in rats (2), but the experience in humans is still limited. These images represent early changes following IRE with demonstration of vessel sparring by IRE.

A Short Walk

And how this book will influence you to do better future? It will relate to how the readers will get the lessons that are coming. As known, commonly many people will believe that reading can be an entrance to enter the new perception. The perception will influence how you step you life. Even that is difficult enough; people with high sprit may not feel bored or give up realizing that concept. Its what a short walk will give the thoughts for you.

The Not-All-That-Invisible College

In mid-1600s London, a group of Five years ago, technology writer But more than making it easier to natural philosophers and physicians started having regular meetings to discuss shared scientific interests. Because the members of this group did not belong to any formal institution, they referred to themselves as the “invisible college” [1,2]. The invisible college begat the Royal Society of London, founded in 1662 [1]. In 1665, the society published the first peer-reviewed scientific journal, Philosophical Transactions [1]. Peer-reviewed journals were a formal way for scientists to share their work and learn from one another’s successes and failures. Of course, the arrival of the formal peer-reviewed journal did not end informal communications among scientists.Groups of scientistswith shared interests would circulate reprints of publications, preprints of publications, and documents detailing work in progress. They would meet at physically sited conferences and institutions. In 1963,Price resurrected the term invisible college to describe groups of scientists in which “everybody who was anybody” had informal communications with “everybody else who was anybody” [2]. Price thought that if an invisible college were to function in this manner, it could consist of no more than 100 scientists (years later, Dunbar established that a social group could not exceed 150 individuals if every individual is to know who each person is and how each person knows every other person) [3].

Corporatized Radiology: From Down Under to Over Here?

In this article, we reflect on the current state of corporatized radiology, forces driving consolidation, and alternatives to corporatization that allow radiologists to maintain their autonomy while providing the highest level of care to their medical communities.

Uber and Us: Radiology and On Demand Platforms, with Commentary from Dr Heilman: Practice Corner.

The Uber Model Need a ride? The Uber (San Francisco, Calif) app uses your smartphone’s global positioning system (GPS) to detect your location and connect you with the nearest available driver. Uber is the best-known example of an on-demand platform. On-demand platforms use technology to repackage one set of peoples’ needs (in this case, a ride) into another set of peoples’ tasks (transporting riders) (1). Uber is a hit. In San Francisco, it has “pretty much destroyed regular taxis” (2). The average number of monthly trips per city taxi has declined from 1424 rides per month in 2012 (the year that Uber added San Francisco service) to 504 in 2014 (2). Other on-demand platforms hope to become the “Uber of X.” With SpoonRocket, you can arrange for a courier to deliver your lunch, while the Handy app can send a worker to help you with household jobs. Since 2010, venture capitalists have invested more than