George Shih

Signal Change in the Dentate Nucleus on T1-Weighted MR Images After Multiple Administrations of Gadopentetate Dimeglumine Versus Gadobutrol

OBJECTIVE The objective of this study was to evaluate signal changes in the dentate nucleus on unenhanced T1-weighted MR images after multiple administrations of gadopentetate dimeglumine versus gadobutrol. MATERIALS AND METHODS Two study groups were identified, each of which included 25 consecutive patients. Each group received six or more administrations of either gadobutrol only or gadopentetate dimeglumine only, without having had exposure to any other gadolinium-based contrast agent (GBCA). The mean signal intensity (SI) in the dentate nucleus on unenhanced T1-weighted MR images was measured, with the use of the pons and the cerebellar peduncle as references to calculate the DNP SI ratio (i.e., the ratio of the SI in the dentate nucleus to the SI in the pons) and the DCP SI ratio (i.e., the ratio of the SI in the dentate nucleus to the SI in the cerebellar peduncle). RESULTS After six administrations of gadopentetate dimeglumine, the SI in the dentate nucleus on unenhanced T1-weighted MR images increased from a DCP SI ratio of 0.997 before administration to 1.034 after the last of six administrations (p = 0.0007) and then to 1.063 after all administrations (p = 0.0004). No statistically significant increase was noted in association with administration of gadobutrol, for which the DCP SI ratio was 0.995 before administration, 1.009 after the last of six administrations (p = 0.1172), and 0.992 after all administrations (p = 0.7592). The change in the DCP SI ratio after administration of gadopentetate dimeglumine correlated with the number of administrations the patient received (p < 0.0001). CONCLUSION Unenhanced T1 signal hyperintensity was observed in the dentate nucleus after multiple administrations of gadopentetate dimeglumine, a linear ionic agent, but not after multiple administrations of gadobutrol, a macrocyclic GBCA.

Intrarenal Color Duplex Ultrasonography A Window to Vascular Complications of Renal Transplants

We analyze and discuss the importance of intrarenal color duplex ultrasonography (CDUS) in the diagnosis and differential diagnosis of vascular complications in renal transplants.

Extent of Signal Hyperintensity on Unenhanced T1-weighted Brain MR Images after More than 35 Administrations of Linear Gadolinium-based Contrast Agents

Purpose To explore the extent of signal hyperintensity in the brain on unenhanced T1-weighted magnetic resonance (MR) images with increasing gadolinium-based contrast agent (GBCA) doses in patients who received 35 or more linear GBCA administrations. Materials and Methods In this institutional review board-approved HIPAA-compliant retrospective study, picture archiving and communication systems of two tertiary referral hospitals were searched to identify patients who received 35 or more linear GBCA administrations. Unenhanced T1-weighted images of the brain in patients after six, 12, and 24 GBCA administrations and after the final GBCA administration were independently reviewed by three radiologists to identify sites where T1 signal intensity was increasing. Areas identified by all three observers as increasing in T1 signal intensity when compared with baseline images were further analyzed with a quantitative region of interest analysis measuring the rate of signal increase per injection and the total change after 24 linear GBCA administrations relative to reference tissues that did not show T1 shortening. Results Qualitative analysis of 13 patients with 39-59 linear GBCA administrations showed visually detectable T1 shortening in the dentate nucleus (n = 13), globus pallidus (n = 13), substantia nigra (n = 13), posterior thalamus (n = 12), red nucleus (n = 10), colliculi (n = 10), superior cerebellar peduncle (n = 7), caudate nucleus (n = 4), whole thalamus (n = 3), and putamen (n = 2). Quantitative analysis enable confirmation of signal intensity increases on unenhanced T1-weighted images relative to reference tissues in the dentate nucleus (0.53% signal intensity increase per injection, P < .001), globus pallidus (0.23% increase, P = .009), posterior thalamus (0.26% increase, P < .001), substantia nigra (0.25% increase, P = .01), red nucleus (0.25% increase, P = .01), cerebellar peduncle (0.19% increase, P = .001), and colliculi (0.21% increase, P = .02). Conclusion Increased signal intensity on unenhanced T1-weighted images was seen in the posterior thalamus, substantia nigra, red nucleus, cerebellar peduncle, colliculi, dentate nucleus, and globus pallidus.

Is Android or iPhone the Platform for Innovation in Imaging Informatics

It is clear that ubiquitous mobile computing platforms will be a disruptive technology in the delivery of healthcare in the near future. While radiologists are fairly sedentary, their customers, the referring physicians, and the patients are not. The need for closer collaboration and interaction with referring physicians is seen as a key to maintaining relationships and integrating tightly with the patient management team. While today, patients have to settle for their images on a CD, in short time, they will be taking them home on their cell phone. As PACS vendors are moving ever outward in the enterprise, they are already actively developing clients on mobile platforms. Two major contenders are the Apple’s iPhone and the Android platform developed by Google. These two designs represent two entirely different architectures and business models.

Effect of Renal Function on Gadolinium-related Signal Increases on Unenhanced T1-weighted Brain Magnetic Resonance Imaging

ObjectivesThe purpose of this study was to determine if renal function affects signal changes in the deep brain nuclei on unenhanced T1-weighted images after administration of linear gadolinium-based contrast agents (GBCAs). MethodsAn electronic medical records search of 2 large medical centers identified 25 patients who received linear GBCA while on hemodialysis and had unenhanced T1-weighted images of the brain before and after. The dentate-to-cerebellar peduncle (DCP) ratio, globus pallidus-to-mid thalamus (GPT) ratio, and choroid plexus-to-nearby white matter ratio were measured and compared with 25 age/sex/GBCA exposure–matched control patients with normal or near-normal renal function (estimated glomerular filtration rate >60 mL/min per 1.73 m2). Two additional control groups included 13 patients on hemodialysis without GBCA exposure and 13 age/sex-matched patients with estimated glomerular filtration rate greater than 60 mL/min per 1.73 m2. ResultsHemodialysis patients (n = 25) with an average of 1.8 linear GBCA administrations had a 4.9% mean increase (1.00 ± 0.04 vs 1.05 ± 0.05; P < 0.001) in DCP, which was greater than the 1.6% change (0.99 ± 0.04 vs 1.00 ± 0.05; P = 0.08) observed in matched controls (P = 0.01). There was no significant signal change in the DCP ratio in the 13 hemodialysis patients (0.99 ± 0.04 vs 0.99 ± 0.04; P = 0.78) and 13 age/sex-matched patients (0.99 ± 0.02 vs 0.99 ± 0.03; P = 0.78) who did not receive GBCA. The hemodialysis patients had a baseline GPT that was higher than nondialysis patients (P < 0.001). However, the GPT change after GBCA administration was not significantly different from controls. Increased signal in the choroid plexus on unenhanced T1-weighted images after GBCA administration was noted in hemodialysis patients (0.72 ± 0.20 vs 0.86 ± 0.23; P = 0.006); however, a multivariate analysis showed this to be primarily related to hemodialysis (P = 0.003) with only a trend toward relating to GBCA exposure (P = 0.07). ConclusionsHemodialysis patients receiving linear GBCA have greater dentate nucleus signal increases on unenhanced T1-weighted images, suggesting that renal function may affect the rate of gadolinium accumulation in the brain after linear GBCA-enhanced magnetic resonance imaging.

Changes in hepatic venous morphology with cirrhosis on MRI

To identify changes in vascular morphology on magnetic resonance imaging (MRI) in patients with cirrhosis and to compare these findings to liver donors.

Use of Mobile Devices for Medical Imaging

Mobile devices have fundamentally changed personal computing, with many people forgoing the desktop and even laptop computer altogether in favor of a smaller, lighter, and cheaper device with a touch screen. Doctors and patients are beginning to expect medical images to be available on these devices for consultative viewing, if not actual diagnosis. However, this raises serious concerns with regard to the ability of existing mobile devices and networks to quickly and securely move these images. Medical images often come in large sets, which can bog down a network if not conveyed in an intelligent manner, and downloaded data on a mobile device are highly vulnerable to a breach of patient confidentiality should that device become lost or stolen. Some degree of regulation is needed to ensure that the software used to view these images allows all relevant medical information to be visible and manipulated in a clinically acceptable manner. There also needs to be a quality control mechanism to ensure that a devices display accurately conveys the image content without loss of contrast detail. Furthermore, not all mobile displays are appropriate for all types of images. The smaller displays of smart phones, for example, are not well suited for viewing entire chest radiographs, no matter how small and numerous the pixels of the display may be. All of these factors should be taken into account when deciding where, when, and how to use mobile devices for the display of medical images.

Doppler angle correction in the measurement of intrarenal parameters

Background: The aim of this study was to assess differences in intrarenal artery Doppler parameters measured without and with Doppler angle correction. Methods: We retrospectively reviewed color duplex sonography in 30 normally functioning kidneys (20 native kidneys in 10 subjects and 10 transplanted kidneys in 10 subjects) performed between January 26, 2010 and July 26, 2010. There were 10 age-matched men and 10 age-matched women (mean 39.8 ± 12.2, range 21–60 years) in this study. Depending on whether the Doppler angle was corrected in the spectral Doppler measurement, Doppler parameters including peak systolic velocity (PSV), end-diastolic velocity (EDV), and resistive index (RI) measured at the interlobar artery of the kidney were divided into two groups, ie, initial Doppler parameters measured without Doppler angle correction (Group 1) and remeasured Doppler parameters with Doppler angle correction (Group 2). Values for PSV, EDV, and RI measured without Doppler angle correction were compared with those measured with Doppler angle correction, and were analyzed statistically with a paired-samples t-test. Results: There were statistical differences in PSV and EDV at the interlobar artery in the upper, mid, and lower poles of the kidney between Group 1 and Group 2 (all P < 0.001). PSV and EDV in Group 1 were significantly lower than in Group 2. RI in Group 1 was the same as that in Group 2 in the upper, mid, and lower poles of the kidneys. Conclusion: Doppler angle correction plays an important role in the accurate measurement of intrarenal blood flow velocity. The true flow velocity converted from the maximum Doppler velocity shift is produced only when the Doppler angle is 0°, so that the emission sound beam is parallel to the direction of blood flow at the sampled artery. Therefore, the Doppler angle correction should be routinely applied and displayed on renal color duplex sonography.

Imaging Properties of 3D Printed Materials: Multi-Energy CT of Filament Polymers

Clinical applications of 3D printing are increasingly commonplace, likewise the frequency of inclusion of 3D printed objects on imaging studies. Although there is a general familiarity with the imaging appearance of traditional materials comprising common surgical hardware and medical devices, comparatively less is known regarding the appearance of available 3D printing materials in the consumer market. This work detailing the CT appearance of a selected number of common filament polymer classes is an initial effort to catalog these data, to provide for accurate interpretation of imaging studies incidentally or intentionally including fabricated objects. Furthermore, this information can inform the design of image-realistic tissue-mimicking phantoms for a variety of applications, with clear candidate material analogs for bone, soft tissue, water, and fat attenuation.

Ultrasound strain elastography in assessment of resting biceps brachii muscle stiffness in patients with Parkinson's disease: a primary observation.

The aim of this study was to evaluate the feasibility of ultrasound strain elastography (SE) for the assessment of resting biceps brachii muscle (BBM) stiffness in patients with Parkinsons diseases (PD). From May 2014 to December 2014, we prospectively performed SE of BBM in 14 patients with PD and 10 healthy controls. Based on the Unified Parkinsons Disease Rating Scale for scoring muscle rigidity (UPDRS, part III), muscle rigidity scores in 14 patients with PD included 3 patients with high rigidity (UPDRS III-IV) and 11 patients with low rigidity (UPDRS I-II). Ultrasound strain was represented by the deformation of the BBM and subcutaneous soft tissues that was produced by external compression with a sand bag (1.5 kg) tied onto an ultrasound transducer. Deformation was estimated with two-dimensional speckle tracking. The difference in strain ratio (SR, defined as mean BBM strain divided by mean subcutaneous soft tissue strain) between PD and healthy controls was tested by unpaired t test. The correlation between SR and muscle rigidity score was analyzed by Pearson correlation coefficient. The reliability of SR in assessment of BBM stiffness was tested using intraclass correlation coefficient. In our result, the SR in PD and healthy controls measured 2.65±0.36 and 3.30±0.27, respectively. A significant difference in SR was noted between the healthy controls and PD (P=.00011). A negative correlation was found between SR and UPDRS rigidity score (r=-0.78). Our study suggests that the SR of BBM to reference tissue can be used as a quantitative biomarker in assessing resting muscle stiffness associated with muscle rigidity in PD.