The history of MR imaging as seen through the pages of radiology

Incidentally detected acromegaly: single-center study of surgically treated patients over 22 years

Acromegaly is a rare disease associated with comorbidities that are common in the general population. Most patients undergo screening for classic phenotypical (CP) or mass effect manifestations. By retrospective review of pituitary tumor surgeries performed between 1994 and 2016 (1836), we identified patients with acromegaly (112). Main presentations were: CP (43%), mass effect (26%), incidentally detected (ID) tumors (17%), and other (14%). We compared the ID and CP groups regarding prevalence, clinical, biochemical, radiological and histopathological characteristics, and postoperative outcomes. The prevalence of ID among all surgeries increased after 2011 from 0.6% to 1.9% (p=0.01), while prevalence of CP remained stable (2.8% and 2.33%, p=0.65). Almost half of ID (47.4%) presented with otolaryngological manifestations. The ID and CP groups were similar regarding age, gender, comorbidities (hypertension, diabetes, hypopituitarism), tumor diameter and cavernous sinus invasion. Median insulin-like growth factor (IGF-1) and growth hormone (GH) levels were lower in the ID than CP (p<0.05 and p=0.07). Patients younger than 40 had smaller tumors in the ID than CP, while the opposite was true for older patients. The 3-month biochemical remission rates were similar (68% ID and 58% CP). A similar number of patients had normal IGF-1 at last follow-up (89.5% ID and 81.25% CP) after surgery alone and multimodality treatment. In conclusion, an increased number of patients with GH-secreting adenomas were ID in recent years. Education of physicians other than endocrinologists regarding presentation and comorbidity clustering may lead to an earlier diagnosis of acromegaly and improved outcomes.

Assessment of cardiac function, blood flow and myocardial tissue relaxation parameters at 0.35 T

A low field strength (B0) system could increase cardiac MRI availability for patients otherwise contraindicated at higher field. Lower equipment costs could also broaden cardiac MR accessibility. The current study investigated the feasibility of cardiac function with steady-state free precession and flow assessment with phase contrast (PC) cine images at 0.35 T, and evaluated differences in myocardial relaxation times using quantitative T1, T2 and T2* maps by comparison with 1.5 and 3 T results in a small cohort of six healthy volunteers. Signal-to-noise ratio (SNR) differences across systems were characterized with proton density-weighted spin echo phantom data. SNR at 0.35 T was lower by factors of 5.5 and 15.0 compared with the 1.5 and 3 T systems used in this study. All cine images at 0.35 T scored 3 or greater on a five-point image quality scale. Normalized blood-myocardium contrast in cine images, left ventricular volumes (end diastolic volume, end systolic volume) and function (ejection fraction and stroke volume) measures at 0.35 T matched 1.5 and 3 T results. Phase-to-noise ratio in 0.35 T PC images (11.7 ± 1.9) was lower than 1.5 T (18.7 ± 5.2) and 3 T (44.9 ± 16.5). Peak velocity and stroke volume determined from PC images were similar across systems. Myocardial T1 increased (564 ± 13 ms at 0.35 T, 955 ± 19 ms at 1.5 T and 1200 ± 35 ms at 3 T) while T2 (59 ± 4 ms at 0.35 T, 49 ± 3 ms at 1.5 T and 40 ± 2 ms at 3 T) and T2* (42 ± 8 ms at 0.35 T, 33 ± 6 ms at 1.5 T and 24 ± 3 ms at 3 T) decreased with increasing B0. Despite SNR deficits, cardiovascular function, flow assessment and myocardial relaxation parameter mapping is feasible at 0.35 T using standard cardiovascular imaging sequences.

Magnetic Resonance Imaging of Hard Tissues and Hard Tissue Engineered Bio-substitutes

Magnetic resonance imaging (MRI) is a non-invasive diagnostic imaging tool based on the detection of protons into the tissues. This imaging technique is remarkable because of high spatial resolution, strong soft tissue contrast and specificity, and good depth penetration. However, MR imaging of hard tissues, such as bone and teeth, remains challenging due to low proton content in such tissues as well as to very short transverse relaxation times (T₂). To overcome these issues, new MRI techniques, such as sweep imaging with Fourier transformation (SWIFT), ultrashort echo time (UTE) imaging, and zero echo time (ZTE) imaging, have been developed for hard tissues imaging with promising results reported. Within this article, MRI techniques developed for the detection of hard tissues, such as bone and dental tissues, have been reviewed. The main goal was thus to give a comprehensive overview on the corresponding (pre-) clinical applications and on the potential future directions with such techniques applied. In addition, a section dedicated to MR imaging of novel biomaterials developed for hard tissue applications was given as well.

Long-term causes of death among pediatric patients with cancer

BACKGROUND

The objectives of this study were to characterize the risk of death (1) from the primary cancer vs competing cause of death; and (2) from various causes of death vs the general poplation. The relative risk of death after a pediatric cancer diagnosis versus the general population and the risk of death from a primary cancer diagnosis versus competing causes of death.

METHODS

This retrospective, population-based study used the Surveillance, Epidemiology, and End Results database (1980-2015) and included patients aged 0 to 19 years at the time of diagnosis. Observed deaths were calculated; the risk of death versus the general population was assessed with standardized mortality ratios (SMRs). Competing risk models for the cause of death were performed.

RESULTS

There were 58,356 patients who were diagnosed, and the mortality rate was 22.8%. To assess causes of death, 6996 patients who died during the study period were included (45,580 total person-years at risk): 5128 (73%) died of their primary cancer, and 1868 (27%) died of a competing cause. Among all patients, the rate of death from the index cancer was higher than the rate of death from another cause within the first 5 years after diagnosis. The risk of death from a nonprimary cancer began to supersede the rate of death from the primary cancer 10 years after diagnosis for patients with germ cell tumors, lymphomas, and sarcomas. SMRs for the primary cancer were highest within the first 5 years after diagnosis for all cancers (SMRs, 100-50,000; P < .0001). The risk of death from competing causes (heart disease, suicide, and sepsis) was elevated (SMR, >100; P < .001). The risk of dying of heart disease was high, especially for patients with astrocytomas (SMR, 47.84; 95% confidence interval [CI], 27.87-76.59) and neuroblastomas (SMR, 98.59; 95% CI, 47.28-181.32). The risk of dying of suicide was high in most patients, particularly for those with osteosarcomas (SMR, 111.40; 95% CI, 2.82-620.69), Hodgkin lymphomas (SMR, 62.35; 95% CI, 34.89-102.83), and gonadal germ cell tumors (SMR, 28.97; 95% CI, 12.51-57.09).

CONCLUSIONS

The cause of death for patients with gonadal germ cell tumors, lymphomas, and sarcomas is more commonly a secondary cancer or noncancerous cause than the primary disease; their risk of death from competing causes (heart disease, suicide, and sepsis) rises throughout life.

Efficient spiral in-out and EPI balanced steady-state free precession cine imaging using a high-performance 0.55T MRI

PURPOSE

Low-field MRI offers favorable physical properties for SNR-efficient long readout acquisitions such as spiral and EPI. We used a 0.55 tesla (T) MRI system equipped with high-performance hardware to increase the sampling duty cycle and extend the TR of balanced steady-state free precession (bSSFP) cardiac cine acquisitions, which typically are limited by banding artifacts.

METHODS

We developed a high-efficiency spiral in-out bSSFP acquisition, with zeroth- and first-gradient moment nulling, and an EPI bSSFP acquisition for cardiac cine imaging using a contemporary MRI system modified to operate at 0.55T. Spiral in-out and EPI bSSFP cine protocols, with TR = 8 ms, were designed to maintain both spatiotemporal resolution and breath-hold length. Simulations, phantom imaging, and healthy volunteer imaging studies (n = 12) were performed to assess SNR and image quality using these high sampling duty-cycle bSSFP sequences.

RESULTS

Spiral in-out bSSFP performed favorably at 0.55T and generated good image quality, whereas EPI bSSFP suffered motion and flow artifacts. There was no difference in ejection fraction comparing spiral in-out with standard Cartesian imaging. Moreover, human images demonstrated a 79% ± 21% increase in myocardial SNR using spiral in-out bSSFP and 50% ± 14% increase in SNR using EPI bSSFP as compared with the reference Cartesian acquisition. Spiral in-out acquisitions at 0.55T recovered 69% ± 14% of the myocardial SNR at 1.5T.

CONCLUSION

Efficient bSSFP spiral in-out provided high-quality cardiac cine imaging and SNR recovery on a high-performance 0.55T MRI system.

Magnetoencephalography—Established but not yet Essential

Magnetoencephalography for Epileptic Focus Localization in a Series of 1000 Cases

Rampp S, Stefan H, Wu X, et al. Brain. 2019;142(10):3059-3071. doi:10.1093/brain/awz231.

The aim of epilepsy surgery in patients with focal, pharmacoresistant epilepsies is to remove the complete epileptogenic zone to achieve long-term seizure freedom. In addition to a spectrum of diagnostic methods, magnetoencephalography (MEG) focus localization is used for planning of epilepsy surgery. We present results from a retrospective observational cohort study of 1000 patients, evaluated using MEG at the University Hospital Erlangen over the time span of 28 years. One thousand consecutive cases were included in the study, evaluated at the University Hospital Erlangen between 1990 and 2018. All patients underwent MEG as part of clinical workup for epilepsy surgery. Of these, 405 patients underwent epilepsy surgery after MEG, with postsurgical follow-ups of up to 20 years. Sensitivity for interictal epileptic activity was evaluated, in addition to concordance of localization with the consensus of presurgical workup on a lobar level. We evaluate MEG characteristics of patients who underwent epilepsy surgery versus patients who did not proceed to surgery. In operated patients, resection of MEG localizations was related to postsurgical seizure outcomes, including long-term results after several years. In comparison, the association of lesionectomy with seizure outcomes was analyzed. Measures of diagnostic accuracy were calculated for MEG resection and lesionectomy. Sensitivity for interictal epileptic activity was 72% with significant differences between temporal and extra-temporal lobe epilepsy. MEG was concordant with the presurgical consensus in 51% and showed additional or more focal involvement in an additional 32%. Patients who proceeded to surgery showed a significantly higher percentage of monofocal MEG results. Complete MEG resection was associated with significantly higher chances to achieve seizure freedom in the short term and long term. Diagnostic accuracy was significant in temporal and extra-temporal lobe cases but was significantly higher in extra-temporal lobe epilepsy (diagnostic odds ratios of 4.4 and 41.6). Odds ratios were also higher in non-lesional versus lesional cases (42.0 vs 6.2). The results show that MEG provides nonredundant information, which significantly contributes to patient selection, focus localization, and ultimately long-term seizure freedom after epilepsy surgery. Specifically in extra-temporal lobe epilepsy and non-lesional cases, MEG provides excellent accuracy.

Lumbar arachnoiditis: Does imaging associate with clinical features?

OBJECTIVES

Lumbar arachnoiditis is a rare and debilitating neurologic disorder with multiple etiologies and a spectrum of imaging and clinical characteristics. Prior reports have anecdotally claimed that no association exists between findings of arachnoiditis observed on magnetic resonance imaging (MRI) and those assessed clinically. The purpose of this study was to determine if MRI features of lumbar arachnoiditis associate with the clinical findings of the disorder.

PATIENTS AND METHODS

Twenty eight patients with lumbar arachnoiditis reported on MRI between 2012 and 2018 were retrospectively identified. A variety of MRI and clinical features of lumbar arachnoiditis were cataloged for these patients based on common findings discovered through literature review. Imaging findings included cauda equina nerve root contour and thickening, adhesion location, level of involvement, enhancement, and Delamarter group. Clinical findings included demographics, etiology, symptom dynamics, and signs/symptoms. Fisher's exact tests were used to determine associations between the imaging and clinical features of lumbar arachnoiditis.

RESULTS

In general, MRI findings did not associate with the clinical features of lumbar arachnoiditis with a few exceptions. Most notably, confounding lumbar pathology was associated with symptom dynamics (p = 0.004) and nerve root contour was associated with motor and sensory symptoms (p = 0.01). The suspected arachnoiditis etiology of the majority of patients was either post-operative or post-infectious in nature.

CONCLUSION

MRI findings in lumbar arachnoiditis offer limited insight into the clinical presentation of the disorder.

Multifunctional Magnetic Resonance Imaging Probes

Magnetic resonance imaging is characterized by high spatial resolution and unsurpassed soft tissue discrimination. Development and characterization of both intrinsic and extrinsic magnetic resonance (MR) imaging probes in the last decade has further strengthened the pivotal role MR imaging holds in the assessment of cancer in preclinical and translational settings. Sophisticated chemical modifications of a variety of nanoparticulate probes hold the potential to deliver valuable multifunctional tools applicable in diagnostics and/or treatment in human oncology. MR imaging suffers from a lack of sensitivity achievable by, e.g., nuclear medicine imaging methods. Advantages of including additional functionality/functionalities in a probe suitable for MR imaging are thus numerous, comprising the addition of fundamentally different imaging information (diagnostics), drug delivery (therapy), or the combination of both (theranostics). In recent years, we have witnessed a plethora of preclinical multimodal or multifunctional imaging probes being published mainly as proof-of-principle studies, yet only a handful are readily applicable in clinical settings. This chapter summarizes recent innovations in the development of multifunctional MR imaging probes and discusses the suitability of these probes for clinical transfer.

A Web-Based Educational Magnetic Resonance Simulator: Design, Implementation and Testing

A new web-based education-oriented magnetic resonance (MR) simulator is presented. We have identified the main requirements that this simulator should comply with, so that trainees can face useful practical tasks such as setting the exact slice position and its properties, selecting the correct protocol or fitting the parameters to acquire an image. The tool follows the client-server model. The client contains the interface that mimics the console of a real machine and several of its features. The server stores anatomical models and executes the bulk of the simulation. This cross-platform simulator has been used in two real educational scenarios. The acceptance of the tool has been measured using two criteria, namely, the System Usability Scale and the Likelihood to Recommend, both with satisfactory results. Therefore, we conclude that given the potential of the tool, it may play a relevant role for the training of MRI operators and other involved personnel.

Nitrogen-vacancy centers in diamond for nanoscale magnetic resonance imaging applications

The nitrogen-vacancy (NV) center is a point defect in diamond with unique properties for use in ultra-sensitive, high-resolution magnetometry. One of the most interesting and challenging applications is nanoscale magnetic resonance imaging (nano-MRI). While many review papers have covered other NV centers in diamond applications, there is no survey targeting the specific development of nano-MRI devices based on NV centers in diamond. Several different nano-MRI methods based on NV centers have been proposed with the goal of improving the spatial and temporal resolution, but without any coordinated effort. After summarizing the main NV magnetic imaging methods, this review presents a survey of the latest advances in NV center nano-MRI.

Imaging in Spine Surgery: Current Concepts and Future Directions

OBJECTIVE

To review and highlight the historical and recent advances of imaging in spine surgery and to discuss current applications and future directions.

METHODS

A PubMed review of the current literature was performed on all relevant articles that examined historical and recent imaging techniques used in spine surgery. Studies were examined for their thoroughness in description of various modalities and applications in current and future management.

RESULTS

We reviewed 97 articles that discussed past, present, and future applications for imaging in spine surgery. Although most historical approaches relied heavily upon basic radiography, more recent advances have begun to expand upon advanced modalities, including the integration of more sophisticated equipment and artificial intelligence.

CONCLUSIONS

Since the days of conventional radiography, various modalities have emerged and become integral components of the spinal surgeon's diagnostic armamentarium. As such, it behooves the practitioner to remain informed on the current trends and potential developments in spinal imaging, as rapid adoption and interpretation of new techniques may make significant differences in patient management and outcomes. Future directions will likely become increasingly sophisticated as the implementation of machine learning, and artificial intelligence has become more commonplace in clinical practice.

Pathology of liver disease: advances in the last 50 years

Liver disease has been recognized in various forms for centuries. Incredible advances, however, have been made especially in the last 50 years, driven by improvements in histology, the development of immunostains, the development of high resolution imaging methods, improved biopsy and resection methods, and the emergence of the molecular era. With these tools, pathologists and their clinical and basic science colleagues moved from classifying liver disease using an observational, pattern-based approach to a refined classification of disease, one based on etiology for medical disease and tumor classification for neoplastic disease. Examples of liver specific diseases are used to illustrate these exciting advances. These impressive advances of the past provide the foundation for hope in the future, as liver pathology continues to play an important role in improving patient care through disease identification and classification and emerging roles in guiding therapy for cures.

The Evolution of MRI of the Prostate: The Past, the Present, and the Future

OBJECTIVE. The purpose of this article is to discuss the evolution of MRI in prostate cancer from the early 1980s to the current day, providing analysis of the key studies on this topic. CONCLUSION. The rapid diffusion of MRI technology has meant that residual variability remains between centers regarding the quality of acquisition and the quality and standardization of reporting.

Improvement in radiological reading efficiency and residents' education and clinical contribution using the modified reading system "Triage Reader"

PURPOSE

To assess whether the modified reading system "Triage Reader" (TR) can improve the radiological reading work environment.

MATERIALS AND METHODS

This retrospective, single-center study analyzed two reading systems for 26,786 computed tomography and magnetic resonance imaging examinations. In the conventional system (January 1-May 31, 2016), all reading work was mostly completed within the day. In the TR system (January 1-May 31, 2017), a radiology resident (TR) first read every image immediately after the examination and tagged each examination according to actual image findings and clinical demands. Routine reading work was finished when all high-priority cases were completed. Low-priority cases were assessed the following day.

RESULTS

When using the TR system, the mean reading number in the evening decreased (P = 0.009). The mean elapsed time to finalize report of case with actual urgent image finding shortened from 4.26 to 1.97 h (P < 0.0001). The mean number of cases experienced per resident increased from 5.4 to 28.7 (P < 0.001). Subjective evaluation revealed a significant improvement in "Reading efficiency" and "Contribution to clinical practice."

CONCLUSION

Introduction of the TR system can improve the reading efficiency and quality, educational effect among residents by increasing the number of experienced cases and work satisfaction.

Self-calibrated correlation imaging with k-space variant correlation functions

PURPOSE

Correlation imaging is a previously developed high-speed MRI framework that converts parallel imaging reconstruction into the estimate of correlation functions. The presented work aims to demonstrate this framework can provide a speed gain over parallel imaging by estimating k-space variant correlation functions.

METHODS

Because of Fourier encoding with gradients, outer k-space data contain higher spatial-frequency image components arising primarily from tissue boundaries. As a result of tissue-boundary sparsity in the human anatomy, neighboring k-space data correlation varies from the central to the outer k-space. By estimating k-space variant correlation functions with an iterative self-calibration method, correlation imaging can benefit from neighboring k-space data correlation associated with both coil sensitivity encoding and tissue-boundary sparsity, thereby providing a speed gain over parallel imaging that relies only on coil sensitivity encoding. This new approach is investigated in brain imaging and free-breathing neonatal cardiac imaging.

RESULTS

Correlation imaging performs better than existing parallel imaging techniques in simulated brain imaging acceleration experiments. The higher speed enables real-time data acquisition for neonatal cardiac imaging in which physiological motion is fast and non-periodic.

CONCLUSION

With k-space variant correlation functions, correlation imaging gives a higher speed than parallel imaging and offers the potential to image physiological motion in real-time. Magn Reson Med 79:1483-1494, 2018. © 2017 International Society for Magnetic Resonance in Medicine.

Historical Perspective of Imaging Contrast Agents

Contrast agents were introduced early in the history of medical imaging. Iodine-based intravascular agents became the radiographic compounds of choice and refinements of their chemical structures led to the highly tolerated low-osmolarity agents in use today. Gadolinium became the most popular compound for MR imaging; however, recognition of nephrogenic systemic fibrosis and in vivo dechelation intensified research on their safety profile. Ultrasonography contrast media evolved from manual injections of air through agitated saline solutions to microbubbles with different gases. Research has concentrated on bubble stabilization and development of small but sufficiently echogenic particles.

The Empirical Foundations of Teleradiology and Related Applications: A Review of the Evidence

INTRODUCTION

Radiology was founded on a technological discovery by Wilhelm Roentgen in 1895. Teleradiology also had its roots in technology dating back to 1947 with the successful transmission of radiographic images through telephone lines. Diagnostic radiology has become the eye of medicine in terms of diagnosing and treating injury and disease. This article documents the empirical foundations of teleradiology.

METHODS

A selective review of the credible literature during the past decade (2005-2015) was conducted, using robust research design and adequate sample size as criteria for inclusion.

FINDINGS

The evidence regarding feasibility of teleradiology and related information technology applications has been well documented for several decades. The majority of studies focused on intermediate outcomes, as indicated by comparability between teleradiology and conventional radiology. A consistent trend of concordance between the two modalities was observed in terms of diagnostic accuracy and reliability. Additional benefits include reductions in patient transfer, rehospitalization, and length of stay.

Normal saline as a natural intravascular contrast agent for dynamic perfusion-weighted MRI of the brain: Proof of concept at 1.5T

PURPOSE

Gadolinium-based contrast agents have associated risks. Normal saline (NS) is a nontoxic sodium chloride water solution that can significantly increase the magnetic resonance imaging (MRI) relaxation times of blood via transient hemodilution (THD). The purpose of this pilot study was to test in vivo in the head the potential of normal saline as a safer, exogenous perfusion contrast agent.

MATERIALS AND METHODS

This Health Insurance Portability and Accountability Act (HIPAA)-compliant prospective study was approved by the local Institutional Review Board (IRB): 12 patients were scanned with T₁ -weighted inversion recovery turbo spin echo pulse sequence at 1.5T. The dynamic inversion recovery pulse sequence was run before, during, and after the NS injection for up to 5 minutes: 100 ml of NS was power-injected via antecubital veins at 3-4 ml/s. Images were processed to map maximum enhancement area-under-the-curve, time-to-peak, and mean-transit-time. These maps were used to identify the areas showing significant NS injection-related signal and to generate enhancement time curves. Hardware and pulse sequence stability were studied via phantom experimentation. Main features of the time curves were tested against theoretical modeling of THD signal effects using inversion recovery pulse sequences. Pearson correlation coefficient (R) mapping was used to differentiate genuine THD effects from motion confounders and noise.

RESULTS

The scans of 8 out of 12 patients showed NS injection-related effects that correlate in magnitude with tissue type (gray matter ∼15% and white matter ∼3%). Motion artifacts prevented ascertaining NS signal effects in the remaining four patients. Positive and negative time curves were observed in vivo and this dual THD signal polarity was also observed in the theoretical simulations. R-histograms that were approximately constant in the range 0.1 < |R| < 0.8 and leading to correlation fractions of F_corr (|R| > 0.5) = 0.45 and 0.59 were found to represent scans with genuine THD signal effects.

CONCLUSION

A measurable perfusion effect in brain tissue was demonstrated in vivo using NS as an injectable intravascular contrast agent. J. Magn. Reson. Imaging 2016;44:1580-1591.