CME Radiology Grand Rounds

Fee-for-service payment models have served radiology well for many years, but policy makers are working hard to curtail this system which incentivizes volume, and implement a variety of systems which promote value. Evolving payment models, including pay-for-performance, and bundled/episodic care reimbursement, will be discussed. Advice will be offered to radiologists as to how to best succeed in this changing environment.

The physis, the main organ of skeletal growth, is a cartilaginous disc composed of multiple parallel columns of cells. This columnar arrangement is continued in the adjacent metaphyseal spongiosa by vessels, calcifying cartilage and newly formed bone. The interface between physeal cartilage and metaphyseal bone is the weakest link of the pediatric skeleton, and the site of many of the childhood fractures, particularly those of the Salter-Harris type. Injury to the physis or growth plate can result in shortening or deformity. The metaphyseal spongiosa is also weak and is the site of fractures in child abuse. MRI can be used to see the morphology of the cartilaginous structures and adjacent bone. Diffusion-weighted imaging and diffusion tensor imaging can be used to define the architecture of the skeletal structures and dynamic post-contrast imaging the perfusion of various structures. MR techniques that are useful for evaluation of articular cartilage matrix have limited application in the physeal cartilage as its signal characteristics is primarily determined by cells and vessels rather than matrix. The metaphysis is highly vascularized and is the site of blood-borne disease, such as infection or tumor. Osteomyelitis results in marrow edema or abscess formation and in collections of fluid under the periosteum and soft tissues, all of which are well detected by MR imaging. In younger patients, infection tends to be multifocal and it is useful to image the entire body (in infants and young children) or the lower extremities (in older children). Radiographic techniques including CT can show the disturbances of bone formation that result from insults to the physeal/metaphyseal region. When imaging the skeleton in children it is fundamental to take into consideration age-related changes in the normal appearance and in the susceptibility to disease and injury, and the age specific advantages and limitations of the various imaging modalities. This presentation will review the structural and functional aspects of the physeal/metaphyseal junction, the most important pathologies affecting it during infancy and childhood, and the best modalities to image it.

Breast cancer and Prostate cancer are the most prevalent potentially lethal malignancies of adult men and women in the United States. Although the mortality of both cancers has begun to decrease slightly there is still ample opportunity for reducing cancer-specific mortality through improved early detection and treatment. Magnetic Resonance Imaging technology has been tried for breast and prostate cancer detection since MRI was first developed in the early 1980’s. Over the subsequent 30 years, some techniques, and applications have flourished, while others have been abandoned. This presentation will consider successes and failures of MRI. A range of MRI techniques, including T1- and T2-weighted imaging, dynamic contrast-enhanced imaging, MR spectroscopy, and diffusion weighted imaging will be discussed in relation to specific clinical scenarios for early detection. The impact of emerging understanding of breast and prostate cancer natural history, subtypes, and targeted therapies will be discussed in relationship to emerging new technologies for early detection of these major cancer threats.

Positron emission tomography was developed nearly 40 years ago, but its diffusion into clinical practice was quite slow. This was related, at least in part, to the quality of available evidence regarding its effect on health outcomes, resulting in unwillingness of third-party payers to provide coverage. The lecture will review the history of PET reimbursement in the United States, focusing on the Medicare experience. Coverage has been achieved over the last decade as a result of improved scientific evidence of clinical benefit from randomized controlled trials and from a large observational study—the National Oncologic PET Registry (NOPR)—conducted under Medicare’s Coverage with Evidence Development policy. NOPR results have shown that PET for oncologic indications leads to changes in intended patient management in about one-third of Medicare beneficiaries, and NOPR data were critical to expansion of Medicare coverage for PET. However, evolving Medicare policies suggest that a focus on more robust measures of improved patient outcomes are likely to be necessary in the future, which may prove to be a particularly challenging barrier to the introduction of new molecular imaging methods into clinical practice.

Integrated PET/MR devices are commercially available for the last four years. Simultaneous PET/MR data acquisition has become possible with the introduction of new detector technology (APD, SiPM) which allow data acquisition within magnetic fields. Initially, attenuation correction measures have been developed in order to provide quantitative estimates of regional tracer distribution. Clinical evaluation proved accurate determination of FDG standard uptake values in a variety of tumor entities and concentrated on indications which are traditionally addressed by separate MR and PET imaging. As most promising application emerged PET/MR studies of the prostate, offering the combination of multi-parametric MR imaging and the use of specific markets for prostate cancer. First data indicate very high sensitivity and specificity for detection of malignant lesions. The multimodal information can not only be used to diagnose cancer, but also to direct biopsy. Data in patients with biochemical recurrence showed superior results as compared to PET/CT C/F choline data.

Application of PET/MR in the heart is primarily driven by research interest, comparing MR signals of atherosclerosis and of acute myocardial infarctions with molecular imaging of inflammation and repair processes, following ischemic injury. Comprehensive cardiac exam offered by PET/MR produces unrivaled imaging data, integrating multiple aspects of cardiac function.

Overall, PET/MR remains primarily an attractive research tool for multimodality in-vivo tissue characterization and phenotyping of disease. First clinical results are promising, but further prospective evaluation is needed to define cost efficiency and improvement of patient care. New developments in detector technology will further improve sensitivity and resolution of devices, making PET/MR a valuable tool for translational research in humans.

Many disease processes cause profound changes in the mechanical properties of tissues. This accounts for the efficacy of palpation for detecting abnormalities and provides motivation for developing practical methods to quantitatively image tissue elasticity.

Magnetic Resonance Elastography (MRE) is an emerging imaging technique that uses a modified phase-contrast MRI technique to visualize propagating acoustic waves generated by surface drivers, inertial effects, acoustic radiation pressure, or endogenous mechanisms. MRE acquisition sequences are capable of visualizing waves of less a micron in amplitude in vivo. Inversion algorithms are used to process the wave data to generate maps of properties such as stiffness, viscosity, attenuation, and anisotropic behavior, providing access to a new range of previously unexplored tissue imaging biomarkers.

Human studies have demonstrated that it is feasible to quantitatively image the mechanical properties of skeletal muscle, gray and white matter in the brain, thyroid, myocardium, kidney, liver, and skin. The first established clinical application of the technology is for detection of hepatic fibrosis. Growing clinical experience indicates that MRE is at least as accurate as liver biopsy for this diagnosis, while also being safer, more comfortable, and less expensive.

The incidence of primary malignancies of the liver in the US has tripled in the past three decades. Secondary malignancies of the liver are even more common than primary. Despite development of better surgical and medical options to treat hepatic malignancies, these continue to result in formidable morbidity and mortality. Intraarterial brachytherapy using injectable radioactive microspheres, or radioembolization, is a new and promising option for treatment of both primary and metastatic disease. Although radioembolization is approved by the FDA only for metastatic colorectal carcinoma and for hepatocellular carcinoma, many other cell types have been treated. Many of these cell types appear to be responsive to radioembolization, including ones that are traditionally considered radiation-resistant.

The human brain undergoes tremendous changes in size, shape and complexity over the first few years of life. On physical exam, we observe a change in the head shape and the head circumference, as well as the attainment of developmental milestones. Magnetic Resonance Imaging (MRI) is a non-invasive method perfectly suited for characterization of the underlying structural changes in the brain that accompany the outward changes that parents and pediatrician observe. Furthermore, MR imaging does not use ionizing radiation so there is no risk of cancer, which is important in the pediatric population since they are more sensitive to ionizing radiation than adults.

MRI of the brain uses radiofrequency (RF) energy in the presence of magnetic fields to excite the protons in water and then capture the signal the is emitted when the excess energy dissipates. The process of energy dissipation is called relaxation. Two fundamental tissue relaxation constants govern this process: T1 and T2. Almost all MRI protocols produce images with either T1-weighting or T2-weighting. T1-weighted images are hyperintense (bright) when T1 relaxation occurs quickly. The key driver for T1 relaxation in the brain is lipid (fat). Brain lipid content is greatest in the myelin sheath that covers the axons. At birth, there is very little mature myelin and thus very little lipid. As the brain matures, the white matter myelinates, which changes contrast from dark to bright on T1-weighted images. T2-weighted image contrast, on the other hand, is governed predominately by the tissue water content. More water in the brain leads to brighter signal on T2-weighted images. Over the first few years of life, the brain dries out in general and the water content in the white matter drops substantially. The result is that white matter changes contrast from bright at birth to dark by age 2 on T2-weighted images. At first glance, one would say that brain image contrast reverses on T1- and T2-weighted images between birth and age 2.

By observing the signal changes on T1- and T2-weighted images, we can track the change in brain size, the decrease in brain water content and the increased complexity of the folding pattern that result from the maturational process. What is more, we can see regional changes in white matter myelination that follow a predictable pattern and time course over the first few years of life. Specifically, brain myelination proceeds from bottom to top, back to front, and inside out. The onset of the signal changes due to myelination is delayed for T2-weighted images relative to T1- weighted scans, which adds to the precision of our temporal estimates.

After attending this presentation, you should be able to describe how water and myelin content changes during brain development influence the MR image appearance. Armed with this knowledge, you will understand that the time course and regional variation of brain MRI signal is dictated by maturational changes. The next step in the process will be to use a systematic approach to determine the child’s brain age using MRI. The final aim of this presentation is to review how brain development is different in young children with autism compared with brain development in typically developing children.

The evaluation of patients with acute and stable chest pain remains challenging as symptom and risk factor based prediction of the presence of obstructive coronary artery disease is inefficient. Coronary CT angiography permits ruling out CAD with high accuracy if performed with expertise in properly selected and prepared patients. Several observational and randomized trials have established cardiac CT as a safe and more efficient alternative to functional testing in the evaluation of acute and stable chest pain. Current investigations explore whether advanced anatomic and functional assessments such as high risk coronary plaque, resting myocardial perfusion and left ventricular function, or the simulation of the fractional coronary flow reserve will add information to the anatomic assessment for stenosis that would allow expanding the benefits of cardiac CT from triage to treatment. In addition, the combination of high-sensitive troponins and coronary CTA may play a valuable role in future strategies for the management of patients presenting with acute chest pain.

Approaches for the diagnosis of and follow up of differentiated thyroid carcinoma have changed rapidly in an era of cost restraints and personalized medicine. This lecture series will explore the impetus for and controversies surrounding current thyroid nodule biopsy consensus guidelines. Recent trends in postoperative imaging surveillance of differentiated thyroid carcinoma will then be presented.

Chronic obstructive pulmonary disease (COPD) is the third leading cause of mortality in the United States and is increasing in prevalence. The traditional imaging of chronic obstructive pulmonary disease (COPD) has been the chest radiograph, limited in sensitivity and in the ability to characterize COPD. As COPD is recognized as a highly heterogeneous and complex disorder, the detection of COPD subtypes by image biomarkers has substantially evolved and is evolving to enable individualized treatment and improve patient outcome. While emphysema and small airway wall thickening measures have been used on CT traditionally, CT metrics have not been able to capture the functional small airway disease which precedes the development of emphysema histologically. A voxel-wise image analysis technique known as parametric response mapping (PRM) applied to paired inspiration and expiration CT identifies functional small airways disease (fSAD) and emphysema, and provided CT-based evidence that supports the concept that fSAD precedes emphysema, and provides detailed spatial information of disease distribution and location, allowing differentiation between specific COPD phenotypes and more accurate diagnosis of individual patients. When applied to other small airway disease such as graft versus host disease, PRM allows the identification of bronchiolitis obliterans syndrome before patients meet clinical diagnostic criteria, which may facilitate earlier diagnosis, intervention and better outcome.

MR in Radiology has experienced such growth that it is now a key modality in nearly every Department. Each year reveals further potential, expanding an already wide range of MR methods, many of which are still seeking clinical applications for their unique tissue contrast mechanisms. Because of the popularity of MR despite relative high costs, MR in Radiology faces two increasingly difficult challenges as both other disciplines and less expensive diagnostic tools have appeared on the doorsteps of Radiology. Are we in a Golden Age of MR in Radiology, or will markets limit or dictate future MR growth and influence?

18F-FDG has been the workhorse in oncologic molecular imaging for a long time. However, very few new oncologic imaging agents have seen the light of clinical routine since the introduction of 18F-FDG. Could the old workhorse tracer 18F-FDG be used then for new application in molecular imaging? As one possible application, we developed recently Positron Lymphography, where 18F-FDG is injected locally to image the sentinel lymph nodes. This opens interesting possibilities for oncologic imaging due to the power of PET imaging. Furthermore, 18F-FDG also allows for Cerenkov imaging, where highly sensitive cameras detect the blue Cerenkov light originating from radioactive decay. We have shown that it is possible to detect tumorpositive lymph nodes after 18F-FDG injection using Cerenkov imaging. Cerenkov imaging therefore enables optical imaging of clinical tracers, e.g. in an intraoperative setting.

The heterogeneity and largely indolent nature of prostate cancer require better tools to avoid over-detection of low-risk disease and improve diagnostic accuracy in high-risk patients. During the last 3 decades, magnetic resonance imaging (MRI) has evolved to become the most accurate imaging technique for prostate cancer detection and staging, with a promising role in risk stratification. Because each MRI sequence has advantages and limitations, state of the art prostate imaging with the so-called multiparametric MRI is achieved combining anatomical T2-weighted imaging integrated with other techniques in which image contrast is related to the pathophysiology of the disease, such diffusion-weighted imaging, dynamic contrast-enhanced imaging, and, less commonly, MR spectroscopy. Important structured descriptions are emerging to enhance the characterization of disease, including a determination of cancer likelihood and location. Most recently, innovations in MRI have been combined to improve the relevant positive biopsy yield for men with known or suspected prostate cancer.

a. The “Night Simulator” - A Virtual Real-Time Call-Experience Simulator To Aid in Preparing Radiology Residents for Independent Call

b. Effect of Apron Material and Primary Beam Energy on Radiologist Exposure During CT-Guided Procedures

c. Quantitative Image Texture Analysis Using Riesz Wavelets for Predicting Malignancy in Prostate Lesions PI-RADS 3 or Higher

d. A Low Cost Phantom Model for Tracking Residents in Ultra-sound Guided Procedures

The Radiology Department at Stanford has made pioneering contributions to the field of quality and performance improvement. These will be illustrated and contrasted with the many quality tools and approaches that are now being used in the department to foster the formidable basic research program. As competition for scarce resources intensifies, the quality, methodology, significance and impact of radiology research will undergo intense scrutiny demanding that these be linked to our new value-added healthcare paradigm. This presentation will describe contemporary improvement methodologies and opportunities that every successful academic radiology department will need to embrace in order to thrive.