Volume 36, Issue 6, June 2009
Index of content:
- Imaging Continuing Education Course: Room 213A
- CE ‐ Imaging: Ultrasound I
36(2009); http://dx.doi.org/10.1118/1.3182196View Description Hide Description
The purpose of this course is to acquaint participants with recent signal processing techniques and modes on ultrasound instruments. Emphasis is on second harmonic imaging, a processing and display mode implemented on most scanners. Harmonic imaging was originally applied to enhance echo signals due to nonlinear scattering by ultrasound contrast agents. However, the modality is much more commonly used in “native tissue harmonic” mode, where echoes originating from nonlinear components of propagating acoustic beams are detected and displayed. The source of these echo signals and the advantages and disadvantages of harmonic imaging will be described. When applied effectively, harmonic imaging provides significant improvements in image quality compared to that obtained using conventional signal processing. A primary reason for harmonic imaging's improved image quality is reduction of acoustic noise caused by reverberations within overlying tissues. Other contributors to high quality ultrasoundimages include spatial and frequency compounding and speckle reduction. These techniques also will be described and placed in context with harmonic imaging.
After completing this course, participants will:
1. Describe the origin of harmonic echo signals for both conventional and contrast agent imaging modes;
2. Contrast resolution and penetration capabilities for harmonic imaging and linear imaging;
3. Identify clinical situations where harmonic imaging is used advantageously;
4. Describe how harmonic imaging is used to enhance detection of contrast agents;
5. State the benefits of spatial and frequency compounding, and speckle reduction.
- CE ‐ Imaging: Safety/Risk I
MO‐B‐213A‐01: Magnitude of Radiation Exposure to US Population (NCRP Report ♯160) with Focus On CT Dose36(2009); http://dx.doi.org/10.1118/1.3182203View Description Hide Description
National Council of Radiation of Protection (NCRP) recently released a long awaiting report (NCRP report ♯ 160) on the radiation exposure of the US population from various sources including medical exposure. This new report replaces the current NCRP report ♯ 93 published in 1987.
According to the newly released NCRP report ♯ 160 (March 2009), the medicalradiation exposure to US population has increased by nearly 6 times compared to the previous NCRP publication (NCRP 93). The previous pie‐chart published in 1987 (NCRP report ♯93) indicated contribution of 3 mSv from background radiation, 0.53 mSv from medical exposure and 0.07 mSv from other sources (consumer products, occupational and other sources) exposure while the new pie‐chart published in March 2009 (NCRP report ♯160) indicates contribution of 3.1 mSv from background radiation and 3.0 mSv from medical and 0.1 mSv from all other sources (consumer products, occupational and other sources).
The largest contributor to the collective dose to US population is from CT and Nuclear Medicine.CT scanning has increased nearly 10–11% annually in the US in the past two decade. The number of CT procedures has increased from 3 million CT scans in 1980 to more than 69 million CT scans in 2007.
The purpose of this talk is to provide an overview of the newly released NCRP report ♯160. As a member of the NCRP scientific committee 6‐2 that developed the above report, the author will also focus on the medicalradiation exposure including CT.
1. To become familiar with the NCRP report number 160.
2. To learn about the various sources and magnitude of radiation exposure including medicalradiation exposure to US population
3. To familiarize with the types and distribution of medical imaging procedures in US.
4. To examine the various aspects related to CT use and CT dose.
- CE ‐ Imaging: Multi‐Modality Imaging I
36(2009); http://dx.doi.org/10.1118/1.3182311View Description Hide Description
Computed tomography is not the most frequent radiologic imaging procedure, but is arguably the most important in terms of clinical impact. CT is used extensively for emergencies, cardiovascular, pulmonary, gastrointestinal, endocrine, neurological, orthopedic and other applications — often as the first and only imaging procedure needed for diagnosis. The chances are very high that a patient will have a CT scan in the emergency department, as an outpatient or as an inpatient for a multitude of indications — pain, trauma, suspected infection or malignancy, and frequently to investigate symptoms such as pain, or to answer a question raised by another abnormal test, such as an EKG abnormality or ultrasound finding.
Despite the universality of CT in hospitals and clinics as well as free‐standing imaging centers, the technology continues to evolve with greater coverage, faster acquisition and multienergy sources or detectors. Multimodality scanners based on CT incorporate PET/SPECT and in the future, MRI to combine morphologic and functional imaging.
The most demanding imaging applications are cardiovascular, where complex motion and small morphologic features coexist, so imaging methods that are very satisfactory elsewhere in the body may not be successful. Clinical CT scanning consists of administering toxic materials, e.g., contrast media, often monitoring the EKG and illuminating the body with high brightness x‐rays. Larger area detectors and higher acquisition rates are welcome improvements, but don't solve all of the problems encountered with scan variability due to respiratory, random body, and cardiac motion, especially in a spectrum of patients from infant to massively obese adult sizes (< 1 kg to 250 kg or more). The challenges and pitfalls in CT and multimodality imaging will be delineated and evaluated relative to current and future technology.
1. The role of x‐ray computed tomography(CT) in clinical medicine is central to diagnostic radiology and its functions as a hospital‐based department and service to outpatients.
2. CT technology developments, including wide area coverage multirow detector scanners, dual energy acquisition systems, visualization and post‐processing introduce changes in CT applications and utilization.
3. The limitations of a single modality, such as CT, can be overcome by integrating complementary instrumentation, especially PET/SPECT, MRI and others (such as ultrasound and fluoroscopy) to provide simultaneous morphologic and functional imaging capabilities.
TU‐A‐213A‐02: Quantitative PET/CT Imaging for Drug Discovery, Clinical Trials, and Individual Response to Therapy36(2009); http://dx.doi.org/10.1118/1.3182312View Description Hide Description
Recent publications have established quantitative measures of tracer uptake used in positron emission tomography(PET)imaging as a predictor of patient outcome including pathologic response, disease‐free survival and overall survival in single institution imaging and therapy trials. There is increasing interest in using PET as a biomarker to evaluate response to therapy and possibly as an endpoint for cancertherapeutic response in multi‐center trials. However, several sources of variance and inherent in quantifying PET tracer uptake should understood and determined in order to ascertain the significance of differences in serial measurements and aid estimation of expected variances during clinical trial design.
In this presentation we will review the major sources of bias and variability from the patient, imaging protocol, data processing, and image analysis. We will also briefly discuss artifacts from PET and PET/CT imaging.
The presentation will conclude with a review of efforts to address complexities that arise from combining quantitative PET/CT data from multiple patients at multiple sites. Research partially supported by NCI Contract 24XS036‐004 (RIDER).
- CE ‐ Imaging: Safety/Risk II
36(2009); http://dx.doi.org/10.1118/1.3182317View Description Hide Description
An NCRP report on Radiation Safety Issues for Fluoroscopically Guided Interventional (FGI) Procedures is currently being developed by Scientific Committee 2–3. Because of time limitations, this course provides only an outline of the current draft report and focuses on key proposed recommendations.
The full NCRP report will review FGI procedures, technology, radiobiology, and available information on patient and staff doses. It will also discuss managing patient irradiation and staff radiation protection in the interventional medical environment.
FGI procedures are intended to deliver a specific therapeutic result to a patient. An individual patient's benefit from a successful procedure must be balanced against the radiation risk and numerous other risks associated with the procedure. The performing physician is expected to continually reevaluate benefit and risk as the procedure progresses.
Some individual FGI procedures will affect the patient's skin and hair. Inadequate radiation management on the part of the operator or poor calibration of imaging equipment may result in additional deterministic injuries in the patient. Forcing lower patient doses to eliminate these reactions might result in procedural failures that are not in the patient's best interest. The NCRP report will include a significantly updated review of skin reactions. This review is also being published separately and is in press.
At present, FGI usually result in unavoidable irradiation of physicians and staff. While staff dose should be appropriately limited, common personnel monitoring practices greatly overestimate staff radiation risk. An exaggerated focus on radiation risk diverts attention from other risk factors and may decrease overall staff safety. Patient safety can also be compromised when administrative pressures attempt to drive staff doses to zero.
Increased procedure complexity has resulted in increased total patient dose despite technological reductions in dose rate. The amount of radiation used in FGI procedures is greatly dependent on the technical knowledge and clinical experience of the performing physician. In many patients, tissue reactions are the result of substandard performance. Appropriate clinical privileging and clinical quality assurance feedback processes are essential for safety.
Recommendations are grouped into the following categories:
• Justification, Optimization, Limitation for FGI
• Patient Risk Estimation & Assessment
• Equipment & Facilities
• Protection of Patients During Procedures
• Pregnant Patients
• Patient Dose Documentation
• Patient Discharge and Follow‐up
• Protection of Workers and Worker Risk Evaluation
• Administrative Topics
This course embodies current opinions of the SC 2–3 writing committee. When completed, the draft report will be submitted for NCRP Council review and public comment. The final contents of the report are likely to be modified by the committee and/or the review process.
1. Understand issues related to patient and staff safety in the FGI setting.
2. Be able to develop policies for both patient and staff safety.
3. Know the essential elements and features of fluoroscopic equipment and procedure room design for FGI procedures.
- CE ‐ Imaging: Ultrasound II
36(2009); http://dx.doi.org/10.1118/1.3182450View Description Hide Description
Modern technologically intensive diagnostic ultrasound systems are utilizing numerous new and powerful beamformation and image construction processes integrated into the design of the transmit, receive and processing chain of the system. These new processes, how the imaging and Doppler data is captured, processed and displayed need to be well understood by both medical physicists and clinicians to ensure proper testing and performance evaluation of the ultrasound device, as well as their attendant transducers (probes), and to ensure the safety and clinical efficacy of the ultrasound study. This presentation will focus on these new processes and advanced imaging technologies, how they can be tested and evaluated for effectiveness and what new imaging and display formats we will likely see in the next 2 to 3 years.
1. Understand modern beamforming techniques
2. Understand ultrasoundimage processing
3. Understand modern image reconstruction techniques
- CE ‐ Imaging: Safety/Risk III
36(2009); http://dx.doi.org/10.1118/1.3182456View Description Hide Description
Planning for and exercising the medical response to potential mass casualty radiological and nuclear (rad/nuc) events from accidents or terrorism are very new responsibilities for most physicians, nurses, emergency medical technicians/paramedics and other healthcare professionals. Many medical professional societies are attempting to define the essential knowledge base and performance skills needed to certify readiness and competence in this area of disaster medicine.
Medical physicists and the entire spectrum of radiation safety professionals have critical expertise needed for event preparedness. They can
• Help educate medical personnel to understand radiation issues and gain comfort with techniques and procedures needed to perform effectively and safely
• Help develop appropriate response plans if plans are non‐existent or inadequate, and assist with iterative plan improvement and assessment in formal exercises
• Identify, procure, store, and maintain required response equipment
During events they will help protect first responders, victim transport personnel, and first receivers in hospitals and other medical facilities along the entire continuum of the medical response. Radiation safety professionals may be asked to
• Assist event managers and security personnel in establishing safe response zones
• Supervise or perform radiation surveys of victims and responders
• Assist with estimates of absorbed dose received by both victims and responders,
• Support the implementation of appropriate protective actions
• Participate in the collection and transport of radiationbioassays for contamination
• Supervise decontamination of victims and responders
• Assist with short and long term tracking of both victims and responders
Threat analysis has identified a list of isotopes of potential concern for mass casualty events. Selected medical countermeasures will be recommended for victims with certain levels of contamination and/or exposure.
For physics professionals planning to assist in rad/nuc mass casualty responses, knowledge about existing Federal, State, and local medical response plans in your area is crucial. Implementation of the Hospital Incident Command System will integrate medical activities with other response activities, including public information, forensics, and security.
This lecture will provide an overview of
• The kinds of mass casualty rad/nuc events that have received the most attention from homeland security and medical planners
• The isotopes of concern for mass casualty events
• Available radiation countermeasures for exposure and contamination
• Some of the issues surrounding the assessment of contamination and performance of decontamination in mass casualty events
• The “radiation response zones” likely to be established during certain events
• Suggestions for initiating and equipping rad/nuc medical response teams in your hospital
• How to volunteer to be on rad/nuc response teams
• A bibliography of useful publications and web sites
Learning objectives: After attending this lecture, students will be able to
1. Describe the radiological and nuclear events of greatest concern to US government response planners
2. Identify isotopes of concern and medical countermeasures likely to be associated with various kinds of events
3. Identify the radiation zones likely to be associated with managing the response to a nuclear detonation
- CE ‐ Imaging: Multi‐Modality Imaging II
TH‐A‐213A‐01: Multi‐Modality Image‐Guided Near Infrared Spectroscopy: Optimization and Clinical Applications36(2009); http://dx.doi.org/10.1118/1.3182593View Description Hide Description
Image‐guidednear infraredspectroscopy (IG‐NIRS) provides deep tissue functional characterization at high resolution. This approach combines conventional imaging techniques such as MRI and CT with optical near infrared technologies, giving information directly relating to the vascular and metabolic status of tissue in‐vivo. The resultant estimates of total hemoglobin, oxygen saturation, water, lipids and scatter provide a window towards understanding the mechanisms of cancer in terms of angiogenesis, hypoxia, changes in the interstitium and cell organelle structural changes. This type of spectroscopy has been applied for breast cancer diagnosis and treatment monitoring, as well as image‐guided fluorescence in small‐animals.
Optimization of these systems is essential to provide quantitative and accurate spectroscopy. This optimization encompasses system design for simultaneous multi‐modality image acquisition, methods for intelligently combining spatial anatomical structure from MRI/CT into optical recovery, image segmentation, visualization and interpretation of novel combined optical and MRI/CT parameters.
This talk will provide an over‐view of these aspects of multi‐modality imaging as well as results from in‐vivo clinical applications.
1. Understanding the rationale for multi‐modality IG‐NIRS systems
2. Understanding the type of information and contrast available through these systems
3. Understanding the challenges towards clinical use of these systems.
36(2009); http://dx.doi.org/10.1118/1.3182594View Description Hide Description
Monitoring the efficacy of braintumor therapy is a clinical dilemma. Results of biopsy provide the most reliable indicator but biopsy is too invasive for frequent use. The clinical standard of practice is to perform serial magnetic resonance scans and to assess changes to tumor “size” as seen on gadolinium enhanced images, with “size” measured in one, two, or three dimensions. This review discusses the advantages and disadvantages of the three measurement methods as well as some of the effects of voxel size on the calculation. Problems inherent to the use of gadolinium enhanced images include the effect of steroids and the confounding appearance of radiation necrosis. The limitations of the approach have led multiple groups to explore alternative methods of assessing tumor activity.
1. Understand the clinical standard of practice of monitoring braintumor therapy from T1 gadolinium enhanced images and its strengths/weaknesses.
2. Understand some of the different experimental approaches, often involving different image types, to assessing tumor activity.
- CE ‐ Imaging: Safety/Risk IV
36(2009); http://dx.doi.org/10.1118/1.3182600View Description Hide Description
Radiologists and radiologic technicians were among the earliest occupational groups to be exposed to ionizing radiation, and still constitute one of the largest groups of workers exposed to man‐made sources of radiation whilst at work. Studies of human populations exposed to acute, high doses of ionizing radiation have proved valuable in assessing the link between radiation and cancer and have been used to derive quantitative estimates of risk. However, the applicability of these estimates to the assessment of risks following fractionated or low level exposures remains uncertain. A number of epidemiologic studies have been conducted therefore to assess the potential risks from medical occupational exposure directly, including studies of radiologists in the UK, US and China and a cohort of radiologic technicians radiographers in the U.S.
This lecture will provide an overview of these epidemiological studies and their findings, as well as a description of a new study of physicians that perform fluoroscopically guided procedures that we are currently running at the National Cancer Institute. The use of cancer risk projection models that we have developed to estimate potential lifetime cancer risk following specified exposure histories will also be described with examples.
1. Understand the strengths and limitations of the epidemiologic studies of medical radiation workers
2. Understand the strengths and limitations of risk projection models to estimate lifetime cancer risks from occupational radiation exposures