Measuring observer performance in chest radiology: some experiences.

All decisions made under conditions of uncertainty have error rates. All meaningful decisions are made under conditions of uncertainty. Can this uncertainty be measured? Can variations in how different observers deal with this uncertainty be ascertained? The ability to measure observer performance in diagnostic imaging was one of the issues that initiated the field of medical decision analysis.

Transformative technology: a conversation with E. James Potchen and Bill Clarke. Interview by John K. Inglehart.

In this interview, a representative of academe (E. James Potchen) and one from industry (Bill Clarke) discuss the ways in which their interests intersect for the good of U.S.

Cortical activation during rhythmic hand movements performed under three types of control: an fMRI study.

Echoplanar fMRI was used to measure changes in cortical activation during the performance of a simple hand movement task under three types of voluntary control. Each of three imaging series alternated a task with rest: passive (in which the experimenter moved the hand), voluntary against low resistance, and voluntary against higher resistance. Contralateral activation was observed in the supplementary motor area (SMA), the primary motor cortex (M1), and the somatosensory cortex (S1) in all three tasks in each subject, whereas ipsilateral activation differed in each cortical region for each task.

Measuring performance in chest radiography.

Purpose: To use a standardized set of chest radiographs to quantify interobserver differences and to provide a basis for comparing the diagnostic performance of physicians.

Materials And Methods: A standardized set of 60 chest radiographs was presented to 162 study participants. Each participant reviewed the radiographs and recorded his or her diagnostic impression by using a fixed five-point scale.

Prospects for progress in diagnostic imaging.

New fast-imaging MRI systems designed specifically for cardiac magnetic resonance enable new applications of noninvasive vascular imaging. The use of functional MRI and diffusion tensor imaging to map brain function and structure offers a new dimension to an understanding of the human condition. Clinical applications of functional MRI will influence many specialties including surgery, education, and rehabilitation.

Reflections on the early years of nuclear medicine.

In the early years of nuclear medicine, physicians explored applied nuclear physics, and physicists pursued uncharted areas in medicine. Reflections from Jim Adelstein, MD, PhD, John McAfee, MD, Henry Wagner, MD, Fred Bonte, MD, Dave Kuhl, MD, and Alex Gottschalk, MD, add to the appreciation of the diversity in those early years. These reflections may serve many purposes.

Different effects of exercise and edema on T2 relaxation in skeletal muscle.

The hypothesis that increased muscle T2 after exercise is caused by increased extracellular fluid volume was tested by comparing the effects of exercise versus external leg negative pressure on muscle T2 relaxation in normal human subjects. T2 in lower leg muscles was measured by echo-planar imaging at 63 echo times from 24 to 272 ms, and the relaxation spectrum was calculated by using a non-negative least squares algorithm. T2 relaxation in anterior leg muscle before exercise was characterized by a single component with mean T2 = 29.

Force of voluntary exercise does not affect sensorimotor cortex activation as detected by functional MRI at 1.5 T.

Echo-planar brain images (1.5 T, 1-shot GRE, TR/TE = 3000/45) were acquired during 30-60 s cycles of repetitive (1.3-1.

Medical-legal issues in radiology: prevention and control.

Concerns about legal implications affect many decisions of the average radiologist, and physicians do not always appreciate the validity of these concerns. However, such concerns often influence radiologists' decisions more than is warranted. An improved understanding of the law and its ramifications may serve to prevent adverse legal effects found in the everyday practice of radiology.

Rapid MR imaging of the liver: comparison of twelve techniques for single breath-hold whole volume acquisition.

Twelve magnetic resonance imaging pulse sequences for single breath-hold whole volume acquisition of the liver were evaluated on volunteers. Liver and spleen contrast to noise ratio (C/N), overall image quality, and grade of artifacts were compared. The 12 sequences included T2-weighted fast spin echo (FSE) with or without fat suppression (FS), fast multiplanar spoiled gradient recalled imaging (FMPSPGR), fast gradient recalled imaging without preparation pulses (FGR), FGR with inversion recovery preparation pulse nulling the liver or fat (IR-FGR-L and IR-FGR-F), FGR with driven equilibrium preparation pulse (DE-FGR), single shot moderately or heavily T2-weighted spin echo echo planar imaging (SE-EPI-mT2 and SE-EPI-hT2), multi-shot moderately T2-weighted spin echo echo planar imaging (multi-shot SE-EPI-mT2), inversion recovery EPI, and gradient echo EPI.

Flow velocity and volume measurement of superior and inferior mesenteric artery with cine phase contrast magnetic resonance imaging.

The flow velocity and volume of the superior and inferior mesenteric arteries (SMA, IMA) were measured with cine phase contrast magnetic resonance (MR) imaging in five healthy volunteers. Each volunteer was first measured in a fasting state, and then one, two, and three hours after a meal. The average SMA flow volume of the volunteers was 230.

The history and the effect of the mammography quality assurance legislation in Michigan.

This paper describes the history of mammography quality assurance legislation in Michigan, the first of its kind in the nation. It discusses the collaboration of multiple organizations in the legislative process as well as in the implementation of it. It describes the effect of the legislation on the quality of mammography throughout the state and summarizes the lessons learned from the process, especially as they apply to the implementation of the Mammography Quality Standards Act at the national level.

Changes in magnetic resonance images of muscle depend on exercise intensity and duration, not work.

Echo-planar magnetic resonance imaging was used to study the effect of exercise rate and duration on magnetic resonance imaging signal intensity (SI) of anterior tibialis muscle in normal human subjects (mean age 35 yr, n = 6). Axial midcalf echo-planar images (repetition time/echo time = 6,000/45, acquisition time = 80 ms) were acquired every 6 s for 1 min before and during 15 min of dynamic ankle dorsiflexion exercise (peak force 36% of 1 repetition maximum) at 10, 20, and 30 contractions/min. At each rate, muscle SI rose along an approximately exponential time course (mean time constant 1.

Measurement of total and unilateral renal blood flow by oblique-angle velocity-encoded 2D-cine magnetic resonance angiography.

Two independent measurements of total renal blood flow (RBF) were made in healthy human subjects (n = 14, mean age 30 yr) by CINE phase-contrast magnetic resonance angiography. RBF, measured by summing the flows measured in the right and left renal arteries, was 1152 +/- 44 ml/min (mean +/- SE). RBF, measured from the difference between supra- and infrarenal abdominal aorta flow, was 1109 +/- 68 ml/min.

Magnetic resonance measurement of blood flow in peripheral vessels after acute exercise.

Velocity-encoded Cine magnetic resonance imaging (MRI) was used to measure blood flow in the anterior tibial artery (AT), posterior tibial artery (PT), and popliteal artery of adult human subjects (mean age 29 yr) before and after 90 s of ankle dorsiflexion exercise. Before exercise, mean flow, peak systolic velocity, and end-diastolic velocity in AT were 8.1 +/- 1.

Determination of blood flow direction using velocity-phase image display with 3-D phase-contrast MR angiography.

The authors describe their use of phase-contrast MRA to depict vascular anatomy and to define the direction of blood flow. Documentation of flow reversal can provide information regarding prognosis and can facilitate surgical planning. The technique requires no additional scan-time.

Magnetic resonance angiography in intracranial vascular disease.

Magnetic resonance angiography (MRA) offers a noninvasive alternative for studying normal and pathological blood vessels within the brain. Insights from important clinical aspects of intracranial vascular disease enable the effective application of MRA. Several MRA techniques have demonstrated clinical utility for the detection and characterization of intracranial vascular pathology.

Physical principles and application of magnetic resonance angiography.

This paper reviews the physical principles of magnetic resonance angiography (MRA) acquisition methods, explains image presentation strategies for MRA, and discusses the advantages and disadvantages of various MRA methods. These methods include the time-of-flight, phase contrast, and black blood techniques. The essential goal of each of these flow imaging methods is to maximize signal differences between flowing and stationary tissues in order to provide morphological and physiological information.