Screening for pulmonary metastases. American College of Radiology. ACR Appropriateness Criteria.
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Diagnosis, Differential↗
Biomedical subjects
W B Gefter
Publications and source records attributed to W B Gefter.
T2* and proton density measurement of normal human lung parenchyma using submillisecond echo time gradient echo magnetic resonance imaging.
OBJECTIVE: To obtain T2* and proton density measurements of normal human lung parenchyma in vivo using submillisecond echo time (TE) gradient echo (GRE) magnetic resonance (MR) imaging. MATERIALS AND METHODS: Six normal volunteers were scanned using a 1.5-T system equipped with a prototype enhanced gradient (GE Signa, Waukausha, WI). Images were obtained during breath-holding with acquisition times of 7-16 s. Multiple TEs ranging from 0.7 to 2.5 ms were tested. Linear regression was performed on the logarithmic plots of signal intensity versus TE, yielding measurements of T2* and proton density relative to chest wall muscle. Measurements in supine and prone position were compared, and effects of the level of lung inflation on lung signal were also evaluated. RESULTS: The signal from the lung parenchyma diminished exponentially with prolongation of TE. The measured T2* in six normal volunteers ranged from 0.89 to 2.18 ms (1.43 +/- 0.41 ms, mean +/- S.D.). The measured relative proton density values ranged between 0.21 and 0.45 (0.29 +/- 0.08, mean +/- S.D.). Calculated T2* values of 1.46 +/- 0.50, 1.01 +/- 0.29 and 1.52 +/- 0.18 ms, and calculated relative proton densities of 0.20 +/- 0.03, 0.32 +/- 0.13 and 0.35 +/- 0.10 were obtained from the anterior, middle and posterior portions of the supine right lung, respectively. The anterior-posterior proton density gradient was reversed in the prone position. There was a pronounced increase in signal from lung parenchyma at maximum expiration compared with maximum inspiration. The ultrashort TE GRE technique yielded images demonstrating signal from lung parenchyma with minimal motion-induced noise. CONCLUSION: Quantitative in vivo measurements of lung T2* and relative proton density in conjunction with high-signal parenchymal images can be obtained using a set of very rapid breath-hold images with a recently developed ultrashort TE GRE sequence.
Artifacts↗
Fast magnetic resonance imaging of the lung.
The impact of fast MR techniques developed for MR imaging of the lung will soon be recognized as equivalent to the high-resolution technique in chest CT imaging. In this article, the difficulties in MR imaging posed by lung morphology and its physiological motion are briefly introduced. Then, fast MR imaging techniques to overcome the problems of lung imaging and recent applications of the fast MR techniques including pulmonary perfusion and ventilation imaging are discussed. Fast MR imaging opens a new exciting window to multi-functional MR imaging of the lung. We believe that fast MR functional imaging will play an important role in the assessment of pulmonary function and disease process.
Humans↗
Spontaneous tension pneumopericardium complicating staphylococcal pneumonia.
The authors describe a patient with spontaneous pneumopericardium complicating staphylococcal pneumonia and empyema that resulted in cardiac tamponade. Spontaneous pneumopericardium is an unusual disorder. The causes and clinical findings of pneumopericardium are reviewed, as are the radiographic features that differentiate this condition from pneumomediastinum. Early recognition of pneumopericardium is important, because emergent pericardiocentesis may be required if there is clinical evidence of tamponade.
Adult↗
Advanced emphysema: preoperative chest radiographic findings as predictors of outcome following lung volume reduction surgery.
PURPOSE: To determine whether preoperative chest radiographic findings alone can reliably predict which patients will achieve the best functional outcome of lung volume reduction surgery. MATERIALS AND METHODS: The preoperative chest radiographs obtained in 57 patients who had undergone lung volume reduction surgery were retrospectively scored by five blinded readers for severity and distribution of emphysema, evidence of lung compression, disease heterogeneity, and other features. Comparisons were made with the 3-6-month postoperative functional outcome for each patient. RESULTS: High disease heterogeneity (score > 2) and unequivocal lung compression (score 1) both were 100% predictive of a favorable outcome (FEV1 increase, > or = 30%). Low heterogeneity (score < 1) was 94% predictive of an unfavorable outcome (FEV1 increase < 30%), as was a lack of lung compression, which was 92% predictive of an unfavorable outcome. These two features also correlated with an improved 6-minute walk test result, although this correlation was weaker. CONCLUSION: Chest radiography alone may be sufficient for initial screening. High disease heterogeneity and lung compression on chest radiographs are highly predictive of a favorable functional outcome.
Aged↗
Pulmonary perfusion: respiratory-triggered three-dimensional MR imaging with arterial spin tagging--preliminary results in healthy volunteers.
The authors used a spin-tagging method of magnetic resonance perfusion imaging to measure pulmonary perfusion in eight healthy volunteers with use of a respiratory-triggered three-dimensional pulse sequence. The average signal intensity (SI) decrease upon arterial labeling was 24%. The perfusion SI increased by 21% after exercise (P = .02). Focal blood flow abnormalities were observed in a patient with chronic obstructive pulmonary disease.
Adult↗
Recent advances in pulmonary imaging.
Recent years have witnessed an explosion in imaging technology applicable to chest medicine. These include CT and magnetic resonance angiography (MRA) for the diagnosis of pulmonary embolism, and high-resolution CT for the detection and characterization of diffuse lung diseases and the quantification of emphysema. Newly developed approaches to pulmonary functional imaging using CT and MRI have been applied to the evaluation of pulmonary ventilation and perfusion and to the detection of small airways disease. Volumetric CT imaging techniques together with advanced image processing have made possible "virtual bronchoscopy." Positron emission tomography provides an important new approach to the accurate detection and staging of chest malignancies and to the evaluation of pulmonary nodules. Finally, new digital imaging techniques, which are rapidly replacing conventional x-ray film, offer the possibility of computer-aided diagnosis.
Diagnostic Imaging↗
MRI study of regional variations of pharyngeal wall compliance in cats.
Upper airway compliance indicates the potential of the airway to collapse and is relevant to the pathogenesis of obstructive sleep apnea. We hypothesized that compliance would vary over the rostral-to-caudal extent of the pharyngeal airway. In a paralyzed isolated upper airway preparation in cats, we controlled static upper airway pressure during magnetic resonance imaging (MRI, 0.391-mm resolution). We measured cross-sectional area and anteroposterior and lateral dimensions from three-dimensional reconstructed MRIs in axial slices orthogonal to the airway centerline. High-retropalatal (HRP), midretropalatal (MRP), and hypopharyngeal (HYP) regions were defined. Regional compliance was significantly increased from rostral to caudal regions as follows: HRP < MRP < HYP (P < 0.0001), and compliance differences among regions were directly related to collapsibility. Thus our findings in the isolated upper airway of the cat support the hypothesis that regional differences in pharyngeal compliance exist and suggest that baseline regional variations in compliance and collapsibility may be an important factor in the pathogenesis and treatment of obstructive sleep apnea.
Air Pressure↗
State-related changes in upper airway caliber and surrounding soft-tissue structures in normal subjects.
State-dependent changes in upper airway caliber were studied with magnetic resonance imaging (MRI) techniques. We hypothesized that changes in airway caliber during sleep in normal subjects would result from positional and dimensional changes in upper airway soft-tissue structures, including the lateral pharyngeal walls, tongue, and soft palate. We used MRI to study 15 normal subjects during wakefulness and sleep. Sleep was facilitated by one night of sleep deprivation prior to MRI. During sleep, the volume of the retropalatal (RP) airway was reduced by 19% (p = 0.03). The volume of the retroglossal (RG) airway was not significantly reduced during sleep, suggesting that the RP region may be more likely to collapse. The mean minimal cross-sectional airway area was reduced by 228% (p = 0.004) in the RP and by 22% (p = 0.02) in the RG region during sleep as compared with values in anatomically matched axial images during wakefulness. Airway anteroposterior (AP) and lateral dimensions were also significantly reduced in the RP region. Airway narrowing in the RP region was associated with a 7% increase in thickness of the lateral pharyngeal walls (p = 0.04). In nine subjects, sagittal data showed significant posterior displacement of the soft palate during sleep as compared with wakefulness. Multiple linear regression analyses indicated that reduction in the RP airway area during sleep resulted from posterior movement of the soft palate, thickening of the lateral pharyngeal walls, and an increase in tongue oblique distance. We conclude that the lateral pharyngeal walls play an important role in upper airway narrowing during sleep in normal subjects.
Adult↗
Pulmonary MR angiography.
Recent technical improvements have made pulmonary MR angiography (MRA) feasible. The technique is attractive because it is noninvasive, provides a full three-dimensional (3D) display of the pulmonary vasculature, and potentially can be combined with MR venography of the lower extremities and pelvis for the comprehensive diagnosis of thromboembolism. Approaches to acquiring pulmonary MR angiograms are currently being developed and include both two-dimensional and 3D time-of-flight methods, breath-hold and non-breath-hold techniques, and the use of gadolinium-based contrast enhancement. The results of initial studies using pulmonary MRA for the detection of pulmonary embolism are encouraging, but they must be evaluated in conjunction with newly developed fast CT scanning techniques. This article reviews the state of development of pulmonary MRA, the current clinical applications of the technique, and the prospects for future development.
Humans↗
Upper airway and soft tissue structural changes induced by CPAP in normal subjects.
Nasal continuous positive airway pressure (CPAP) is the treatment of choice for adults with obstructive sleep apnea. CPAP is known to increase upper airway size; however, the direct effects of CPAP on soft tissue structures surrounding the upper airway are less well understood. Magnetic resonance imaging was used to study the effect of incremental levels (0, 5, 10, and 15 cm H2O) of CPAP on the upper airway and surrounding soft tissue structures in 10 normal subjects. Progressive increases in CPAP resulted in the following major findings: (1) airway volume and airway area (measured at several different locations [midregion, minimal, maximal]) within the retropalatal and retroglossal regions increased; (2) lateral airway dimensional changes were greater than anterior-posterior changes; (3) lateral upper airway soft tissue structural changes were significantly greater than anterior-posterior changes; (4) lateral pharyngeal wall thickness decreased and the distance between the lateral parapharyngeal fat pads increased. An inverse relationship was demonstrated between CPAP level and pharyngeal wall thickness; (5) minimal changes were noted in the soft palate and tongue. These data suggest that the lateral pharyngeal walls are more "compliant" than the soft palate and tongue. This investigation provides further evidence that the lateral pharyngeal walls play an important role in mediating upper airway caliber.
Adult↗
Preoperative MR imaging in hyperparathyroidism: results and factors affecting parathyroid detection.
OBJECTIVE: To determine the sensitivity of MR imaging for the detection of abnormal parathyroid glands in patients with biochemical evidence of hyperparathyroidism and to identify the factors affecting detection. SUBJECTS AND METHODS: Between 1985, 82 patients with biochemical proof of hyperparathyroidism were referred for MR imaging of the parathyroid glands prior to surgery. Axial T1- (600/20 [TR/TE]) and T2-weighted (2500/40, 80) spin-echo images were obtained using an anterior neck surface coil. The interpretation of the MR image was compared with the findings at surgery and also correlated with gland histology, volume, and weight. Cases in which a false-positive or false-negative diagnosis was made were reviewed to determine the factors affecting detection. RESULTS: MR imaging detected 71 of 92 (77%) surgically proven abnormal glands (sensitivity, 77%; 95% confidence interval (CI), 68-86%) and misdiagnosed five (1.6%) of 314 normal glands as abnormal. There was no difference in the detection of enlarged glands in patients presenting for the first time (n = 71) (sensitivity, 77%; 95% CI, 66-86%) compared with patients with recurrent hyperparathyroidism (n = 12) (sensitivity, 77%; 95% CI, 46-95%). There was no significant difference in the detection of adenomas (sensitivity, 77%; 95% CI, 65-86%) compared with hyperplasia (sensitivity, 71%; 95% CI, 42-92%). Of five patients with ectopic parathyroid glands (1.6%), four had had previous surgery. All five glands were successfully located (three mediastinal, two in the neck). Factors contributing to a false-negative MR imaging diagnosis included small gland size and thyroid disease. Four of five false-positive diagnoses were due to enlarged lymph nodes being mistaken for parathyroid glands. CONCLUSIONS: MR imaging is an accurate technique for investigation of hyperparathyroidism. Pitfalls include low sensitivity for the identification of small glands, misinterpretation of enlarged lymph nodes as parathyroid adenomas, and misinterpretation because of thyroid disease. MR imaging is particularly useful in the investigation of patients who remain hypercalcemic following initial surgery.
Adult↗
Drug-induced pulmonary disorders.
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Diagnostic Imaging↗
Pulmonary thromboembolism: recent developments in diagnosis with CT and MR imaging.
Recent technical advances in computed tomography (CT; helical and electron beam) and magnetic resonance (MR) imaging have spurred a renewed interest in these modalities for the diagnosis of acute and chronic pulmonary embolism (PE). These techniques can enable accurate clot detection down to segmental pulmonary arteries, with CT currently allowing more accuracy than that with MR imaging. Ongoing technical advances, particularly in MR angiography, will likely increase diagnostic accuracy. Inability to reliably detect subsegmental acute emboli may not prove to be a clinically significant limitation if lung imaging is coupled with evaluation for deep venous thrombosis. MR imaging can potentially accomplish this within a single examination. Incorporation of CT and MR imaging into diagnostic algorithms for suspected PE can be cost-effective. Evaluation of these new modalities should be based on patient outcome, not solely on clot detectability. Well-designed clinical trials are warranted before CT and MR imaging can be used routinely in the diagnosis of acute PE.
Acute Disease↗
Upper airway and soft tissue anatomy in normal subjects and patients with sleep-disordered breathing. Significance of the lateral pharyngeal walls.
The geometry and caliber of the upper airway in apneic patients differs from those in normal subjects. The apneic airway is smaller and is narrowed laterally. Examination of the soft tissue structures surrounding the upper airway can lead to an understanding of these apneic airway dimensional changes. Magnetic resonance imaging was utilized to study the upper airway and surrounding soft tissue structures in 21 normal subjects, 21 snorer/mild apneic subjects, and 26 patients with obstructive sleep apnea. The major findings of this investigation in the 68 subjects were as follows: (1) minimum airway area was significantly smaller in apneic compared with normal subjects and occurred in the retropalatal region; (2) airway narrowing in apneic patients was predominantly in the lateral dimension; there was no significant difference in the anterior-posterior (AP) airway dimension between subject groups; and (3) distance between the rami of the mandible was equal between subject groups, and thus the narrowing of the lateral dimension was not explained by differences in bony structure; (4) lateral airway narrowing was explained predominantly by larger pharyngeal walls in apneic patients (the parapharyngeal fat pads were not closer together as one would expect if the airway walls were compressed by fat); and (5) fat pad size at the level of the minimum airway was not greater in apneic than normal subjects. At the minimum airway area, thickness of the lateral pharyngeal muscular walls rather than enlargement of the parapharyngeal fat pads was the predominant anatomic factor causing airway narrowing in apneic subjects.
Adult↗
MR imaging with spatial modulation of magnetization in the evaluation of chronic central pulmonary thromboemboli.
PURPOSE: To assess the diagnostic value of magnetic resonance (MR) imaging with SPAMM (spatial modulation of magnetization) in the identification of chronic central pulmonary thromboemboli. MATERIALS AND METHODS: Twelve patients with pulmonary hypertension and five healthy volunteers were prospectively studied with a 1.5-T MR imaging system. The SPAMM technique was integrated into a conventional cardiac-synchronized spin-echo (SE) sequence. Six of the 12 patients had central thromboemboli. RESULTS: In the healthy subjects, intravascular stripes in the central pulmonary arteries disappeared as a result of flow within 100 msec after the R wave. Areas of persistent stripes were identified in seven of eight central pulmonary arteries with thromboemboli. Conversely, in the 16 central pulmonary arteries without clot, intraluminal stripes disappeared despite the presence of flow-related signal (sensitivity = 88%, specificity = 100%, accuracy = 96%). CONCLUSION: SPAMM appears to be a simple and effective technique for differentiating central pulmonary arterial thromboemboli from flow-related signal frequently observed with pulmonary hypertension.
Adult↗