Magnetic resonance elastography (MRE) is a phase-contrast technique that can spatially map shear stiffness within tissuelike materials. To date, however, MRE of the lung has been too technically challenging-primarily because of signal-to-noise ratio (SNR) limitations and phase instability. We describe an approach in which shear wave propagation is not encoded into the phase of the MR signal of a material, but rather from the signal arising from a polarized noble gas encapsulated within. To determine the feasibility of the approach, three experiments were performed. First, to establish whether shear wave propagation within lung parenchyma can be visualized with phasecontrast MR techniques, MRE was performed on excised porcine lungs inflated with room air. Second, a phantom consisting of open-cell foam filled with thermally polarized 3 He gas was imaged with MRE to determine whether shear wave propagation can be encoded by the gas. Third, preliminary evidence of the feasibility of MRE in vivo was obtained by using a longitudinal driver on the chest of a normal volunteer to generate shear waves in the lung. The results suggest that MRE in combination with hyperpolarized noble gases is potentially useful for noninvasively assessing the regional elastic properties of lung parenchyma, and merits further investigation. In the United States lung disease is a significant and growing public health issue, with mortality rates ranking fourth behind diseases of the heart, malignant neoplasms, and cerebrovascular diseases (1). This condition is also chronic and impacts the lives of over 35 million Americans. Within the spectrum of lung disorders, obstructive lung disease is of particular concern since it accounts for over 35% of all lung-related fatalities (second only to lung cancer) (1). In obstructive lung disease, it is generally accepted that not only the type but also the spatial heterogeneity of the disease affect the intrinsic mechanical properties of lung parenchyma. Within the asthma model, both the parenchymal bulk, K (volumetric stress/strain) and shear moduli, (shear stress/shear strain), have been reported to increase with bronchoconstriction in the rat lung (2), which suggests that parenchyma stiffness should increase with asthma severity. Simulation studies have also identified the relationship between airway patency and the mechanical properties of the parenchyma (3-5). In particular, bronchioconstriction has been identified as a method by which these elastic properties can increase (2,5), which highlights the relationship between asthma and parenchymal stiffness.Unfortunately, our ability to quantify changes in the mechanical properties of the lung is limited. Spirometry, the measurement of the volume of inhaled or exhaled air as a function of time, merely provides a global measure of lung and airway properties. While repeated spirometry can provide insight into the volatility of the bronchi, the technique does not quantify remodeling-induced changes in airway plasticity, is limited by its global nature (i.e...

Object The authors report the evolution of linear accelerator (LINAC)–based radiosurgery in the treatment of patients with intracranial meningiomas. They describe the technical aspects as well as clinical and radiological outcomes. Methods The authors performed a retrospective review of 161 patients harboring 194 intracranial meningiomas treated with various types of stereotactic irradiation at their institution between May 1991 and July 2002. Clinical and radiological follow-up data (mean follow-up period 32.5 months, range 6–125 months) were obtained in 128 patients (79.5%) with 156 meningiomas (80.4%). There were 88 women and 40 men whose mean age was 57.2 years (range 18–87 years). Stereotactic irradiation was the primary treatment in 44 patients, and 84 patients underwent resection prior to radiosurgery. Stereotactic radiosurgery (SRS) was used to treat 79 lesions and fractionated stereotactic radiotherapy (SRT) was used to treat 77. The mean dose for SRS was 1567 cGy (range 1200–2285 cGy) prescribed to a mean isodose line of 66.6% (range 50–90%). Stereotactic radiotherapy was delivered using a mean dose of 4839 cGy (range 2380–5400 cGy), prescribed to a mean isodose line of 89% (range 50–90%). The mean follow-up periods were 40 and 24 months in SRS- and SRT-treated patients, respectively. Tumor control was achieved in 58 SRT-treated benign meningiomas (90%) and in 70 SRT-treated lesions (97.2%). In patients with atypical meningiomas a considerably poorer prognosis was seen. Clinical improvement or stabilization of symptoms was observed in the majority of patients. Symptomatic complications were limited to four patients (5%) treated with SRS and four (5.2%) treated with SRT. Conclusions Stereotactic irradiation techniques have changed the neurosurgical approach to intracranial meningiomas. Either SRS or SRT delivered as a primary treatment in selected cases of skull base lesions or as an adjuvant after conservative resection has improved the management of these complex intracranial tumors.

Automatic tube potential selection provides an efficient and quantitativeway to guide the selection of the optimal tube potential for CTA and abdominopelvic CT examinations.

The application of a dedicated linear accelerator (DLINAC) as a noninvasive surgical treatment for trigeminal neuralgia has not yet been demonstrated. This work evaluates the outcome and indications of 22 patients submitted to DLINAC radiosurgery as a primary treatment for essential trigeminal neuralgia. At last follow-up evaluation, 21 patients (95.5%) had sustained significant pain relief. DLINAC radiosurgery is safe and effective as a primary noninvasive surgical treatment for selected patients with essential trigeminal neuralgia.

Speech recognition software can increase the frequency of errors in radiology reports, which may affect patient care. We retrieved 213,977 speech recognition software-generated reports from 147 different radiologists and proofread them for errors. Errors were classified as "material" if they were believed to alter interpretation of the report. "Immaterial" errors were subclassified as intrusion/omission or spelling errors. The proportion of errors and error type were compared among individual radiologists, imaging subspecialty, and time periods. In all, 20,759 reports (9.7%) contained errors, of which 3992 (1.9%) were material errors. Among immaterial errors, spelling errors were more common than intrusion/omission errors ( p < .001). Proportion of errors and fraction of material errors varied significantly among radiologists and between imaging subspecialties ( p < .001). Errors were more common in cross-sectional reports, reports reinterpreting results of outside examinations, and procedural studies (all p < .001). Error rate decreased over time ( p < .001), which suggests that a quality control program with regular feedback may reduce errors.