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Human observer performance tests were conducted to identify optimal imaging techniques in dual-energy (DE) imaging of the chest with respect to a variety of visualization tasks for soft and bony tissue. Specifically, the effect of kVp selection in low- and high-energy projection pairs was investigated. DE images of an anthropomorphic chest phantom formed the basis for observer studies, decomposed from low-energy and high-energy projections in the range 60–90 kVp and 120–150 kVp, respectively, with total dose for the DE image equivalent to that of a single chest radiograph. Five expert radiologists participated in observer preference tests to evaluate differences in image quality among the DE images. For visualization of soft-tissue structures in the lung, the [60/130] kVp pair provided optimal image quality, whereas [60/140] kVp proved optimal for delineation of the descending aorta in the retrocardiac region. Such soft-tissue detectability tasks exhibited a strong dependence on the low-kVp selection (with 60 kVp providing maximum soft-tissue conspicuity) and a weaker dependence on the high-kVp selection (typically highest at 130–140 kVp). Qualitative examination of DE bone-only images suggests optimal bony visualization at a similar technique, viz., [60/140] kVp. Observer preference was largely consistent with quantitative analysis of contrast, noise, and contrast-to-noise ratio, with subtle differences likely related to the imaging task and spatial-frequency characteristics of the noise. Observer preference tests offered practical, semiquantitative identification of optimal, task-specific imaging techniques and will provide useful guidance toward clinical implementation of high-performance DE imaging systems. [ABSTRACT FROM AUTHOR]

Experimental and theoretical studies were conducted to determine optimal acquisition techniques for a prototype dual-energy (DE) chest imaging system. Technique factors investigated included the selection of added x-ray filtration, kVp pair, and the allocation of dose between low- and high-energy projections, with total dose equal to or less than that of a conventional chest radiograph. Optima were computed to maximize lung nodule detectability as characterized by the signal-difference-to-noise ratio (SDNR) in DE chest images. Optimal beam filtration was determined by cascaded systems analysis of DE image SDNR for filter selections across the periodic table (Zfilter=1–92), demonstrating the importance of differential filtration between low- and high-kVp projections and suggesting optimal high-kVp filters in the range Zfilter=25–50. For example, added filtration of ∼2.1 mm Cu, ∼1.2 mm Zr, ∼0.7 mm Mo, and ∼0.6 mm Ag to the high-kVp beam provided optimal (and nearly equivalent) soft-tissue SDNR. Optimal kVp pair and dose allocation were investigated using a chest phantom presenting simulated lung nodules and ribs for thin, average, and thick body habitus. Low- and high-energy techniques ranged from 60–90 kVp and 120–150 kVp, respectively, with peak soft-tissue SDNR achieved at [60/120] kVp for all patient thicknesses and all levels of imaging dose. A strong dependence on the kVp of the low-energy projection was observed. Optimal allocation of dose between low- and high-energy projections was such that ∼30% of the total dose was delivered by the low-kVp projection, exhibiting a fairly weak dependence on kVp pair and dose. The results have guided the implementation of a prototype DE imaging system for imaging trials in early-stage lung nodule detection and diagnosis. [ABSTRACT FROM AUTHOR]

Abstract Endoscopic ultrasound-guided fine-needle aspiration biopsy (EUS FNA) is a relatively new imaging modality that has been reported to be useful for mediastinal nodal staging of lung cancer and for the evaluation of mediastinal adenopathy of unknown cause. However, the technique is not commonly used in Australia. A retrospective review of all patients who had mediastinal EUS FNA was undertaken. Of a total of 787 patients who had undergone endoscopic ultrasound (EUS) studies from November 1999 to March 2004, 27 patients were identified to have had mediastinal EUS FNA. Details were recorded including study indication, history of malignancy, source of referral, prior attempts for tissue diagnosis, EUS and EUS FNA findings, complications, surgical pathology if available and clinical outcome after diagnosis. Mediastinal EUS FNA was performed on an outpatient basis and no complications were recorded. Diagnostic material was obtained from all patients with a mean number of three passes. Nodal stations sampled included left paratracheal, subcarinal, aortopulmonary window and inferior mediastinum. Indications for the studies included mediastinal adenopathy of uncertain cause (17), lung cancer staging (7) and gastrointestinal cancer staging (3). EUS FNA confirmed malignancy in 16/27 patients, sarcoidosis in three patients, tuberculosis in one patient and seven patients were deemed to have reactive adenopathy. Primary cytopathological diagnosis of malignancy was determined by EUS FNA in nine patients. EUS FNA is a safe, efficient and effective modality for mediastinal staging of lung cancer and for the diagnosis of mediastinal adenopathy of uncertain origin. EUS FNA has the potential to significantly impact on patient management, avoiding more invasive procedures as well as unnecessary operations. (Intern Med J 2005; 35: 392–398) [ABSTRACT FROM AUTHOR]