Non-invasive screening of lung nodules in mice comparing a novel volumetric computed tomography with a clinical multislice CT

Abstract

In vivo imaging of small animal models will play an increasingly important role in cancer research, as new imaging systems that employ non-invasive protocols and offer high-resolution capability become available. A flatpanel volumetric computed tomograph (fpvCT) was evaluated to determine if minimally invasive protocols can be used to provide the spatial resolution required for lung imaging in small animals. The detection of small pulmonary nodules in a Lewis carcinoma model was investigated, and fpvCT was compared with a multislice computed tomograph (MSCT). Five C57/BL6 mice with Lewis lung carcinoma were monitored with both modalities over two weeks. Sensitivity of the systems was measured by comparing the results with histology, and the incidence of first visualization of the tumors in the two systems was determined. Compared to MSCT, fpvCT proved its superior sensitivity in detection of lung nodules. Due to its isotropic resolution and a significant reduction of partial volume effects, early detection and reasonable determination of growth in very small tumors was only possible with fpvCT. fpvCT is a high-resolution imaging system that proved its ability to perform in vivo monitoring of a pulmonary lung tumor model in mice. This permits longitudinal investigations in small animals for cancer research.

Rapid and efficient mapping of regional ventilation in the rat lung using hyperpolarized 3He with Flip angle variation for offset of RF and relaxation (FAVOR)

“…It is anticipated that 3 He MR will provide a favorable approach for measurement of ventilation in animal cohorts to track lung disease over time without the complications associated with accumulated x-ray dose (3). This method measures the dynamic change in lung 3 He signal as a function of breath number and extracts the relative refreshment of gas in a given lung voxel per breath.…”

“…It is anticipated that 3 He MR will provide a favorable approach for measurement of ventilation in animal cohorts to track lung disease over time without the complications associated with accumulated x-ray dose (3). This method measures the dynamic change in lung 3 He signal as a function of breath number and extracts the relative refreshment of gas in a given lung voxel per breath. However, the conventional 3 He ventilation measurement requires knowledge of the longitudinal relaxation time, T 1 , of the 3 He gas in the ventilator system and in the lung, the latter requiring knowledge of the alveolar oxygen partial pressure (p A O 2 ).…”

“…Furthermore, without accurate knowledge of the RF pulse history the method requires multiple 3 He breathing cycles (i.e., 3 He wash-in breaths) with air wash-out breaths between cycles in order to completely clear the lung of 3 He gas, which is time-consuming (i.e., several minutes), an inefficient use of hyperpolarized 3 He gas (i.e., costly), and can lead to imprecision due to variations in tidal volume from the ventilator.…”

“…This method measures the dynamic change in lung 3 He signal as a function of breath number and extracts the relative refreshment of gas in a given lung voxel per breath. However, the conventional 3 He ventilation measurement requires knowledge of the longitudinal relaxation time, T 1 , of the 3 He gas in the ventilator system and in the lung, the latter requiring knowledge of the alveolar oxygen partial pressure (p A O 2 ).…”

“…MR imaging with hyperpolarized 3 He gas has been proposed for measurement of regional ventilation in the rodent lung (1) and has been recently validated with xenon-enhanced CT imaging (2). It is anticipated that 3 He MR will provide a favorable approach for measurement of ventilation in animal cohorts to track lung disease over time without the complications associated with accumulated x-ray dose (3).…”