THz phase-contrast computed tomography based on Mach-Zehnder interferometer using continuous wave source: proof of the concept.

In this study, we propose a THz computed tomography (CT) method based on phase contrast, which retrieves the phase shift information at each data point through a phase modulation technique using a Mach-Zehnder interferometer with a continuous wave (CW) source. The THz CT is based on first-generation CT, which acquires a set of projections by translational and rotational scans using a thin beam. From the phase-shift projections, we reconstruct a spatial distribution of refractive indices in a cross section of interest. We constructed a preliminary system using a highly coherent CW THz source with a frequency of 0.54 THz to prove the concept and performed an imaging experiment using phantoms to investigate its imaging features such as artifact-immune imaging, quantitative measurement, and selective detection.

Small cell carcinoma of the lung exclusively localized within the left descending pulmonary artery.

We encountered a 69-year-old woman displaying a filling defect within the left descending pulmonary artery (PA) on a chest CT scan and pulmonary angiography. A subsequent 2-[18F]fluoro-2-deoxy-D-glucose (FDG) positron emission tomography (PET) scan demonstrated focal uptake in the left hilum. A cytologic examination of transbronchial needle aspiration specimens revealed small cell carcinoma. The patient underwent concurrent radiation therapy and chemotherapy with cisplatin and etoposide, resulting in tumor shrinkage and recanalization of the involved PA. This is the first case of small cell carcinoma localized exclusively within the PA, and positive findings on FDG-PET facilitated the unexpected diagnosis.

[A case of vagus nerve schwannoma in the middle mediastinum presenting with dyspnea].

A 67-year-old woman complaining of dyspnea was referred to our hospital because of an abnormal chest radiography shadow. Computed tomographic (CT) scans as well as magnetic resonance images (MRI) demonstrated a mid-mediastinal mass of 9 cm in diameter, surrounded by the superior vena cava (SVC), the ascending aorta, the azygos vein arch and the trachea at the subaortic level. The left main bronchus was stenotic, probably because of expansion of the tumor, which seemed to be the cause of the dyspnea. Routine examinations disclosed no metastatic or primary lesions elsewhere. The tumor was surgically resected. It measured 8 x 7 x 5 cm. The pathological diagnosis was benign vagus nerve Schwannoma, consisting of the histologies of both Antoni A and B types. We have reported this case because Schwannoma should be included in the differential diagnosis of mediastinal tumors even when it occurs in the middle of the mediastinum.

Pulmonary Langerhans' cell histiocytosis presenting with an endobronchial lesion.

A 19-year-old man visited our hospital complaining of cough, sputum and low-grade fever. Chest radiograph and computed tomography findings suggested that he was suffering from pulmonary Langerhans' cell histiocytosis (PLCH). Bronchoscopy revealed a whitish elevated lesion at the bifurcation of the right upper lobe bronchus, and a specimen of this lesion showed the same pathological findings as pulmonary parenchymal lesions. Although there have been only a few reports of endobronchial LCH without pulmonary parenchymal lesions, this is, to our knowledge, the first case of PLCH with an endobronchial lesion, which was confirmed by bronchoscopy, and disappeared several months later.