Subtraction lung image for evaluating pulmonary ventilation in xenon-enhanced CT.

PURPOSE: The goal of this work was to develop a method of transforming a xenon-enhanced CT (Xe-CT) image of the lung, so as to overlap well with its baseline CT image, and creating a subtraction image (enhanced image minus baseline image), and to demonstrate the possibility of evaluating pulmonary ventilation using the subtraction image. METHODS: Eight healthy men (37.1 +/- 10.1 yr) underwent Xe-CT lung studies. In protocol 1 for five subjects, 30% nonradioactive xenon (Xe) was inhaled for 2 min (washin) followed by air breathing for 4 min (washout). In protocol 2 for three subjects, only washin (30% Xe) for 2 min was applied. In each study, a specific range of the thorax (30 mm) in the supine position was scanned cranio-caudally three times in the helical mode: At the start and end of washin and at the end of washout in protocol 1 and at 1 min intervals from the start to end of washin in protocol 2. After each study, 10-mm-thick CT images were reconstructed to have similar anatomical structures throughout the study. Two-dimensional geometrical warping was performed on enhanced CT images so that they could geometrically overlap with the baseline CT image. Second to eighth degree polynomials were applied to the warping functions. RESULTS: It was derived from the Kety model that subtraction images during washin would directly reflect pulmonary ventilation. Geometrical warping achieved an increase of 0.3%-22.0% in the area, for which ventilation could be evaluated in the subtraction image. In the cases in protocol 2 where the initial lung volume was well retained throughout the study, the ratios of the specific ventilation from the subtraction image to that from the specific ventilation map were 0.88 +/- 0.06 and 0.96 +/- 0.10 for the right and left lungs, respectively. CONCLUSIONS: A subtraction lung image during washin would provide quantitative information on pulmonary ventilation when the baseline and enhanced images could have close lung volume and these two images could overlap well. Image subtraction requires only two scans and therefore less radiation exposure compared to ordinary protocols in Xe-CT. The proposed Xe-CT subtraction method with the geometrical warping technique could be clinically utilized for evaluating pulmonary ventilation.

Successful thoracoscopic lobectomy for lung cancer in a patient with anatomic variation of the left inferior pulmonary vein.

We present a case of primary lung cancer with a rare distribution pattern of left inferior pulmonary vein (PV), encountered in the thoracoscopic left lower lobectomy. Thoracoscopic observation revealed 2 trunks of inferior PV (ventral and dorsal branch) at the stem level. The ventral trunk consisted of a branch of vein (V(5)) from the lingular segment and venous ramifications (V(8)a, V(9) and V(10)a) from the basal segment. On the other hand, a branch of vein (V(6)) from the superior segment in the lower lobe and other veins (V(8)b and V(10)b + c) from the basal segment emptied together into the dorsal trunk. We successfully carried out a thoracoscopic left lower lobectomy without excision of the aberrant vein (V(5)). Retrospective review of the preoperative chest CT demonstrates the double trunk inferior PV and the aberrant lingular branch emptying with V(8)a into the ventral trunk. Knowledge of the branching variations of PV from preoperative evaluations leads to appropriate thoracoscopic procedures for lung cancer.

A thoracoscopically resected case of mediastinal parathyroid cyst.

A 67-year-old male visited his physician because of a 2-month history of cough and sputum. An abnormal shadow at the left upper mediastinum on chest x-ray film was detected, and the patient was referred to our department for further examination. Chest x-ray film revealed a round shadow at the left upper posterior mediastinum. Computed tomography(CT)revealed a uniform iso density mass about 4 cm in diameter, with a well-defined border. After the intravenous contrast administration, a slight peripheral enhancement was seen around the mass. On magnetic resonance imaging, the mass was hypointense in T1-weighting and hyperintense in T2-weighting. The contrast pattern was the same as that observed in the CT scan. On sagittal and coronal sections, the mass was adjacent to the aortic arch. Although a benign tumor was mostly suspected based on imaging findings, a malignant tumor was also possible. Accordingly, we resected this mass with video-assisted thoracoscopy. Findings at operation were a cystic mass. The pathological findings were compatible with benign parathyroid cyst, which was suspected to be the cystic degeneration of a parathyroid adenoma.

Effect of gravitation for detection of bronchioloalveolar carcinoma on computed tomography.

A 64-year-old female was found to have localized ground-glass opacity (GGO) in the middle lobe on a chest computed tomography (CT) for screening. Middle lobectomy with video-assisted thoracoscopic surgery (VATS) was undertaken, and pathological diagnosis was a bronchioloalveolar carcinoma (BAC) in stage IA. A follow-up CT a year following the surgery revealed localized GGO in area S6 of the left lung. However, it disappeared during the gravitation-dependent gradient in the observation period. The patient was scanned again under prone position to exclude the gravitational effect, resulting in definite detection of the GGO. Left extended S6 segmentectomy with VATS was performed, and pathological diagnosis was a BAC in stage IA. As GGO existing in a gravitation-dependent area may be masked by the gravitation-dependent density, a change of the scanning position may lead to a proper detection of the tumor for the diagnosis of BAC.

Mediastinal cyst with rim calcification.

A 58-year-old man who had been undergoing treatment for chronic pericarditis for 15 months was found to have a calcified mediastinal mass shadow on a chest X-ray and was referred to us for further study and treatment. Chest computed tomography and magnetic resonance imaging showed an anterior mediastinal multilocular tumor with rim calcification. Tumor markers were within normal limits. The patient was preoperatively diagnosed as having a calcified mediastinal cyst, and median sternotomy was performed to remove the cystic tumor and the surrounding thymic tissues. Histological examination revealed that the cyst wall consisted of dense fibrous tissue and calcification without epithelial cell lining on the inner surface. Thymic tissue was present around the cyst wall. Although we suspected a thymic cyst from the intraoperative findings, the final diagnosis was made as mediastinal cyst with rim calcification. We herein present a rare case of mediastinal cyst with rim calcification.

Primary thymic adenocarcinoma with production of carbohydrate antigen 19-9 and carcinoembryonic antigen.

A 59-year-old male, whose chest X-ray showed an abnormal shadow, visited us for further study. Laboratory examination showed the elevated level for both carbohydrate antigen 19-9 (CA19-9) and carcinoembryonic antigen (CEA) in serum, and the chest X-ray and computed tomography showed an anterior mediastinal mass. Under a diagnosis of thymic malignancy, extended thymectomy with combined resection of the pleura and pericardium was performed. Histopathological findings showed a well-differentiated adenocarcinoma of the thymus, in which CA19-9 and CEA were positive immuno-histochemically. The level of serum CA19-9 and CEA returned to normal ranges postoperatively, however, the tumor recurred in local site with re-elevation of these tumor markers at the 20th month after surgery. He died at 4th month after the first recurrence despite the intensive chemotherapy. We report an extremely rare case of primary thymic adenocarcinoma with the production of CA19-9 and CEA.

[Comparison of cerebral blood flow with Xe-inhalation CT and perfusion CT].

Cerebral blood flow (ml/min/100g) (CBF) was detected by two methods, static xenon inhalation dynamic CT (Xe-CT) and perfusion CT, and a comparison of these two methods (Xe-CBF and perfusion CBF) was carried out in the same cases. Xe CT used 30% static xenon, 4 min wash-in, and 5 min wash-out, while perfusion CT was done by injecting 30 ml of non-ionic contrast medium at a rate of 9 ml/sec. Forty-eight patients underwent these examinations (30 serious cases and 18 mild). The correlation coefficients in the hemispheric area were r=0.713 (p<0.01) with Xe-CBF and perfusion CBF in mild cases and r=0.567 (p<0.01) in serious cases. The two CBF values were especially disparate in serious cases. The value for perfusion CBF was almost double that of Xe-CBF in these cases. Perfusion CT was a useful examination for the detection of CBF, but in serious cases, CBF needs to be determined by Xe-CT as well.

Pulmonary inflammatory pseudotumor with rapid growth and serum carcinoembryonic antigen elevation.

Inflammatory pseudotumors consist of chronic inflammatory cells, predominantly plasma cells. We report a rare case of pulmonary inflammatory pseudotumor associated with rapid growth and elevated serum carcinoembryonic antigen (CEA). A 75-year-old man referred for bloody sputum was found in chest computed tomography (CT) to have a round circumscribed tumor with a cavity located in the periphery of the right lower pulmonary lobe. Cytological examination of a biopsy specimen obtained by CT-guided transthoracic fine needle aspiration showed no malignancy. Two months later, the tumor had noticeably grown, accompanied by a notable rise in serum CEA. We conducted right lower pulmonary lobectomy with regional lymph node dissection, since malignancy could not be ruled out by frozen-section examination. Histological examination of the resected specimen showed an inflammatory pseudotumor with CEA production.

[Investigation of cerebral blood volume measurement].

PURPOSE: Cerebral blood blow (ml/100g/min) (CBF) and cerebral blood volume (%) (CBV) were determined in 102 patients (68 men and 34 women; average age, 55.6 years) with diagnostic cerebral blood flow accident. METHODS: CBF was obtained by xenon inhalation computed tomography (Xe CT) and transit time (TT) by perfusion CT. CBV was calculated under the expression CBV=CBF x TT. The patients were divided into three categories: mild (outpatient), moderate (inpatient), and serious (dead), and CBF and CBV were compared between categories. RESULTS: On regions of interest (ROI) in the thalamus, the value for mild cases was 58.8+/-10.4 ml/100g/min (CBF) and that for moderate cases was 40.2+/-19.4, a significant difference. In serious cases, CBV was decreased in the thalamus, but there was no difference in CBF between mild and moderate cases. CONCLUSION: CBV was useful for determining prognosis in severe cases of diagnostic cerebral blood flow accident.

[Method of injection of contrast medium for brain perfusion CT].

Perfusion computed tomography (CT) has great value for detecting stroke and evaluating blood flow in the brain. With perfusion CT, it is possible to obtain two absolute values, cerebral blood flow (CBF) (ml/min/100g) and cerebral blood volume (CBV) (%). In using this examination, the main problem is the method of iodine injection. The maximum slope of time-attenuation curve in organs must be reached before the peak enhancement time of the sagittal sinus. To solve this problem, we used a new method in which total injection volume is 30ml, and the rate of injection is 9ml/sec. The data acquisition time is one second for each scan, and the time interval is one second, for 20 scans in total. With this method, we can obtain reliable information on blood flow in the damaged brain. The most common examination used for the detection of brain blood flow is single-phased dynamic CT with Xe inhalation. However, the Xe inhalant examination is difficult to use in the routine clinical setting. Perfusion CT will be more useful for the detection of brain blood flow.