Ichiro Hasegawa

Dynamic expiratory volumetric CT imaging of the central airways: Comparison of standard-dose and low-dose techniques

RATIONALE AND OBJECTIVES Investigators in this study compared standard-dose and low-dose inspiratory and expiratory computed tomographic (CT) images with regard to their usefulness for measuring the tracheal lumen in patients with or without tracheobronchomalacia (TBM). MATERIALS AND METHODS; Hospital records were reviewed to identify 10 consecutive patients with bronchoscopically proved TBM and 10 control subjects without TBM who underwent paired volumetric inspiratory and dynamic expiratory examinations with multisection CT. A low-dose (40-80 mA) technique was used for dynamic expiratory CT in 14 (70%) of the 20 subjects, and a standard dose (240-280 mA) was used in the remaining six (30%). All images were reviewed in a randomized, blinded fashion by two observers, who measured the tracheal lumen to determine the presence of TBM by consensus. The degree of confidence in measuring the tracheal lumen was graded on a four-point scale from 0(no confidence) to 3 (highest level of confidence), also by consensus of the two observers. Statistical analysis for differences in confidence level was performed with the Mann-Whitney U test. The image noise level was assessed by measuring the standard deviation of the presternal soft tissue, and statistical analysis for differences in noise level was performed with the t test. RESULTS The level of confidence in tracheal lumen measurement was high, regardless of respiratory phase and dose (inspiratory mean, 2.9; median, 3; range, 2-3; expiratory low-dose mean, 2.6; median, 3; range, 2-3; expiratory standard-dose mean, 2.8; median, 3; range, 2-3). There was no significant difference in confidence level between standard- and low-dose techniques (P = .53). Excessive central airway collapse (expiratory reduction in cross-sectional diameter, > 50%) was seen in all 10 patients with TBM and in none of the control subjects. CONCLUSION The acquisition of paired inspiratory and dynamic expiratory images with multisection helical CT is a promising method for diagnosing TBM. The low-dose technique performs as well as the standard-dose technique for the dynamic expiratory phase, with a similar degree of confidence for measuring the tracheal lumen.

Characterization of regional pulmonary mechanics from serial magnetic resonance imaging data1

RATIONALE AND OBJECTIVES The aim of this study was to investigate a method for quantifying lung motion from the registration of successive images in serial magnetic resonance imaging acquisitions during normal respiration. MATERIALS AND METHODS Estimates of pulmonary motion were obtained by summing the normalized cross-correlation over serially acquired lung images to identify corresponding locations between the images. The estimated motions were modeled as deformations of an elastic body and thus reflect to a first order approximation the true physical behavior of lung parenchyma. The Lagrangian strain, derived from the calculated motion fields, were used to quantify the tissue deformation induced in the lung over the serial acquisition. RESULTS The method was validated on a magnetic resonance imaging study, for which breath-hold images were acquired of a healthy volunteer at different phases of the respiratory cycle. Regional parenchymal strain was observed to be oriented toward the pulmonary hilum, with strain magnitude maximal at the midcycle of the expiratory phase. CONCLUSION In vivo magnetic resonance imaging quantification of lung motion holds the potential of providing a new diagnostic dimension in the assessment of pulmonary function, augmenting the information provided by studies of ventilation and perfusion.

Fast scanning tomosynthesis for the detection of pulmonary nodules: diagnostic performance compared with chest radiography, using multidetector-row computed tomography as the reference.

Objectives:To evaluate the diagnostic performance of fast scanning tomosynthesis in comparison with that of chest radiography for the detection of pulmonary nodules, using multidetector-row computed tomography (MDCT) as the reference, and to assess the association of the true-positive fraction (TPF) with the size, CT attenuation value, and location of the nodules. Materials and Methods:The institutional review board approved this study, and written informed consent was obtained from all patients. Fifty-seven patients with and 59 without pulmonary nodules underwent chest MDCT, fast scanning tomosynthesis, and radiography. The images of tomosynthesis and radiography were randomly read by 3 blinded radiologists; MDCT served as the reference standard. Free-response receiver-operating characteristic (FROC) and receiver-operating characteristic (ROC) analyses, Cochran-Armitage trend or Fisher exact test, a conditional logistic regression model, and McNemar test were used. Results:Both FROC and ROC analyses revealed significantly better performance (P < 0.01) of fast scanning tomosynthesis than radiography for the detection of pulmonary nodules. For fast scanning tomosynthesis, the average TPF and false-positive rate as determined by FROC analysis were 0.80 and 0.10, respectively. For both fast scanning tomosynthesis and radiography, the average TPF increased with increasing nodule size and CT attenuation values, and was lower for subpleural nodules (all P < 0.01). Conclusions:The diagnostic performance of fast scanning tomosynthesis for the detection of pulmonary nodules was significantly superior to that of radiography. The TPF was affected by the size, CT attenuation value, and location of the nodule, in both fast scanning tomosynthesis and radiography.

Mediastinal lymph nodes in patients with non-small cell lung cancer: preliminary experience with diffusion-weighted MR imaging.

Objectives The purpose of our study was to describe our preliminary experience of evaluating mediastinal lymph node metastases with diffusion-weighted magnetic resonance (MR) imaging in patients with non-small cell lung cancer. Materials and Methods Forty-two consecutive patients with non-small cell lung cancer underwent preoperative diffusion-weighted MR imaging using a non-breath-hold short inversion time inversion recovery-echo planar imaging sequence with a high b value of 1000 s/mm2. An experienced thoracic radiologist prospectively evaluated each study for mediastinal lymph node metastases on a per-patient basis. On diffusion-weighted MR imaging, mediastinal lymph node metastasis was defined as a focus of low signal intensity at the site of a visible lymph node on corresponding T2-weighted image. The MR results were correlated with histopathologic findings. Results Diffusion-weighted MR imaging demonstrated mediastinal lymph node metastasis in 4 (80%) of 5 patients with pathologically proven metastasis and accurately identified 36 (97%) of 37 patients without mediastinal lymph node metastasis. Thus, 40 (95%) of 42 patients were accurately diagnosed. The sensitivity, specificity, positive predictive value, negative predictive value, and accuracy of diffusion-weighted MR imaging for mediastinal lymph node metastasis were 80%, 97%, 80%, 97%, and 95%, respectively. Conclusions Our preliminary results show that diffusion-weighted MR imaging has a high negative predictive value for excluding mediastinal lymph node metastases from non-small cell lung cancer and has the potential to be a reliable alternative non-invasive imaging method for the preoperative staging of mediastinal lymph node in patients with non-small cell lung cancer.

Characterization of Regional Pulmonary Mechanics from Serial MRI Data

We describe a method for quantification of lung motion from the registration of successive images in serial MR acquisitions during normal respiration. MR quantification of pulmonary motion enables in vivo assessment of parenchymal mechanics within the lung in order to assist disease diagnosis or treatment monitoring. Specifically, we obtain estimates of pulmonary motion by summing the normalized cross-correlation over the lung images to identify corresponding locations between the images. The normalized correlation is robust to linear intensity distortions in the image acquisition, which may occur as a consequence of changes in average proton density resulting from changes in lung volume during the respiratory cycle. The estimated motions correspond to deformations of an elastic body and reflect to a first order approximation the true physical behavior of lung parenchyma. The method is validated on a serial MRI study of the lung, for which breath-hold images were acquired of a healthy volunteer at different phases of the respiratory cycle.

Pulmonary hilar lymph nodes in lung cancer: assessment with 3D-dynamic contrast-enhanced MR imaging.

PURPOSE We performed 3D-dynamic MRI on patients with primary lung cancer to identify its usefulness for detecting hilar adenopathy shown at surgery. METHODS AND MATERIALS 30 consecutive patients with peripheral lung cancer underwent preoperative 3D-dynamic Gd-DTPA-enhanced MRI. Two thoracic radiologists blinded to histopathologic findings reviewed those studies independently for hilar adenopathy visualization. The results were correlated with surgical and histopathologic findings. Interreader agreement for the detection of hilar adenopathy was assessed by means of the kappa statistic. RESULTS Dynamic MRI demonstrated hilar adenopathy, with or without metastasis revealed at surgery, in all of 15 patients. Adenopathy without metastasis was shown in four patients. Dynamic MRI also revealed metastatic adenopathy in 11 of 12 patients with pathologically proven metastasis. There was only one case with lymph node metastasis that did not have adenopathy either on MRI or even at surgery. The diagnostic accuracy of dynamic MRI for adenopathy with or without metastases revealed at surgery were as follows; sensitivity, 100%; specificity, 100%; positive predictive value, 100%; and negative predictive value, 100%, respectively. The diagnostic accuracy of dynamic MRI for hilar lymph nodes metastasis were as follows; sensitivity, 92%; specificity, 78%; positive predictive value, 73%; and negative predictive value, 93%. Interreader agreement was substantial (kappa=0.73) for detection of hilar adenopathy. CONCLUSION Hilar adenopathy on 3D-dynamic MRI correlated well with that of surgical finding on patients with primary lung cancer. It may have the potential to make an accurate preoperative evaluation of hilar lymph node metastasis from lung cancer.

Voxelwise mapping of magnetic resonance ventilation-perfusion ratio in a porcine model by multimodality registration: technical note1

RATIONALE AND OBJECTIVES The purpose of this study was to demonstrate the construction of voxelwise ventilation-perfusion (V/Q) ratio maps in a porcine model by nonrigidly aligning the respective ventilation and perfusion images using a multimodality registration algorithm. MATERIALS AND METHODS The first-pass contrast agent technique for a blood flow map and 3He used for ventilation imaging were performed using a normal porcine model. The registered 3He-ventilation image was then aligned to the blood flow map using a multimodality registration algorithm. The voxelwise V/Q ratios were calculated by dividing the registered 3He-ventilation image by the blood flow map. The V/Q ratios were also semi-logarithmically scatter-plotted against the number of voxels. RESULTS From perfusion magnetic resonance images, a voxel-by-voxel blood flow map was produced. Registered 3He ventilation image was successfully obtained as well as V/Q ratio map. Plots of the V/Q ratios obtained by this registration approach were similar to the logarithmic normal distribution. CONCLUSION Registration of MR perfusion and ventilation images can potentially enable quantitative evaluation of regional pulmonary function and thus yield deeper insight into the physiology and pathophysiology of the lung.

Preliminary Experience of Endovascular Embolization Using N-Butyl Cyanoacrylate for Hemoptysis due to Infectious Pulmonary Artery Pseudoaneurysms via Systemic Arterial Approach

We report 5 patients with hemoptysis due to infectious pulmonary artery pseudoaneurysm (PAP) treated with endovascular embolization using N-butyl cyanoacrylate (NBCA) injected via bronchial and nonbronchial systemic arterial approaches. Infectious diseases included inactive tuberculosis (n = 3), nontuberculous mycobacteriosis (n = 1), and chronic infection of unknown origin (n = 1). Seven PAPs were detected on selective systemic angiography, and injection of NBCA was performed. Disappearance of all PAPs was confirmed on systemic arteriography after the intervention. In all patients, hemoptysis was stopped without major complications, and it did not recur during the follow-up period (mean, 351 d; range, 285-427 d).

Interventional Therapeutic Strategy for Hemoptysis Originating from Infectious Pulmonary Artery Pseudoaneurysms

This study reports 6 cases of hemoptysis originating from infectious pulmonary artery pseudoaneurysms (PAPs). Selective pulmonary angiography revealed PAPs in 5 cases, and segmental pulmonary artery embolization was performed using coils and gelatin sponge particles. Systemic arterial embolization also was performed in 5 cases because of inadequate initial control or for shunts from systemic to pulmonary arteries. At a median follow-up time of 9 months (range, 25 d to 25 mo), no recurrence occurred, although 2 patients died of respiratory failure. Segmental artery embolization combined with systemic artery embolization may be useful in patients with hemoptysis secondary to PAPs.

Mediastinal Schwannoma Diagnosed Preoperatively as a Cyst

Mediastinal schwannomas are sometimes diagnosed as pericardial or bronchogenic cysts, if cystic degeneration is extensive. When mediastinal schwannomas are not diagnosed as primary cardiac tumors, the use of cardiopulmonary bypass in their resection appears to be infrequent. We report the case of a 48-year-old woman who presented with symptoms from a suspected intrapericardial cyst. Multiple diagnostic images revealed a large mass, potentially a proteinaceous or hemorrhagic cyst, in the transverse sinus behind the ascending aorta and against the left main trunk. After complete resection with the use of cardiopulmonary bypass, the mass was identified as a benign extracardiac schwannoma. More than 3 years postoperatively, the patient had no relevant symptoms. We discuss the preoperative diagnosis, the method of resection, and our broad strategy for dealing with such a case.