Kazuyoshi Suga

Impaired respiratory mechanics in pulmonary emphysema: Evaluation with dynamic breathing MRI

To evaluate impaired respiratory mechanics in pulmonary emphysema, dynamic breathing magnetic resonance imaging (BMRI) was acquired with fast‐gradient echo pulse sequences at fixed thoracic planes over two to three slow, deep respiratory cycles in 6 controls and 28 patients with pulmonary emphysema including 9 patients undergoing lung volume reduction surgery (LVRS). Respiratory motions of the diaphragm and chest wall (D/CW) were assessed by a cineloop view, a fusion display of maximal inspiratory and expiratory images, and the time‐distance curves. By contrast with normal subjects with regular synchronous D/CW motions, the patients frequently showed reduced, irregular, or asynchronous motions, with significant decreases in the maximal amplitude of D/CW motions (MAD and MACW), and the length of apposition of the diaphragm (LAD) (P < 0.0001, P < 0.001, P < 0.01, respectively). After LVRS, nine patients showed improvements in D/CW configuration and mobility, with significantly increased MAD, MACW, and LAD (P < 0.01, P < 0.0001, and P < 0.05, respectively). In 40 studies of 28 patients including the post‐LVRS examinations, the normalized MAD and MACW significantly correlated with %FEV1 (r = 0.881 and r = 0.906; P < 0.0001, respectively). BMRI seems useful for noninvasively and directly assessing the impaired respiratory mechanics associated with abnormal ventilation in pulmonary emphysema, and also for monitoring the effects of LVRS. J. Magn. Reson. Imaging 1999;10:510–520.

Technical and analytical advances in pulmonary ventilation SPECT with xenon-133 gas and Tc-99m-Technegas

This paper describes the recent advances in technical and analytical methods in pulmonary ventilation SPECT studies, including a respiratory-gated image acquisition of Technetium-99m (99mTc)-labeled Technegas SPECT, a fusion image between Technegas SPECT and chest CT images created by a fully automatic image registration algorithm, and a three-dimensional (3D) display of xenon-133 (133Xe) gas SPECT data, and new analytical approaches by means of fractal analysis or the coefficient of variations of the pixel counts for Technegas SPECT data. The respiratory-gated image acquisition can partly eliminate problematic effects of the SPECT images obtained during non-breath-hold. The fusion image is available for routine clinical use, and provides complementary information on function and anatomy. The 3D displays of dynamic 133Xe SPECT data are helpful for accurate perception of the anatomic extent and locations of impaired ventilation, and the assessment of the severity of ventilation abnormalities. The new analytical approaches facilitate the objective assessment of the degrees of ventilation abnormalities.

Computed Tomography–Diagnosed Emphysema, Not Airway Obstruction, Is Associated with the Prognostic Outcome of Early-Stage Lung Cancer

Purpose: Because both emphysema and lung cancer can arise from biological damage caused by cigarette smoking, we investigated if the development of emphysema is associated with the clinical features of smokers lung cancer. Experimental Design: The subjects were a consecutive series of 100 smokers who underwent lobectomy with hilar and mediastinal dissection for clinical stage I non–small cell lung cancer. We studied the relationship between the presence or absence of emphysema at the onset of the lung cancer and clinicopathologic features. Emphysema was diagnosed by measuring the low-attenuation area using computed tomography densitometry. Results: There were no differences in clinicopathologic variables, including the degree of smoking exposure between the patients with (n = 58) and those without (n = 42) emphysema, although male gender and airflow limitation were predominant in the patients with emphysema. The presence of emphysema, but neither male gender nor airflow limitation, adversely affected both overall and disease-specific survival. According to Cox regression analysis, emphysema was an independent prognosticator among age, gender, degree of smoking exposure, tumor size, nodal status, histologic subtype, histologic grade, and microvessel invasion. These results were stabilized by a bootstrap sampling model. Conclusions: Computed tomography–diagnosed emphysema, but not airway obstruction, is associated with poor prognosis in smokers with early-stage lung cancer. Thus, routine computed tomography densitometry in smokers with lung cancer should be mandatory.

Breast sentinel lymph node navigation with three-dimensional interstitial multidetector-row computed tomographic lymphography.

Objective:Three-dimensional multidetector-row computed tomographic lymphography (3D MDCT-LG) with interstitial injection of a widely available nonionic monometric contrast medium iopamidol was used for navigation of breast sentinel lymph node (SLN) biopsy. Methods:3D MDCT-LG was obtained after massage of the interstitially injection sites of a total of 4–5 mL undiluted iopamidol at periareolar and peritumoral areas in 68 consecutive patients with early-stage breast cancer, using a 4 detector-row CT scanner. Drainage lymphatic patterns and SLN anatomy were assessed on 3D MDCT-LG images. 3D MDCT-LG-navigated SLN biopsy with combined use of blue dye was followed by backup axillary lymph node dissection to evaluate accuracy of SLN biopsy. Results:The 3D MDCT-LG images clearly localized primary SLNs by visualizing the direct connection between these nodes and their afferent lymphatic vessels on detailed anatomy of the surrounding structures in all patients. Drainage lymphatic pathways on these images were classified into 4 patterns: single route/single SLN (39 cases, 57%), multiple routes/multiple SLNs (10 cases, 15%), single route/multiple SLNs (9 cases, 13%), and multiple routes/single SLN (10 cases, 15%). Under 3D MDCT-LG navigation, SLNs was found at the accurate location in all patients. With backup axillary lymph node dissection, metastasis was found in 14 (20%) patients, and 8 of these patients had metastasis only in the preoperatively identified SLNs. In other 5 positive patients, metastasis was found both in the SLN and non-SLNs. However, micrometastasis eventually was found only in non-SLN in an elderly patient. Overall, the sensitivity, false-negative rate, and accuracy of 3D CT-L-navigated SLN biopsy were 92% (13/14 patients), 7% (1/14 patients), and 98% (67/68 patients), respectively. Conclusions:Topographic 3D interstitial MDCT-LG can be a widely available and reliable navigator for breast SLN biopsy.

Nonlinear motion correction of respiratory-gated lung SPECT images

We propose a method for correcting the motion of the lungs between different phase images obtained by respiratory-gated single photon emission computed tomography (SPECT). This method is applied to SPECT images that show a preserved activity distribution in the lungs such as 99m-Tc macro aggregated albumin (99m-Tc-MAA) perfusion images and 99m-Tc-Technegas ventilation images. In the proposed method, an objective function, which consists of both the degree of similarity between a reference image and a deformed image, and the smoothness of deformation is defined and optimized using a simulated annealing algorithm. For the degree of similarity term in the objective function, an expansion ratio, defined as the ratio of change in local volume due to deformation, is introduced to preserve the total activity during the motion correction process. This method was applied to data simulated from computer phantoms, data acquired from a physical phantom, and 17 sets of clinical data. In all cases, the motion correction between inspiration and expiration phase images was successfully achieved.

Comprehensive assessment of lung CT attenuation alteration at perfusion defects of acute pulmonary thromboembolism with breath-hold SPECT-CT fusion images.

Regional computed tomography attenuation (CTA) alteration at perfusion defects in acute pulmonary thromboembolism (PTE) was comprehensively assessed using deep-inspiratory breath-hold SPECT-CT fusion images. Subjects were 14 acute and 9 chronic PTE patients and 13 control subjects. Regional perfusion, CTA, and intravascular clots were correlated on deep-inspiratory breath-hold SPECT-unenhanced/angiographic CT fusion images. Fusion images visualized hypo-CTA in 57% of the acute PTE patients, which preferentially occurred at extensively and severely decreased perfusion areas caused by central clots. CTA at 35 defects of acute PTE was significantly decreased compared with that of normal lungs (P < 0.001), but the degree was less compared with chronic PTE (P < 0.0001). Fusion images also revealed variable relationships of clots and regional perfusion/CTA in the distal lungs of each central clot. Fusion images provide important information about the actual effects of intravascular clots on peripheral perfusion/CTA and indicate that lung CTA can be decreased at perfusion defects in acute PTE.

Regional lung functional impairment in acute airway obstruction and pulmonary embolic dog models assessed with gadolinium-based aerosol ventilation and perfusion magnetic resonance imaging.

Suga K, Ogasawara N, Okada M, et al. Regional lung functional impairment in acute airway obstruction and pulmonary embolic dog models assessed with gadolinium-based aerosol ventilation and perfusion magnetic resonance imaging. Invest Radiol 2002;37:281–291. rationale and objectives. Gadolinium diethylenetriaminepentaacetic acid (Gd-DTPA)-based aerosol ventilation and perfusion magnetic resonance (MR) images were used to define regional functional impairment in acute airway obstruction (AO) and pulmonary embolic (PE) dog models. methods. The aerosol study was performed in 10 anesthetized normal dogs in a supine position during 20-minute spontaneous inhalation of an aerosol of 100- or 200-mmol-Gd/L Gd-DTPA solute produced by an ultrasonic nebulizer in an open-circuit delivery system, combined with a dynamic perfusion study after a 3-second intravenous bolus injection of a 0.1 mmol/kg dose of Gd-DTPA. These MR studies were also performed in the same 10 dogs approximately 30 minutes after obstructing the segmental (n = 6) or lobar (n = 4) bronchus with a balloon catheter, and in another six dogs after segmental (n = 6) and lobar (n = 4) pulmonary arterial embolization with enbucrilate. Regional lung enhancement was assessed on time-signal intensity (SI)-curves and ventilation- and perfusion-weighted images produced by a subtraction technique. results. The normal lungs were gradually and gravity-dependently enhanced with time after Gd-DTPA aerosol inhalation regardless of the respiratory SI changes, except for three animals with the fastest breathing rate. The averaged maximal relative lung SI increase against the baseline in the successful animals was significantly greater in the slowly and deeply breathing animals than in the fast and shallow breathing animals, regardless of the difference in Gd-concentration (100 mmol Gd/L: 153.3% ± 69.7% vs. 54.2% ± 23%;P < 0.001; and 200 mmol Gd/L: 189.7% ± 68.0% vs. 75.6% ± 42.2%;P < 0.0001, respectively). There was an additional enhancement of 382% ± 101 in the ventral lung and 722% ± 160 in the dorsal lung on the pulmonary arterial phase perfusion image even in the slowly and deeply breathing animals who inhaled 200-mmol-Gd/L aerosol, and the enhancement effect was significantly greater compared with that with the aerosol (P < 0.0001). The ventilation- and perfusion-weighted images clearly defined the regionally matched perfusion-ventilation deficits in all the AO models, and the regionally mismatched perfusion-ventilation in all the PE models. conclusion. Gd-based aerosol can provide efficient lung enhancement in spontaneously and adequately breathing animals, using a relatively noninvasive aerosol delivery system. The combined use of Gd-based perfusion MR imaging may be acceptable for defining regionally impaired function associated with acute AO and PE.

Automated Breath-Hold Perfusion SPECT/CT Fusion Images of the Lungs

OBJECTIVE The purpose of this study was to evaluate the clinical applicability and feasibility of deep-inspiratory breath-hold (DIBrH) perfusion SPECT for improving adverse respiratory motion effects and for accuracy of SPECT/CT image fusion. MATERIALS AND METHODS Eighty-seven consecutive patients with chronic obstructive pulmonary disease (COPD) (n = 43), acute pulmonary thromboembolism (PTE) (n = 26), and interstitial lung disease (ILD), (n = 18), underwent respiratory-monitored DIBrH SPECT with a dual-headed SPECT system. Two COPD and four acute PTE patients were excluded because of inappropriate scanning due to DIBrH difficulty. DIBrH SPECT was automatically fused with DIBrH CT. Perfusion defect clarity and heterogeneity and SPECT/CT matching were compared between DIBrH SPECT and non-breath-hold SPECT. RESULTS Compared with non-breath-hold SPECT, DIBrH SPECT significantly enhanced defect clarity in acute PTE (p < 0.0001) and perfusion heterogeneity (coefficient of variations [CV] of pixel counts) in COPD and ILD (p < 0.0001). CV in COPD was also better correlated with lung diffusing capacity for carbon monoxide (p < 0.05). DIBrH SPECT also significantly improved SPECT/CT matching (p < 0.0001), with excellent matching of CT lung internal landmarks and pathology with corresponding defects. Fusion images confirmed wedge-shaped defects extending along specific pulmonary arterial branches in acute PTE and heterogeneous defects associated with airway or lung parenchymal abnormalities in COPD and ILD, with perfusion distribution consistent with lung CT attenuation changes. CONCLUSION DIBrH SPECT is acceptable for routine application to improve respiratory motion effects and accuracy of SPECT/CT image fusion. Confirmative perfusion-morphologic correlation with reliable fusion images appears useful for clarifying the cause of perfusion defects and abnormal lung CT attenuation.

Difference in 201Tl accumulation on single photon emission computed tomography in benign and malignant thoracic lesions.

The difference in 201Tl-chloride (201Tl) accumulation on single photon emission computed tomography (SPECT) between 58 benign (58 cases) and 48 malignant (46 cases) thoracic lesions, each of more than 20 mm in diameter was investigated. In the 34 benign and 48 malignant lesions depicted in both early (15 min) and delayed (3 h) images there was no significant difference in the mean early and delayed uptake ratios of lesion to normal contralateral lung between benign and malignant. However, the retention index in the lesion derived from (delayed ratio — early ratio)/(early ratio) ± 100% showed a significant difference (benign −4.30 ± 13.6% versus malignant 23.3 + 18.9%, P < 0.01), indicating the poor 201Tl retention in the benign lesions. Using the criteria of nondepiction in the delayed image or a negative retention index, 81.1% accuracy and 95.2% predictive value for diagnosis of benign lesions were obtained. Thus, 201Tl SPECT appears to have potential usefulness in the diagnosis of benign thoracic lesions.

Perfusion characteristics of radiation-injured lung on Gd-DTPA-enhanced dynamic magnetic resonance imaging.

Ogasawara N, Suga K, Karino Y, et al. Perfusion Characteristics of Radiation-injured Lung on Gd-DTPA-enhanced Dynamic Magnetic Resonance Imaging. Invest Radiol 2002;37:448–457. rationale and objectives. A contrast-enhanced dynamic magnetic resonance (MR) study was performed experimentally and clinically to describe perfusion characteristics of radiation-injured lung according to pathologic phases. methods. The MR study was performed before and at 0.5, 1, 2, 3, 4, and 7 months after 40 Gy-dose irradiation to the right hemithorax in 8 dogs, and clinically in 12 lung lesions of 9 patients with acute or fibrotic radiation pneumonitis. Altered Gd-DTPA kinetics in the affected lungs was assessed by time-signal intensity curves. MR findings were correlated with lung histology and CT images. results. Within 1 month after irradiation, the irradiated animal lungs showed focal and persistent contrast enhancement relative to nonirradiated lungs. This abnormality was pronounced during the next 2 months. After 4 months, irradiated lungs conversely showed lower enhancement during the Gd-DTPA first-pass but were followed by persistently greater enhancement during Gd-DTPA redistribution phase. Similar differences in enhancement abnormalities between acute and fibrotic radiation pneumonitis were clinically observed. conclusion. These findings indicate that Gd-DTPA kinetics can be altered according to the histopathologic change in early/acute radiation pneumonitis and radiation fibrosis and that the contrast-enhanced perfusion MRI may help differentiate the phases of radiation pneumonitis.