Semi-quantitation of pulmonary perfusion heterogeneity on respiratory-gated inspiratory and expiratory perfusion SPECT in patients with pulmonary emphysema.

OBJECTIVE: Pulmonary perfusion heterogeneity (PPH) in pulmonary emphysema (PE) was semi-quantified by functional lung volume rate (FLVR) curves obtained from respiratory-gated inspiratory and expiratory single-photon emission computed tomography (SPECT). METHODS: Gated and ungated SPECT were obtained in 36 PE patients [25 with stage IIA and 11 with stage IIB for global initiative for chronic obstructive lung disease (GOLD) stage classification] and 12 controls, using a triple-head SPECT system and a respiratory tracking device. On gated SPECT, the voxel numbers calculated at the 10% cutoff threshold for the maximum lung radioactivity were assumed to be the functional lung volume of the lung (V). FLVR (%) was calculated as FLV divided by V at every additional 10% thresholds, yielding inspiratory and expiratory FLVR curves. The dissociations between these curves (DeltaFLVRinsp-exsp) and the total difference (D index) of these curves from the normal standard curve (averaged inspiratory and expiratory curve in controls) were calculated. D index and the extent of low attenuation area (%LAA) on CT were correlated with the transfer coefficient for carbon monoxide (KCO) in PE patients. RESULTS: Although gated and ungated SPECT showed fairly uniform perfusion in controls, gated SPECT-enhanced PPH compared with ungated SPECT in PE patients, with significantly higher dissociation (DeltaFLVRinsp-exsp) than that in controls (24.9%+/-9.5% vs. 4.5%+/-1.3%; P<0.0001). DeltaFLVRinsp-exsp was significantly higher even in stage IIA patients (P<0.0001). Expiratory D index was significantly higher than the inspiratory one in PE patients (P<0.01). This index was significantly higher in stage IIB patients than in stage IIA patients (44.1%+/-19.0% vs. 29.4%+/-13.7%; P<0.05), and was significantly correlated with KCO (R=0.642, P<0.0001) in all PE patients, although %LAA was not correlated with KCO. CONCLUSIONS: FLVR curve analysis on gated SPECT appears useful for semi-quantitation of respiratory change of PPH in PE. Expiratory D index may better reflect the lung pathophysiology of PE than morphologic CT.

Percutaneous radiologic gastrostomy using push-type gastrostomy tubes with CT and fluoroscopic guidance.

OBJECTIVE: The purpose of this study was to evaluate the safety and feasibility of percutaneous radiologic gastrostomy with endoscopic push-type gastrostomy tubes using CT and fluoroscopic guidance. CONCLUSION: Percutaneous radiologic gastrostomy using CT and fluoroscopic guidance with push-type tubes is a safe and effective means of gastric feeding that has few complications and offers an alternative to introducer-placed gastrostomy tubes.

Characterization of 133Xe gas washout in pulmonary emphysema with dynamic 133Xe SPECT functional images.

PURPOSE: To characterize regional ventilation impairment of pulmonary emphysema using dynamic 133Xe single photon emission computed tomography (SPECT) functional images, compared with other forms of chronic obstructive pulmonary disease (COPD). METHODS: Dynamic 133Xe SPECT was performed in 34 patients with emphysema and 15 patients with other forms of COPD. Three-dimensional voxel-based functional images of the half-clearance time (T1/2) mainly reflecting the initial rapid washout of 133Xe gas from the large airways, and of the mean transit time (MTT) reflecting 133Xe gas washout from the entire lungs, including the small airways and alveoli, were created based on an area-over-height method. T1/2 and MTT values were compared with the regional extent of low attenuation areas (%LAA) on density-mask computed tomography images and the diffusing capacity of the lungs for carbon monoxide (DLCO). RESULTS: The MTT/T1/2 ratio in each lung in emphysema was significantly higher than that in other forms of COPD (1.60+/-0.74 vs. 1.21+/-0.26; P<0.01). In the selected unilateral lungs with similar T1/2 values, MTT values were also significantly higher in emphysema. MTT values in each lung showed a significantly closer correlation with the corresponding %LAA values compared with T1/2 values in emphysema (R=0.698, P<0.0001 vs. R=0.338, P<0.01; P<0.05); while only the T1/2 values showed a significant correlation in other forms of COPD (P<0.0001). In correlation with DLCO, MTT values showed a significantly closer correlation compared with T1/2 values in emphysema (R=0.909, P<0.0001 vs. R=0.555, P<0.001; P<0.05); while either value did not show a significant correlation in other forms of COPD. CONCLUSION: MTT values are more critically affected in emphysema compared with other forms of COPD without significant alveolar destruction, and MTT and T1/2 values appear to be differently correlated with the regional extent of LAA between these two disorders. Direct comparison of regional T1/2 and MTT values on functional images may contribute to the demarcation of lung pathology of these two disorders.

Enhanced perfusion defect clarity and inhomogeneity in smokers' lungs with deep-inspiratory breath-hold perfusion SPECT images.

PURPOSE: Deep-inspiratory breath-hold (DIBrH) Tc-99m-macroaggregated albumin (MAA) SPECT images were developed to accurately evaluate perfusion impairment in smokers' lungs. METHODS: DIBrH SPECT was performed in 28 smokers with or without low attenuation areas (LAA) on CT images, using a triple-headed SPECT system and a laser light respiratory tracking device. DIBrH SPECT images were reconstructed from every 4 degrees projection of five adequate 360 degrees projection data sets with almost the same respiratory dimension at 20 sec DIBrH. Perfusion defect clarity was assessed by the lesion (defect)-to-contralateral normal lung count ratios (L/N ratios). Perfusion inhomogeneity was assessed by the coefficient of variation (CV) values of pixel counts and correlated with the diffusing capacity of the lungs for carbon monoxide/alveolar volume (DLCO/VA) ratios. The results were compared with those on conventional images. RESULTS: Five DIBrH projection data sets with minimal dimension differences of 2.9+/-0.6 mm were obtained in all subjects. DIBrH images enhanced perfusion defects compared with conventional images, with significantly higher L/N ratios (P<0.0001), and detected a total of 109 (26.9%) additional detects (513 vs. 404), with excellent inter-observer agreement (kappa value of 0.816). CV values in the smokers' lungs on DIBrH images were also significantly higher compared with those on conventional images (0.31+/-0.10 vs. 0.19+/-0.06, P<0.0001). CV values in smokers on DIBrH images showed a significantly closer correlation with DLCO/VA ratios compared with conventional images (R = 0.872, P<0.0001 vs. R=0.499, P<0.01). CONCLUSION: By reducing adverse effect of respiratory motion, DIBrH SPECT images enhance perfusion defect clarity and inhomogeneity, and provide more accurate assessment of impaired perfusion in smokers' lungs compared with conventional images.

Preferential location of acute pulmonary thromboembolism induced consolidative opacities: assessment with respiratory gated perfusion SPECT-CT fusion images.

PURPOSE: Preferential location of acute pulmonary thromboembolism (PTE) induced consolidative opacities (infarction/atelectasis) was determined on respiratory gated perfusion SPECT-CT fusion images. METHOD: Gated end-inspiratory perfusion SPECT images were obtained in 21 patients with acute PTE and 17 patients with inflammatory diseases, using a triple-headed SPECT system and a respiratory tracking device. Anatomical relationships of consolidative opacities and perfusion defects were assessed on gated SPECT-rest inspiratory CT fusion images. The size and radioactivity of perfusion defects with acute PTE consolidative opacities were compared with those of defects without these opacities. The contribution of fusion images for differential diagnosis of acute PTE induced and inflammatory disease induced lesions was evaluated by receiver operating characteristic (ROC) curve analysis. RESULTS: Of the total 56 acute PTE induced consolidative opacities, 42 (75%) were located at the peripheral interface between the severely decreased and adjacent relatively preserved perfusion areas within wedge shaped perfusion defects on fusion images. These defects with consolidative opacities were significantly larger and had taken up less radioactivity compared with those in the 86 defects without these lesions (P<0.0001). In contrast, of the 29 inflammatory disease induced opacities, 14 (48.2%) had the matched defects and 13 (44.8%) were located at the proximal portion of defects. These preferential locations of acute PTE induced and inflammation induced lesions were significantly different (P<0.01). In ROC curves, the combined reading of fusion images showed a significantly higher differential diagnostic accuracy compared with the reading of CT and SPECT images alone (P<0.01). CONCLUSIONS: Acute PTE induced consolidative opacities preferentially occur at the peripheral lung interface between severely decreased and adjacent relatively preserved perfusion areas within relatively large and severely decreased perfusion defects. The fusion images, which provide an accurate assessment of the morphological-perfusion defect relationship could, potentially, provide a differential diagnosis between acute PTE induced and inflammatory disease induced lesions.

Initial application of respiratory-gated 201Tl SPECT in pulmonary malignant tumours.

AIM: Respiratory-gated thallium-201 chloride (201Tl) single photon emission computed tomography (SPECT) was used in preliminary investigations to reduce the adverse respiratory motion effects observed on standard ungated SPECT images and to obtain reliable fusion images with computed tomography (CT) in patients with malignant lung tumours. METHODS: Fifteen patients with primary lung cancer (n=10) or metastatic lung tumours (n=5) underwent gated SPECT 20 min after intravenous injection of 148 MBq 201Tl, using triple-headed SPECT and laser light respiratory tracking units. Projection data were acquired by a step and shoot mode, with 20 stops over 120 degrees for each detector and a preset time of 30 s for each 6 degrees stop. Gated end-inspiratory and ungated images were obtained from 1/8 data centred at peak inspiration for each regular respiratory cycle and for the full respiratory cycle data, respectively. The degree and size of tumour 201Tl uptake were compared between these images by regions of interest (ROI) analysis. Gated SPECT images were registered with rest inspiratory CT images using an automated three-dimensional (3D) image registration tool. Registration mismatch was assessed by measuring the 3D distance of the centroid of 14 201Tl-avid peripheral tumours. Attenuation correction of gated SPECT images was performed using CT attenuation values of these fusion images. RESULTS: Gated SPECT images improved image clarity and contrast of tumour 201Tl uptakes compared with ungated images, regardless of the decreased count density due to the use of gated images. The lesion-to-normal (L/N) lung count ratios and ROI size in 18 well-circumscribed 201Tl-avid tumours were significantly higher and smaller on gated images (both P<0.0001). Gated images showed positive 201Tl uptakes in two small peripheral tumours, although negative on ungated images, and demarcated 201Tl-avid tumours from adjacent 201Tl-avid lymph node or surrounding focal 201Tl uptakes caused by other pathology, although these were not clearly demarcated on ungated images. On fusion images, gated images yielded a significantly better SPECT-CT matching compared with ungated images (P<0.0001). Fusion images accurately localized 201Tl uptakes of tumour/lymph node and other focal pathological/physiological conditions. Attenuation-corrected gated SPECT images further facilitated the detection of 201Tl uptake in small or deeply located lesions, with significantly increased L/N ratios. CONCLUSION: Gated SPECT images facilitate the detection of tumour 201Tl uptake and provide reliable SPECT-CT fusion images, which contribute to accurate interpretation and attenuation correction of Tl SPECT images.

Clinical utility of co-registered respiratory-gated( 99m)Tc-Technegas/MAA SPECT-CT images in the assessment of regional lung functional impairment in patients with lung cancer.

PURPOSE: The aim of the study was to provide preliminary validation of the utility of co-registered respiratory-gated ventilation/perfusion single-photon emission computed tomography-computed tomography (SPECT-CT) images in the assessment of regional lung functional impairment in patients with lung cancer. METHODS: Twenty untreated and three radiotherapy-treated patients with lung cancer underwent gated( 99m)Tc-Technegas/macroaggregated albumin (MAA) SPECT, using a triple-headed SPECT unit and a respiratory synchroniser. Gated SPECT images were obtained from 1/8 data centered at peak inspiration for each regular respiratory cycle and co-registered with tidal inspiration CT images using an automated three-dimensional registration tool. RESULTS: Gated SPECT images detected 10.2% more ventilation defects (205 vs 186) and 9% more perfusion defects (218 vs 200) compared with ungated images, with a significantly higher lesion-to-normal lung contrast ( P<0.0001). Co-registered gated SPECT-CT images accurately visualised the anatomy of ventilation and/or perfusion defects associated with bronchial and/or vascular involvement by tumours, resulting in changes in surgical planning in two patients with lung cancer. In the three patients who had received radiotherapy, perfusion defects along the radiation field were identified even in the lung areas without abnormal opacities on CT images. In the operated patients, the co-registered gated SPECT-CT images allowed accurate placement of regions of interest over the lung lobes to be resected, yielding a significantly better prediction of postoperative forced expired volume in 1 s (FEV(1)) compared with that predicted without use of these images ( R=0.993 vs R=0.890; P<0.05), with an excellent inter-observer reproducibility. CONCLUSION: Detailed functional-morphological correlation on co-registered gated SPECT-CT images contributes to accurate assessment of regional functional impairment, and may be useful for surgical planning, prediction of postoperative function and assessment of external beam radiotherapy effects in patients with lung cancer.

Assessment of regional lung function impairment in airway obstruction and pulmonary embolic dogs with combined noncontrast electrocardiogram-gated perfusion and gadolinium diethylenetriaminepentaacetic acid aerosol magnetic resonance images.

PURPOSE: To define regional function impairment in airway obstruction (AO) and pulmonary embolic (PE) dogs with a combination study of noncontrast electrocardiogram (ECG)-gated perfusion and gadolinium diethylenetriaminepentaacetic acid (Gd-DTPA) aerosol magnetic resonance (MR) images. METHODS: After acquisition of multiphase fast-spin-echo (FSE) MR images during cardiac cycles in 14 AO dogs and 19 PE dogs, ECG-gated perfusion-weighted (PW) images were obtained by subtraction between two-phase images of the minimum lung signal intensity (SI) during systole and maximum SI during diastole. Each dog subsequently inhaled Gd-DTPA aerosol for 20 minutes, and subtracted Gd-DTPA aerosol images were obtained from precontrast and maximally enhanced images. ECG-gated PW images were compared with intravenous Gd-DTPA-enhanced pulmonary arterial perfusion phase (PAPP) images. RESULTS: ECG-gated PW images were consistent with Gd-DTPA-enhanced PAPP images in all dogs, with significant correlations in the affected-to-unaffected lung perfusion ratios (P < 0.005). Gd-DTPA aerosol images showed sufficient and uniform enhancement in the unaffected lungs. In all the AO areas, these combined images showed the matched perfusion and aerosol deposition defects. These images showed perfusion defects without aerosol deposition defects in the relatively small embolized areas, but showed the matched defects in the widely embolized areas probably due to hypoxic bronchial constriction. CONCLUSION: The combination MR studies may be acceptable for noninvasively defining regionally impaired lung function in AO and PE.

Assessment of regional lung functional impairment with co-registered respiratory-gated ventilation/perfusion SPET-CT images: initial experiences.

In this study, respiratory-gated ventilation and perfusion single-photon emission tomography (SPET) were used to define regional functional impairment and to obtain reliable co-registration with computed tomography (CT) images in various lung diseases. Using a triple-headed SPET unit and a physiological synchroniser, gated perfusion SPET was performed in a total of 78 patients with different pulmonary diseases, including metastatic nodules (n = 15); in 34 of these patients, it was performed in combination with gated technetium-99m Technegas SPET. Projection data were acquired using 60 stops over 120 degrees for each detector. Gated end-inspiration and ungated images were reconstructed from 1/8 data centered at peak inspiration for each regular respiratory cycle and full respiratory cycle data, respectively. Gated images were registered with tidal inspiration CT images using automated three-dimensional (3D) registration software. Registration mismatch was assessed by measuring 3D distance of the centroid of the nine selected round perfusion-defective nodules. Gated SPET images were completed within 29 min, and increased the number of visible ventilation and perfusion defects by 9.7% and 17.2%, respectively, as compared with ungated images; furthermore, lesion-to-normal lung contrast was significantly higher on gated SPET images. In the nine round perfusion-defective nodules, gated images yielded a significantly better SPET-CT match compared with ungated images (4.9 +/- 3.1 mm vs 19.0 +/- 9.1 mm, P<0.001). The co-registered SPET-CT images allowed accurate perception of the location and extent of each ventilation/perfusion defect on the underlying CT anatomy, and characterised the pathophysiology of the various diseases. By reducing respiratory motion effects and enhancing perfusion/ventilation defect clarity, gated SPET can provide reliable co-registered images with CT images to accurately characterise regional functional impairment in various lung diseases.

Pulmonary perfusion assessment with respiratory gated 99mTc macroaggregated albumin SPECT: preliminary results.

PURPOSE: Respiratory gated perfusion single photon emission computed tomography (SPECT) was applied to reduce respiratory lung motion effects and to reliably assess perfusion impairment in various lung diseases. METHODS: After injection of 259 MBq of 99mTc macroaggretated albumin (99mTc-MAA), gating was performed using a triple-headed SPECT unit connected to a physiological synchronizer in a total of 35 patients with either obstructive lung diseases (n = 14), pulmonary embolism (n = 8), small lung nodules (n = 7) or acute interstitial pneumonia (n = 6). Projection data were acquired in a 64 x 64 matrix, with 20 stops over 120 degrees for each detector with a preset time of 15 s for each stop. Inadequate data for the respiratory cycle were automatically eliminated. In addition to end inspiration images and end expiration images derived from 12.5% threshold data centred at peak inspiration and expiration for each respiratory cycle, respectively, an ungated image was obtained from full respiratory cycle data. RESULTS: Gated images were completed for 13.7 +/- 1.8 min in all subjects. Although the total lung radioactivity of the gated images were reduced to approximately 13% of that of the ungated images, these gated images showed uniform perfusion in the unaffected lungs and visualized a total of 94 (21.9%) additional perfusion defects against 429 defects visualized on ungated images in 31 patients with focal perfusion defects. Among the perfusion defects visualized on both gated images, the defect size was occasionally larger on the end inspiration images. The end expiration images showed significantly higher lesion-to-normal lung radioactivity ratios compared with those on the end expiration and ungated images in the affected lower lungs throughout the lung diseases. Radioactivity changes per pixel between end inspiration and end expiration images in the affected lower lungs of the obstructive lung diseases were significantly lower compared with those of pulmonary embolism and acute interstitial pneumonia (P<0.0001 and P<0.01, respectively). CONCLUSION: This technique appears to enhance the clarity of perfusion defects, and lung radioactivity changes between end inspiration and end expiration may characterize regionally impaired ventilation status.