Mohammed Zaki

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

PurposeRespiratory 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. MethodsAfter 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 64×64 matrix, with 20 stops over 120° 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. ResultsGated 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). ConclusionThis 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.

Computed tomography lymphography with intrapulmonary injection of iopamidol for sentinel lymph node localization.

Purpose:Experimental and clinical evaluation of the potential utility of indirect computed tomographic lymphography (CT-LG) with intrapulmonary injection of iopamidol for preoperative localization of sentinel lymph node station in non-small cell lung cancer. Methods:CT-LG with intrapulmonary injection of 0.5 mL of undiluted iopamidol was performed in 10 dogs using a multidetector-row CT unit, followed by postmortem examination of enhanced lymph nodes in 5 of these dogs. The CT-LG with peritumoral injection of 1 mL of the contrast agent was also performed in 9 patients with non-small cell lung cancer without lymphadenopathy. At surgery, enhanced lymph nodes were resected under CT-LG guide, followed by standard lymph node dissection with macroscopic and histologic examination. A significant enhancement of lymph nodes was determined when CT attenuation value was increased with 30 Hounsfield units (HU) compared with precontrast images. Results:CT-LG visualized a total of 15 enhanced lymph nodes (on average, 1.5 nodes per animal) within 2 minutes after contrast injection in the 10 dogs, with average size of 6.7 ± 1.9 mm and average maximum CT attenuation of 149 ± 41 HU. All the 8 enhanced nodes in 5 dogs were found in the appropriate anatomic locations in postmortem examinations. Without noticeable complications, CT-LG visualized 30 ipsilateral intrathoracic lymph nodes including 19 hilar/pulmonary and 11 mediastinal nodes in the 9 patients (on average, 2.2 hilar/pulmonary and 1.1 mediastinal nodes per patient) within 2 minutes after contrast injection, with average size of 4.7 ± 0.4 mm and average maximum CT attenuation of 134 ± 52 HU. At surgery, all these enhanced nodes could be accurately found and resected under CT-LG guidance. Metastasis was not evident in either of these enhanced lymph nodes or the remaining distant nodes in all patients. Conclusion:Quick and accurate localization of sentinel lymph node station on detailed underlying lung anatomy by using indirect CT-LG may be of value to guide selective lymph node dissection for minimally invasive surgery in non-small cell lung cancer.

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

PurposePreferential location of acute pulmonary thromboembolism (PTE) induced consolidative opacities (infarction/atelectasis) was determined on respiratory gated perfusion SPECT–CT fusion images. MethodGated 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. ResultsOf 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). ConclusionsAcute 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.

Assessment of lung perfusion impairment in patients with pulmonary artery‐occlusive and chronic obstructive pulmonary diseases with noncontrast electrocardiogram‐gated fast‐spin‐echo perfusion MR imaging

To evaluate the ability of noncontrast electrocardiogram (ECG)‐gated fast‐spin‐echo (FSE) perfusion MR images for defining regional lung perfusion impairment, as compared with technetium (Tc)‐99m macroaggregated albumin (MAA) single‐photon emission computed tomography (SPECT) images.

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

AimRespiratory-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. MethodsFifteen 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° for each detector and a preset time of 30 s for each 6° 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. ResultsGated 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. ConclusionGated 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 201Tl SPECT images.

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

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.