Regional alterations in lung ventilation in end-stage primary pulmonary hypertension: correlation between CT and scintigraphy.

OBJECTIVE: The purpose of this study was to correlate scintigraphic findings of regional alterations in lung ventilation and perfusion with regional variations in CT attenuation in patients with primary pulmonary hypertension. SUBJECTS AND METHODS: Chest CT scans and ventilation-perfusion scans obtained within 24 hr of each other in 18 patients with primary pulmonary hypertension referred for lung transplantation were reviewed. The lungs were divided into eight regions (left/right, superior/inferior relative to the carina, and anterior/posterior relative to the trachea). CT scans were evaluated and areas of parenchymal inhomogeneities were tabulated for the eight regions. Areas of reverse mismatch (perfusion without ventilation) were established by blinded analysis of planar scintigraphic studies in six projections using 99mTc-labeled DTPA-aerosol and macroaggregated albumin for the eight regions and then were correlated with the CT findings. RESULTS: Abnormal findings on ventilation scans and reverse ventilation-perfusion mismatches indicating an inadequate hypoxic vasoconstriction reflex were found in 91 regions in all 18 patients. Nonuniform parenchymal CT density was found in 12 patients. There was a significant correlation (p = .009) of scintigraphic reverse mismatches with abnormal CT density in 38 regions in 11 patients. In one patient, there was no scintigraphic correlation with abnormal CT attenuation. The specificity of abnormal CT density for scintigraphic reverse mismatches was 81%, with a sensitivity of 42%. CONCLUSION: Scintigraphic reverse mismatches indicate a high prevalence of significant pulmonary arterial shunting in patients with ventilatory defects. Increased relative CT attenuation in areas of impaired ventilation as shown on the ventilation scans is amplified in primary pulmonary hypertension by an inadequate hypoxic vasoconstriction reflex. This finding does not signify underlying infiltrative lung disease and correlates with regions with reverse mismatches.

Volumetric high-resolution CT in the diagnosis of interstitial lung disease and bronchiectasis: diagnostic accuracy and radiation dose.

OBJECTIVE: The purpose of this study was to evaluate the diagnostic accuracy and radiation dose of volumetric high-resolution CT in the diagnosis of interstitial lung disease and bronchiectasis when four contiguous sections were acquired at each of three levels. The potential benefits were weighed against the increased radiation dose of multiple scans. SUBJECTS AND METHODS: High-resolution CT scans of four contiguous sections were obtained at each of three locations (the aortic arch, the carina, and 2 cm above the diaphragm) in 50 consecutive patients (mean age, 44 years old) with known or suspected interstitial lung disease or bronchiectasis who were referred for evaluation with high-resolution CT. Each individual scan was analyzed for the presence of motion-induced streaking, blurring, or doubling. The diagnostic information contained in each set of four scans was compared with that contained in the first of the four scans in the set. RESULTS: Motion degraded at least one of the four images in each set in 69 (46%) of 150 volumetric acquisitions. When the full set of four images was considered instead of just the first scan from the set, the number of motion-free studies in patients with suboptimal respiratory suspension was increased by 40% (from 99 to 139). Diagnostic accuracy was improved as more features were identified on contiguous scans: the sensitivity of the first scan compared with that of the complete set of four scans was 84% for the detection of bronchiectasis, 97% for ground-glass opacity, 88% for honeycombing, 88% for septal thickening, and 86% for nodular opacities. Although the integral radiation exposure for a set of four CT scans was 2.8 times that of a single scan obtained with standard technique, peak skin exposure was unchanged. Slightly increased image noise with the reduced technique compromised diagnostic ability in 6% of studies. CONCLUSION: The use of volumetric high-resolution CT increased diagnostic accuracy, particularly for bronchiectasis at the lung bases, without increasing peak skin radiation exposure. With the availability of four contiguous scans per anatomic level, the subjective confidence in interpretation and number of motion-free studies also increased.

Shifting pneumothorax after heart-lung transplantation.

Heart-lung transplantation involves the total replacement of two of the most complex organs of the thoracic cavity. This procedure is usually reserved for patients with failure of both systems, such as in primary pulmonary hypertension or chronic Eisenmenger physiology. The en bloc replacement of the heart and lungs leaves an open communication between the two sides of the thorax that may allow air or fluid to shift from one side to the other. To evaluate this possibility, the authors reviewed the chest radiographs of 25 heart-lung transplant recipients for signs of rapidly changing pneumothoraces that could not be explained by the conventional dynamics of pleural physiology. A series of postoperative radiographs showed unusual shifting or apparently rapid disappearance of pneumothoraces in eight patients. Decompression of a pneumothorax with a contralateral chest tube was a phenomenon observed in six of these patients.

Liver transplant rejection and cholestasis: comparison of technetium 99m-diisopropyl iminodiacetic acid hepatobiliary imaging with liver biopsy.

To determine whether the scintigraphic evaluation of technetium-99m diisopropyl iminodiacetic acid (DISIDA) uptake and excretion can distinguish among liver transplant patients with biopsy evidence for rejection, cholestasis or neither condition, we reviewed scintigrams and biopsies in 36 patients. There were 76 scintigrams with corresponding biopsies. Uptake and excretion were graded from image data on scales reflecting normal through severely abnormal values. Biopsies were evaluated for findings of cholestasis and rejection. The majority of scintigrams demonstrated normal uptake (60/75, 80%) and delayed excretion (65/76, 85%), which was most marked immediately after transplantation. One-way analysis of variance showed that the mean excretion values significantly differed between patients with normal biopsies and those with cholestasis and/or rejection (P = 0.0003). However, mean uptake scores demonstrated no statistically significant difference between these two groups of patients (P = 0.1). These findings suggest that 99mTc-DISIDA scintigraphy can differentiate between transplants with and without rejection/cholestasis but not between rejection and cholestasis. If 99mTc-DISIDA excretion is normal, rejection and cholestasis are unlikely.

Correlation of technetium-99m-DISIDA hepatobiliary studies with biopsies in liver transplant patients.

We compared 76 99mTc-DISIDA hepatobiliary studies with corresponding liver biopsies in 36 liver transplant patients to determine the histopathologic abnormalities that corresponded to scintigraphic abnormalities in uptake and excretion. Uptake was judged normal if the cardiac blood pool was barely visible or invisible on the ten minute image. Excretion was judged normal if images subsequent to the 15-min image showed a subjectively normal rate of decreasing parenchymal intensity. Biopsies were graded subjectively for hepatocyte damage and for findings of cholestasis. Uptake criteria were successful in differentiating high from low hepatocyte damage scores (p less than 0.0001), and excretion criteria were successful in differentiating high from low cholestasis scores (p = 0.002), while uptake criteria were not capable of differentiating high from low cholestasis scores, nor were excretion criteria capable of differentiating high from low hepatocyte damage scores (p's greater than 0.05). These results suggest that scintigraphy can distinguish intrahepatic cholestasis from pure hepatocyte damage.

Ectopic splenomegaly in Felty's syndrome.

A 50-year-old woman with Felty's syndrome, who presented with "menopausal" symptoms, was found to have a large pelvic mass on physical exam. Computed tomography of the pelvis led to an incorrect diagnosis of malignancy, while radionuclide imaging using Tc-99m sulfur colloid confirmed the diagnosis of ectopic splenomegaly.

Therapeutic embolization: enhanced radiolabeled monitoring.

Radiolabeling of Ivalon (polyvinyl alcohol sponge) particles permits localization of injected particles during embolization through the use of a portable gamma camera and provides a means to prevent potentially fatal complications such as pulmonary embolization. A more efficient technique of labeling Ivalon particles with technetium-99m sulfur colloid was developed. An increase in labeling efficiency allowed more accurate determination of the distribution of injected Ivalon particles. Scanning electron microscopy demonstrated the stability of the Ivalon particles during this new labeling process. Two patients with arteriovenous malformations underwent therapeutic embolization with radiolabeled Ivalon particles; gamma camera imaging of the lesion and chest was performed throughout the procedure.

Detection of impending pericardial tamponade during skeletal imaging.

Bone imaging using Tc-99m MDP was performed on a 68-year-old man with a newly diagnosed adenocarcinoma of the lung. The image unexpectedly showed increased activity in the heart area. Emergent echocardiography demonstrated impending pericardial tamponade. A malignant pericardial effusion was verified by pericardiocentesis.