Magnetic resonance imaging evaluation of pulmonary vascular malformations.

OBJECTIVE: The purpose of our study was to establish magnetic resonance imaging (MRI) criteria for the diagnosis of pulmonary vascular malformations (PVMs). MATERIALS AND METHODS: Since 1987, 11 patients have been referred for chest MRI at our institution because of findings suggestive of a PVM. They were evaluated with a 1.5-T MRI system, incorporating a combination of spin-echo, gradient-recalled echo (GRE) cine, and 2-D phase contrast (PC) cine sequences. We used the following MRI criteria to diagnose PVM: (1) flow void or intermediate gray signal on spine-echo sequences; (2) bright signal on GRE cine sequences; and (3) bright signal consistent with flow detected on PC cine sequences using relatively low velocity ranges. Twelve patients not suspected of having a PVM served as controls; all had both MRI and pulmonary angiography to evaluate for central pulmonary embolus. RESULTS: Eight patients in the study group had PVM as determined with MRI using these criteria. In four of these patients, a PVM was confirmed by subsequent pulmonary angiography. Three patients did not have PVM utilizing these criteria; two had neoplasms and one had presumed mucus plugging and/or atelectasis that resolved spontaneously. The smallest vascular malformation detected by MRI was 1 cm. None of the control patients had PVM by MRI or pulmonary angiography. CONCLUSION: Utilizing these criteria, we believe that MRI is potentially an excellent noninvasive modality to evaluate PVM, and we stress that some form of PC cine sequence must be performed to determine if indeed there is blood flow within a suspicious lesion.

Quantitative differential pulmonary perfusion: MR imaging versus radionuclide lung scanning.

PURPOSE: To compare the results of quantitative analysis of differential pulmonary artery blood flow performed with phase-contrast cine magnetic resonance (MR) images with those of differential radionuclide pulmonary perfusion scanning in preoperative lung transplantation patients. MATERIALS AND METHODS: Forty preoperative lung transplantation patients underwent prospective, quantitative analysis of differential pulmonary artery blood flow performed with MR imaging and radionuclide pulmonary perfusion scanning. MR imaging analysis was performed at 1.5 T with a phase-contrast cine pulse sequence to acquire data perpendicular to each central pulmonary artery. RESULTS: Comparative analysis of differential pulmonary perfusion showed excellent correlation between the two modalities in all patients (P = .0001). MR imaging enabled calculation of the pulmonary artery blood flow to each lung; radionuclide lung scanning enabled only calculation of relative perfusion to each lung. CONCLUSION: MR imaging is as effective as radionuclide lung scanning in assessment of relative, and superior for determination of absolute differential, pulmonary perfusion.

Use of laser energy to treat central pulmonary emboli: a preliminary report.

We evaluated the ability and safety of a laser fiber placed percutaneously into a pig's lobar pulmonary artery to lyse pulmonary artery blood clots that were created in situ. We developed a model to create blood clots in situ that could be placed in any desired location with a radio-opaque marker at the clot position. An excimer laser delivered energy to a flexible 600 microns fiber in three experiments and a coaxial 1.6 mm multifiber catheter in the last experiment. Pre- and postprocedure angiograms obtained from each experiment demonstrated that partial laser dissolution of central pulmonary emboli in four pigs was accomplished successfully. To avoid perforation, it is imperative that the laser fiber remain coaxial during the entire lasing process. These results suggest that laser dissolution may become an adjunctive procedure for the treatment of central pulmonary emboli in those patients who cannot be treated medically.

Improvement in exercise performance after pulmonary arteriovenous malformation embolization.

Balloon or coil embolization has become established therapy for multiple PAVMs. We were able to evaluate a 32-year-old woman with multiple PAVMs characterized by significant orthodeoxia, intrapulmonary shunt, dyspnea and limited exercise tolerance before and after balloon and coil embolization. After embolization of three of her largest PAVMs, repeat evaluation revealed improvement in her symptoms, orthodeoxia and intrapulmonary shunt. She was able to exercise two additional work rates with a sustained improvement in oxygenation, a decrease in the P(A-a)O2 difference and higher maximum oxygen consumption. These studies provide objective evidence of persistent improvement in function and endurance at rest and during exercise after embolization.

MR imaging of pulmonary emboli: an experimental study in dogs.

Experimental pulmonary emboli, consisting of tantalum-labeled autologous blood clots and barium-labeled 3-mm plastic spheres that did not produce an MR signal, were introduced through the femoral vein into each of five dogs. The sensitivity of MR to detect autologous clots of known size was assessed, and the size of the clot on MR was compared with its actual size. Emboli were localized by using chest radiographs made in multiple projections. Cardiac-synchronized MR imaging was performed on a 0.35-T superconducting magnet and was followed by a 99mTc macroaggregated lung scan. All 12 blood clots larger than 3 mm, and three of 20 clots less than 3 mm in transverse diameter were correctly visualized with MR. Five of the 15 clots seen on MR were larger than 150% of the actual size. There were nine false-positive emboli on MR. Two of six plastic spheres resulted in an abnormal signal on MR. MR signal from pulmonary emboli results from the thrombus itself and probably also from slow blood flow proximal to the obstruction. MR may be of value in detecting pulmonary emboli; clinical trials to evaluate its usefulness should be carried out.

Gallium scintigraphy in bronchogenic carcinoma. The effect of tumor location on sensitivity and specificity.

Fifty-one patients with primary lung cancer were evaluated using 67Ga citrate scintigraphy with respect to detection of peripheral primary, hilar metastasis, and mediastinal metastasis. The results demonstrated the necessity for an understanding of the criteria used in considering the gallium scintigram as either positive or negative, as well as the instrumentation employed in performing the test before any meaningful sensitivity and specificity figures can be derived within a given institution. Only with this understanding can actual strategy for instituting invasive procedures be achieved.

Resolution of pulmonary lymphangitic carcinoma of the breast.

Pulmonary lymphangitic carcinomatosis, a grave complication of malignant neoplasms, usually progresses rapidly and is fatal despite all modes of therapy. We recently observed complete resolution of pulmonary lymphangitic involvement from an adenocarcinoma of the breast following both chemotherapy and bilateral oophorectomy. The patient's chest radiograph has remained clear for 1 1/2 years.

Gastrointestinal complications following renal transplantation.

Gastrointestinal complications developed in 29 (6%) of 510 patients following renal transplantation. Thirteen patients (45%) died as a result. Gastrointestinal bleeding, usually considered the commonest complication, was seen in only 7 cases. Other complications included pancreatitis and hyperamylasemia, massive ileus, fistulas with abscesses, bowel infarction, peptic ulcers without bleeding, obstruction, gangrenous cholecystitis, esophagitis, spontaneous perforation of the sigmoid colon, and pneumatosis cystoides intestinalis. Six patients had no clinical or laboratory findings suggesting the underlying gastrointestinal complication; it was the radiographic findings that called attention to the acute problem.