Pulmonary Embolism: Imaging Modalities-V/Q Scan, Spiral (Helical) CT, and MRI

Management of a huge right atrial thrombus in a patient with multiple comorbidities

BACKGROUND

Floating right heart thrombi (RHT) represent an underdiagnosed, potentially hazardous, and to some extent rare phenomenon in patients presenting with acute pulmonary embolism (APE). Emergent treatment is usually required for such a condition.

CASE PRESENTATION

A 19-year-old young lady presented with progressive shortness of breath, marked renal impairment, thrombocytopenia, and a highly oscillating huge right atrial mass. After she was admitted to the intensive care unit, she arrested in asystole and was resuscitated, and her electrocardiogram (ECG) showed evidence of acute anterior myocardial infarction. Urgent cardiac surgery to remove the right atrial mass was proposed by the heart team as the best option of management. Surgery was emergently performed with extra-corporeal membrane oxygenator (ECMO) as a support. Following surgery, mechanical support and vasopressors were successfully weaned and the patient achieved a good recovery.

CONCLUSIONS

A pulmonary embolism response team (PERT) approach should always be considered where a multidisciplinary team involving a cardiologist, radiologist, cardio-thoracic surgeon, radiologist, and intensivist shall determine the management strategy for a challenging presentation of a massive pulmonary embolism or floating right heart thrombi causing the hemodynamically unstable clinical condition.

Laser-targeted photosensitizer-induced lung injury: noninvasive rat model of pulmonary infarction

Pulmonary infarction is a life-threatening lung injury that requires rapid and accurate diagnosis for proper treatment. Targetable and reproducible small-animal models that would allow experimental development and preclinical evaluation of diagnostic methods for detecting pulmonary infarction are critically missing. The authors report here a novel procedure to selectively induce pulmonary infarction by photodestructive laser-light irradiation in a targeted location within a specific lung compartment after administration of a photosensitizer. Histopathological analysis of the illuminated lung tissue revealed massive hemorrhage and vascular occlusion after acute injury localized to the site of irradiation. Collapse of alveolar structure, neutrophil influx, and necrosis were subsequently observed. Computed tomography (CT) scans showed evidence of abnormal density and airspace consolidation in the irradiated area of the lung, but not elsewhere in the lung compartment. Perfusion imaging using 99mTc-labeled macroaggregated albumin by single-photon emission computed tomography revealed diminished scintigraphic signal in the opaque area of infarcted lung tissue. The histological changes, CT findings, and perfusion characteristics of pulmonary infarction are mimicked using laser-irradiated, photosensitizer-mediated photodestruction to selectively induce chronic lung injury in a localized area. This small-animal model can be easily and readily used for targeted induction of pulmonary infarction in a designated area of lung compartment and offers the potential for use in evaluating novel diagnostic and therapeutic methods.

Dual energy CT for the assessment of lung perfusion--correlation to scintigraphy

Purpose of this study was to determine the diagnostic value of dual energy CT in the assessment of pulmonary perfusion with reference to pulmonary perfusion scintigraphy. Thirteen patients received both dual energy CT (DECT) angiography (Somatom Definition, Siemens) and ventilation/perfusion scintigraphy. Median time between scans was 3 days (range, 0-90). DECT perfusion maps were generated based on the spectral properties of iodine. Two blinded observes assessed DECT angiograms, perfusion maps and scintigrams for presence and location of perfusion defects. The results were compared by patient and by segment, and diagnostic accuracy of DECT perfusion imaging was calculated regarding scintigraphy as standard of reference. Diagnostic accuracy per patient showed 75% sensitivity, 80% specificity and a negative predictive value of 66%. Sensitivity per segment amounted to 83% with 99% specificity, with 93% negative predictive value. Peripheral parts of the lungs were not completely covered by the 80 kVp detector in 85% of patients. CTA identified corresponding emboli in 66% of patients with concordant perfusion defects in DECT and scintigraphy. Dual energy CT perfusion imaging is able to display pulmonary perfusion defects with good agreement to scintigraphic findings. DECT can provide a pulmonary CT angiogram, high-resolution morphology of the lung parenchyma and perfusion information in one single exam.

99mTc-NC100668, an agent for imaging venous thromboembolism: The effect of anticoagulant or thrombolytic therapy on the uptake and retention of radioactivity in blood clots in vivo

BACKGROUND

The purpose of this study was to evaluate the uptake of (99m)Tc-NC100668 into blood clots and elucidate the potential for medications commonly used to treat thromboembolism to interfere with the uptake and retention of (99m)Tc-NC100668.

METHODS

(99m)Tc-NC100668 in vivo uptake and retention in a range of blood clot of various ages (up to 4 h. old) and in the presence of anticoagulants or thrombolytic therapies was measured in a rat model of deep vein thrombosis.

RESULTS

(99m)Tc-NC100668 was rapidly absorbed into and retained by blood clots and was not significantly affected by the presence of unfractionated or low molecular weight heparin or thrombin inhibitor. Tissue plasminogen activator reduced the uptake of (99m)Tc-NC100668 into blood clot by a factor of 3 when adjusted to allow for changes in the weight of the blood clot.

CONCLUSIONS

This study has demonstrated that the uptake and retention of (99m)Tc-NC100668 into blood clots in the rat model of deep vein thrombosis is rapid and maintained over at least a 4 h. post-injection period. It has been shown that (99m)Tc-NC100668 is retained in blood clots even in the presence of therapeutic doses of those anticoagulant and thrombolytic therapies typically used to treat pulmonary embolism and venous thrombosis.

(99m)Tc-NC100668, a new tracer for imaging venous thromboemboli: pre-clinical biodistribution and incorporation into plasma clots in vivo and in vitro

PURPOSE

(99m)Tc-NC100668 is a new radiotracer being developed to aid the diagnosis of thromboembolism. The structure of NC100668 is similar to a region of human alpha(2)-antiplasmin, which is a substrate for factor XIIIa (FXIIIa). The purpose of this study was to confirm the uptake of (99m)Tc-NC100668 into forming plasma clot and to establish the biodistribution of (99m)Tc-NC100668 in Wistar rats.

METHODS

The in vitro plasma clot uptake of (99m)Tc-NC100668 and other compounds with known affinities to FXIIIa was measured using a plasma clot assay. The biodistribution and blood clot uptake of radioactivity of (99m)Tc-NC100668 in normal Wistar rats and those bearing experimentally induced deep vein thrombi were investigated.

RESULTS

The in vitro uptake of (99m)Tc-NC100668 was greater than that for [(14)C]dansyl cadaverine, a known substrate of FXIIIa in the plasma clot assay. The biodistribution of (99m)Tc-NC100668 in male and female Wistar rats up to 24 h p.i. showed that radioactivity was rapidly excreted, predominantly into the urine, with very little background tissue retention. In vivo the uptake and retention of (99m)Tc-NC100668 into the blood clot was greater than could be accounted for by non-specific accumulation of the radiotracer within the blood clot.

CONCLUSION

(99m)Tc-NC100668 was retained by plasma clots in vitro and blood clots in vivo. No significant tissue retention which could interfere with the ability to image thrombi in vivo was observed. This evidence suggests that (99m)Tc-NC100668 might be useful in the detection of thromboembolism.

Imaging Manifestations of Complications Associated with Uterine Artery Embolization

Uterine artery embolization (UAE) is an increasingly performed, minimally invasive alternative to hysterectomy or myomectomy for women with symptomatic uterine fibroids. A growing body of literature documents symptomatic improvement in the majority of women who undergo UAE. Although UAE is usually safe and effective, there are a number of known complications associated with the procedure. Major complications include fibroid passage, infectious disease (endometritis, pelvic inflammatory disease-tubo-ovarian abscess, pyomyoma), deep venous thrombosis, pulmonary embolism, inadvertent embolization of a malignant leiomyosarcoma, ovarian dysfunction, fibroid regrowth, uterine necrosis, and even death. Minor complications include hematoma, urinary tract infection, retention of urine, transient pain, and vessel or nerve injury at the puncture site. As UAE takes its place in the treatment arsenal for women with symptomatic fibroids, radiologists need to be familiar with UAE-associated complications, which may require further treatment and may even be life threatening in some cases. Knowledge of these complications and their imaging features should lead to prompt diagnosis and appropriate treatment.

Acute pulmonary embolectomy: a contemporary approach

BACKGROUND

Acute pulmonary embolism confers a high mortality rate despite advances in diagnosis and therapy. Thrombolysis is often effective but has a high frequency of major bleeding complications, especially intracranial hemorrhage. Therefore, we liberalized our criteria for acute pulmonary embolectomy and considered operating on patients with anatomically extensive pulmonary embolism and concomitant moderate to severe right ventricular dysfunction despite preserved systemic arterial pressure.

METHODS AND RESULTS

We report 29 (17 men and 12 women) consecutive patients who underwent embolectomy from October 1999 through October 2001. Twenty-six patients (89%) survived surgery and were alive more than 1 month postoperatively. Median follow-up is 10 months.

CONCLUSION

The high survival rate of 89% can be attributed to improved surgical technique, rapid diagnosis and triage, and careful patient selection. We hope that other tertiary centers will evaluate pulmonary embolism patients with an algorithm that includes surgical embolectomy as one of several therapeutic options. Our contemporary approach to pulmonary embolectomy no longer confines this operation to a treatment of last resort reserved for clinically desperate circumstances.

Venous thromboembolism guidebook

This venous thromboembolism guidebook incorporates evolving contemporary concepts in diagnosis and management of pulmonary embolism (PE) and deep venous thrombosis (DVT) into a user-friendly menu. The purpose of this document is to provide a literature-based review of the current clinical approach to venous thromboembolism and up-to-date references for further study in this important topic.