Ventilation/Perfusion SPECT Imaging-Diagnosing Other Cardiopulmonary Diseases Beyond Pulmonary Embolism

Ventilation/perfusion single-photon emission computed tomography (V/P SPECT) is the scintigraphic technique recommended primarily for the diagnosis of acute pulmonary embolism (PE) and is golden standard for the diagnosis of chronic PE. Furthermore, interpreting ventilation and corresponding perfusion images enables pattern recognition of many other cardiopulmonary disorders that affect lung function and also allows quantification of their extent. Using Technegas for the ventilation imaging, grading of small airway disease in COPD is possible and the method is recommended for PE diagnosis in patients with severe COPD that is not possible with radiolabelled liquid aerosols. An optimal combination of nuclide activities, acquisition times for ventilation and perfusion, collimators, and imaging matrix yields an adequate V/P SPECT study in approximately 20 minutes of imaging time. The holistic interpretation strategy of V/P SPECT uses all relevant information about the patient and ventilation/ perfusion patterns. PE is diagnosed when there is more than one subsegment showing a V/P mismatch representing an anatomic lung unit. Apart from PE, other pathologies should be identified and reported, such as obstructive lung disease, heart failure, and pneumonia according to the European Association of Nuclear Medicine guidelines. Semin Nucl Med 49:4-10 (C) 2018 Published by Elsevier Inc.Peer reviewe

Ventilation/Perfusion SPECT for Diagnosis of Pulmonary Embolism and Other Diseases

V/PSPECT has the potential to become a first hand tool for diagnosis of pulmonary embolism based on standardized technology and new holistic interpretation criteria. Pretest probability helps clinicians choose the most appropriate objective test for diagnosis or exclusion of PE. Interpretation should also take into account all ventilation and perfusion patterns allowing diagnosis of other cardiopulmonary diseases than PE. In such contexts, V/PSPECT has excellent sensitivity and specificity. Nondiagnostic reports are ≤3%. V/PSPECT has no contraindication; it is noninvasive and has very low radiation exposure. Moreover, acquisition time for V/PSPECT is only 20 minutes. It allows quantification of PE extension which has an impact on individual treatment. It is uniquely useful for followup and research

Continuous positive airway pressure and body position alter lung clearance of the radiopharmaceutical 99mtechnetium-diethylenetriaminepentaacetic acid (99mTc-DTPA)

The purpose of this investigation was to evaluate the pulmonary clearance rate of 99mtechnetium-diethylenetriaminepentaacetic acid (99mTc-DTPA) through the use of continuous positive airway pressure (CPAP) in different postures. It was a quasi-experimental study involving 36 healthy individuals with normal spirometry. 99mTc-DTPA, as aerosol, was nebulized for 3 min with the individual in a sitting position. The pulmonary clearance rate was assessed through pulmonary scintigraphy under spontaneous breathing and under 20 and 10 cmH2O CPAP in the sitting and supine positions. The clearance rate was expressed as the half-time (T1/2), that is, the time for the activity to decrease to 50% of the peak value. 20 cmH2O CPAP produced significant reduction of the T1/2 of 99mTc-DTPA in the supine position (P = 0.009) and in the sitting position (P = 0.005). However, 10 cmH2O CPAP did not alter the T1/2 of DTPA in both positions. The postural variation from supine to the sitting position with 10 cmH2O CPAP (P = 0.01) and 20 cmH2O (P = 0.02) also reduced the T1/2 of 99mTc-DTPA. High levels of positive pressure in normal lungs resulted in faster 99mTc-DTPA clearance. Moreover, the sitting position further increased the clearance rate of the 99mTc radioaerosol imaging in the two pressure levels studied.Key words: Continuous positive airway pressure, 99mTc-DTPA, scintigraphy, posture

EANM guideline for ventilation/perfusion single-photon emission computed tomography (SPECT) for diagnosis of pulmonary embolism and beyond

These guidelines update the previous EANM 2009 guidelines on the diagnosis of pulmonary embolism (PE). Relevant new aspects are related to (a) quantification of PE and other ventilation/perfusion defects; (b) follow-up of patients with PE; (c) chronic PE; and (d) description of additional pulmonary physiological changes leading to diagnoses of left ventricular heart failure (HF), chronic obstructive pulmonary disease (COPD) and pneumonia. The diagnosis of PE should be reported when a mismatch of one segment or two subsegments is found. For ventilation, Technegas or krypton gas is preferred over diethylene triamine pentaacetic acid (DTPA) in patients with COPD. Tomographic imaging with V/P-SPECT has higher sensitivity and specificity for PE compared with planar imaging. Absence of contraindications makes V/P-SPECT an essential method for the diagnosis of PE. When V/P-SPECT is combined with a low-dose CT, the specificity of the test can be further improved, especially in patients with other lung diseases. Pitfalls in V/P-SPECT interpretation are discussed. In conclusion, V/P-SPECT is strongly recommended as it accurately establishes the diagnosis of PE even in the presence of diseases like COPD, HF and pneumonia and has no contraindications.Peer reviewe

Ventilation/Perfusion SPECT - A New Challenge for Detection of Pulmonary Embolism. Can Multi Detector Computed Tomography Replace Lung Scintigraphy?

ventilation/perfusion scintigraphy (V/P-SCAN) was the procedure of choice for studying patients with suspected pulmonary embolism (PE) until the prospective evaluation of V/P imaging in the study known as PIOPED I revealed high number of non diagnostic findings. This has challenged development of computed tomography (CT) during 1990s. Since beginning of 2000, multidetector CT (MDCT) is widely applied and has become the most commonly used technique in patients with suspected PE. The current MDCT have very advanced technology and have improved ability to detect small emboli. Unfortunately, results of the most advanced MDCT are still compared with V/P-SCAN results performed in PIOPED I 20 years ago. However V/P-SCAN has further developed. Tomographic technique V/P-SPECT is taking over V/P-PLANAR. Probabilistic criteria are replaced by holistic criteria for interpretation, taking lessons learned from PIOPED I. Discussion is focused on diagnostic value for MDCT and V/P-SPECT. MDCT and V/P-SPECT are both indispensible imaging techniques to study patients with suspected PE. However, when available, V/P-SPECT should be the preferred method for diagnosis of PE, primarily due to the lower radiation exposure and applicability to all patients. Therefore it is our duty to make V/P-SPECT generally more available, to use holistic interpretation knowledge and to communicate daily with the clinicians, so that the best technique is used in all patients. In conclusion MDCT cannot replace V/P-SPECT. MDCT and V/P-SPECT are complementary rather the competitive

Hepato-pulmonary shunts

Hepato-pulmonary shunts might develop in some patients with severe liver disease, usually when cirrhosis has developed. At this stage, a dilatation of intra-pulmonary vessels might develop causing defects in blood oxygenation. Shortness of breath is a common symptom. The disease might be asymptomatic but it has an impact of patient's quality of life. The identification of shunt dysfunction is based on the arterial blood gas test. The dilatation of pulmonary vessels and shunting index can be identified by macro aggregated albumin lung perfusion scintigraphy (99mTc-MAA) or a transthoracic contrast-enhanced echocardiography