Marika Bajc

Diagnostic evaluation of planar and tomographic ventilation/perfusion lung images in patients with suspected pulmonary emboli.

Planar lung ventilation/perfusion scintigraphy (V/PPLANAR) is a standard method for diagnosis of pulmonary embolism (PE). The goals of this study were to test whether the diagnostic information of ventilation/perfusion tomography (V/PSPET) applied in clinical routine might enhance information compared with V/PPLANAR and to streamline data processing for the demands of clinical routine. This prospective study includes 53 patients suspected for PE referred for lung scintigraphy. After inhalation of 99mTc‐DTPA planar ventilation imaging was followed by tomography, using a dual‐head gamma camera. 99mTc‐MAA was injected i.v. for perfusion tomography followed by planar imaging. Patients were examined in supine position, unchanged during V/P tomography. Two reviewers evaluated V/PPLANAR and V/PSPET images separately and randomly. Mismatch points were calculated on the basis of extension of perfusion defects with preserved ventilation. Patients were followed up clinically for at least 6 months. With V/PSPET the number of patients with PE was higher and 53% more mismatch points were found. In V/PSPET interobserver variation was less compared with V/PPLANAR. Ancillary findings were observed by both techniques in half of the patients but more precisely interpreted with V/PSPET. V/PSPET shows more and better delineated mismatch defects, improved quantification and less interobserver variation compared with V/PPLANAR. V/PSPET is amenable to implementation for clinical routine and suitable even when there is demand for a high patient throughput.

Ventilation/Perfusion SPECT for diagnostics of pulmonary embolism in clinical practice.

Aim.  The aim of this retrospective study is to illustrate clinical utility and impact of pulmonary embolism (PE) diagnostics of up to date Ventilation/Perfusion SPECT (V/PSPECT) applying holistic interpretation criteria.

Heart failure diagnostics based on ventilation/perfusion single photon emission computed tomography pattern and quantitative perfusion gradients.

OBJECTIVE Left heart failure (LHF) is a common and frequently overlooked condition owing to insufficient diagnostic methods. This can potentially delay onset of treatment. Our clinical experience with ventilation/perfusion single photon emission computed tomography (V/P SPECT) indicates that perfusion shows an antigravitational distribution pattern in LHF. The aim of the study was to test the hypothesis that LHF diagnosis can be made on the basis of V/P SPECT, and to develop and perform a first evaluation of objective parameters for LHF diagnostics in terms of perfusion gradients. METHODS This retrospective study included 247 consecutive patients with clinical suspicion of pulmonary embolism (PE), who were examined with V/P SPECT. Perfusion gradients were developed and quantified in dorso-ventral and cranio-caudal directions. Quantitative results were compared with visual interpretation of patients with normal and heart failure patterns. Patients with LHF pattern were retrospectively followed up by review of medical records to confirm or discard heart failure diagnosis at the time of V/P SPECT examination. RESULTS LHF pattern on V/P SPECT was identified in 36 patients (15%), normal ventilation/perfusion pattern was found in 67 patients (27%), and PE in 62 patients (25%). The follow-up confirmed heart failure diagnosis in 32 of the 36 cases with LHF pattern, leading to a positive predictive value of 88% for LHF diagnosis based on V/P SPECT. Dorso-ventral perfusion gradients discriminated normal from LHF patients. CONCLUSION In patients with suspected PE, LHF is common. Appropriate V/P SPECT pattern recognition, supported by objectively determined dorso-ventral perfusion gradients, allows the diagnosis of LHF. A positive perfusion gradient in the dorso-ventral direction should lead to consideration of heart failure as a possible explanation for the symptoms in these patients.The objectives of this study were to evaluate the diagnostic accuracy of fluorodeoxyglucose (FDG)-PET and FDG-PET/computed tomography (CT) in the detection of primary tumors in patients presenting with carcinoma of unknown primary (CUP) unidentified by conventional workup, and to compare the statistical difference between the FDG-PET and FDG-PET/CT. Twenty-eight studies (involving a total of 910 patients) published between 1990 and 2007 were reviewed. These studies evaluated the role of FDG-PET and FDG-PET/CT in the detection of unknown primary tumors after physical examination and conventional workup failed to detect a primary tumor. Systematic methods were used to identify, select, and evaluate the methodological quality of the studies as well as to summarize the overall findings of sensitivity, specificity, and detection capacity of the primary tumor. The overall sensitivity and specificity of FDG-PET in detecting unknown primary tumors were 0.78 [95% confidence interval (CI): 0.72–0.84)] and 0.79 (95% CI: 0.74–0.83), respectively. Furthermore, FDG-PET detected 28.54% of tumors that were not apparent after CUP failed to be detected by conventional workup. Data were collected on the locations of primary tumors detected by FDG-PET in 17 studies and detected by FDG-PET/CT in seven studies. Tumors from the base of the tongue accounted for 20.7% (six of 29) of all false-positive FDG-PET scans, corresponding to a false-positive rate of 28.6% (six of 29), much higher than tumors from the others. FDG-PET exhibited a lower sensitivity with respect to the tumors at the base of the tongue and tonsils, which was 68.2 and 76.7%, respectively. In the eight studies with 430 patients diagnosed with CUP by FDG-PET/CT, 31.4% (n=135) of primary tumors were detected. The pooled sensitivity and specificity were 0.81 (95% CI: 0.74–0.87) and 0.83 (95% CI: 0.78–0.87), respectively. FDG-PET and FDG-PET/CT can detect primary tumors that went undetected by physical examination and conventional workup. FDG-PET exhibited lower sensitivity with respect to the tumors at the base of the tongue and the tonsils.

Comparison of ventilation/perfusion scintigraphy and helical CT for diagnosis of pulmonary embolism; strategy using clinical data and ancillary findings

Study objective: To address the question whether ventilation/perfusion scintigraphy (SCINT) or helical computed tomography (CT) should be the first hand method for diagnosis of pulmonary embolism (PE).

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.

Controversies in Diagnosis of Pulmonary Embolism

The approach to the diagnosis of acute pulmonary embolism (PE) is under constant revision with advances in technology, noninvasive approaches, and increasing awareness of the risks of ionizing radiation. Optimal approaches in some categories of patients are controversial. Data are insufficient for evidence-based recommendations. Therefore, this survey of investigators in the field was undertaken. Even among experts there were marked differences of opinion regarding the approach to the diagnosis of acute PE. Although CT pulmonary angiography was usually the imaging test of choice, the respondents were keenly aware of the dangers of ionizing radiation. In view of advances in scintigraphic diagnosis since the Prospective Investigation of Pulmonary Embolism Diagnosis (PIOPED) trial, ventilation/perfusion (V/Q) lung scans or perfusion scans alone and single photon emission computed tomography (SPECT) V/Q lung scans are often recommended. The choice depends on the patient’s age, gender, and complexity of the findings on the plain chest radiograph.

Methodology for ventilation/perfusion SPECT.

Ventilation/perfusion single-photon emission computed tomography (V/Q SPECT) is the scintigraphic technique of choice for the diagnosis of pulmonary embolism and many other disorders that affect lung function. Data from recent ventilation studies show that the theoretic advantages of Technegas over radiolabeled liquid aerosols are not restricted to the presence of obstructive lung disease. Radiolabeled macroaggregated human albumin is the imaging agent of choice for perfusion scintigraphy. An optimal combination of nuclide activities and acquisition times for ventilation and perfusion, collimators, and imaging matrix yields an adequate V/Q SPECT study in approximately 20 minutes of imaging time. The recommended protocol based on the patient remaining in an unchanged position during the initial ventilation study and the perfusion study allows presentation of matching ventilation and perfusion slices in all projections as well as in rotating volume images based upon maximum intensity projections. Probabilistic interpretation of V/Q SPECT should be replaced by a holistic interpretation strategy on the basis of all relevant information about the patient and all ventilation/perfusion patterns. PE is diagnosed when there is more than one subsegment showing a V/Q mismatch representing an anatomic lung unit. Apart from pulmonary embolism, other pathologies should be identified and reported, for example, obstructive disease, heart failure, and pneumonia. Pitfalls exist both with respect to imaging technique and scan interpretation.

Radioisotope evaluation of the esophageal remnant and the gastric conduit after gastric pull-up esophagectomy

BACKGROUND The act of swallowing after gastric pull-up esophagectomy has not been thoroughly investigated. The aim of this study was to evaluate deglutition in the esophageal remnant and in the gastric conduit in patients who have undergone this operation. METHODS The residual radionuclide activity was measured 15 seconds after a swallow in the esophageal remnant and at intervals up to a maximum of 120 minutes after a swallow in the gastric conduit. The scintigraphic rate of transit of a bolus in both areas was compared in patients who had anastomosis in the neck (n = 15) versus patients who had anastomosis in the chest (n = 19). Comparisons were also made between patients with and without symptoms of dysphagia. The scintigraphic measurements were also correlated with anastomotic diameters, measured with use of a volumetric balloon insufflation method, at 3, 6, and 12 months after operation. RESULTS There were no significant differences in esophageal residual radionuclide activity at 15 seconds after a swallow in the groups with anastomosis in the neck versus anastomosis in the chest, with 30% residual activity up to 12 months after operation in both groups (P = .24). In the patients as a whole the 50% gastric conduit emptying time of 44 to 61 minutes did not change during the first postoperative year (P = .12). There was no association between anastomotic diameter and residual activity in the remaining esophagus (P < .126). Moderate and severe dysphagia was reported in only a few patients, and there was no correlation between dysphagic symptoms and retention in the residual esophagus or slower emptying in the gastric conduit. CONCLUSIONS The amount of peristaltic activity in the remaining esophagus after esophagectomy with gastric replacement is unaffected by the level of the anastomosis. The gastric conduit empties slowly in all patients, and there is no correlation between the rate of emptying and either anastomotic diameter or symptoms of dysphagia.

Tomographic ventilation/perfusion lung scintigraphy in the monitoring of the effect of treatment in pulmonary embolism: serial follow-up over a 6-month period.

BackgroundPulmonary embolism (PE) is a severe condition with nonspecific symptoms. Diagnosis relies on medical imaging but follow-up is currently based on clinical symptoms and general risk factors. The duration of anticoagulant treatment after an acute episode of PE is still subject to debate and the best method of identifying the risk of recurrence in individual patients is undefined. Tomographic lung scintigraphy [ventilation/perfusion single photon emission computed tomography (V/P SPECT)] has improved the diagnostic accuracy with regard to PE but has not been evaluated for PE follow-up. AimThe aim of this prospective study was to quantitatively follow the natural history of treated PE using V/P SPECT, which could prove helpful in defining an anticoagulant treatment regime for individual patients. MethodsOf 83 consecutive patients with clinically suspected PE examined with V/P SPECT, 23 patients with confirmed PE were followed by serial V/P SPECT examinations over a 6-month period. All patients were also followed clinically. ResultsThe mean relative decrease in PE extent compared with the time of diagnosis was 54±26% at 2 weeks, 79±30% at 3 months, and 82±30% at 6 months. Significant resolution of mismatched perfusion defects occurred between V/P SPECT controls within the first 3 months of anticoagulation (P<0.001) but not thereafter. V/P SPECT identified four patients with chronic PE, even though all patients were free from symptoms at 3-month follow-up. ConclusionFollow-up of PE with V/P SPECT is feasible to evaluate treatment effectiveness in individual patients and to identify patients that develop chronic PE. This study also confirms that resolution of perfusion defects after PE occurs within the first 3 months of treatment. It is therefore recommended that V/P SPECT follow-up should be considered at 3 months after diagnosis.

The value of tomographic ventilation/perfusion scintigraphy (V/PSPECT) for follow-up and prediction of recurrence in pulmonary embolism

BACKGROUND Pulmonary embolism (PE) is diagnosed with imaging techniques such as ventilation/perfusion (V/P) lung scintigraphy or multidetector computed tomography of the pulmonary arteries (MDCT). Lung scintigraphy can be performed with planar (V/P PLANAR) and tomographic (V/P SPECT) techniques. V/P SPECT has higher sensitivity and specificity than V/P PLANAR. As nephrotoxic contrast media are not used during V/P SPECT, examinations can be repeated for evaluation of resolution of perfusion defects after PE. However, the value of residual perfusion defects identified using V/P SPECT for the prediction of recurrent PE has not been thoroughly evaluated. MATERIAL AND METHODS We evaluated resolution and recurrence of PE in 227 patients (mean age 63 ± 17 years, 134[59%] women) with PE undergoing ≥ 2 SPECT examinations in 2005-2007. PE was defined as minor (<20% perfusion defect on SPECT, n=86), medium (20-50% perfusion defect on SPECT, n=99), or major (>50% perfusion defect on SPECT, n=42). RESULTS At second V/P SPECT examination, complete resolution of perfusion defects had occurred in 45 (52%) patients with minor PE after 8.2 ± 7.4 months, in 29 (29%) of patients with medium PE after 6.2 ± 5.9 months, and in 2(5%) of patients with major PE after 6.5 ± 0.7 months. During 47 ± 24 months of follow up, 37(16 %) patients suffered recurrent PE. Of these 37, 34 (92%) showed residual perfusion defects at the second V/P SPECT examination. Recurrence of PE was also predicted by advanced age and female gender. However, in multivariate regression analysis, recurrence was only predicted by age (p=0.0013) and residual perfusion defect on V/P SPECT (p=0.0039). CONCLUSION In conclusion, complete resolution of PE was common in patients with minor PE, whereas residual perfusion defects were widespread in patients with medium and major PE. PE patients identified with persistent perfusion defects at follow-up SPECT have a high risk of PE recurrence.