Tomographic ventilation-perfusion lung scintigraphy in cardiopulmonary disease

Respiration relies, among other things, on the balance between regional ventilation and perfusion in the lungs. There are many cardiopulmonary diseases, such as pulmonary embolism (PE), chronic obstructive pulmonary disease (COPD) and left heart failure (LHF), which can affect respiration negatively. The diagnosis of PE, COPD and LHF follows separate diagnostic pathways. However, the symptoms that cause the patient to seek medical care are overlapping. This results in a diagnostic dilemma that is complicated by the fact that cardiopulmonary diseases often coexist. Ventilation and perfusion can be imaged with lung scintigraphy. Lung scintigraphy is primarily used to diagnose PE. The introduction of 3-dimensional tomographic lung scintigraphy (V/P SPECT) has resulted in an improved accuracy in the diagnosis of PE. Follow-up with V/P SPECT may lead to better individualization of PE treatment, but has not yet been evaluated. Changes in ventilation and perfusion are also found in COPD and LHF. V/P SPECT may have a clinical role in the diagnosis and characterization of COPD and LHF, but this has been insufficiently studied. Therefore, this thesis focuses on the potential role for V/P SPECT in the follow-up of PE and in the diagnosis and classification of LHF and COPD. In study I, we found that V/P SPECT can be used to diagnose LHF with a high positive predictive value. We developed an algorithm to objectively calculate perfusion gradients and found that an inverted gravitational gradient in the lungs is indicative of LHF. It was also shown that LHF was common among patients with suspected PE. In study II we compared ventilation studies performed with 99mTc-DTPA and 99mTc-Technegas, in patients with and without COPD. This study showed that 99mTc-Technegas, due to a more homogeneous distribution with less focal deposition and better peripheral penetration, should be regarded as the preferred radioaerosol in V/P SPECT studies. Study III indicated an additional value of V/P SPECT in the diagnosis of COPD. V/P SPECT could also be used to characterize the severity of COPD. In study IV, we found that restoration of regional perfusion after acute PE occurred during the first 3 months of treatment, but not thereafter. Follow-up after an episode of PE, using V/P SPECT, seems important since about 20% of the patients in the study had remaining perfusion defects at 3 months after diagnosis, although all were free from symptoms

Reduced administered activity, reduced acquisition time, and preserved image quality for the new CZT camera.

BACKGROUND: For a 1-day myocardial perfusion SPECT (MPS) the recommendations for administered activity stated in the EANM guidelines results in an effective dose of up to 16 mSv per patient. Recently, a gamma camera system, based on cadmium zinc telluride (CZT) technology, was introduced. This technique has the potential to reduce the effective dose and scan time compared to the conventional NaI gamma camera. The aim of this study was to investigate if the effective dose can be reduced with a preserved image quality using CZT technology in MPS. METHODS: In total, 150 patients were included in the study. All underwent a 1-day (99m)Tc-tetrofosmin stress-rest protocol and were divided into three subgroups (n = 50 in each group) with 4, 3, and 2.5 MBq/kg body weight of administered activity in the stress examination, respectively. The acquisition time was increased in proportion to the decrease in administered activity. All examinations were analyzed for image quality by visual grading on a 4-point scale (1 = poor, 2 = adequate, 3 = good, 4 = excellent), by two expert readers. RESULTS: The total effective dose (stress + rest) decreased from 9.3 to 5.8 mSv comparing 4 to 2.5 MBq/kg body weight. For the patients undergoing stress examination only (35%) the effective dose, administrating 2.5 MBq/kg, was 1.4 mSv. The image acquisition times for 2.5 MBq/kg body weight were 475 and 300 seconds (stress and rest) compared to 900 seconds for each when using conventional MPS. The average image quality was 3.7 ± 0.5, 3.8 ± 0.5, and 3.8 ± 0.4 for the stress images and 3.5 ± 0.6, 3.6 ± 0.6, and 3.5 ± 0.6 for the rest images and showed no statistically significant difference (P = .62) among the 4, 3, and 2.5 MBq/kg groups. CONCLUSIONS: The new CZT technology can be used to considerably decrease the effective dose and acquisition time for MPS with preserved high image quality

Home treatment of patients with small to medium sized acute pulmonary embolism.

Most patients with acute pulmonary embolism (PE) are still treated as inpatients. This is a retrospective cohort study of patients with acute PE, diagnosed using V/P SPECT between 2007 and 2011. Patients were treated at home if they were hemodynamically stable, did not require oxygen or parenteral analgetics, had no contraindications to anticoagulant treatment and V/P SPECT showed an extension of the PE of less than 40 %. The aim of the study was to evaluate the efficacy and safety of home treatment with our algorithm. During the study period 416 outpatients were diagnosed with acute symptomatic PE of whom in total 260 (62.5 %) were discharged home from the emergency unit and another 47 (11 %) within 24 h from admission. During 3 months follow-up one (0.3 %) patient had a recurrent thrombotic event. Eleven (3.6 %) patients had a major or clinically relevant bleed and the overall mortality was 2 % (n = 6). There were no PE-related mortality. Home treatment should be considered and is safe in the majority of hemodynamically stable outpatients with small to medium size PE, quantified using V/P SPECT

Ventilation-Perfusion SPECT with Tc-99m-DTPA Versus Technegas: A Head-to-Head Study in Obstructive and Nonobstructive Disease

Lung scintigraphy is primarily used to diagnose pulmonary embolism. Ventilation imaging is often performed using Tc-99m-DTPA or Technegas, an ultrafine dispersion of Tc-99m-labeled carbon. Despite the common use of these radioaerosols, they have not been compared in an intraindividual study, and not with ventilation-perfusion (V/P) SPECT. The aim of the present head-to-head study was to systematically investigate differences in ventilation studies performed with Tc-99m-diethylenetriaminepentaacetate (DTPA) and Technegas. Methods: Sixty-three patients, 28 without and 35 with obstructive lung disease, were examined with V/P SPECT using both Tc-99m-DTPA and Technegas. V/P SPECT images were randomized and assessed independently by 2 masked physicians according to a predefined scoring system. A paired comparison was performed using the Wilcoxon signed-rank test. Results: In both obstructive and nonobstructive disease, the overall unevenness of radiotracer deposition and the degree of central deposition were more pronounced in Tc-99m-DTPA than Technegas studies. Because of better peripheral penetration, the extent of reverse mismatch was less when Technegas was used. Additionally, in obstructive disease, the degree of focal deposition in distal airways was more pronounced with Tc-99m-DTPA. Mismatched perfusion defects were more frequently found with Technegas in obstructive disease. Conclusion: This intraindividual comparative study shows that Technegas is the preferred radioaerosol, particularly in obstructive disease

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

[18F]PSMA-1007 renal uptake parameters: Reproducibility and relationship to estimated glomerular filtration rate

BackgroundScintigraphy with technetium-99m-labelled dimercaptosuccinic acid ([99mTc]Tc-DMSA) is widely used for renal cortical imaging. Uptake of [99mTc]Tc-DMSA has been shown to correlate with glomerular filtration rate (GFR). Prostate-specific membrane antigen (PSMA) radiopharmaceuticals used for positron emission tomography (PET) show high renal uptake and are being investigated for renal imaging. [68Ga]Ga-PSMA-11 PET parameters have been shown to correlate with estimated GFR (eGFR). The aim of this study was to investigate the relationship between renal [18F]PSMA-1007 uptake and eGFR.MethodsHundred and eighty-five patients underwent PET imaging at 1 and 2 h after injection of 4.0 ± 0.2 MBq [18F]PSMA-1007. Serum creatinine levels were measured and GFR estimated using the Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) and Modification of Diet in Renal Disease (MDRD) equations. Fifteen patients were excluded due to missing or incorrect data. Thus, data from 170 patients were analyzed. Kidneys were segmented in the PET images using a convolutional neural network with manual correction. For each kidney, mean standardized uptake value (SUVmean) and segmentation volume in millilitres were measured. Linear regression analyses were performed with eGFR as the outcome variable.ResultsVariation in the eGFR values was explained to a significant degree by SUVmean and renal segmentation volume in both the 1 and 2 h images. This correlation was stronger for CKD-EPI eGFR (1 h R2 = 0.64; 2 h R2 = 0.64) than for MDRD eGFR (1 h R2 = 0.47; 2 h R2 = 0.45).ConclusionRenal [18F]PSMA-1007 uptake parameters correlate with eGFR and are indicative of renal cortical function