Lung perfusion scintigraphy in the assessment of pulmonary circulation after completion of surgical treatment of a hypoplastic left heart syndrome (HLHS).

INTRODUCTION: Hypoplastic left heart syndrome (HLHS) is an inborn complex heart malformation. A multi-stage treatment is initiated in a neonatal period with a Norwood surgery. The next step is Glenn surgery - a bidirectional superior cavo-pulmonary anastomosis. At the last stage anastomosis of inferior vena cava (IVC) with the right pulmonary artery (RPA) is formed as a result of a Fontan surgery. The aim of this study was to assess lung perfusion in patients with HLHS after completion of a surgical therapy, using a scintigraphic method. MATERIAL AND METHODS: In 92 patients with HLHS a planar lung scintigraphy in anterior and posterior projections after administration of 99mTc-macroaggregates in activity 18-111MBq was carried out twice (in several day intervals). At first, a radiopharmaceutical was administered to the right extremity in order to assess the lung distribution of blood flowing through the anastomosis of superior vena cava (SVC) with RPA. In the next study, after administration of the tracer to the right lower extremity, the distribution of blood flowing through the anastomosis of IVC with RPA was assessed. The relative percentage of each lung in the total lung perfusion was calculated on a Xeleris workstation using the "Lung perfusion analysis" program. Lung perfusion was considered close to symmetrical when the proportion was in the range of 40-60%. RESULTS: In spite of the fact that mean relative values of distribution of blood flowing through the anastomosis of SVC with RPA to the left lung (LL) and right lung (RL) in the entire study group did not differ significantly: LLmean = 47%; RLmean = 53%, p = 0.14, relative values of perfusion of both lungs were differentiated - in 26% of patients LL was better perfused, in 38% RL was better perfused and in 36% a perfusion of both lungs was similar. The analysis of blood distribution by anastomosis of IVC with RPA showed that the mean relative perfusion of RL was significantly higher than that of LL (70% vs. 30%, p < 0.0000001). No signs of pulmonary emboli were detected. In 13% of studied patients, uptake of the radiopharmaceutical in kidneys was shown indicating the presence of shunt "from right to left". CONCLUSIONS: After completion of surgical treatment of patients with HLHS, differentiated blood supply of the lungs was observed through SVC with RPA anastomosis and a tendency to higher blood supply of RL than LL by anastomosis of IVC with RPA. No signs of pulmonary embolism were detected. The study revealed a "right to left" shunt in some patients.

Diagnostic performance of myocardial perfusion single-photon emission computed tomography with attenuation correction.

BACKGROUND: Myocardial perfusion single-photon emission computed tomography (SPECT) is one of the basic tools used for the purpose of diagnosis of coronary artery disease (CAD), prognosis of its unfavourable consequences, and evaluation of therapy effectiveness. However, its efficacy is compromised by a relatively low specificity of detection of perfusion defects, which is attributed to attenuation of gamma rays inside the patient's body, causing artefacts erroneously taken for perfusion defects. It is expected that attenuation correction (AC) could eliminate such artefacts. AIM: To evaluate whether visual, semi-quantitative analysis of attenuation-corrected myocardial perfusion imaging provides an advantage over a non-corrected study. METHODS: A retrospective study applying AC was performed in 107 patients who had coronary angiography within three months. Patients underwent a stress/rest Tc-99m methoxyisobutylisonitrile (MIBI, POLATOM) double day SPECT/CT myocardial perfusion imaging. Images were analysed by two experienced nuclear medicine specialists (a consensus) applying a visual semiquantitative method. Coronary angiography findings were used as a reference for the analysis of diagnostic performance of myocardial perfusion study protocols. RESULTS: AC increased the specificity of detection of CAD in the whole group of patients from 63% to 86% (p = 0.0005), with a slight reduction in sensitivity (from 83% to 79%). The improved specificity was also noted in subgroups of male and female patients. Accuracy in the whole group of patients increased from 71% to 83% (p = 0.01). AC improved the specificity and accuracy of the method in the detection of perfusion defects in the right coronary artery (RCA) area from 73% to 88% (p = 0.005) and from 74% to 83% (p = 0.04), respectively, and the accuracy of the method in the left anterior descending (LAD) artery area from 79% to 87% (p = 0.043). It also reduced the number of ambiguous results of the study. CONCLUSIONS: AC improved the diagnostic performance of myocardial perfusion study in the detection of CAD and identification of critically stenosed LAD and RCA vessels, with enhanced comfort of study interpretation.

Perfusion lung scintigraphy for the prediction of postoperative residual pulmonary function in patients with lung cancer.

BACKGROUND: Accurate prediction of postoperative pulmonary function in patients with non-small cell lung cancer is crucial for proper qualification for surgery, the only effective therapeutic method. The aim of the study was to select the most accurate method for acquisition and processing of lung perfusion scintigraphy (LPS) combined with spirometry for prediction of postoperative pulmonary function in patients qualified for surgery. MATERIAL AND METHODS: LPS was performed in 70 patients (40 males, 30 females), with preoperative spirometry (mean FEV1preop = 2.26 ± 0.72 L), after administration of 185 MBq of 99mTc-microalbumin/macroaggregate, using planar (appa) and SPECT/CT methods. Predicted postoperative lung function (FEV1pred) was calculated as a part of active lung parenchyma to remain after surgery. A non-imaging segment counting method was also applied. FEV1pred(appa, SPECT, SPECT/CT, segm.) were further compared with actual FEV1postop values obtained from postoperative spirometry. RESULTS: In the whole studied group (47 lobectomies, 23 pneumonectomies) mean value of FEV1postop was equal to 1.76 (± 0.56) L. FEV1pred(appa, SPECT, SPECT/CT, segm.) were equal to 1.75 (± 0.58) L, 1.71 (± 0.57) L, 1.72 (± 0.57) L and 1.57 (± 0.58) L, respectively. A segment counting method systematically lowered predicted FEV1 values (p < 10-5). Moreover, in 31 patients with FEV1preop < 2 L error of predicted values was assessed with Bland-Altman method. Mean absolute differences FEV1postop - FEV1pred amounted to: appa - (0.04 ± 0.13) L, SPECT - (0.07 ± 0.14) L, SPECT/CT - (0.06 ± 0.14) L and segm. - (0.21 ± 0.19) L, respectively. Lower limit of 95% confidence interval calculated for planar - optimal method, was equal to -220 mL (also determined separately in subgroups after lobectomy and pneumonectomy). CONCLUSIONS: This study shows that planar LPS may be applied for prediction of postoperative pulmonary function in patients qualified for pneumonectomy and lobectomy. If actual FEV1postop value is to be ≥ 800 mL, predicted value should exceed 1000 mL.

The effect of image translation table on diagnostic efficacy of myocardial perfusion SPECT studies.

BACKGROUND: The aim of this study was to determine which of the most popular colour scales used in the Xeleris processing system (GE) should preferably be used during a clinical interpretation of myocardial perfusion images, and to find out whether a colour scale saturation level affects the diagnostic efficacy of the study. MATERIAL AND METHODS: From among 100 patients in whom a myocardial perfusion scintigraphy had been performed, a subgroup of people referred for coronary angiography, with neither prior history nor ECG signs of a myocardial infarction has been selected retrospectively. This group consisted of 41 patients (14 females) in the age group 46 to 76 years. All patients underwent two-day myocardial perfusion SPECT imaging using 99mTc-MIBI as a radiopharmaceutical. Reconstructed slices were interpreted in 3 colour scales: white-red-yellow-green-blue-black with computer-assigned thresholds (French 100%), the same French scale but without a white colour (image maximum set manually to a border value between red and white - French w.w.), and a white-yellow-violet- pink-blue-black scale (GEcolor), by consensus of two experienced nuclear medicine specialists. A semiquantitative method for evaluation of perfusion images was applied, based on myocardium segmentation. Perfusion in each segment was scored using a five-point system. Study interpretation (normal/ abnormal perfusion) was based on summed stress scores (SSS), being equal/above or below a given threshold value. The choice of optimal SSS threshold value was based on sensitivity and specificity of the study in detection of perfusion defects resulting from critical stenoses of main coronary arteries RESULTS: SSS values differed among colour scales (p < 0.00001). The lowest values were obtained for a French 100% scale (mean value = 5.0, SD = 8.0), the highest for French w.w. (mean values = 8.1, SD = 8.7), and for GE colour scale - mean value - 5.6, SD - 7.9. A French 100% scale gave high sensitivity (88%), as well as specificity (83%), but only when a low SSS threshold value of 2, hardly acceptable for study interpreters, was used. When higher threshold values were applied, they compromised the sensitivity of the study. A French w.w. scale with SSS threshold values lower than 3 provided a slightly higher sensitivity (94%), but with a significant reduction in specificity (to values below 50%). Only a threshold value of 4 provided acceptable, but still low specificity (63%) with preserved high sensitivity (88%). At the same time, the scale GE colour provided indices of diagnostic efficacy with the SSS threshold value of 3 as high as a scale French 100% with threshold value of 2. CONCLUSIONS: A French scale (Xeleris, GE) is not the scale of choice for the interpretation of myocardial perfusion SPECT images. It seems that a GE colour scale is better suited for this purpose. SSS threshold values accepted as diagnostic criteria for the detection of myocardial perfusion abnormalities should be suited separately for every translation table. The choice of optimal value should be verified by results of coronary angiography.

Effect of attenuation correction on normal (99)mTc-MIBI myocardial perfusion scintigrams acquired with a hybrid SPECT/CT camera.

The aim of this study was to evaluate the effect of the CT-derived attenuation correction on (99m)Tc-MIBI normal myocardial perfusion scintigrams. Rest perfusion scintigrams of patients in whom coronary artery disease was suspected, without a history or any signs in ECG of a myocardial infarction, were analysed. Patients were included in the material if their rest perfusion scintigrams were normal. This criterion was fulfilled by 61 patients (29 men and 32 women) aged between 40 and 74 (mean value 57) years, with body mass between 50 and 120 (mean value 70) kg. Tomographic reconstruction of a radionuclide study was performed with an iterative OSEM method (10 subsets, 2 iterations) sequentially without and with attenuation and scatter corrections on a dedicated Xeleris workstation, applying an ACQC tool to enable manual realignment of SPECT and CT images. SPECT studies were evaluated visually and semiquantitatively. Visual analysis of tomograms was performed with the aim of finding sites of significantly lower counts in comparison with the maximal level (in the lateral wall). Semiquantitative analysis was based on counts in 20 segments of a polar map. Attenuation correction caused a complete (in 32 of 40 - 80% of patients) or partial (in 8 of 40 - 20% of patients) filling out of all areas of lower counts in the inferior wall. However, although in the anterior wall attenuation correction caused a complete (in 11 of 35 - 31% of cases) or partial (10 of 35 - 29% of cases) filling of areas of lower counts, in 14 cases (40%) those areas remained unchanged or increased, and in 8 cases (13% of all patients) new areas of decreased counts appeared. The same was true for the apical region, in which areas of decreased counts were detected in 14 of 61 (23%) cases without attenuation correction, but after application of the correction number of apical defects, this figure grew to 22 (36%) patients. Altogether, attenuation correction reduced the total number of lower count areas from 104 to 66. Semi-quantitative analysis revealed that attenuation correction reduced nonuniformity in counts in the whole myocardium - the mean difference between segment with maximum counts and values in all segments was reduced from 17.5 +/- +/- 12% to 11.0 +/- 10.3% (p < 0.0001) in male patients, and in female patients, from 11.5 +/- 9% to 10.5 +/- 8.6%, thus equalling non-uniformities in myocardial scintigrams of both sexes. Misalignment of CT and SPECT studies was observed in 17 (28%) patients but only in 2 (3% of all patients) patients did CT realignment evidently change the attenuation corrected scintigrams. Although attenuation correction can cause artefacts, its use is justified by the reduction of the total number of areas of lower counts and the improvement of uniformity of images of normally perfused myocardium.