Xavier Palard

Additional value of combining low-dose computed tomography to V/Q SPECT on a hybrid SPECT-CT camera for pulmonary embolism diagnosis.

ObjectivesThe aim of the study was to assess the potential interest of combining a low-dose computed tomography (ldCT) to ventilation/perfusion (V/Q) single-photon emission computed tomography (SPECT) for the diagnosis of pulmonary embolism (PE). We addressed three main questions: Could ldCT be used in substitution to ventilation SPECT? Could ldCT improve the diagnostic performance of V/Q SPECT? Could ldCT provide alternative diagnoses to PE? MethodsA total of 393 patients previously analysed in a management outcome study that aimed at assessing the safety of V/Q SPECT for PE diagnosis were assessed. All patients underwent an ldCT under the same SPECT-computed tomography camera, which was not used at the time of initial interpretation. Three retrospective analyses were performed: Q SPECT combined with ldCT, V/Q SPECT combined with ldCT and ldCT only. ResultsOn the basis of initial V/Q SPECT interpretation, 110 (28%) patients were positive and 283 (72%) were negative for PE.With Q SPECT-ldCT, 139 (35%) patients were positive and 254 (65%) were negative, with 55 (19%) discrepancies when compared with V/Q SPECT. Of the 283 patients with negative V/Q SPECT, 42 were positive with V/Q SPECT-ldCT, and among the 110 patients with positive V/Q SPECT 13 were negative with V/Q SPECT-ldCT. On using V/Q SPECT-ldCT, 97 (25%) patients were positive and 296 (75%) were negative, with 13 (3%) discrepancies when compared with V/Q SPECT (all had had a positive V/Q SPECT but a negative V/Q SPECT-ldCT). Finally, 67 (24%) ldCT scans showed a potential alternative diagnosis to PE. ConclusionFor PE diagnosis with lung SPECT, the use of ldCT in substitution to ventilation SPECT is associated with a high risk of overdiagnosis. The diagnostic value of ldCT in addition to V/Q SPECT remains unclear. Further studies are needed to determine its potential role in PE diagnosis.

FDG PET/CT for Initial Staging of Diffuse Large B-Cell Lymphoma: Is Diffuse Bone Marrow Uptake a Reflection of Disease Involvement?

Objectives: Bone marrow assessment is a diagnostic challenge in staging diffuse large B-cell lymphoma (DLBCL). Diffuse bone marrow uptake (BMU) can be observed on FDG PET/CT performed for initial staging of DLBCL, but remains difficult to analyze. The aim of this study was to evaluate the meaning of this diffuse BMU, and especially to assess its correlation with bone marrow involvement (BMI). Methods: Patients who underwent FDG PET/CT for initial staging of DLBCL were analyzed. Diffuse BMU was assessed using a visual qualitative analysis according to liver uptake (grade 1=below liver uptake, 2=equal to liver uptake, 3=above liver uptake), and a semi-quantitative analysis, by measurement of maximum standardized uptake value (SUV) in the sacral promontory. We compared the BMU with BMI, parameters of disease extension and inflammatory markers. Results: 86 patients (median age 59, range: 19-91, 54 men, 32 women) were included. BMU grade was 1, 2 and 3 in 45, 28 and 13 cases respectively. Bone marrow was considered involved in 13 patients. No statistical correlation was found between diffuse BMU and BMI, using qualitative (p=0.594) or semi-quantitative method (p=0.116). Diffuse BMU visual grading was correlated with inflammatory markers: biological systemic symptoms (p=0.003), CRP (p=0.002) and fibrinogen (p=0.020). Conclusions: Our study suggests that a diffuse BMU seen on FDG PET/CT at initial staging of DLBCL is not representative of bone marrow involvement, but can be due to inflammatory changes.