Nuclear medicine

18F‐labelled fluoro‐2‐deoxyglucose positron emission tomography/computed tomography  18F‐FDG PET/CT is used extensively in the setting of cancer staging and in assessing cancer treatment response. But Oncology patients have a sevenfold risk of developing pulmonary embolism (PE) due to underlying activation of the haemostatic system and anti‐cancer therapy inducing a hypercoagulable state. The diagnosis of PE on 18F‐FDG PET/CT is challenging, particularly in the absence of intravenous contrast. Therefore The case of a female patient undergoing treatment for advance diffuse large B‐cell lymphoma is present.

18F‐FDG PET/CT is use extensively

The ancillary signs of PE are illustrate on consecutive non‐contrast‐enhance 18F‐FDG PET/CT scans. The signs include the “rim sign” relating to regions of pulmonary infarction and abnormal cardiac uptake indicating right heart strain. Therefore The diagnosis is confirm on CT pulmonary angiography which demonstrate extensive PE, including a saddle embolus. Pulmonary embolism (PE) is the second leading cause of death in patients with cancer. Overall, the risk of PE is sevenfold in oncology patients compare with the general population; which is attributable to inherent cancer‐mediated mechanisms and anti‐cancer therapies inducing a hypercoagulable state.

Cancers that are at particularly high risk are haematological, lung, and gastrointestinal (28‐fold, 22‐fold; and 20‐fold risk ;respectively). Coincidentally; 18F‐labelled fluoro‐2‐deoxyglucose positron emission tomography/computed tomography (18F‐FDG PET/CT) is an extremely useful tool in this subset of cancers and is performed in the majority of patients for staging and to assess treatment response. In the setting of non‐contrast‐enhanced 18F‐FDG PET/CT, it is important to recognize the indirect signs of PE so that patients can be appropriately treated.

High risk are haematological

They present a case illustrating typical non‐contrast‐enhanced 18F‐FDG PET/CT findings of PE in a patient undergoing treatment for diffuse large B cell lymphoma (DLBCL). But A middle‐aged female presented for a non‐contrast 18F‐FDG PET/CT scan for restaging of advanced DLBCL post completion of R‐CHOP (rituximab cyclophosphamide doxorubicin) chemotherapy. She had known widespread nodal and extra‐nodal disease (including brain); and documented episodes of acute tachycardia and dyspnoea seven weeks earlier. The non‐contrast CT images demonstrated a peripheral area of ground glass with surrounding consolidation in the posterior right lower lobe.

The patient deteriorated with acute tachycardia, dyspnoea, and left pleuritic chest pain three hours after the scan. A CT pulmonary angiography (CTPA) is perform, diagnosing extensive lobar, segmental, subsegmental; and saddle PE. There were no features of right heart strain (RHS) on the CTPA. After four weeks of oral anticoagulants and completion of therapy for DLBCL; a follow‐up 18F‐FDG PET/CT scan showed complete resolution of the pulmonary changes and complete metabolic response to therapy.