LAFOV PET presents an excellent sensitivity, offering the ability of high-quality extra short images. We assess through a case report the additional value of performing 68GA-PSMA-11 PET/CT dynamic acquisitions on an LAFOV PET system to improve discrimination between pathological uptakes, such as lymph nodes, from urinary physiological uptake. We performed a single-bed 4-minute list-mode acquisition, reconstructed in 4 frames of 1 minute, providing a dynamic visualization of 68GA-PSMA-11 urinary ureteral excretion over time. This additional reconstruction is easy to implement in clinical practice, requiring no additional acquisition time or radiological exposure.

Pulmonary vascular obstruction index (PVOI), assessed using the Qanadli index on computed tomography pulmonary angiography (CTPA) at pulmonary embolism (PE) diagnostic, has been associated with recurrence after unprovoked PE, but its complexity limits routine use. We aimed to evaluate simplified semiquantitative (Sq) measures of initial PVOI for predicting recurrent PE after anticoagulation discontinuation.This post hoc analysis, based on the double-blind, randomized PADIS-PE trial where patients with a first unprovoked PE initially treated during 6 months were allocated to receive either an additional 18-month warfarin or placebo, was restricted on the 180 patients who had PE diagnosed by CTPA. Initial PVOI was assessed using four methods: Qanadli score, modified Qanadli score, anatomical-based SqPVOI1, and lobe-based SqPVOI2. Accuracy and associations with recurrent PE were evaluated using area under the curve (AUC) analysis and Cox regression models.Among the 180 included patients (mean age 66.2 ± 16.5 years; 45.2% female), recurrent PE occurred in 42 patients (36-month median follow-up). Accuracy was comparable across the four PVOI scores, with AUCs ranging from 0.70 to 0.74. All scores showed comparable ability to predict recurrent PE. When using the anatomical-based SqPVOI1, recurrence risk increased progressively with more proximal thrombus location: compared with segmental artery involvement (36-month cumulative incidence, 10.5%; n = 76), risk was 2- to 3-fold with lobar artery involvement (HR 2.90, 95%CI, 1.20-7.05, p = 0.005; 36-month cumulative incidence, 25.6%; n = 63) and 4- to 5-fold increased risk (HR 4.59, 95%CI, 1.85-11.42, p = 0.001; 36-month cumulative incidence, 46.8%; n = 41) with main pulmonary artery involvement.Simplified anatomical assessment of PVOI showed prognostic information comparable to quantitative indices. Further prospective validation is needed.

Venous thromboembolism (VTE), manifesting as deep vein thrombosis and pulmonary embolism, is a common, recurrent and potentially fatal condition. Anticoagulation remains the cornerstone of therapy, yet determining optimal treatment duration (eg, decision to shorten or extend anticoagulant treatment) is difficult due to the uncertain balance between long-term bleeding risk and recurrence. Future advances in vascular nuclear molecular imaging could critically help support this decision-making process. Current VTE diagnostic imaging relies on structural or perfusion-based techniques to infer thrombosis from abnormal vasculature structure or filling defects. While highly effective in localizing thrombi and assessing hemodynamic impact, they provide little insight into the biological activity or age of the clot. Consequently, anticoagulation strategies (duration and management) often proceed without direct clot-specific molecular information, potentially leading to suboptimal outcomes and increased risk of fatal bleeding. By contrast, nuclear VTE molecular imaging-using radiolabeled probes that selectively target key thrombus components such as fibrin or activated platelets-enables direct visualization of the clot. Single-photon emission computed tomography and positron emission tomography targeted imaging of VTE, beyond enhancing diagnostic accuracy, are expected to provide valuable insights into the structure, age, and activity of the clot. In particular, integration of these modalities with molecular findings from high throughput technologies could further elucidate the cellular and molecular mechanisms driving thrombus formation and resolution. When coupled with positron emission tomography's ability to assess molecular processes in vivo, such approaches may establish precision imaging biomarkers, bridging the gap between clot biology and clinical imaging, and ultimately transform VTE management from a structural or perfusion based to molecularly informed paradigm.

Pulmonary embolism (PE) remains a major diagnostic challenge due to its potentially life-threatening nature and the clinical burden associated with anticoagulation therapy. While computed tomography pulmonary angiography (CTPA) has become the dominant imaging modality for suspected PE, limitations including radiation exposure - particularly to breast tissue-iodinated contrast administration, and concerns about overdiagnosis have prompted renewed interest in alternative strategies. Ventilation-perfusion (V/Q) scintigraphy, grounded in physiological assessment of pulmonary ventilation and perfusion, offers a non-invasive approach with substantially lower radiation and an excellent safety profile. However, planar V/Q imaging is limited by a high proportion of nondiagnostic studies. Recent advances in single-photon emission computed tomography (SPECT) and hybrid SPECT/CT have significantly improved diagnostic accuracy, reduced inconclusive results, and enhanced the ability to distinguish embolic from non-embolic causes of perfusion defects. Despite widespread adoption, formal outcome validation of SPECT-based diagnostic algorithms has been lacking until the recent completion of the international SPECTACULAR randomized controlled trial, designed to compare planar V/Q, CTPA, and SPECT V/Q strategies using three-month thromboembolic recurrence as the reference for clinical safety. Results will be available shortly following presentation at SNMMI annual meeting 2025. Lung scintigraphy plays an essential role in specific populations, including pregnancy or contrast use is restricted. Moreover, ongoing developments in V/Q PET imaging and artificial intelligence-driven post-processing promise improved spatial resolution, quantification, and workflow efficiency, while advanced molecular tracers may enable characterization of thrombus biology. In summary, V/Q scintigraphy - particularly SPECT and SPECT/CT - remains a robust and clinically valuable modality for diagnosing acute PE, offering a radiation-sparing alternative to CTPA. Technological innovation and high-quality outcome evidence are likely to support its broader integration into future diagnostic pathways.

BACKGROUND:While single-photon emission computed tomography (SPECT) ventilation/perfusion (V/Q) has been widely adopted for pulmonary embolism (PE) diagnosis, it is not currently endorsed by clinical guidelines due to insufficient evidence. METHODS:We conducted a non-inferiority randomised trial comparing SPECT V/Q-, computed tomography pulmonary angiography (CTPA)- and planar V/Q-based diagnostic strategies using a 2:1:1 allocation. The primary end-point was the 3-month risk of venous thromboembolism (VTE) in untreated patients with a negative workup, comparing SPECT V/Q to the combined CTPA and planar V/Q arms. A non-inferiority margin of 1% absolute difference in 3-month VTE risk was defined. Secondary outcomes included PE diagnosis rates. The trial ended prematurely in October 2024 due to slow recruitment and funding limitations. RESULTS:From July 2017 to October 2024, 603 patients were randomised. PE was diagnosed in 61/303 (20.1%) in the SPECT V/Q arm, 31/150 (20.7%) in the CTPA arm and 24/150 (16.0%) in the planar V/Q arm. The 3-month VTE risk in patients left untreated after a negative workup was 0.5% (1/221) for SPECT V/Q, 0.0% (0/107) for CTPA and 0.8% (1/118) for planar V/Q. The difference in outcome between SPECT V/Q and the combined arms was 0.0% (95% CI -1.2-1.3%). CONCLUSION:After being prematurely discontinued, this randomised trial did not demonstrate the non-inferiority of a SPECT V/Q-based strategy to reference standards for PE diagnosis. However, the results suggest a low 3-month VTE risk in patients managed using a SPECT V/Q-based diagnostic strategy. Among patients with clinically suspected acute PE requiring chest imaging, a SPECT V/Q-based algorithm might be a reliable alternative in clinical practice.

Chronic thromboembolic pulmonary hypertension (CTEPH) is a severe complication of pulmonary embolism (PE), often diagnosed late due to nonspecific symptoms and limitations of current screening tools like V/Q scintigraphy. This study investigated whether computational fluid dynamics (CFD)-derived hemodynamic parameters, specifically time-averaged wall shear stress (TAWSS) and oscillatory shear index (OSI), in the proximal pulmonary arteries could serve as noninvasive biomarkers for CTEPH and chronic thromboembolic disease without pulmonary hypertension (CTEPD, non-CTEPH with V/Q mismatches). We retrospectively analyzed 90 patients (30 CTEPH, 30 CTEPD, and 30 controls without mismatch) using patient-specific 3D CFD models reconstructed from CTPA, with RCR boundary conditions tuned to RHC data. We found significantly reduced median TAWSS in CTEPH (16.5 dyn/cm2) and CTEPD (27.5 dyn/cm2) groups compared to controls (42.0 dyn/cm2) (p < 0.001), with TAWSS also significantly lower in CTEPH versus CTEPD. OSI showed no significant inter-group differences. Importantly, TAWSS exhibited a strong inverse correlation with V/Q mismatch status (ρ = -0.673, p < 0.001). ROC analysis revealed that TAWSS accurately predicted perfusion mismatches (AUC = 0.918), with an optimal cutoff of 27.0 dyn/cm2 yielding 100.0% specificity and 70.0% sensitivity. These findings demonstrate that CFD-derived proximal pulmonary artery TAWSS is a promising noninvasive indicator of chronic thromboembolic burden, including subclinical perfusion abnormalities, offering a potential tool to enhance early detection and management of CTEPH.

Background: In patients with pulmonary embolism (PE), identifying predictors of recurrence is important to risk-stratify patients and tailor anticoagulation duration. After PE, a significant proportion of patients demonstrate residual pulmonary vascular obstruction (RPVO) on lung imaging. However, the exact prognostic significance of RPVO for venous thromboembolism recurrence remains unclear. Objectives: The primary objective is to assess whether RPVO on ventilation/perfusion (V/Q) single photon emission computed tomography (SPECT)/CT imaging after completion of 3 to 6 months of anticoagulation is an independent predictor of venous thromboembolism recurrence in patients with PE. Methods: The PRONOSPECT trial is a prospective multicenter cohort study. Participants are patients who experienced an objectively proven PE, provoked by a minor transient risk factor or unprovoked; who have been treated with anticoagulant therapy for 3 to 6 uninterrupted months; and for whom anticoagulation will not be prolonged. A standardized baseline patient assessment will be conducted including V/Q SPECT/CT imaging, collection of other potential predictor variables, and a functional evaluation. Anticoagulants will be withdrawn at the 3- or 6-month points from diagnosis and patients will be followed up for up to 2 years. Conclusion: The PRONOSPECT cohort study has the potential to determine whether the presence of RPVO on V/Q SPECT/CT imaging predicts the risk of recurrence in patients with PE in whom there remains a doubt on duration of anticoagulation.

Introduction The current gold standard techniques for venous thromboembolism (VTE) diagnosis are compression ultrasonography (CUS), computed tomography pulmonary angiography (CTPA), and ventilation/perfusion (V/Q) scan. However, these imaging modalities, although well validated for the exclusion of VTE at the acute phase, do not provide any information on thrombus molecular composition. Targeting D-Dimers (DD) using specific molecular imaging anti-DD probes has the potential to better characterize VTE, ultimately improving diagnosis accuracy for VTE patients. Objective This study presents a proof-of-concept for using an anti-DD probe for in vivo real time imaging of thrombosis. Method A murine monoclonal anti-DD IgG antibody was produced and labelled with a water soluble fluochrome (CF555[red], Biotium) and used in in vitro clotting assays to label DD within thrombi under static and flow conditions. Both human and mouse in vitro plasma and whole blood clots were formed by induction of coagulation with human tissue factor (TF). AlexaFluor488(green)-prelabelled fibrinogen and CF350-WGA(blue) were skipped in samples shortly prior to induction of coagulation to label neo-formed fibrin fibers and platelets, respectively. The conjugate binding of DD on real preformed human and murine thrombi was also investigated. Results The anti-DD IgG-CF555 conjugate was capable to specifically recognise DD in in vitro clots formed either under static (no flow) or flow conditions. Importantly, DD staining profile on in vitro clots was very similar to that on preformed real human and mouse thrombi and to that obtained when the conjugate was incubated with human purified DD fragments. Our anti-DD IgG-CF555 conjugate represents a valuable probe for real time confocal and intravital imaging of thrombus formation and resolution. Conclusion This study shows that an anti-DD probe may specifically target thrombus components. Our suggested approach for VTE imaging might show higher specificity than current imaging modalities. In vivo preclinical experiments are however needed to confirm these interesting findings.

Introduction Pulmonary embolism (PE) is a challenge to diagnose and when missed, exposes patients to potentially fatal recurrent events. Beyond CT pulmonary angiography (CTPA) and planar ventilation/perfusion (V/Q) scan, single photon emission CT (SPECT) V/Q emerged a new diagnostic modality of scintigraphic acquisition that has been reported to improve diagnostic performances. To date, no management outcome study or randomised trial evaluated an algorithm based on SPECT V/Q for PE diagnosis. We present the design of a randomised multicentre, international management study comparing SPECT V/Q with validated strategies.Material and methods We will include a total of 3672 patients with suspected PE requiring chest imaging, randomised into three different groups, each using a different diagnostic strategy based on SPECT V/Q, CTPA and planar V/Q scan. Randomisation will be unbalanced (2:1:1), with twice as many patients in SPECT V/Q arm (n=1836) as in CTPA and planar V/Q arms (n=918 in each). Our primary objective will be to determine whether a diagnostic strategy based on SPECT V/Q is non-inferior to previously validated strategies in terms of diagnostic exclusion safety as assessed by the 3-month risk of thromboembolism in patients with a negative diagnostic workup. Secondary outcomes will be the proportion of patients diagnosed with PE in each arm, patients requiring additional tests, the incidence of major and clinically relevant non-major bleeding and the incidence and cause of death in each arm.Ethics and dissemination This trial is funded by a grant from Brest University Hospital and by INVENT. The study protocol was approved by Biomedical Research Ethics Committee. The investigator or delegate will obtain signed informed consent from all patients prior to inclusion in the trial. Our results will inform future clinical practice guidelines and solve the current discrepancy between nuclear medicine guidelines and clinical scientific society guidelines.Trial registration number NCT02983760

Head and neck squamous cell carcinoma (HNSCC) remains a malignancy with high rates of locoregional recurrence and poor prognosis for recurrent cases. Early detection of subclinical lesions is challenging but critical for effective patient management. Imaging surveillance after treatment, particularly 18F-FDG PET/CT, has shown promise in the diagnosis of HNSCC recurrence. The aim was to evaluate the diagnostic performance of 18F-FDG PET/CT according to delay after treatment in detecting subclinical recurrence (SCR) in HNSCC patients. Methods: In this retrospective study, all 18F-FDG PET/CT scans were performed at a single center. All adults with histologically proven HNSCC who were treated with curative intent between January 1, 2006, and December 31, 2021, were included. They had a normal clinical examination before each scan. Patients who underwent an intensive follow-up strategy after treatment had 18F-FDG PET/CT with an intravenous contrast agent at 3-6 mo and annually thereafter for 5 y. The primary endpoint was diagnostic performance (positive and negative predictive values, sensitivity, specificity, and accuracy). Results: In total, 2,566 18F-FDG PET/CT scans were performed among 852 patients, with an average of 3 scans per patient. The overall diagnostic performance measures were as follows: positive predictive value (88%), negative predictive value (98%), sensitivity (98%), specificity (89%), and accuracy (93%). There were no significant differences in diagnostic performance over time. The scans detected 126 cases of SCR (14.8%) and 118 cases of metachronous cancer (13.8%). The incidence of SCR decreased over time, with the highest detection rate in the first 2 y after treatment. Positive predictive value improved over time, reaching 90% for the digital Vision 600 system (third period) compared with 76% for the analog Gemini GXLi system (first period, P < 0.001). Multivariate analysis identified advanced stage, high body mass index, and initial PET/CT upstaging as predictive factors for detection of SCR. Conclusion: Our study demonstrates that 18F-FDG PET/CT has high diagnostic performance in detecting SCR during follow-up after treatment of HNSCC, especially in the first 2 y. Advanced tumor stage, initial PET/CT upstaging, and high body mass index were associated with a higher likelihood of SCR detection. The routine use of 18F-FDG PET/CT during follow-up seems justified for patients with HNSCC.

Primary objective was to compare the per-patient detection rates (DR) of [18F]DCFPyL versus [18F]fluoromethylcholine positron emission tomography/computed tomography (PET/CT), in patients with first prostate cancer (PCa) biochemical recurrence (BCR). Secondary endpoints included safety and impact on patient management (PM). This was a prospective, open label, cross-over, comparative study with randomized treatment administration of [18F]DCFPyL (investigational medicinal product) or [18F]fluoromethylcholine (comparator). Men with rising prostate-specific antigen (PSA) after initial curative therapy were enrolled. [18F]DCFPyL and [18F]fluoromethylcholine PET/CTs were performed within a maximum time interval of 12 days. DR was defined as the percentage of positive PET/CT scans identified by 3 central imaging readers. PM was assessed by comparing the proposed pre-PET/CT treatment with the local treatment", defined after considering both PET/CTs. A total of 205 patients with first BCR after radical prostatectomy (73

The detection rate of PSMA-11 PET/CT in biochemical recurrence prostate cancer patients and negative choline PET/CT is not well known. Our study showed that PSMA-11 PET/CT is able to detect occult biochemical recur-rence even in this selected population of patients, and even at low PSA levels. A majority of patients with a positive examination initiated a treatment following PSMA-11 PET/CT. Patient management changed in 39.8%. Introduction: Prostate adenocarcinoma (CaP) is the leading cancer in men. After curative treatment, from 27% to 53% of patients will experience biochemical recurrence (BR). With the development of focal therapies, precise early identification of recurrence's sites is of utmost importance in order to deliver individualized treatment on positive lesions. The aim of this study was to assess the detection rate (DR) of 68Ga-PSMA-11 positron emission tomography/computed tomography (PET/CT) in selected patients with prostate cancer BR and recent negative 18F-choline PET/CT. Patients and Methods: We performed a retrospective analysis including all patients with CaP referred for BR with a negative 18F-choline PET/CT, and who underwent 68Ga-PSMA-11 PET/CT between October, 2018 and December, 2019. The overall DR of 68Ga-PSMA-11 PET/CT was calculated, and described according to BR characteristics especially PSA levels and velocity. Patients were followed up for at least 1 year. Patient management following 68 Ga-PSMA-11 PET/CT and PSA levels evolution after treatment were also recorded. Results: One hundred fifty-nine patients comprising 164 examinations were analyzed. The overall DR of 68Ga-PSMA-11 PET/CT for BR was 65.9% (95CI, 58.6-73.1). The DR was 52.5% (95CI, 39.9-65.0), 70.6% (95CI, 55.3-85.9), 70.4% (95CI, 53.1-87.6), and 78.6% (95CI, 66.2-91.0) for PSA levels between 0.2 and 0.49 ng/mL, 0.5 to 0.99 ng/mL, 1 to 1.99 ng/mL and PSA >= 2 ng/mL, respectively. The DR was 70.7% (95CI, 59.0-82.4) with a PSA doubling time (PSA-DT) <= 6 months and 65.2% (95CI, 55.5-74.9) with a PSA-DT > 6 months. Around 3/4 of patients (75.9%) with a positive 68Ga-PSMA-11 PET/CT initiated treatment, including surgery (2.4%), stereotactic radiotherapy +/- androgen deprivation therapy (ADT) (22%) or external conformational radiotherapy +/- ADT (46.3%). Patient management changed in 43 cases (39.8%). Conclusion: Our study confirmed the ability of 68Ga-PSMA-11 PET/CT to detect occult biochemical recurrence, even in a selected population of CaP patients with negative 18F-choline PET/CT, even at low PSA levels.

PURPOSE:Primary objective was to compare the per-patient detection rates (DR) of [18F]DCFPyL versus [18F]fluoromethylcholine positron emission tomography/computed tomography (PET/CT), in patients with first prostate cancer (PCa) biochemical recurrence (BCR). Secondary endpoints included safety and impact on patient management (PM). METHODS:This was a prospective, open label, cross-over, comparative study with randomized treatment administration of [18F]DCFPyL (investigational medicinal product) or [18F]fluoromethylcholine (comparator). Men with rising prostate-specific antigen (PSA) after initial curative therapy were enrolled. [18F]DCFPyL and [18F]fluoromethylcholine PET/CTs were performed within a maximum time interval of 12 days. DR was defined as the percentage of positive PET/CT scans identified by 3 central imaging readers. PM was assessed by comparing the proposed pre-PET/CT treatment with the local treatment", defined after considering both PET/CTs. RESULTS:A total of 205 patients with first BCR after radical prostatectomy (73%; median PSA = 0.46 ng/ml [CI 0.16;27.0]) or radiation therapy (27%; median PSA = 4.23 ng/ml [CI 1.4;98.6]) underwent [18F]DCFPyL- and/or [18F]fluoromethylcholine -PET/CTs, between July and December 2020, at 22 European sites. 201 patients completed the study. The per-patient DR was significantly higher for [18F]DCFPyL- compared to [18F]fluoromethylcholine -PET/CTs (58% (117/201 patients) vs. 40% (81/201 patients), p < 0.0001). DR increased with higher PSA values for both tracers (PSA ≤ 0.5 ng/ml: 26/74 (35%) vs. 22/74 (30%); PSA 0.5 to ≤ 1.0 ng/ml: 17/31 (55%) vs. 10/31 (32%); PSA 1.01 to < 2.0 ng/ml: 13/19 (68%) vs. 6/19 (32%);PSA > 2.0: 50/57 (88%) vs. 39/57 (68%) for [18F]DCFPyL- and [18F]fluoromethylcholine -PET/CT, respectively). [18F]DCFPyL PET/CT had an impact on PM in 44% (90/204) of patients versus 29% (58/202) for [18F]fluoromethylcholine. Overall, no drug-related nor serious adverse events were observed. CONCLUSIONS:The primary endpoint of this study was achieved, confirming a significantly higher detection rate for [18F]DCFPyL compared to [18F]fluoromethylcholine, in men with first BCR of PCa, across a wide PSA range. [18F]DCFPyL was safe and well tolerated.

La durée optimale du traitement anticoagulant après une embolie pulmonaire (EP) non provoquée est controversée en raison du rapport bénéfice/risque du traitement anticoagulant. Une meilleure évaluation du risque de récidive à l’arrêt du traitement est nécessaire pour déterminer la stratégie de prise en charge optimale. L’objectif de cette revue systématique avec méta-analyse sur données individuelles des participants était d’évaluer la relation entre l’index d’obstruction vasculaire pulmonaire résiduelle (OVPR) en scintigraphie pulmonaire planaire réalisée à l’arrêt d’au moins 3 mois de traitement anticoagulant après EP aiguë et le risque de récidive ou de décès lié à une EP un an après l’arrêt du traitement. L’étude a été enregistrée dans le Registre prospectif international des revues systématiques (PROSPERO : CRD42017081080). La population comportait des adultes (18 ans ou plus) ayant survécu à une EP aiguë confirmée, non provoquée ou provoquée par un facteur de risque transitoire et/ou persistant, et ayant bénéficié d’au moins 3 mois de traitement anticoagulant sans récidive pendant la durée du traitement. Le critère d’évaluation principal était d’estimer le taux de récidive à un an chez les patients présentant une OVPR en scintigraphie pulmonaire planaire réalisée au terme d’au moins 3 mois de traitement anticoagulant. Les données individuelles ont été obtenues pour 809 patients. L’index d’OVPR (c.-à-d. obstruction > 0 %) a été identifié chez 407 patients (50,3 %) après une durée médiane de traitement anticoagulant de 6,6 mois. Une récidive ou un décès en lien avec une EP sont survenus chez 114 patients (14,1 %), soit un risque annuel de 6,4 % (IC95 % : 4,7 %–8,6 %). Sur les 114 récidives, 63 sont survenues dans l’année suivant l’arrêt du traitement anticoagulant, correspondant à un risque de 8,1 % (6,4 %–9,8 %) à un an. Le risque de récidive à un an était de 5,8 % (4,4–7,2) chez les participants ayant un index d’OVPR < 5 %, contre 11,7 % (9,5–13,8) chez les participants ayant un index d’OVPR ≥ 5 %. L’index d’OVPR apparaît comme un facteur prédictif significatif du risque de récidive. Cependant, le risque de récidive reste trop élevé chez les patients sans obstruction vasculaire pulmonaire résiduelle pour que l’index d’OVPR puisse être utilisé à lui seul pour décider de l’arrêt du traitement anticoagulant.

Lung ventilation/perfusion (V/Q) positron emission tomography-computed tomography (PET/CT) is a promising imaging modality for regional lung function assessment. The same carrier molecules as a conventional V/Q scan (i.e., carbon nanoparticles for ventilation and macro aggregated albumin particles for perfusion) are used, but they are labeled with gallium-68 (68Ga) instead of technetium-99m (99mTc). For both radiopharmaceuticals, various production processes have been proposed. This article discusses the challenges associated with the transition from 99mTc- to 68Ga-labelled radiopharmaceuticals. The various production and optimization processes for both radiopharmaceuticals are reviewed and discussed for optimal clinical use.

18F-Fluorodeoxyglucose Positron Emission/Computed Tomography (FDG PET/CT) is a non-invasive whole-body imaging modality that has the potential for replacing multiple cancer screening tests by one. Previous studies showed that FDG PET/CT has an excellent sensitivity and negative predictive value for occult cancer screening in patients with unprovoked venous thromboembolism (VTE). In this patient population, FDG PET/CT is a reproducible imaging procedure with a kappa value estimated at 0.75. Although false positive results may lead to unnecessary investigations, it seems from recent evidence that invasive procedures triggered by a positive scan often resulted in cancer diagnosis. Trials assessing use of FDG PET/CT for occult cancer screening in patients with VTE at high risk for occult cancer diagnosis are ongoing.

ObjectiveThe diagnosis of chronic thromboembolic pulmonary hypertension (CTEPH) is a major challenge as it is a curable cause of pulmonary hypertension (PH). Ventilation/Perfusion (V/Q) lung scintigraphy is the imaging modality of choice for the screening of CTEPH. However, there is no consensus on the criteria to use for interpretation. The aim of this study was to assess the accuracy of various interpretation criteria of planar V/Q scintigraphy for the screening of CTEPH in patients with PH.MethodsThe eligible study population consisted of consecutive patients with newly diagnosed PH in the Brest University Hospital, France. Final diagnosis (CTEPH or non-CTEPH) was established in a referential center on the management of PH, based on the ESC/ERS guidelines and a minimum follow-up of 3 years. A retrospective central review of planar V/Q scintigraphy was performed by three nuclear physicians blinded to clinical findings and to final diagnosis. The number, extent (sub-segmental or segmental) and type (matched or mismatched) of perfusion defects were reported. Sensitivity and specificity were evaluated for various criteria based on the number of mismatched perfusion defects and the number of perfusion defects (regardless of ventilation). Receiver operating characteristic (ROC) curves were generated and areas under the curve (AUC) were calculated for both.ResultsA total of 226 patients with newly diagnosed PH were analyzed. Fifty six (24.8%) were diagnosed with CTEPH while 170 patients (75.2%) were diagnosed with non-CTEPH. The optimal threshold was 2.5 segmental mismatched perfusion defects, providing a sensitivity of 100 % (95% CI 93.6–100%) and a specificity of 94.7% (95%CI 90.3–97.2%). Lower diagnostic cut-offs of mismatched perfusion defects provided similar sensitivity but lower specificity. Ninety five percent of patients with CTEPH had more than 4 segmental mismatched defects. An interpretation only based on perfusion provided similar sensitivity but a specificity of 81.8% (95%CI 75.3–86.9%).ConclusionOur study confirmed the high diagnostic performance of planar V/Q scintigraphy for the screening of CTEPH in patients with PH. The optimal diagnostic cut-off for interpretation was 2.5 segmental mismatched perfusion defects. An interpretation only based on perfusion defects provided similar sensitivity but lower specificity.

Background We aimed to validate and to refine current recurrent venous thromboembolism (VTE) risk classification. Methods We performed a post hoc analysis of a multicentre cohort including 1881 patients with a first symptomatic VTE prospectively followed after anticoagulation discontinuation. The primary objective was to validate the International Society of Thrombosis and Haemostasis (ISTH) risk classification in predicting recurrence risk. The secondary objective was to evaluate a refined ISTH classification based on the recurrence risk estimate for each individual risk factor. Results During a 4.8-year median follow-up after anticoagulation discontinuation, symptomatic recurrent VTE occurred in 230 patients (12.2%). Based on the ISTH classification, patients with unprovoked VTE or VTE with minor or major persistent risk factors had a 2-fold increased recurrence risk compared with those with VTE and major transient risk factors. Recurrence risk was not increased in patients with minor transient factors (hazard ratio (HR) 1.31, 95% CI 0.84-2.06). Individual risk factors analysis identified hormone-related VTE (pregnancy: HR 0.26, 95% CI 0.08-0.82; oestrogens: HR 0.25, 95% CI 0.14-0.47) and amyotrophic lateral sclerosis (HR 5.84, 95% CI 1.82-18.70). After reclassification of these factors as major transient for the former and major persistent for the latter, the modified ISTH classification allowed us to accurately discriminate between patients at low risk of recurrence (i.e. with major transient risk factors) and those at high risk of recurrence (i.e. without major transient risk factors). Conclusions Among patients who stopped anticoagulation after a first VTE, a refined ISTH classification based on recurrence risk intensity of individual factors allowed discrimination between patients at low recurrence risk, including hormonal exposure in women, and patients at high recurrence risk.

Introduction Ventilation/Perfusion (V/Q) PET/CT is an emerging imaging modality for regional lung function evaluation. The same carrier molecules as conventional V/Q scintigraphy are used but they are radiolabelled with gallium-68 (68Ga) instead of technetium-99m (99mTc). A recurrent concern regarding V/Q PET imaging is the radiation dose to the healthcare workers. The aim of this study was to evaluate the total effective dose and the finger dose received by the technologist when performing a V/Q PET procedure, and to compare them with the radiations doses received with conventional V/Q scintigraphy, FDG PET and Ga DOTATOC PET procedures. Materials and methods The whole body dose measurement was performed 10 times for each of the evaluated procedures using an electronic personal dosimeter (ED). For V/Q PET and V/Q scintigraphy procedures, ventilation and perfusion stages were separately evaluated. Internal exposure was measured for ventilation procedures. Finger dose measurements were performed 5 times for each of the PET procedures using Thermoluminescence (TL) pellets. Results The technologist effective dose when performing a V/Q PET procedure was 2.83 ± 0.67 μSv, as compared with 1.16 ± 0.34 μSv for conventional V/Q scintigraphy, 2.13 ± 0.77 μSv for [68Ga]Ga-DOTATOC, and 2.86 ± 1.79 μSv for FDG PET procedures, respectively. The finger dose for the V/Q PET procedure was similar to the dose for a [68Ga]Ga-DOTATOC scan (0.35 mSv and 0.32 mSv, respectively). Conclusion The technologist total effective dose for a V/Q PET procedure is ~2.4 higher than the dose for a conventional V/Q scintigraphy, but in the same range than the radiation exposure when performing common PET procedures, both in terms of total effective dose or finger dose. These results should be reassuring for the healthcare workers performing a V/Q PET procedure.