Influence of Covariates on 18F-FDG PET/CT Diagnostic Accuracy for Liver Metastasis.

(1) Background: 18F-FDG PET/CT diagnostic accuracy for liver metastasis (LM) could be influenced by technical parameters, lesion size, and the patient's covariates. This retrospective study aimed to evaluate these covariates' impact on PET/CT sensitivity. (2) Methods: Consecutive patients with suspected LMs who underwent 18F-FDG PET/CT scans were included. PET/CT scans were interpreted visually. The reference standard integrated histopathological and imaging follow-up. Logistic regression modeling and average marginal predictions were used to calculate per-lesion diagnostic performance measures with cluster robust 95% confidence intervals and to assess the covariates' impact on PET/CT sensitivity. (3) Results: We included 192 patients with 330 lesions. 18F-FDG PET/CT exhibited a per-lesion sensitivity, specificity, positive predictive value, and negative predictive value of 86%, 79%, 91%, and 69%, respectively. In multivariate analysis, TOF PET/CT exhibited a higher sensitivity than non-TOF PET/CT (91% vs. 78%, p = 0.02). Sensitivity was reduced for lesions < 10 mm compared to larger lesions (56% vs. 93%, p < 0.001). A 5 kg/m2 increase in BMI led to an average 5% sensitivity reduction (p < 0.001). Age, sex, blood glucose level below 11 mmol/L, and liver density did not significantly impact sensitivity (p > 0.05). (4) Conclusions: 18F-FDG PET/CT sensitivity might be reduced with non-TOF PET, lesions < 10 mm, and higher BMI.

Pulmonary Recurrence of Colorectal Mucinous Adenocarcinoma and Sarcoidosis on 18 F-FDG PET/CT.

ABSTRACT: A 67-year-old woman, previously diagnosed with pulmonary sarcoidosis and sigmoid colon mucinous adenocarcinoma with pulmonary metastasis, showed an enlarged pulmonary nodule in routine follow-up. Because of the absence of treatment for either condition over the past 3 years, the nodule raised concerns of cancer recurrence or sarcoidosis progression. Its distinctive 18 F-FDG PET/CT appearance, compared with other pulmonary lesions, suggested a mucinous histology. The diagnosis was confirmed by pathological examination. This emphasizes the importance of knowledge of the 18 F-FDG PET/CT phenotype of neoplastic histological variants to address challenging diagnostic scenarios.

Development of a Novel Bronchodilator Vaping Drug Delivery System Based on Thermal Degradation Properties.

This work aims to investigate bronchodilator delivery with the use of different vaping drug delivery systems (VDDS) by determining the dose equivalence delivered in relation to different references: a clinical jet nebulizer, a pMDI (pressurized metered dose inhaler) and a DPI (dry powder inhaler). Three different bronchodilators were used (terbutaline, salbutamol hemisulfate, ipratropium bromide). The e-liquids contained the active pharmaceutical ingredient (API) in powder form. Two different VDDS were tested (JUUL and a GS AIR 2 atomizer paired with a variable lithium-ion battery (i-stick TC 40 W), 1.5 ohm resistance, and 15 W power). Samples were collected using a glass twin impinger (GTI). High-performance liquid chromatography (HPLC) was used to quantify the drugs. A next-generation impactor (NGI) was used to measure the particle size distribution. Terbutaline emerged as the optimal API for bronchodilator delivery in both VDDS devices. It achieved the delivery of a respirable dose of 20.05 ± 4.2 µg/puff for GS AIR 2 and 2.98 ± 0.52 µg/puff for JUUL. With these delivered doses, it is possible to achieve a dose equivalence similar to that of a jet nebulizer and DPI, all while maintaining a reasonable duration, particularly with the GS AIR 2. This study is the first to provide evidence that vaping bronchodilators work only with appropriate formulation, vaping technology, and specific drugs, depending on their thermal degradation properties.

Impact of gas humidification and nebulizer position under invasive ventilation: preclinical comparative study of regional aerosol deposition.

Successful aerosol therapy in mechanically ventilated patients depends on multiple factors. Among these, position of nebulizer in ventilator circuit and humidification of inhaled gases can strongly influence the amount of drug deposited in airways. Indeed, the main objective was to preclinically evaluate impact of gas humidification and nebulizer position during invasive mechanical ventilation on whole lung and regional aerosol deposition and losses. Ex vivo porcine respiratory tracts were ventilated in controlled volumetric mode. Two conditions of relative humidity and temperature of inhaled gases were investigated. For each condition, four different positions of vibrating mesh nebulizer were studied: (i) next to the ventilator, (ii) right before humidifier, (iii) 15 cm to the Y-piece adapter and (iv) right after the Y-piece. Aerosol size distribution were calculated using cascade impactor. Nebulized dose, lung regional deposition and losses were assessed by scintigraphy using 99mtechnetium-labeled diethylene-triamine-penta-acetic acid. Mean nebulized dose was 95% ± 6%. For dry conditions, the mean respiratory tract deposited fractions reached 18% (± 4%) next to ventilator and 53% (± 4%) for proximal position. For humidified conditions, it reached 25% (± 3%) prior humidifier, 57% (± 8%) before Y-piece and 43% (± 11%) after this latter. Optimal nebulizer position is proximal before the Y-piece adapter showing a more than two-fold higher lung dose than positions next to the ventilator. Dry conditions are more likely to cause peripheral deposition of aerosols in the lungs. But gas humidification appears hard to interrupt efficiently and safely in clinical use. Considering the impact of optimized positioning, this study argues to maintain humidification.

Acoustic Aerosol Delivery: Assessing of Various Nasal Delivery Techniques and Medical Devices on Intrasinus Drug Deposition.

This study aims to evaluate the impact of the nasal delivery technique and nebulizing technologies (using different frequencies of oscillating airflow) for acoustic aerosol targeting of maxillary sinuses. Sodium fluoride (chemical used as a marker), tobramycin (drug used as a marker) and 99mTc-DTPA (radiolabel aerosol) were used to assess the intrasinus aerosol deposition on a nasal cast. Two commercial medical devices (PARI SINUS nebulizer and NL11SN ATOMISOR nebulizer) and various nasal delivery techniques (one or two nostrils connected to the aerosol inlet, the patient with the soft palate closed or open during the acoustic administration of the drug, the presence or not of flow resistance in the nostril opposite to the one allowing the aerosol to be administered) were evaluated. The closed soft palate condition showed a significant increase in drug deposition even though no significant difference in the rest of the nasal fossae was noticed. Our results clearly demonstrated a higher intrasinus aerosol deposition (by a factor 2-3; respectively 0.03 ± 0.007% vs. 0.003 ± 0.0002% in the right maxillary sinus and 0.027 ± 0.006% vs. 0.013 ± 0.004% in the left maxillary sinus) using the acoustic airflow generated by the PARI SINUS compared to the NL11SN ATOMISOR. The results clearly demonstrated that the optimal conditions for aerosol deposition in the maxillary sinuses were obtained with a closed soft palate. Thus, the choice of the nebulizing technology (and mainly the frequency of the pulsating aerosol generated) and also the recommendation of the best nasal delivery technique are key factors to improve intrasinus aerosol deposition.

Brown tumors in nuclear medicine: a systematic review.

Brown tumors (BT) are abnormal bone-repair processes and a consequence of hyperparathyroidism. The diagnosis of these lytic lesions in nuclear medicine, while a challenge, is not so rare, because functional imaging is used both in the management of cancer and hyperparathyroidism. The main objective of this review is to summarize the knowledge and the evidence concerning BT and the different imaging modalities in nuclear medicine. A systematic review was performed in Embase, PubMed and Google Scholar from 2005 to 2022. We included articles describing BT in the following imaging modalities: [18F]-fluorodeoxyglucose PET/CT, [18F]-fluorocholine or [11C]-fluorocholine PET/CT, [99mTc]-Sestamibi scintigraphy, bone scan, [18F]-sodium fluoride PET/CT, [68Ga]-FAPI PET/CT; [68Ga]-DOTATATE PET/CT; [11C]-methionine PET/CT. For each modality, appearance, avidity for radiotracer, available quantitative parameters and imaging evolution after parathyroidectomy were collected and analyzed. Fifty-two articles were included for a total of 392 BT lesions. If the diagnosis of BT is evoked on a known lesion, performing a [18F]-fluorocholine PET/CT imaging seems the most appropriate. In [18F]-fluorodeoxyglucose, [18F]-fluorocholine, [18F]-sodium fluoride PET/CT and bone scan, BT can mimic metastatic disease. BT uptakes appear reversible after parathyroidectomy, with a more or less rapid decrease depending on the imaging modality used.

Technical features of vaping drug delivery system for bronchodilator delivery.

PURPOSE: Several technical features influencing bronchodilator delivery were evaluated using different vaping drug delivery systems (VDDS). METHODS: Terbutaline in powder form, combined with 1, 3- propanediol used as e-liquid was tested at different concentrations (1 and 2.5 mg/mL), power levels (15 W and 30 W), and set applied resistances (0.15 to 1.5 O) to compare the efficiency of three VDDS (GS AIR2, GS TANK, CUBIS). Samples were collected with a Glass Twin Impinger (GTI). A High Performance Liquid Chromatography (HPLC) was used for drug quantification. The Next Generation Impactor (NGI) measured particle size distribution. Results were also considered with a clinical jet nebulizer (Cirrus TM 2, 2 mL of terbutaline at 2.5 mg/mL). RESULTS: GS AIR2 with resistance = 1.5 O; power = 15 W, and [Terbutaline] = 2.5 mg/mL represents the optimal VDDS conditions to deliver a respirable dose of 20.05 ± 4.2 µg/puff with a mass median aerodynamic diameter (MMAD) of 1.41 ± 0.03 µm. Thus, 52 puffs were required (lasting approximately 15 min of vaping) to reach similar respirable dose and MMAD compared to nebulization. CONCLUSION: We proved that several crucial VDDS technical parameters govern the performance of respiratory bronchodilator delivery including the resistance, power level and atomizer design.

Therapeutic optimization in head and neck radiotherapy planning: Advocacy for 18FDG PET-CT in treatment condition.

INTRODUCTION: The necessity to perform 18FDG PET-CT both for initial tumour staging and for target volume delineation in head and neck cancers seems well established. The aim of the present study is to advocate the place and role of 18FDG PET-CT acquired in planning treatment position (18FDG PET-CT/RT). METHODS: Between March 2018 and July 2019, 22 patients with a squamous cell head and neck carcinoma treated by EBRT were included in the analysis. All these consecutive patients had a 18FDG PET-CT/RT. Three GTV volumes were defined. First, "GTV 40%" corresponded to 40% of SUVmax. "Visual GTV" was defined as the tumor volume obtained from the PET the nuclear medicine physician interpreted. The radiation oncologist used the medical record, clinical anatomy, CT simulation and 18FDG PET-CT/RT data ("GTV40%" and "visual GTV") to draw the GTV. RESULTS: Mean GTVs and mean "GTVs40%" were significantly different (P<0.001) with an intraclass index of 0.734. Mean "GTV40%" and mean "visual GTVs" were also significantly different (P<0.001) with an intraclass index of 0.72. Conversely, the difference between mean GTVs and mean "visual GTVs" were not significant (P=0.11) with an intraclass index of 0.91. Mean DICE between "GTVs40%" and GTV was 0.7 (ranging from 0.2 to 0.9). The mean intersection between GTVs and "visual GTVs" volumes was 0.8 (ranging from 0.4 to 1). The difference between DICES was significant (P=0.015), "visual GTV"/GTV DICE was the smallest. CONCLUSION: 18FDG PET-CT/RT definitely remains the imaging modality that individualized/customized head and neck cancer treatment needs.

Performance of quantitative measurements in [18F]fluorocholine positron emission tomography/computed tomography for parathyroid imaging (P2TH study).

Objective: [18F]Fluorocholine positron emission tomography/computed tomography (PET/CT) is used frequently in addition to [99mTc]Tc-Sestamibi scintigraphy and ultrasonography for the location of hyperfunctioning parathyroid glands. The aim of this study is to evaluate the performance of quantitative criteria in [18F]fluorocholine PET/CT for localization of hyperfunctioning parathyroid glands. The secondary objective is to highlight a correlation between the detection rate of [18F]fluorocholine PET/CT and serum parathyroid hormone (PTH) level. Materials and methods: In two academic centers, we retrospectively included patients with biological hyperparathyroidism (HPT) and who had [18F]fluorocholine PET/CT. After a visual analysis, to measure the overall performance of [18F]fluorocholine PET/CT, a blind reading was carried out with standardized measurements of maximum standardized uptake value (SUVmax), liver ratio, thyroid ratio, and size ratio. We analyzed the quantitative criteria of [18F]fluorocholine PET/CT compared to the histological results, in particular to identify differences between adenomas and hyperplasias. We compared the performance of each quantitative criterion to the overall sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), and accuracy of [18F]fluorocholine PET/CT. The detection rate of hyperfunctioning parathyroid glands was calculated in subgroups of serum PTH level. Results: The quantitative criteria in [18F]fluorocholine PET/CT were measured for 120 patients (135 lesions). The areas under the receiver operating characteristic (ROC) curve representing SUVmax and liver ratio were significantly increased. The optimal cut-off values represented by the maximum Youden index was >4.12 for SUVmax and >27.4 for liver ratio. Beyond certain threshold values of SUVmax (>4.12) or liver ratio (>38.1), all the lesions were histologically proven adenomas. SUVmax and liver ratio were significantly higher for adenomas than for hyperplasias and differential diagnosis (p = 0.0085 and p = 0.0002). The positivity of [18F]fluorocholine PET/CT was correlated with PTH level. Detection rates were 55.56, 75.56, and 87.5%, respectively, for serum PTH < 70, 70 to 120, and >120 ng/ml. Conclusion: Semi-quantitative measurements (SUVmax and liver ratio) should be considered as additional tools in interpretation of [18F]fluorocholine PET/CT. These quantitative parameters have lower overall performance but higher specificity than overall visual analysis in identifying an adenoma. Above certain threshold values, all lesions are adenomas. [18F]fluorocholine PET/CT confirms excellent performance for the detection of hyperfunctional parathyroids. For serum PTH levels < 70 ng/ml, the detection rate of [18F]fluorocholine PET/CT is strongly decreased.

Diplopia Related to a Pediatric Cervical Rhabdoid Tumor in 18 F-FDG PET.

ABSTRACT: Increased muscle uptake is commonly seen with 18 F-FDG PET/CT because of an important physiological muscle glucose metabolism. Muscle uptake can express a recent significant muscle activity. However, the absence of muscle uptake is almost never described or interpreted. We describe the case of an 8-year-old boy with extrarenal rhabdoid tumor in the right carotid space. An MRI and an 18 F-FDG PET/CT were performed for the diagnostic workup. There was no uptake in the lateral rectus oculomotor muscle unlike all other oculomotor muscles. The ophthalmological examination found a diplopia confirmed by the Lancaster test.

Assessment of High-Power Electronic Nicotine Delivery System as an Alternative Aerosol Device for Terbutaline Delivery.

PURPOSE: The performance of new-generation high-power electronic nicotine delivery system (ENDS) for the administration of inhaled terbutaline was assessed. METHODS: The formulation of e-liquid was carried out using terbutaline in combination with 1, 3- propanediol. Several terbutaline concentrations (from 0.3125 to 2.500 mg / mL) and power levels (from 15 to 35 W) were assessed using a box type ENDS. The respirable drug dose was determined using a Glass Twin Impinger and quantified by liquid chromatography coupled with a UV-detector. The Next Generation Impactor and the Dekati Low Pressure Impactor were used to measure the aerosol particle size distribution in drug mass. The results were compared with a jet nebulizer (Cirrus TM 2) similar to the usual clinical conditions (2 mL at [terbutaline] of 2.5 mg / mL). RESULTS: The optimal conditions to maximize terbutaline delivery using ENDS are a drug concentration at 1 mg/mL, and a power level at 30 W, to reach a respirable dose of 8.73 ± 0.90 µg/puff. By contrast, during a 5 min nebulization, the respirable dose of terbutaline was 1040 ± 33 µg whatever the cascade impactors and the aerosol devices used. The mass median aerodynamic diameter (MMAD) remains similar for jet nebulizer and ENDS in the 1.74-2.07 µm range. CONCLUSION: Compared to the jet nebulizer, a same respirable dose of terbutaline at the same range of aerosol size distribution was delivered by ENDS if 120 puffs were performed. The ENDS can be considered as an alternative aerosol device for terbutaline delivery.

Outcome Prediction at Patient Level Derived from Pre-Treatment 18F-FDG PET Due to Machine Learning in Metastatic Melanoma Treated with Anti-PD1 Treatment.

(1) Background: As outcome of patients with metastatic melanoma treated with anti-PD1 immunotherapy can vary in success, predictors are needed. We aimed to predict at the patients' levels, overall survival (OS) and progression-free survival (PFS) after one year of immunotherapy, based on their pre-treatment 18F-FDG PET; (2) Methods: Fifty-six metastatic melanoma patients-without prior systemic treatment-were retrospectively included. Forty-five 18F-FDG PET-based radiomic features were computed and the top five features associated with the patient's outcome were selected. The analyzed machine learning classifiers were random forest (RF), neural network, naive Bayes, logistic regression and support vector machine. The receiver operating characteristic curve was used to compare model performances, which were validated by cross-validation; (3) Results: The RF model obtained the best performance after validation to predict OS and PFS and presented AUC, sensitivities and specificities (IC95%) of 0.87 ± 0.1, 0.79 ± 0.11 and 0.95 ± 0.06 for OS and 0.9 ± 0.07, 0.88 ± 0.09 and 0.91 ± 0.08 for PFS, respectively. (4) Conclusion: A RF classifier, based on pretreatment 18F-FDG PET radiomic features may be useful for predicting the survival status for melanoma patients, after one year of a first line systemic treatment by immunotherapy.

Using 99mTc-(V)-DMSA to follow the vascular calcification process in vascular smooth muscle cells based on pit-1 expression.

BACKGROUND: Vascular calcification is an established feature of atherosclerosis process. The sodium/phosphate transporter PiT-1 acts as a biosensor in vascular calcification of VSMCs. [99mTc]-Pentavalent dimercaptosuccinic acid (99mTc-(V)-DMSA) was mediated by PiT-1 transporter in tumoral cells and we propose its evaluation in a vascular calcification in vitro model. The aim of this study was to determine if 99mTc-(V)-DMSA can follow the vascular calcification process in vascular smooth muscle cells (VSMCs) based on PiT-1 expression. METHODS: From a rat aortic VSMC cell line (A7r5), we set up a model of calcification within 7 days using a calcifying medium containing a high inorganic phosphate concentration. Phosphocalcic deposits were monitored with Alizarin red and Von Kossa staining and with phase contrast microscopy. PiT-1 expression was evaluated with an immunofluorescence assay and osteopontin expression, with whole cell ELISA assay. 99mTc-(V)-DMSA uptake was measured in control and calcifying conditions and compared with optical microscopy evaluation. RESULTS: Under hyperphosphatemia conditions, the VSMC cells progressively overexpressed osteopontin protein, PiT-1 transporter, and synthetized mineralized matrix with phosphocalcic deposition. 99mTc-(V)-DMSA uptake was to 2.8±2.08%DA/mg-protein in control cells and 42±24%DA/mg-protein in calcified cells (P<0.001). PiT-1 inhibition with phosphonoformic acid completely reverse the calcium deposition as well as the 99mTc-(V)-DMSA uptake. These results demonstrated that 99mTc-(V)-DMSA in-vitro uptake is mediated by PiT-1 transporter and follow the VSMC calcification process. CONCLUSIONS: These preliminary in-vitro results showed 99mTc-(V)-DMSA uptake follow the phospho-calcic deposition mediated by PiT-1 transporter. This radiotracer may have some potential to detect changes of VSMC metabolism occurring in the atherosclerosis process.

Ventilation/perfusion (V/Q) scanning in contemporary patients with pulmonary embolism: utilization rates and predictors of use in a multinational study.

Ventilation/perfusion (V/Q) imaging and computed tomography pulmonary angiography (CTPA) are common tools for acute pulmonary embolism (PE) diagnosis. Limited contemporary data exist about the utilization of each modality, including the predictors of using V/Q versus CTPA. We used the data from patients diagnosed with PE using V/Q or CTPA from 2007 to 2019 in Registro Informatizado Enfermedad ThromboEmbolica, an international prospective registry of patients with venous thromboembolism. Outcomes was to determine the trends in utilization of V/Q vs. CTPA and, in a contemporary subgroup fitting with current practices, to evaluate predictors of V/Q use with multivariable logistic regression. Among 26,540 patients with PE, 89.2% were diagnosed with CTPA, 7.1% with V/Q and 3.7% with > 1 thoracic imaging modality. Over time, the proportional use of V/Q scanning declined (13.9 to 3.3%, P < 0.001). In multivariable analysis, heart failure history (odds ratio [OR]:1.5; 95% confidence interval [CI] 1.14-1.98), diabetes ([OR 1.71; 95% CI 1.39-2.10]), moderate and severe renal failure (respectively [OR 1.87; 95% CI 1.47-2.38] and [OR 9.36; 95% CI 6.98-12.55]) were the patient-level predictors of V/Q utilization. We also observed an influence of geographical and institutional factors, partly explained by time-limited V/Q availability (less use over weekends) and regional practices. Use of V/Q for the diagnosis of PE decreased over time, but it still has an important role in specific situations with an influence of patient-related, institution-related and logistical factors. Local and regional resources should be evaluated to improve V/Q accessibility than could benefit for this population.

Decision Tree With Only Two Musculoskeletal Sites to Diagnose Polymyalgia Rheumatica Using [18F]FDG PET-CT.

Introduction: The aim of this study was to find the best ordered combination of two FDG positive musculoskeletal sites with a machine learning algorithm to diagnose polymyalgia rheumatica (PMR) vs. other rheumatisms in a cohort of patients with inflammatory rheumatisms. Methods: This retrospective study included 140 patients who underwent [18F]FDG PET-CT and whose final diagnosis was inflammatory rheumatism. The cohort was randomized, stratified on the final diagnosis into a training and a validation cohort. FDG uptake of 17 musculoskeletal sites was evaluated visually and set positive if uptake was at least equal to that of the liver. A decision tree classifier was trained and validated to find the best combination of two positives sites to diagnose PMR. Diagnosis performances were measured first, for each musculoskeletal site, secondly for combination of two positive sites and thirdly using the decision tree created with machine learning. Results: 55 patients with PMR and 85 patients with other inflammatory rheumatisms were included. Musculoskeletal sites, used either individually or in combination of two, were highly imbalanced to diagnose PMR with a high specificity and a low sensitivity. The machine learning algorithm identified an optimal ordered combination of two sites to diagnose PMR. This required a positive interspinous bursa or, if negative, a positive trochanteric bursa. Following the decision tree, sensitivity and specificity to diagnose PMR were respectively 73.2 and 87.5% in the training cohort and 78.6 and 80.1% in the validation cohort. Conclusion: Ordered combination of two visually positive sites leads to PMR diagnosis with an accurate sensitivity and specificity vs. other rheumatisms in a large cohort of patients with inflammatory rheumatisms.

Utility of 18F-FDG PET/CT in medical care of a promyelocytic sarcoma.

Promyelocytic sarcoma is an uncommon solid tumor made up of myeloblasts. It is characterized, like acute promyelocytic leukemia (APL), by a chromosomal translocation t(15;17) involving the retinoic acid receptor alpha (RARalpha) and the promyelocytic gene (PML). The diagnosis and monitoring of promyelocytic sarcoma is a challenge due to the rarity and severity of the disease. We describe a case with several initial sites and without APL. The patient was monitored with regular 18F-FDG PET/CT from diagnosis to complete response. The evolution of PET/CT imageries was compared to the quantification of PML-RARα fusion gene by RQ-PCR. In promyelocytic sarcoma medical care, 18F-FDG PET/CT appears to be an attractive tool for finding targets for biopsy, for the primary staging, for assessing therapeutic response and for detecting early relapse.

Incidental Detection of a Small Cell Lung Cancer by 18F-Choline PET/CT Performed for Recurrent Hyperparathyroidism After Parathyroidectomy.

ABSTRACT: We report the case of a 64-year-old woman with musculoskeletal pain and elevated serum parathyroid hormone who had undergone parathyroidectomy for primary hyperparathyroidism 4 years earlier. An 18F-choline PET/CT scan was performed and incidentally showed an intense uptake in a right upper lobe pulmonary nodule and in the right hilar, mediastinal, and cervical lymph nodes. Histopathological analysis confirmed the diagnosis of a small cell lung cancer. Clinical symptoms and recurrent hyperparathyroidism were therefore consistent with a paraneoplastic syndrome. A complete metabolic response was achieved on 18F-FDG PET/CT scan after chemotherapy.

Usual and Rare Abdominal Location of Giant Cell Arteritis Diagnosed and Follow-up With 18F-FDG PET/CT.

ABSTRACT: Giant cell arteritis is not an uncommon disease, and its extension is furthermore finely assessed with new-generation PET/CT system. 18F-FDG PET/CT is increasingly used in case of large-vessel vasculitis for optimal diagnosis, activity monitoring (even when treated with interleukin 6 receptor inhibitor), and evaluation damage progression. We reported the case of a 61-year-old woman with common giant cell arteritis pattern on 18F-FDG PET/CT (aorta and large arteries) and uptakes in all aorta branches, mainly impressive and uncommon in the abdomen. After 2 years of therapeutic optimization including IV tocilizumab and monitoring with 18F-FDG PET/CT, a complete metabolical response was assessed.

Positron emission tomography for radiotherapy planning in head and neck cancer: What impact?

PET-computed tomography (CT) plays a growing role to guide target volume delineation for head and neck cancer in radiation oncology. Pretherapeutic [18F]FDG PET-CT adds information to morphological imaging. First, as a whole-body imaging modality, it reveals regional or distant metastases that induce major therapeutic changes in more than 10% of the cases. Moreover, it allows better pathological lymph node selection which improves overall regional control and overall survival. Second, locally, it allows us to define the metabolic tumoral volume, which is a reliable prognostic feature for survival outcome. [18F]FDG PET-CT-based gross tumor volume (GTV) is on average significantly smaller than GTV based on CT. Nevertheless, the overlap is incomplete and more evaluation of composite GTV based on PET and GTV based on CT are needed. However, in clinical practice, the study showed that using GTV PET alone for treatment planning was similar to using GTVCT for local control and dose distribution was better as a dose to organs at risk significantly decreased. In addition to FDG, pretherapeutic PET could give access to different biological tumoral volumes - thanks to different tracers - guiding heterogeneous dose delivery (dose painting concept) to resistant subvolumes. During radiotherapy treatment, follow-up [18F]FDG PET-CT revealed an earlier and more important diminution of GTV than other imaging modality. It may be a valuable support for adaptative radiotherapy as a new treatment plan with a significant impact on dose distribution became possible. Finally, additional studies are required to prospectively validate long-term outcomes and lower toxicity resulting from the use of PET-CT in treatment planning.

Nebulised Gadolinium-Based Nanoparticles for a Multimodal Approach: Quantitative and Qualitative Lung Distribution Using Magnetic Resonance and Scintigraphy Imaging in Isolated Ventilated Porcine Lungs.

PURPOSE: This study aims at determining lung distribution of gadolinium-based polysiloxane nanoparticles, AGuIX® (small rigid platform - SRP), as a potential theranostic approach by the pulmonary route. METHODS: First, the aerodynamic size distribution and the aerosol output rate were thoroughly characterized. Then, a multimodal approach using magnetic resonance (MR) and gamma-camera (GC) imaging allows to assess the deposition of the aerosolised nanoparticles in the respiratory tract using isolated ventilated porcine lungs. RESULTS: The SRP has proven to be radiolabelled by radioisotope with a good yield. Crude SRP or radiolabelled ones showed the same aerodynamic size distribution and output as a conventional molecular tracer, as sodium fluoride. With MR and GC imaging approaches, the nebulised dose represented about 50% of the initial dose of nanoparticles placed in the nebuliser. Results expressed as proportions of the deposited aerosol showed approximately a regional aerosol deposition of 50% of the deposited dose in the lungs and 50% in the upper airways. Each technique assessed a homogeneous pattern of deposited nanoparticles in Lungs. MR observed a strong signal enhancement with the SRP, similar to the one obtained with a commonly used MRI contrast agent, gadoterate meglumine. CONCLUSION: As a known theranostic approach by intravenous administration, SRP appeared to be easily aerosolised with a conventional nebuliser. The present work proves that pulmonary administration of SRP is feasible in a human-like model and allows multimodal imaging with MR and GC imaging. This work presents the proof of concept of SRP nebulisation and aims to generate preclinical data for the potential clinical transfer of SRP for pulmonary delivery.