Clinical Performance Comparison of a Long Versus a Short Axial Field-of-View PET/CT Using EARL-Compliant Reconstructions.

PURPOSE: To ensure comparable PET/CT image quality between or within centres, clinical inter-system performance comparisons following European Association of Nuclear Medicine Research Ltd. (EARL) guidelines is required. In this work the performance of the long axial field-of-view Biograph Vision Quadra is compared to its predecessor, the short axial field-of-view Biograph Vision. PROCEDURES: To this aim, patients with suspected tumour lesions received a single weight-based (3 MBq/kg) 2-deoxy-2-[18F]fluoro-D-glucose injection and underwent routine clinical ( ∼ 15 min) scans on the Vision and 3-min scans on the Quadra in listmode in balanced order. Image quality (IQ), image noise (IN), and tumour demarcation (TD) were assessed visually by four nuclear medicine physicians using a 5-point Likert scale and semiquantitative analysis was performed using standardised uptake values (SUVs). Inter-reader agreement was tested using Wilcoxon's signed rank test and the SUVs were statistically compared using a paired t-test. RESULTS: Twenty patients (mean age, 60 years ± 8.8 [standard deviation], 16 male) were enrolled. Inter-reader agreement ranged from good to very good for IQ and IN (0.62 ≤ W ≤ 0.81), and fair for TD (0.29 ≤ W ≤ 0.39). Furthermore, a significant difference was found for TD (p = 0.015) between the systems, showing improved TD for the Quadra. CONCLUSION: This study demonstrates that the Quadra can be used in routine clinical practice with multiple PET/CT systems or in multicentre studies. This system provides comparable diagnostic image quality and semiquantitative accuracy, improved TD, and has the advantage of shorter scan durations.

FDG-PET in the diagnosis of primary progressive aphasia: a systematic review.

Primary progressive aphasia (PPA) is a disease known to affect the frontal and temporal regions of the left hemisphere. PPA is often an indication of future development of dementia, specifically semantic dementia (SD) for frontotemporal dementia (FTD) and logopenic progressive aphasia (LPA) as an atypical presentation of Alzheimer's disease (AD). The purpose of this review is to clarify the value of 2-deoxy-2-[18F]fluoro-D-glucose (FDG)-positron emission tomography (PET) in the detection and diagnosis of PPA. A comprehensive review of literature was conducted using Web of Science, PubMed, and Google Scholar. The three PPA subtypes show distinct regions of hypometabolism in FDG-PET imaging with SD in the anterior temporal lobes, LPA in the left temporo-parietal junction, and nonfluent/agrammatic Variant PPA (nfvPPA) in the left inferior frontal gyrus and insula. Despite the distinct patterns, overlapping hypometabolic areas can complicate differential diagnosis, especially in patients with SD who are frequently diagnosed with AD. Integration with other diagnostic tools could refine the diagnostic process and lead to improved patient outcomes. Future research should focus on validating these findings in larger populations and exploring the therapeutic implications of early, accurate PPA diagnosis with more targeted therapeutic interventions.

Characterization of a Syngeneic Orthotopic Model of Cholangiocarcinoma by [18F]FDG-PET/MRI.

Cholangiocarcinoma (CCA) is a type of primary liver cancer originating from the biliary tract epithelium, characterized by limited treatment options for advanced cases and low survival rates. This study aimed to establish an orthotopic mouse model for CCA and monitor tumor growth using PET/MR imaging. Murine CCA cells were implanted into the liver lobe of male C57BL/6J mice. The imaging groups included contrast-enhanced (CE) MR, CE-MR with static [18F]FDG-PET, and dynamic [18F]FDG-PET. Tumor volume and FDG uptake were measured weekly over four weeks. Early tumor formation was visible in CE-MR images, with a gradual increase in volume over time. Dynamic FDG-PET revealed an increase in the metabolic glucose rate (MRGlu) over time. Blood analysis showed pathological changes in liver-related parameters. Lung metastases were observed in nearly all animals after four weeks. The study concludes that PET-MR imaging effectively monitors tumor progression in the CCA mouse model, providing insights into CCA development and potential treatment strategies.

Unmasking hidden Merkel cell carcinoma recurrences: Three illustrative cases of patients with rising viral oncoprotein antibody levels and challenge of requiring multi-modal imaging to detect clinical disease.

Merkel cell carcinoma (MCC) is a neuroendocrine skin cancer with a high risk of recurrence and metastasis. Regular surveillance through physical exams and imaging studies is crucial for the timely detection of recurrences. MCC patients who produce antibodies to the Merkel cell polyomavirus oncoprotein may benefit from antibody testing in addition to routine imaging surveillance for the early detection of disease recurrence. The clinically available Anti MERKel cell panel (AMERK) is a sensitive tumor marker for Merkel cell polyomavirus positive MCC. Although AMERK is highly sensitive, imaging remains necessary to confirm the location of disease recurrence. MCC exhibits characteristic imaging features, making appropriate imaging modalities, and interpretation important for detection. We present 3 representative patient cases that highlight effective utilization of the AMERK test in addition to imaging for the early detection of MCC recurrence. The rise in the AMERK titer may occur before the disease reaches detectable size on computed tomography scans. Positron emission tomography (PET)-CT can serve as an alternative modality for the early detection of disease. Even subtle abnormalities in 18F-FDG uptake may be significant if accompanied by an increased AMERK titer. Alternative imaging modalities, such as 68Ga-DOTATATE PET-CT and magnetic resonance imaging, can be useful in revealing clinically occult disease in MCC patients. In summary, the AMERK antibody test, alongside imaging, enhances sensitivity in detecting recurrence. By combining these strategies of blood test and imaging, healthcare professionals can identify early signs of MCC recurrence, leading to prompt interventions and improved patient outcomes.

Acute Myelomonoblastic Leukemia (My1/De): A Preclinical Rat Model.

BACKGROUND/AIM: Since acute myeloid leukemias still represent the most aggressive type of adult acute leukemias, the profound understanding of disease pathology is of paramount importance for diagnostic and therapeutic purposes. Hence, this study aimed to explore the real-time disease fate with the establishment of an experimental myelomonoblastic leukemia (My1/De) rat model using preclinical positron emission tomography (PET) and whole-body autoradiography. MATERIALS AND METHODS: In vitro [18F]F-FDG uptake studies were performed to compare the tracer accumulation in the newly cultured My1/De tumor cell line (blasts) with that in healthy control and My1/De bone marrow suspensions. Post transplantation of My1/De cells under the left renal capsule of Long-Evans rats, primary My1/De tumorigenesis, and metastatic propagation were investigated using [18F]F-FDG PET imaging, whole-body autoradiography and phosphorimage analyses. To assess the organ uptake profile of the tumor-carrying animals we accomplished ex vivo biodistribution studies. RESULTS: The tracer accumulation in the My1/De culture cells exceeded that of both the tumorous and the healthy bone marrow suspensions (p<0.01). Based on in vivo imaging, the subrenally transplanted My1/De cells resulted in the development of leukemia in the abdominal organs, and metastasized to the mesenterial and thoracic parathymic lymph nodes (PTLNs). The lymphatic spread of metastasis was further confirmed by the significantly higher %ID/g values of the metastatic PTLNs (4.25±0.28) compared to the control (0.94±0.34). Cytochemical staining of the peripheral blood, autopsy findings, and wright-Giemsa-stained post-mortem histological sections proved the leukemic involvement of the assessed tissues/organs. CONCLUSION: The currently established My1/De model appears to be well-suited for further leukemia-related therapeutic and diagnostic investigations.

Clinical value of whole body 18F-FDG PET/CT imaging in patients with cutaneous melanoma: A multi-center cohort study.

BACKGROUND: 18F-FDG-PET/CT is a valuable tool in the staging and surveillance of cutaneous melanoma; however, recent studies prompt debate on the clinical significance of imaging patients below the lesser trochanter. This study explored two research questions. In patients with a known primary cutaneous melanoma within the standard field of view (SFOV, between the orbits and lesser trochanter), what is the prevalence of metastasis to sites solely within the lower extremities? and, In patients with a known primary cutaneous melanoma within the SFOV what demographic and clinical factors are associated with sole metastasis to the lower extremities? METHODS: A retrospective, multi-centered, observational study of consecutive case reports was conducted. Subjects included 619 patients who underwent extended field of view (EFOV) 18F-FDG-PET/CT (from vertex to toes) for staging and/or follow-up of cutaneous melanoma. Data was collected at three primary healthcare centers in Canada (Nova Scotia, Alberta, and British Columbia). Inclusion criteria were patients >18 years of age, confirmed primary cutaneous melanoma, and a known location of the primary within the SFOV. Patients with primary cutaneous melanoma lesions in lower extremities and previous other cancers were excluded. To determine the prevalence of lesions located below the lesser trochanter, the proportion of such lesions were computed, and 95% confidence intervals ensured a precise estimation of the proportion. RESULTS: 2512 patient charts were reviewed with 619 meeting the inclusion criteria, 298 of these were females. Six percent had metastases in both the lower extremities and sites within the SFOV. The number of subjects who had no metastasis within their SFOV was 361 (58.3%). The number of subjects who presented with confirmed metastasis in the lower extremities without concurrent metastasis in the SFOV region was one (0.58%). Despite a large initial study sample, the number of patients with metastasis in the lower extremities was insufficient to allow correlation of factors associated with risk of spread to the lower extremities. CONCLUSION: Lower extremity 18F-FDG-PET/CT provided additional, relevant clinical data in a sole patient. This finding supports prior research suggesting the prevalence is rare. Future studies should seek to define demographic and clinical factors that predict such rare occurrences, where follow up would be warranted. This study highlights feasibility challenges associated with such investigation.

In Vivo Evaluation of Brain [18F]F-FDG Uptake Pattern Under Different Anaesthesia Protocols.

BACKGROUND/AIM: Since the use of anaesthetics has the drawback of altering radiotracer distribution, preclinical positron emission tomography (PET) imaging findings of anaesthetised animals must be carefully handled. This study aimed at assessing the cerebral [18F]F-FDG uptake pattern in healthy Wistar rats under four different anaesthesia protocols using microPET/magnetic resonance imaging (MRI) examinations. MATERIALS AND METHODS: Post-injection of 15±1.2 MBq of [18F]F-FDG, either while awake or during the isoflurane-induced incubation phase was applied. Prior to microPET/MRI imaging, one group of the rats was subjected to forane-only anaesthesia while the other group was anaesthetised with the co-administration of forane and dexmedetomidine/Dexdor® Results: While as for the whole brain it was the addition of dexmedetomidine/Dexdor® to the anaesthesia protocol that generated the differences between the radiotracer concentrations of the investigated groups, regarding the cortex, the [18F]F-FDG accumulation was rather affected by the way of incubation. To ensure the most consistent and highest uptake, forane-induced anaesthesia coupled with an awake uptake condition seemed to be most suitable method of anaesthetisation for cerebral metabolic assessment. Diminished whole brain and cortical tracer accumulation detected upon dexmedetomidine/Dexdor® administration highlights the significance of the mechanism of action of different anaesthetics on radiotracer pharmacokinetics. CONCLUSION: Overall, the standardization of PET protocols is of utmost importance to avoid the confounding factors derived from anaesthesia.

Preoperative metabolic parameters of 18F-FDG PET/CT are associated with TNM stage and prognosis of colorectal cancer patients.

Background: Colorectal cancer (CRC) is the third most frequent cause of cancer-related death, while tumor/node/metastasis (TNM) stage of American Joint Committee on Cancer is the guideline of making treatment strategy and predicting survival. The aim of this study is to investigate the association of preoperative 2-deoxy-2[18F]fluoro-D-glucose positron emission tomography/computed tomography (18F-FDG PET/CT), TNM stage, and prognosis of patients with CRC. Methods: From September 2016 to August 2022, a total of 132 patients were retrospectively and consecutively enrolled in this cross-sectional study, who were diagnosed as CRC by histopathology and received preoperative 18F-FDG PET/CT. Firstly, the correlation between the metabolic parameters and clinicopathological features of the primary tumors was investigated. Secondly, univariate and multivariate logistic regression analyses were used to estimate the odds ratio of the association between the clinical and metabolic parameters and the advanced TNM stage (stage III-IV). Thirdly, progression-free survival (PFS) was analyzed using Kaplan-Meier curves and Log-rank test. Results: The results revealed that the metabolic tumor volume (MTV) >6.6 cm3 and serum carcinoembryonic antigen (CEA) >5.84 ng/mL were independently associated with advanced TNM stage (P=0.0009, 0.0011, respectively). Larger tumor size, higher tumor-to-liver standardized uptake value ratio, MTV, and total lesion glycolysis (TLG) were significantly correlated with advanced pT stage (stage 4), and higher TLG and MTV were significantly correlated with advanced pN stage (stage 1-2) (P<0.05), while no metabolic parameters were significantly correlated with metastasis status (P>0.05). Higher serum CEA and carbohydrate antigen 19-9 levels were significantly correlated with advanced pT, pN stage, and metastasis status (P<0.05). Patients were followed up for at least 1 year. The MTV >6.6 cm3 was significantly associated with worse PFS (P=0.032). Conclusions: 18F-FDG PET-CT can serve as a noninvasive tool for preoperatively staging CRC. The MTV >6.6 cm3 might be associated with advanced TNM stage and worse PFS.

Different hydration protocols for the quantification of healthy tissue uptake of half-dose 18F-FDG total-body positron emission tomography-computed tomography: a prospective study.

Background: This study aimed to investigate the effects of the volume and time of hydration on the quantification of healthy tissue uptake for 2-deoxy-2-[18F]-fluoro-D-glucose (18F-FDG) total-body positron emission tomography (PET)-computed tomography (CT) with half-dose activity. Methods: This study prospectively enrolled 180 patients who underwent a total-body PET-CT scan 10 min after injection of a half-dose (1.85 MBq/kg) of 18F-FDG. These patients were placed in hydration groups (30 patients in each group) according to different hydration volumes and times: oral hydration with 500 mL of water 20 min before (G1), 5 min after (G2), and 30 min after (G3) the 18F-FDG injection; and oral hydration with 200 mL of water 20 min before (G4), 5 min after (G5), and 30 min after (G6) the 18F-FDG injection. Another 30 patients underwent dynamic imaging without hydration and were used a nonhydration group. The analysis of quantification of healthy tissue uptake included the maximum standardized uptake value (SUVmax) and the mean SUV (SUVmean) of the blood pool and muscle, as well as the SUVmax, SUVmean, and signal-to-noise ratio (SNR) of the liver. Results: The SUVmax of the blood pool (2.33±0.36), liver (3.03±0.42), and muscle (0.81±0.15) was significantly higher in the nonhydration group than in any of the 6 hydrated groups (P<0.05 for all hydration groups vs. nonhydration group). Muscle SUVmax and SUVmean were significantly (P<0.05) lower in G1 and G2 than in G3 and were lower in G4 and G5 than in G6. The SUVmax and SUVmean of the blood pool were significantly (P<0.05) lower in G1 than in G3 and G4 and lower in G3 than in G6. Conclusions: When total-body PET-CT with a half dose of 18F-FDG activity is performed, hydration can significantly affect the quantification of healthy tissue uptake. Oral administration of 500 mL of water 20 min before injection could reduce background radioactivity.

Assessment of anti-GAD65-associated cerebellar ataxia with 18F-FDG cerebellar uptake: ROC analysis.

OBJECTIVE: Anti-glutamic acid decarboxylase 65 (anti-GAD65)-associated neurological disorders include two major phenotypes, namely Stiff person syndrome (SPS) and cerebellar ataxia (CA). Considering the potential for better outcomes with prompt immunotherapy, early detection of CA is crucial. Hence, a non-invasive imaging biomarker to detect CA with high specificity is desired. Herein, we evaluated brain 2-deoxy-2-[18F]fluoro-D-glucose (18F-FDG) PET in detecting CA based on cerebellar uptake using receiver operating characteristic (ROC) analysis and five-fold cross-validation. METHODS: This study was based on STARD 2015 guidelines: thirty patients with anti-GAD65-associated neurological disorders, 11 of whom with CA were studied. Five test sets were created after patients were randomly sorted and divided into 5 equal folds. Each iteration included 24 patients for ROC analysis and 6 patients reserved for testing. The Z scores of left cerebellum, vermis, right cerebellum, and the average of the three regions were used in ROC analysis to determine areas with significant area under the curve (AUC). The cut-off values with high specificity were determined among the 24 patients in each iteration and tested against the reserved 6 patients. RESULTS: Left cerebellum and average of the three regions showed significant AUC above 0.5 in all iterations with left cerebellum being the highest AUC in 4 iterations. Testing the cut-off values of the left cerebellum against the reserved 6 patients in each iteration showed 100% specificity with sensitivities ranging from 0 to 75%. CONCLUSIONS: Cerebellar 18F-FDG PET uptake can differentiate CA phenotypes from patients with SPS with high specificity.

Differentiation of lower limb vasculitis from physiological uptake on FDG PET/CT imaging.

PURPOSES: To analyze the difference of 2-deoxy-2-[18F]fluoro-D-glucose (18F-FDG) uptake between vasculitis and non-vasculitic patients in PET/CT imaging and the factors related to vascular uptake in non-vasculitic patients. To investigate the feasibility of identifying vasculitis of the lower limb and physiological uptake with delayed imaging. PROCEDURES: Among 244 patients who underwent PET/CT examination, imaging features of patients with or without vasculitis were retrospectively analyzed. The factors related to FDG uptake in the lower limb vessels of non-vasculitic patients were analyzed. Another 44 patients with suspected systemic vasculitis in PET/CT were prospectively studied to analyze the efficacy of delayed imaging on differentiating vascular uptake in lower limbs. RESULTS: In PET/CT imaging of patients with vasculitis, involvement of trunk vessels showed segmental or diffuse FDG distribution. Lower limb vascular involvement showed reticular uptake accompanied by nodular or patchy changes. In non-vasculitic patients, vascular uptake mainly showed linear uptake in lower limb vessels and there was no significant difference in uptake degree compared with vasculitis patients. Body weight and interval time were the independent influence factors of vascular uptake in lower limbs of non-vasculitic patients. In delayed imaging, lower limb vasculitis all showed reticular uptake and physiological uptake all showed a linear pattern. ROC analysis showed the change rate of SUVmax (≥ 20%) between early and delayed imaging could delineate physiological vascular uptake with a sensitivity of 100% and specificity of 81.0%. CONCLUSIONS: When PET/CT is used for the diagnosis and classification of vasculitis, the physiological uptake of lower limb vessels may mislead the diagnosis. PET/CT imaging features or delayed imaging improved diagnostic efficacy.

Chronic fluoxetine enhances extinction therapy for PTSD by evaluating brain glucose metabolism in rats: an [18F]FDG PET study.

BACKGROUND: Recent studies suggest that selective serotonin reuptake inhibitors (SSRIs) and exposure therapies have been used to reduced footshock-induced posttraumatic stress disorder (PTSD) symptoms. However, the therapeutic effect of the combination of SSRIs treatment with exposure therapy remains a matter of debate. This study aimed to evaluate these therapeutic effect through the behavioural and the neuroimaging changes by positron emission tomography (PET) in model rats. METHODS: Pavlovian fear conditioning paradigm to establish model rats, and serial PET imaging with 2-deoxy-2-[18F]fluoro-D-glucose ([18F]FDG) was performed during the control, fear-conditioning, and extinction-retrieval phases. The expression of c-Fos was used to identify neural activity. RESULTS: We report that fear conditioning increased glucose metabolism in the right amygdala and left primary visual cortex but decreased glucose metabolism in the left primary somatosensory cortex. After extinction retrieval, there was increased [18F]FDG uptake in the left striatum, left cochlear nucleus and right primary visual cortex but decreased uptake in the anterior cingulate cortex in the extinction group. Fluoxetine increased [18F]FDG uptake in the left hippocampus and right primary visual cortex but decreased uptake in the bilateral primary somatosensory cortex, left primary/secondary motor cortex and cuneiform nucleus. The combined therapy increased [18F]FDG uptake in the left hippocampus, left striatum, right insular cortex, left posterior parietal cortex, and right secondary visual cortex but reduced uptake in the cerebellar lobule. c-Fos expression in the hippocampal dentate gyrus and anterior cingulate cortex in the fluoxetine and combined groups was significantly higher than that in the extinction group, with no significant difference between the two groups. CONCLUSIONS: Chronic fluoxetine enhanced the effects of extinction training in a rat model of PTSD. In vivo PET imaging may provide a promising approach for evaluation chronic fluoxetine treatment of PTSD.

It's Not What You Take Up, It's What You Keep: How Discoveries from Diverse Disciplines Directed the Development of the FDG PET/CT Scan.

Although imaging glucose metabolism with positron emission tomography combined with X-ray CT (FDG-PET/CT) has become a standard diagnostic modality for the discovery and surveillance of malignant tumors and inflammatory processes, its origins extend back to more than a century of notable discoveries in the fields of inorganic and organic chemistry, nuclear physics, mathematics, biochemistry, solute transport physiology, metabolism, and imaging, accomplished by pioneering and driven investigators, of whom at least ten were recipients of the Nobel Prize. These tangled and diverse roots eventually coalesced into the FDG-PET/CT method, that through its many favorable characteristics inherent in the isotope used (18F), the accurate imaging derived from coincidence detection of positron annihilation radiation combined with computed tomography, and the metabolic trapping of 2-deoxy-2-[18F]fluoro-D-glucose (FDG) in tissues, provides safety, sensitivity, and specificity for tumor and inflammation detection. The authors hope that this article will increase the appreciation among its readers of the insight, creativity, persistence, and drive of the many investigators who made this technique possible. This article is followed by a review of the many applications of FDG-PET/CT to the gastrointestinal tract and hepatobiliary system (Mandelkern in Dig Dis Sci 2022).

Atlas of non-pathological solitary or asymmetrical skeletal muscle uptake in [18F]FDG-PET.

Positron emission tomography (PET) using 2-deoxy-2-[18F]fluoro-D-glucose ([18F]FDG) is widely used in oncology and other fields. In [18F]FDG PET images, increased muscle uptake is observed owing exercise load or muscle tension, in addition to malignant tumors and inflammation. Moreover, we occasionally observe non-pathological solitary or unilateral skeletal muscle uptake, which is difficult to explain the strict reason. In most cases, we can interpret them as not having pathological significance. However, it is important to recognize such muscle uptake patterns to avoid misdiagnoses with pathological ones. Therefore, the teaching point of this pictorial essay is to comprehend the patterns of solitary or asymmetrical skeletal muscle uptake seen in routine [18F]FDG-PET scans. As an educational goal, you will be able to mention muscles where intense physiological [18F]FDG uptake can be observed, differentiate between physiological muscle uptake and lesion, and discuss with any physicians or specialists about uncertain muscle uptake.

Developing a clinical and PET/CT volumetric prognostic index for risk assessment and management of NSCLC patients after initial therapy.

BACKGROUND: Currently, individual clinical prognostic variables are used sequentially with risk-stratification after TNM staging in clinical practice for the prognostic assessment of patients with NSCLC, which is not effective for estimating the collective impact of multiple individual variables on patient outcomes. Here, we developed a clinical and PET/CT volumetric prognostic (CPVP) index that integrates the prognostic power of multiple clinical variables and metabolic tumor volume from baseline FDG-PET, for use immediately after definitive therapy. PATIENTS AND METHODS: This retrospective cohort study included 998 NSCLC patients diagnosed between 2004 and 2017, randomly assigned to two cohorts for modeling the CPVP index using Cox regression models examining overall survival (OS) and subsequent validation. RESULTS: The CPVP index generated from the model cohort included pretreatment variables (whole-body metabolic tumor volume [MTVwb], clinical TNM stage, tumor histology, performance status, age, race, gender, smoking history) and treatment type. A clinical variable (CV) index without MTVwb and PET/CT volumetric prognostic (PVP) index without clinical variables were also generated for comparison. In the validation cohort, univariate Cox modeling showed a significant association of the index with overall survival (OS; Hazard Ratio [HR] 3.14; 95% confidence interval [95% CI] = 2.71 to 3.65, p < 0.001). Multivariate Cox regression analysis demonstrated a significant association of the index with OS (HR = 3.13, 95% CI = 2.66 to 3.67, p < 0.001). The index showed greater prognostic power (C-statistic = 0.72) than any of its independent variables including clinical TNM stage (C-statistic ranged from 0.50 to 0.69, all p < 0.003), CV index (C-statistic = 0.68, p < 0.001) and PVP index (C-statistic = 0.70, p = 0.006). CONCLUSIONS: The CPVP index for NSCLC patients has moderately strong prognostic power and is more prognostic than its individual prognostic variables and other indices. It provides a practical tool for quantitative prognostic assessment after initial treatment and therefore may be helpful for the development of individualized treatment and monitoring strategy for NSCLC patients.

Role of Radiomics-Based Baseline PET/CT Imaging in Lymphoma: Diagnosis, Prognosis, and Response Assessment.

Radiomic analysis provides information on the underlying tumour heterogeneity in lymphoma, reflecting the real-time evolution of malignancy. 2-Deoxy-2-[18F] fluoro-D-glucose positron emission tomography ([18F] FDG PET/CT) imaging is recommended before, during, and at the end of treatment for almost all lymphoma patients. This methodology offers high specificity and sensitivity, which can aid in accurate staging and assist in prompt treatment. Pretreatment [18F] FDG PET/CT-based radiomics facilitates improved diagnostic ability, guides individual treatment regimens, and boosts outcome prognosis based on heterogeneity as well as the biological, pathological, and metabolic status of the lymphoma. This technique has attracted considerable attention given its numerous applications in medicine. In the current review, we will briefly describe the basic radiomics workflow and types of radiomic features. Details of current applications of baseline [18F] FDG PET/CT-based radiomics in lymphoma will be discussed, such as differential diagnosis from other primary malignancies, diagnosis of bone marrow involvement, and response and prognostic prediction. We will also describe how this technique provides a unique noninvasive platform to assess tumour heterogeneity. Newly emerging PET radiotracers and multimodality technology will improve diagnostic specificity and further clarify tumor biology and even genetic variations in lymphoma, potentially promoting the development of precision medicine.

PET/MRI and PET/CT Radiomics in Primary Cervical Cancer: A Pilot Study on the Correlation of Pelvic PET, MRI, and CT Derived Image Features.

PURPOSE: To evaluate the correlation of radiomic features in pelvic [2-deoxy-2-18F]fluoro-D-glucose positron emission tomography/magnetic resonance imaging and computed tomography ([18F]FDG PET/MRI and [18F]FDG PET/CT) in patients with primary cervical cancer (CCa). PROCEDURES: Nineteen patients with histologically confirmed primary squamous cell carcinoma of the cervix underwent same-day [18F]FDG PET/MRI and PET/CT. Two nuclear medicine physicians performed a consensus reading in random order. Free-hand regions of interest covering the primary cervical tumors were drawn on PET, contrast-enhanced pelvic CT, and pelvic MR (T2 weighted and ADC) images. Several basic imaging features, standard uptake values (SUVmean, SUVmax, and SUVpeak), total lesion glycolysis (TLG), metabolic tumor volume (MTV), and more advanced texture analysis features were calculated. Pearson's correlation test was used to assess the correlation between each pair of features. Features were compared between local and metastatic tumors, and their role in predicting metastasis was evaluated by receiver operating characteristic curves. RESULTS: For a total of 101 extracted features, 1104/5050 pairs of features showed a significant correlation (ρ ≥ 0.70, p < 0.05). There was a strong correlation between 190/484 PET pairs of features from PET/MRI and PET/CT, 91/418 pairs of CT and PET from PET/CT, 79/418 pairs of T2 and PET from PET/MRI, and 50/418 pairs of ADC and PET from PET/MRI. Significant difference was seen between eight features in local and metastatic tumors including MTV, TLG, and entropy on PET from PET/CT; MTV and TLG on PET from PET/MRI; compactness and entropy on T2; and entropy on ADC images. CONCLUSIONS: We demonstrated strong correlation of many extracted radiomic features between PET/MRI and PET/CT. Eight radiomic features calculated on PET/CT and PET/MRI were significantly different between local and metastatic CCa. This study paves the way for future studies to evaluate the diagnostic and predictive potential of radiomics that could guide clinicians toward personalized patients care.

[Improvement of Cold Artifacts in Body Trunk 18F-FDG PET/CT by Absolute-single scatter simulation: Validation in an Out-of-body High-accumulation Phantom].

PURPOSE: This study aimed to verify whether cold artifacts caused by the gap state between attenuation correction computed tomography (ACCT) and positron emission tomography (PET) data (so-called hot-in-air (HIA) state) in body trunk PET/computer tomography (CT) examinations can be improved by the Absolute-single scatter simulation (SSS), which is a scatter correction method in a phantom experiment using the high-accumulation syringe of out-of-body phantom. METHOD: PET imaging profile curves in the HIA state were evaluated using a high-accumulation syringe that simulated a urinary tract pouch encapsulated with 18F-FDG solution. The hot syringe-to-background ratio (HBR) of the syringe was changed to 5, 7, and 10. Moreover, PET image quality evaluation of the HIA state was performed with a syringe placed on the top of a NEMA IEC body phantom. Six spheres (10-37 mm in diameter) were placed inside the phantom and filled with 18F-FDG solution with a sphere-to-background ratio of 4. The evaluation items of image quality were N10 mm, QH, 10 mm / N10 mm, and recovery coefficient (RC). RESULT: The image quality tended to deteriorate as the HBR of the syringe increased in the relative-SSS, while the effect was small in the Absolute-SSS and the lowest at HBR 10. The RC10 mm of HBR 5 was 0.33 for the Relative-SSS, which was below the criterion for the Relative-SSS, but was 0.5 for the Absolute-SSS, which met the criterion. CONCLUSION: Absolute-SSS significantly improved cold artifacts caused by HIA states on body trunk PET/CT examinations, suggesting that it is highly useful both visually and quantitatively.

Mathematical Models for FDG Kinetics in Cancer: A Review.

Compartmental analysis is the mathematical framework for the modelling of tracer kinetics in dynamical Positron Emission Tomography. This paper provides a review of how compartmental models are constructed and numerically optimized. Specific focus is given on the identifiability and sensitivity issues and on the impact of complex physiological conditions on the mathematical properties of the models.

First case of acrometastases to the wrist reported from penile cancer.

Penile cancer is a rarely diagnosed cancer that affects 0.4%-0.6% of all male population. Metastases to the bones from various human cancers are common; however, acrometastases are extremely rare with the most common primary tumor from lung, kidney, and breast. We report the first case of a patient with acrometastases to the left wrist reported from penile cancer.