Total-body PET Imaging Research Articles

Comparing total-body metabolic PET imaging signatures of lung cancer cachexia to other wasting conditions

Cancer cachexia (CC) is a debilitating wasting condition. While anorexia and muscle wasting are features of cachexia, CC is a distinct and poorly understood metabolic syndrome1. We harnessed preclinical models of lung cancer to study how glucose uptake changes during CC and performed comparative analyses with anorexia and muscle wasting. Lung K-rasG12D/+;Lkb1-/-(KL) mice suffering CC were imaged using [18F]fluorodeoxyglucose (FDG) PET at 15-19% weight loss alongside K-ras wild-type (WT) non-tumour bearing controls. Mice were injected with 12-18MBq of FDG, imaging 80-100 minutes post injection with the Mediso nanoScan® PET/MRI 1T. In non-tumour bearing male animals, we modelled anorexia, muscle wasting, and circulation of cachexia factor GDF15 as follows, respectively: fasted overnight for 20 hr, treated with dexamethasone 21-phosphate (dexa) (2mg/kg, i.p. daily, 21 days) and single injection of recombinant human GDF15 hormone (0.1 mg/kg s.c.). FDG ex vivo biodistribution showed increased uptake in myocardium (p<0.05), brain and liver (both p<0.01) of KL cachexic animals with no significant change in FDG blood pool. Like cachexic KL animals, FDG uptake in fasted animals increased in brain (p<0.0001), perhaps due to increased FDG blood pool. FDG uptake in skeletal muscles and brown adipose tissue decreased (both p<0.05) in fasted state suggesting lower muscle activity and decreased thermogenesis respectively. Dexa-induced muscle atrophy also resulted in decreased FDG uptake in gastrocnemius/soleus muscles (SUVmean 0.63 vehicle vs. 0.45 dexa, p<0.05) but no changes in skeletal muscle FDG uptake were noted in cachexic animals. In contrast to KL animals, GDF15 injection resulted in decreased FDG uptake in myocardium (p<0.05). Overall, the cachexic FDG signature showed differences to other wasting conditions in this mouse model, suggesting different underlying mechanisms. Total-body PET can reveal diverse metabolic wasting states. We aim to elucidate mechanisms of metabolic changes in cachexia to allow metabolic subtyping and personalised treatment options. Please click on the 'PDF' for the full abstract!

Total-body imaging of mu-opioid receptors with [11C]carfentanil in non-human primates

PurposeMu-opioid receptors (MORs) are widely expressed in the central nervous system (CNS), peripheral organs, and immune system. This study measured the whole body distribution of MORs in rhesus macaques using the MOR selective radioligand [11C]carfentanil ([11C]CFN) on the PennPET Explorer. Both baseline and blocking studies were conducted using either naloxone or GSK1521498 to measure the effect of the antagonists on MOR binding in both CNS and peripheral organs.MethodsThe PennPET Explorer was used for MOR total-body PET imaging in four rhesus macaques using [11C]CFN under baseline, naloxone pretreatment, and naloxone or GSK1521498 displacement conditions. Logan distribution volume ratio (DVR) was calculated by using a reference model to quantitate brain regions, and the standard uptake value ratios (SUVRs) were calculated for peripheral organs. The percent receptor occupancy (%RO) was calculated to establish the blocking effect of 0.14 mg/kg naloxone or GSK1521498.ResultsThe %RO in MOR-abundant brain regions was 75–90% for naloxone and 72–84% for GSK1521498 in blocking studies. A higher than 90% of %RO were observed in cervical spinal cord for both naloxone and GSK1521498. It took approximately 4–6 min for naloxone or GSK1521498 to distribute to CNS and displace [11C]CFN from the MOR. A smaller effect was observed in heart wall in the naloxone and GSK1521498 blocking studies.Conclusion[11C]CFN total-body PET scans could be a useful approach for studying mechanism of action of MOR drugs used in the treatment of acute and chronic opioid use disorder and their effect on the biodistribution of synthetic opioids such as CFN. GSK1521498 could be a potential naloxone alternative to reverse opioid overdose.

Advantages and Challenges of Total-Body PET/CT at a Tertiary Cancer Center: Insights from Sun Yat-sen University Cancer Center.

In recent decades, researchers worldwide have directed their efforts toward enhancing the quality of PET imaging. The detection sensitivity and image resolution of conventional PET scanners with a short axial field of view have been constrained, leading to a suboptimal signal-to-noise ratio. The advent of long-axial-field-of-view PET scanners, exemplified by the uEXPLORER system, marked a significant advancement. Total-body PET imaging possesses an extensive scan range of 194 cm and an ultrahigh detection sensitivity, and it has emerged as a promising avenue for improving image quality while reducing the administered radioactivity dose and shortening acquisition times. In this review, we elucidate the application of the uEXPLORER system at the Sun Yat-sen University Cancer Center, including the disease distribution, patient selection workflow, scanning protocol, and several enhanced clinical applications, along with encountered challenges. We anticipate that this review will provide insights into routine clinical practice and ultimately improve patient care.

Intelligent ultrafast total-body PET for sedation-free pediatric [18F]FDG imaging.

This study aims to develop deep learning techniques on total-body PET to bolster the feasibility of sedation-free pediatric PET imaging. A deformable 3D U-Net was developed based on 245 adult subjects with standard total-body PET imaging for the quality enhancement of simulated rapid imaging. The developed method was first tested on 16 children receiving total-body [18F]FDG PET scans with standard 300-s acquisition time with sedation. Sixteen rapid scans (acquisition time about 3 s, 6 s, 15 s, 30 s, and 75 s) were retrospectively simulated by selecting the reconstruction time window. In the end, the developed methodology was prospectively tested on five children without sedation to prove the routine feasibility. The approach significantly improved the subjective image quality and lesion conspicuity in abdominal and pelvic regions of the generated 6-s data. In the first test set, the proposed method enhanced the objective image quality metrics of 6-s data, such as PSNR (from 29.13 to 37.09, p < 0.01) and SSIM (from 0.906 to 0.921, p < 0.01). Furthermore, the errors of mean standardized uptake values (SUVmean) for lesions between 300-s data and 6-s data were reduced from 12.9 to 4.1% (p < 0.01), and the errors of max SUV (SUVmax) were reduced from 17.4 to 6.2% (p < 0.01). In the prospective test, radiologists reached a high degree of consistency on the clinical feasibility of the enhanced PET images. The proposed method can effectively enhance the image quality of total-body PET scanning with ultrafast acquisition time, leading to meeting clinical diagnostic requirements of lesion detectability and quantification in abdominal and pelvic regions. It has much potential to solve the dilemma of the use of sedation and long acquisition time that influence the health of pediatric patients.

The role of dynamic, static, and delayed total-body PET imaging in the detection and differential diagnosis of oncological lesions

ObjectivesCommercialized total-body PET scanners can provide high-quality images due to its ultra-high sensitivity. We compared the dynamic, regular static, and delayed 18F-fluorodeoxyglucose (FDG) scans to detect lesions in oncologic patients on a total-body PET/CT scanner.Materials & methodsIn all, 45 patients were scanned continuously for the first 60 min, followed by a delayed acquisition. FDG metabolic rate was calculated from dynamic data using full compartmental modeling, whereas regular static and delayed SUV images were obtained approximately 60- and 145-min post-injection, respectively. The retention index was computed from static and delayed measures for all lesions. Pearson’s correlation and Kruskal–Wallis tests were used to compare parameters.ResultsThe number of lesions was largely identical between the three protocols, except MRFDG and delayed images on total-body PET only detected 4 and 2 more lesions, respectively (85 total). FDG metabolic rate (MRFDG) image-derived contrast-to-noise ratio and target-to-background ratio were significantly higher than those from static standardized uptake value (SUV) images (P < 0.01), but this is not the case for the delayed images (P > 0.05). Dynamic protocol did not significantly differentiate between benign and malignant lesions just like regular SUV, delayed SUV, and retention index.ConclusionThe potential quantitative advantages of dynamic imaging may not improve lesion detection and differential diagnosis significantly on a total-body PET/CT scanner. The same conclusion applied to delayed imaging. This suggested the added benefits of complex imaging protocols must be weighed against the complex implementation in the future.Clinical relevanceTotal-body PET/CT was known to significantly improve the PET image quality due to its ultra-high sensitivity. However, whether the dynamic and delay imaging on total-body scanner could show additional clinical benefits is largely unknown. Head-to-head comparison between two protocols is relevant to oncological management.

Reducing pediatric total-body PET/CT imaging scan time with multimodal artificial intelligence technology.

This study aims to decrease the scan time and enhance image quality in pediatric total-body PET imaging by utilizing multimodal artificial intelligence techniques. A total of 270 pediatric patients who underwent total-body PET/CT scans with a uEXPLORER at the Sun Yat-sen University Cancer Center were retrospectively enrolled. 18F-fluorodeoxyglucose (18F-FDG) was administered at a dose of 3.7 MBq/kg with an acquisition time of 600s. Short-term scan PET images (acquired within 6, 15, 30, 60 and 150s) were obtained by truncating the list-mode data. A three-dimensional (3D) neural network was developed with a residual network as the basic structure, fusing low-dose CT images as prior information, which were fed to the network at different scales. The short-term PET images and low-dose CT images were processed by the multimodal 3D network to generate full-length, high-dose PET images. The nonlocal means method and the same 3D network without the fused CT information were used as reference methods. The performance of the network model was evaluated by quantitative and qualitative analyses. Multimodal artificial intelligence techniques can significantly improve PET image quality. When fused with prior CT information, the anatomical information of the images was enhanced, and 60s of scan data produced images of quality comparable to that of the full-time data. Multimodal artificial intelligence techniques can effectively improve the quality of pediatric total-body PET/CT images acquired using ultrashort scan times. This has the potential to decrease the use of sedation, enhance guardian confidence, and reduce the probability of motion artifacts.

A cross-staged gantry for total-body PET and CT imaging

Total-body Positron Emission Tomography (PET) scanning is a promising new method for rapidly acquiring comprehensive wide-volume metabolic data with a lower radiation dosage compared to discrete whole-body PET imaging. PET scanners are generally used with Computed Tomography (CT) scanners to precisely understand tumor location and composition with the help of anatomical images. However, PET/CT sequential imaging methods for simultaneous total-body imaging are impractical for claustrophobic patients due to the enclosed gantry design and require large examination rooms because of the need for an exceptionally long patient table. To address this challenge, the Jagiellonian- -PET Tomography (J-PET) Total-body scanner employs an innovative approach: utilizing both PET and CT devices on the same patient table but from different axes. The motion system of the J-PET Total Body scanner requires custom linear stages to move both PET and CT gantries. In this study, a novel cross-staged linear guiding solution is proposed by combining scanners on intersecting separable stages. The proposed sliding system is a combination of different machine elements and will be produced for the J-PET Total-body PET/CT Scanner. Concept designs are shown, and the proposed system is described. The application of the system for the J-PET total-body PET/CT scanner is discussed. The proposed solution is still in the development phase. The system holds the potential to achieve combining CT and PET scanners from different axes and enables motion artifact-free imaging for total-body imaging.

Practical Considerations for Total-Body PET Acquisition and Imaging.

The world's first total-body PET/CT system has been in routine clinical and research use at UC Davis since 2019. The uEXPLORER total-body PET scanner has been designed with an axial field-of-view long enough to completely encompass most human subjects (194cm or 76 inches long), allowing for a 15-68-fold gain in the PET signal collection efficiency over conventional PET scanners. A high-sensitivity PET scanner that can image the entire subject with a single bed position comes with new benefits and challenges to consider for efficient and practical use. In this chapter, we discuss the common clinical and research imaging protocols implemented at our institution, along with the appropriate technical and practical considerations of total-body PET imaging.

A083 The Effects of Gastric Bypass on the Brain-Liver Axis as Studied by Total-body Dynamic PET Imaging: A Pilot Study

A083 The Effects of Gastric Bypass on the Brain-Liver Axis as Studied by Total-body Dynamic PET Imaging: A Pilot Study

Metastatic prostate adenocarcinoma with neuroendocrine differentiation on 18F-FDG PET/CT, 68Ga-PSMA PET/CT and 68Ga-DOTA TATE PET/CT with injected ultra-low-activity

We report the case of a 69-year-old man with prostate cancer (PC), retroperitoneal lymph node metastases, and bone metastases, who received hormone therapy to date. The patient underwent a puncture biopsy in the third thoracic vertebra and was diagnosed with metastatic prostatic acinar adenocarcinoma with partly neuroendocrine differentiation. The patient underwent three different total-body PET/CT scans at ultra-low activities to evaluate tumor heterogeneity by multiple tracers (68Ga-PSMA PET/CT, 18F-FDG PET/CT, 68Ga-DOTA TATE PET/CT). Our case suggests that total-body PET imaging with 194-cm axial FOV using a 10×reduction in injected activity can yield images that meet diagnostic needs and that the results of multi-tracer analysis are encouraging for revealing the characteristics of each lesion.

The feasibility of ultralow-activity 18F-FDG dynamic PET imaging in lung adenocarcinoma patients through total-body PET/CT scanner

To explore the feasibility of ultralow-activity 18F-FDG total-body dynamic PET imaging for clinical practice in patients with lung adenocarcinoma. Eight of 18 patients were randomly injected with 18F-FDG with full activity (3.7MBq/kg) for total-body dynamic PET imaging, while 10 received one-tenth activity (0.37MBq/kg). The generated time-to-activity curves (TACs) according to the regions of interest (ROIs) were processed by PMOD through standard FDG two-tissue compartment model fitting. The kinetic constant rates (K1, K2, K3, and Ki), radiation dose, prompt counts, and data storage size were analysed between the full- and ultralow-activity groups. The SUVmax-Tumour/SUVmax-Liver and SUVmax-Tumour/SUVmax-Muscle on static PET images were also assessed. Each of the fitted models has a satisfactorygoodness-of-fit with R2 greater than 0.9 except 3 (3/234) in ultralow-activity group, where one in pancreas (R2 = 0.851), another one in muscle (R2 = 0.868), and the third one in bone marrow (R2 = 0.895). All the fitted models in the full-activity group had a better goodness-of-fit than those in the ultralow-activity group. However, no significant differences were found in any of the kinetic metrics or image quality between the two groups except in the reduction of radiation dose and data storage size. The 10 × reduction of injected 18F-FDG could achieve comparable kinetic metrics and T/N ratios by total-body dynamic PET imaging in lung adenocarcinoma patients. Ultralow-activity total-body PET imaging is feasible for clinical practice in oncological patients without obesity, especially in dynamic PET scanning.

Total-Body PET: Will It Change Science and Practice?

Total-body (TB) PET scanners with an axial field of view (AFOV) of at least 60 cm can image dynamic radiopharmaceutical distributions in the whole body. Although the benefits of the fine temporal sampling and dramatic increase in system sensitivity afforded by TB PET imaging have been postulated for

Dynamic 18F-FDG Total Body PET Imaging as a Predictive Marker of Induction Chemo-Immunotherapy Followed by Concurrent Chemoradiotherapy Response in Locally Advanced Non-Small Cell Lung Cancer

Purpose/Objective(s)The purpose of this study was to evaluate the efficacy of dynamic 18F-FDG total body PET imaging as a predictive maker of induction chemo-immunotherapy followed by concurrent chemoradiotherapy (CCRT) response in locally advanced non-small cell lung cancer (LA-NSCLC) by a prospective study.Materials/MethodsStage IIIA-IIIC NSCLC patients were prospectively enrolled in a prospective total body PETCT study (NCT04654234, GASTO-1067) and a randomized phase II clinical trial (NCT04085250) between September 2020 and December 2020. Patients underwent a dynamic total-body 18F-FDG PET/CT scan before any treatment, after 2 cycles of induction chemo-immunotherapy (docetaxel + cisplatin + nivolumab), then after CCRT. The primary lung tumor, metastatic regional lymph node and inflammatory lymph node before and after treatment were manually delineated by a nuclear medicine physician and a radiation oncologist. Total Body PET was acquired between 0 – 60 mins after the injection of FDG from the subject's feet. Patients was separated into high dynamic FDG metabolic (H-DFM) group and low DFM(L-DFM) group by the scatter plot of SUV-mean and Ki-mean of baseline scan for primary lung tumor. We compared lesion heterogeneity and different image-derived PET metrics including the metabolic tumor volume (MTV), SUV total lesion glycolysis (SUV-TLG), Patlak-derived influx rate constant (Ki) TLG (Ki-TLG).ResultsFifteen patients completed three scans (before treatment, after induction chemo-immunotherapy, after CCRT). Eight patients were in H-DFM group and 7 in L-DFM group by baseline scan. Patients in H-DFM group had significant decreased levels of MTV (P < 0.001), SUV-TLG (P < 0.001) and Ki-TLG (P < 0.001) both in primary lung tumor and metastatic lymph node by the induction chemo-immunotherapy and CCRT. However, patients in L-DFM group only had a significant reduction of MTV in primary lung tumor (P < 0.05). There was no significant difference in the MTV of metastatic lymph node (P > 0.5), the SUV-TLG (P > 0.5) and Ki-TLG (P > 0.5) of primary lung tumor and metastatic lymph node during the treatment course in L-DFM group.ConclusionPatients in H-DFM group had the better treatment response of induction chemo-immunotherapy and CCRT with significant decreased levels of MTV, SUV-TLG and Ki-TLG. Dynamic 18F-FDG Total body PET Imaging could be regarded as a potential predictive marker of induction chemo-immunotherapy and CCRT response in the setting of LA-NSCLC. The purpose of this study was to evaluate the efficacy of dynamic 18F-FDG total body PET imaging as a predictive maker of induction chemo-immunotherapy followed by concurrent chemoradiotherapy (CCRT) response in locally advanced non-small cell lung cancer (LA-NSCLC) by a prospective study. Stage IIIA-IIIC NSCLC patients were prospectively enrolled in a prospective total body PETCT study (NCT04654234, GASTO-1067) and a randomized phase II clinical trial (NCT04085250) between September 2020 and December 2020. Patients underwent a dynamic total-body 18F-FDG PET/CT scan before any treatment, after 2 cycles of induction chemo-immunotherapy (docetaxel + cisplatin + nivolumab), then after CCRT. The primary lung tumor, metastatic regional lymph node and inflammatory lymph node before and after treatment were manually delineated by a nuclear medicine physician and a radiation oncologist. Total Body PET was acquired between 0 – 60 mins after the injection of FDG from the subject's feet. Patients was separated into high dynamic FDG metabolic (H-DFM) group and low DFM(L-DFM) group by the scatter plot of SUV-mean and Ki-mean of baseline scan for primary lung tumor. We compared lesion heterogeneity and different image-derived PET metrics including the metabolic tumor volume (MTV), SUV total lesion glycolysis (SUV-TLG), Patlak-derived influx rate constant (Ki) TLG (Ki-TLG). Fifteen patients completed three scans (before treatment, after induction chemo-immunotherapy, after CCRT). Eight patients were in H-DFM group and 7 in L-DFM group by baseline scan. Patients in H-DFM group had significant decreased levels of MTV (P < 0.001), SUV-TLG (P < 0.001) and Ki-TLG (P < 0.001) both in primary lung tumor and metastatic lymph node by the induction chemo-immunotherapy and CCRT. However, patients in L-DFM group only had a significant reduction of MTV in primary lung tumor (P < 0.05). There was no significant difference in the MTV of metastatic lymph node (P > 0.5), the SUV-TLG (P > 0.5) and Ki-TLG (P > 0.5) of primary lung tumor and metastatic lymph node during the treatment course in L-DFM group. Patients in H-DFM group had the better treatment response of induction chemo-immunotherapy and CCRT with significant decreased levels of MTV, SUV-TLG and Ki-TLG. Dynamic 18F-FDG Total body PET Imaging could be regarded as a potential predictive marker of induction chemo-immunotherapy and CCRT response in the setting of LA-NSCLC.

Can the BMI-based dose regimen be used to reduce injection activity and to obtain a constant image quality in oncological patients by 18F-FDG total-body PET/CT imaging?

PET image quality is influenced by the patient size according to the current guideline. The study aimed to propose an optimized dose regimen to yield a constant image quality independent of patient habitus to meet the clinical needs. A first patient cohort of 78 consecutive oncological patients (59.7 ± 13.7years) who underwent a total-body PET/CT scan were retrospectively enrolled to develop the regimen. The patients were randomly distributed in four body mass index (BMI) groups according to the World Health Organization (WHO) criteria. The liver SNR (signal-to-noise ratio, SNRL) was obtained by manually drawing regions of interest (ROIs) and normalized (SNRnorm) by the product of injected activity and acquisition time. Fits of SNRnorm against different patient-dependent parameters were performed to determine the best correlating parameter and fit method. A qualitative assessment on image quality was performed using a 5-point Likert scale to determine the acceptable threshold of SNRL. Thus, an optimized regimen was proposed and validated by a second patient cohort consisted of prospectively enrolled 38 oncological patients. The linear fit showed SNRnorm had the strongest correlation (R2 = 0.69) with the BMI than other patient-dependent parameters and fit method. The qualitative assessment indicated a SNRL value of 14.0 as an acceptable threshold to achieve sufficient image quality. The optimized dose regimen was determined as a quadratic relation with BMI: injected activity (MBq) = 39.2 (MBq)/(- 0.03*BMI + 1.49)2. In the validation study, the SNRL no longer decreased with the increase of BMI. There was no significant difference of the image quality regarding the value of SNRL between different BMI groups (p > 0.05). In addition, the injected activity was reduced by 75.6 ± 2.9%, 72.1 ± 4.0%, 67.1 ± 4.4%, and 64.8 ± 3.5% compared with the first cohort for the four BMI groups, respectively. The study proposed a quadratic relation between the 18F-FDG injected activity and the patient's BMI for total-body 18F-FDG PET imaging. In this regimen, the image quality can maintain in a constant level independent of patient habitus and meet the clinical requirement with a reduced injected activity.

Dynamic 18F-FDG Total body PET Imaging as a predictive marker of induction chemo-immunotherapy response in locally advanced non-small cell lung cancer.

e20551 Background: The purpose of this study was to evaluate the efficacy of dynamic 18F-FDG total body PET imaging as a predictive maker of induction chemo-immunotherapy response in locally advanced non-small cell lung cancer(NSCLC) by a prospective study. Methods: Stage IIIA-IIIC NSCLC patients were prospectively enrolled in a prospective total body PETCT study ( NCT04654234, GASTO-1067) and a randomized phase II clinical trial ( NCT04085250) between September 2020 and December 2020. All patients underwent a dynamic total-body 18F-FDG PET/CT scan before any treatment and after 2 cycles of induction chemo-immunotherapy (docetaxel+cisplatin+nivolumab). The primary lung tumor, metastatic regional lymph node and inflammatory lymph node before and after treatment were manually delineated by a nuclear medicine physician and a radiation oncologist. Total Body PET was acquired between 0 – 60 mins after the injection of FDG from the subject’s feet. Patients was separated into high dynamic FDG metabolic (H-DFM) group and low DFM(L-DFM) group by the scatter plot of SUV-mean and Ki-mean of primary lung tumor. We compared lesion heterogeneity and different image-derived PET metrics including the metabolic tumor volume(MTV), SUV total lesion glycolysis(SUV-TLG), Patlak-derived influx rate constant (Ki) TLG (Ki-TLG). Results: Fifteen patients were analyzed, 8 patients was in H-DFM group and 7 in L-DFM group. Patients in H-DFM group had significant decreased levels of MTV(p &lt; 0.001), SUV-TLG(p &lt; 0.001) and Ki-TLG(p &lt; 0.001) both in primary lung tumor and metastatic lymph node by the induction chemo-immuotherapy. However, patients in L-DFM group only had a significant reduction of MTV in primary lung tumor(p &lt; 0.05). There was no significant difference in the MTV of metastatic lymph node(p &gt; 0.5), the SUV-TLG(p &gt; 0.5) and Ki-TLG(p &gt; 0.5) of primary lung tumor and metastatic lymph node, before and after induction chemo-radiotherapy. Conclusions: Patients in H-DFM group had the better treatment response of induction chemo-immunotherapy with significant decreased levels of MTV, SUV-TLG and Ki-TLG. Dynamic 18F-FDG Total body PET Imaging could be regard as a potential predictive marker of induction chemo-immunotherapy response in the setting of LA-NSCLC.

Total Body PET Imaging From Mice to Humans

Small animal PET scanning is destined to offer programs of the pre-clinical development of paradigms and protocols that are translatable for undertaking “systems biology” research in humans using total body PET Scanning.

Total-Body PET Imaging for up to 30 Days After Injection of 89Zr-Labeled Antibodies.

See the associated article on page [453][1]. After the continued efforts toward the development of PET scanners over the last several decades, a major milestone was achieved with the recent completion of total-body PET scanners. Both clinical and preclinical total-body PET scanners have been

First Human Imaging Studies with the EXPLORER Total-Body PET Scanner.

Within the EXPLORER Consortium, the construction of the world's first total-body PET/CT scanner has recently been completed. The 194-cm axial field of view of the EXPLORER PET/CT scanner is sufficient to cover, for the first time, the entire human adult body in a single acquisition in more than 99% of the population and allows total-body pharmacokinetic studies with frame durations as short as 1 s. The large increase in sensitivity arising from total-body coverage as well as increased solid angle for detection at any point within the body allows whole-body 18F-FDG PET studies to be acquired with unprecedented count density, improving the signal-to-noise ratio of the resulting images. Alternatively, the sensitivity gain can be used to acquire diagnostic PET images with very small amounts of activity in the field of view (25 MBq, 0.7 mCi or less), with very short acquisition times (∼1 min or less) or at later time points after the tracer's administration. We report here on the first human imaging studies on the EXPLORER scanner using a range of different protocols that provide initial evidence in support of these claims. These case studies provide the foundation for future carefully controlled trials to quantitatively evaluate the improvements possible through total-body PET imaging.

NTCT-04SPINAL CORD TOXICITY FROM INTRATHECAL CHEMOTHERAPY: A CASE WITH CLINICOPATHOLOGIC CORRELATION

We report antemortem pathologic and neuroimaging findings of severe myelotoxicity from intrathecal chemotherapy in a case of blastic plasmacytoid dendritic cell neoplasm (BPDCN) complicated by leptomeningeal disease. A 73 year old male was diagnosed with BPDCN after fine needle aspiration of an enlarged cervical lymph node. Total body PET imaging revealed extensive systemic hypermetabolic lymphadenopathy and a staging lumbar puncture was positive for malignant cells. He was treated with etoposide, vincristine, doxorubicin, cyclophosphamide, prednisone (EPOCH) and five doses of intrathecal cytosine arabinoside with the last dose administered on 2 months after diagnosis with CSF clearing. One year later, he developed progressive lower extremity weakness, numbness and bowel/bladder dysfunction. Lumbar spine imaging 4 weeks later revealed subtle linear enhancement along the cauda equina and within the dependent thecal sac, but cervical and thoracic spine MRI at this time were unremarkable. CSF showed atypical lymphoid cells and an Ommaya reservoir was placed. Intrathecal chemotherapy with methotrexate and cytarabine was started. Subsequent CSF analysis showed no malignant cells. However, the patient continued to have progressive ascending weakness and numbness, and his neurologic condition progressed to tetraplegia, low of bowel and bladder control and severe sensory loss, especially to vibration and joint position modalities. Spine MRI showed high signal intensity involving the posterior columns diffusely in the cervico-thoracic spinal cord. Metabolic and infectious work up was negative. A subsequent biopsy of the posterior columns of the lower thoracic spinal cord demonstrated cord destruction with profuse macrophage infiltration without evidence of malignant cells or microorganisms. Treatment with folate and cyanocobalamin resulted in no improvement, and the patient elected for palliative care only. This case illustrates central nervous system involvement by a rare myeloid tumor and demonstrates neuroimaging and unique antemortem pathology of intrathecal chemotherapy-induced myelotoxicity.

Carcinomas of the ampulla of vater and the duodenum.

<b>2695</b> <h3><b>Introduction:</b></h3> <b>This exhibit explores the utility of FDG PET in renal cell carcinoma subtypes. Additionally, the use of FDG in Total Body PET imaging of renal cancer will also be discussed.</b> <b>Unlike its routine use in imaging of other malignancies, 18F-fluorodeoxyglucose PET/CT has limited application in renal cell carcinoma (RCC). This is due to the kidneys9 natural excretion of FDG, which lowers the contrast between renal lesions and normal tissue, potentially obscuring or masking renal tumors. Despite its drawbacks, FDG PET imaging of kidney cancers has certain benefits that are worth investigating. In individuals with recurrent or metastatic RCCs, hybrid PET/CT was demonstrated to have a greater sensitivity and specificity. FDG PET scans have also been demonstrated to be effective in monitoring response to therapy to tyrosine kinase inhibitors (TKIs) in advanced RCC; PET/CT is therefore being utilized more often to assess therapeutic response to TKIs. Additionally, FDG PET has greater sensitivity and accuracy for detecting renal metastases to the bone than a bone scan.</b> <h3><b>Methods:</b></h3> <b>This exhibit aims to provide an overview of the key conventional and novel applications of FDG-PET in various kidney cancers imaging including the use of FDG-PET in a) primary RCC, b) metastatic RCC c) type II papillary and sarcomatoid d) staging of RCC e) assessing treatment response. Additionally, we will explore the utilization of new technologies such as Total Body PET (TB-PET) that are more sensitive and allow for opportunities for delayed imaging.</b> <h3><b>Results:</b></h3> <b>Advantages of FDG PET/CT imaging of RCC subtype</b> <b>FDG PET/CT for prediction prognosis of RCC</b> <b>Delayed imaging and multi-time point imaging</b> <b>Beyond multi-time point imaging: Utility of TB-PET in renal cancer dynamic imaging and patlak modeling to extract kinetic information and capture the complete time course of 18F-FDG diffusion throughout the body.</b> <h3><b>Conclusions:</b></h3> <b>FDG PET/CT is not routinely done in the majority of primary RCCs, however, some RCC subtypes are extremely receptive to the agent. Delayed imaging or multi-time point imaging is also an area that has been explored but currently has low adoption clinically. FDG PET may be beneficial for preoperative staging in high-risk, larger individuals, and is especially useful when conventional non-contrast CT images are negative or there is a suspected acute or subacute tumor thrombus. FDG PET/CT is increasingly being utilized to assess targeted molecular therapy such as Tyrosine Kinase inhibitors (TKI) in metastatic RCC. </b>