Total-body PET Research Articles

P394 FROM A PET THE FIRST AND UNEXPECTED DIAGNOSTIC ORIENTATION

Abstract Introduction Nuclear medicine plays an important role in the diagnosis and treatment of numerous pathologies. In the cardiology field it can be used to obtain a lot of information about ischemic heart disease, infiltrative heart disease and inflammatory and infectious diseases such as endocarditis. The greatest impact in the field of these latter pathologies was obtained using F–fluorodeoxyglucose (FDG) in the study of patients with implantable electronic devices and replaced valves or valve prostheses. In this regard, I report the case of a patient with results of valve tube implantation in which a PET performed to investigate an inflammatory pathology has allowed to make a diagnosis of endocarditis. Discussion The case concerns a 66–year–old man subjected to intervention of Bentall for type A aortic dissection (in 2015); chronic aortic dissection remains (Stanford B). Diabetic with chronic renal failure and COPD. Recovered in medicine for low back pain, dysuria and episodes of chills without pyrexia. High inflammatory indices but with urine culture and negative blood cultures performed on isolated febrile peak. CT scan of the chest negative for phlogistic localizations and for intense rachialgia in the suspicion of spondylodiscitis is subjected to total body PET that shows accumulation of radio compound in the first tract of the ascending aorta with greater anterior focality: hyper fixation is associated at the level of the lower limiter of L4 and L5. With these results therefore posed the suspicion of endocarditis for which started to perform transthoracic echocardiogram that did not identify certain pathological elements and transesophageal elements that instead showed suggestive images for endocarditic vegetation in aortic mechanical prosthesis (intravalvular mobile filiform appearance) and on the atrial side of the tricuspid valve (“soft” appearance of large dimensions). It is not associated with valvular dysfunction. After the echocardiographic finding, therapy with daptomycin in addition to piperacillin/tazobactam is initiated and the patient transferred to the infectious diseases department. Conclusions Bacterial endocarditis in particular in patients undergoing cardiac surgery or wearing implantable devices is often characterized by unusual clinical presentation as in this case, so it is not excessive to resort to second–level imaging such as transesophageal echocardiography and nuclear cardiology diagnostics.

Blanching Defects at the Pressure Points: Observations from Dynamic Total-Body PET/CT Studies.

Total-body PET/CT allows simultaneous acquisition of all the body parts in a single bed position during the radiotracer uptake phase. Dynamic imaging protocols employing total-body PET could demonstrate findings that may not have been previously visualized or described using conventional PET/CT scanners. We examined the characteristics of blanching defects, areas of markedly reduced (partial defect) or absent (complete defect) radiotracer uptake seen at the skin/subcutaneous tissues opposite the bony prominences at pressure points. Methods: In this observational study, 77 participants underwent dynamic total-body PET/CT imaging using 18F-FDG (Group 1, N = 47, 60-min dynamic, arms-down, divided into 3 subgroups according to the injected dose) or 18F-fluciclovine (Group 2, N = 30, 25-min dynamic, arms above the head). 40 out of 47 participants in Group 1 were re-imaged at 90 min after being allowed off the scanning table. Blanching defects, partial or complete, were characterized opposite the bony prominences at 7 pressure points (the skull, scapula, and calcaneus bilaterally, as well as the sacrum). Association of the blanching defects with different clinical and technical characteristics were analyzed using uni- and multi-variate analyses. Results: A total of 124 blanching defects were seen in 68 out of 77 (88%) participants at one or more pressure points. Blanching defects were higher, on average, in Group 2 participants (3.5±1.7) compared to Group 1 (2.1±1.4; P <0.001), but it did not vary within Group 1 for different 18F-FDG dose subgroups. All defects resumed normal pattern on delayed static (90-min) images except for 14 partial defects. No complete blanching defects were seen on the 90-min images. By multivariate analysis, arm positioning above the head was associated with skull defects; scapular and sacral defects were significantly more encountered in men and with lower BMI, while calcaneal defects could not be associated to any factor. Conclusion: Blanching defects opposite the bony pressure points are common on dynamic total-body PET/CT images using different radiopharmaceuticals and injection doses. Their appearance should not be immediately interpreted as an abnormality. The current findings warrant further exploration in a prospective setting and may be utilized to study various mechano-pathologic conditions, such as pressure ulcers.

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

Advantages and Applications of Total-Body PET Scanning.

Recent studies have focused on the development of total-body PET scanning in a variety of fields such as clinical oncology, cardiology, personalized medicine, drug development and toxicology, and inflammatory/infectious disease. Given its ultrahigh detection sensitivity, enhanced temporal resolution, and long scan range (1940 mm), total-body PET scanning can not only image faster than traditional techniques with less administered radioactivity but also perform total-body dynamic acquisition at a longer delayed time point. These unique characteristics create several opportunities to improve image quality and can provide a deeper understanding regarding disease detection, diagnosis, staging/restaging, response to treatment, and prognostication. By reviewing the advantages of total-body PET scanning and discussing the potential clinical applications for this innovative technology, we can address specific issues encountered in routine clinical practice and ultimately improve patient care.

Perspectives d’utilisation clinique de la tomographie par émission de positons grand-champ (TEP-GC)

In the last decade, PET scanners have benefited from new technologies such as TOF support, PSF correction and SiPM detectors. More recently, the increase of detector number allowed an axial FOV as large as a human body length in total-body PET (TB-PET) innovative systems. Two different scanners called Quadra© and uEXPLORER© have been respectively proposed by Siemens Healthineers and United Imaging Healthcare. These TB-PET have two major advantages over actual systems on the market: a gain in detection sensitivity and a possibility of whole-body dynamic multiple organs analysis [1,2]. More than reducing drastically the acquisition duration and/or injected activities, these systems open up very interesting clinical perspectives to address specific issues encountered in routine clinical practice and thus improve patient care. We aimed in this brief communication to highlight some situations for which a TB-PET might help to settle current clinical issues.

Monte Carlo evaluation of hypothetical long axial field-of-view PET scanner using GE Discovery MI PET front-end architecture.

The development of total-body PET scanners is of growing interest in the PET community. Investigation into the imaging properties of a hypothetical extended axial field-of-view (AFOV) GE Healthcare SiPM-based Discovery MI (DMI) system architecture has not yet been performed. In this work, we assessed its potential as a whole-body scanner using Monte Carlo simulations. The aim of this work was to (1) develop and validate a Monte Carlo model of a four-ring scanner and (2) extend its AFOV up to 2m to evaluate performance gain through NEMA-based evaluation. The DMI four-ring geometry and its pulse digitization scheme were modeled within the GATE Monte Carlo platform using published literature. The GATE scanner model was validated by comparing results against published NEMA performance measurements. Following the validation of the four-ring model, the model was extended to simulate 8-, 20-, 30-, and 40-ring systems. Spatial resolution, sensitivity, NECR, and scatter fraction were characterized with modified NEMA NU-2 2018 standards; however, the image quality measurements were not acquired due to computational limitations. Spatial resolutions were simulated for all scanner ring configurations using point sources to examine the effects of parallax errors. NEMA count rates were estimated using a standard 70cm scatter phantom and an extended version of scatter phantom of length 200cm with (1-800) MBq of 18 F for all scanners. Sensitivity was evaluated using NEMA methods with a 70cm standard and a 200cm long line source. The average FWHM of the radial/tangential/axial spatial resolution reconstructed with filtered back-projection at 1 and 10cm from the scanner center were 3.94/4.10/4.41mm and 5.29/4.89/5.90mm for the four-ring scanner. Sensitivity was determined to be 14.86cps/kBq at the center of the FOV for the four-ring scanner using a 70cm line source. Sensitivity enhancement up to 21-fold and 60-fold were observed for 1 and 2m AFOV scanners compared to four-ring scanner using a 200cm long line source. Spatial resolution simulations in a 2m AFOV scanner suggest a maximum degradation of ∼23.8% in the axial resolution compared to the four-ring scanner. However, the transverse resolution was found to be relatively constant when increasing the axial acceptance angle up to ±70°. The peak NECR was 212.92 kcps at 22.70 kBq/ml with a scatter fraction of 38.9% for a four-ring scanner with a 70cm scatter phantom. Comparison of peak NECR using the 200cm long scatter phantom relative to the four-ring scanner resulted in a NECR gain of 15 for the 20-ring and 28 for the 40-ring geometry. Spatial resolution, sensitivity, and scatter fraction showed an agreement within ∼7% compared with published measured values. The four-ring DMI scanner simulation was successfully validated against published NEMA measurements. Sensitivity and NECR performance of extended 1 and 2 m AFOV scanners based upon the DMI architecture were subsequently simulated. Increases in sensitivity and count-rate performance are consistent with prior simulation studies utilizing extensions of the Siemens mCT architecture and published NEMA measurements with the uEXPLORER system.

Potential and Most Relevant Applications of Total Body PET/CT Imaging.

The introduction of total body (TB) PET/CT instruments over the past 2 years has initiated a new and exciting era in medical imaging. These instruments have substantially higher sensitivity (up to 68 times) than conventional modalities and therefore allow imaging the entire body over a short period. However, we need to further refine the imaging protocols of this instrument for different indications. Total body PET will allow accurate assessment of the extent of disease, particularly, including the entire axial and appendicular skeleton. Furthermore, delayed imaging with this instrument may enhance the sensitivity of PET for some types of cancer. Also, this modality may improve the detection of venous thrombosis, a common complication of cancer and chemotherapy, in the extremities and help prevent pulmonary embolism. Total body PET allows assessment of atherosclerotic plaques throughout the body as a systematic disease. Similarly, patients with widespread musculoskeletal disorders including both oncologic and nononcologic entities, such as degenerative joint disease, rheumatoid arthritis, and osteoporosis, may benefit from the use of TB-PET. Finally, quantitative global disease assessment provided by this approach will be superior to conventional measurements, which do not reflect overall disease activity. In conclusion, TB-PET imaging may have a revolutionary impact on day-to-day practice of medicine and may become the leading imaging modality in the future.

Efficient Delay Correction for Total-Body PET Kinetic Modeling Using Pulse Timing Methods.

Quantitative kinetic modeling requires an input function. A noninvasive image-derived input function (IDIF) can be obtained from dynamic PET images. However, a robust IDIF location (e.g., aorta) may be far from a tissue of interest, particularly in total-body PET, introducing a time delay between the IDIF and the tissue. The standard practice of joint estimation (JE) of delay, along with model fitting, is computationally expensive. To improve the efficiency of delay correction for total-body PET parametric imaging, this study investigated the use of pulse timing methods to estimate and correct for delay. Methods: Simulation studies were performed with a range of delay values, frame lengths, and noise levels to test the tolerance of 2 pulse timing methods-leading edge (LE) and constant fraction discrimination and their thresholds. The methods were then applied to data from 21 subjects (14 healthy volunteers, 7 cancer patients) who underwent a 60-min dynamic total-body 18F-FDG PET acquisition. Region-of-interest kinetic analysis was performed and parametric images were generated to compare LE and JE methods of delay correction, as well as no delay correction. Results: Simulations demonstrated that a 10% LE threshold resulted in biases and SDs at tolerable levels for all noise levels tested, with 2-s frames. Pooled region-of-interest-based results (n = 154) showed strong agreement between LE (10% threshold) and JE methods in estimating delay (Pearson r = 0.96, P < 0.001) and the kinetic parameters vb (r = 0.96, P < 0.001), Ki (r = 1.00, P < 0.001), and K1 (r = 0.97, P < 0.001). When tissues with minimal delay were excluded from pooled analyses, there were reductions in vb (69.4%) and K1 (4.8%) when delay correction was not performed. Similar results were obtained for parametric images; additionally, lesion Ki contrast was improved overall with LE and JE delay correction compared with no delay correction and Patlak analysis. Conclusion: This study demonstrated the importance of delay correction in total-body PET. LE delay correction can be an efficient surrogate for JE, requiring a fraction of the computational time and allowing for rapid delay correction across more than 106 voxels in total-body PET datasets.

Unparalleled and revolutionary impact of PET imaging on research and day to day practice of medicine

Abstract Positron emission tomography (PET) imaging is the most quantitative modality for assessing disease activity at the molecular and cellular levels, and therefore, it allows monitoring its course and determining the efficacy of various therapeutic interventions. In this scientific communication, we describe the unparalleled and revolutionary impact of PET imaging on research and day to day practice of medicine. We emphasize the critical importance of the development and synthesis of novel radiotracers (starting from the enormous impact of F-Fluorodeouxyglucose (FDG) introduced by investigators at the University of Pennsylvania (PENN)) and PET instrumentation. These innovations have led to the total-body PET systems enabling dynamic and parametric molecular imaging of all organs in the body simultaneously. We also present our perspectives for future development of molecular imaging by multiphoton PET systems that will enable users to extract substantial information (owing to the evolving role of positronium imaging) about the related molecular and biological bases of various disorders, which are unachievable by the current PET imaging techniques.

New Radionuclides and Technological Advances in SPECT and PET Scanners.

Simple SummaryAdvances in nuclear medicine are made by technological and radionuclide improvements. Throughout nuclear medicine’s history, these advances were often intertwined and complementary based on different clinical questions, availability and need. This paper covers some of these developments in radionuclides and instrumentation.Developments throughout the history of nuclear medicine have involved improvements in both instrumentation and radionuclides, which have been intertwined. Instrumentation developments always occurred during the search to improving devices’ sensitivity and included advances in detector technology (with the introduction of cadmium zinc telluride and digital Positron Emission Tomography—PET-devices with silicon photomultipliers), design (total body PET) and configuration (ring-shaped, Single-Photon Emission Computed Tomography (SPECT), Compton camera). In the field of radionuclide development, we observed the continual changing of clinically used radionuclides, which is sometimes influenced by instrumentation technology but also driven by availability, patient safety and clinical questions. Some areas, such as tumour imaging, have faced challenges when changing radionuclides based on availability, when this produced undesirable clinical findings with the introduction of unclear focal uptakes and unspecific uptakes. On the other end of spectrum, further developments of PET technology have seen a resurgence in its use in nuclear cardiology, with rubidium-82 from strontium-82/rubidium-82 generators being the radionuclide of choice, moving away from SPECT nuclides thallium-201 and technetium-99m. These continuing improvements in both instrumentation and radionuclide development have helped the growth of nuclear medicine and its importance in the ever-evolving range of patient care options.

159 Acute coronary syndrome in patient with giant cell arteritis: a fascinating case

Abstract Aims The diagnosis of acute coronary syndrome with persistent ST segment elevation, although apparently simple to detect by electrocardiographic abnormalities, can sometimes be insidious due to a difficult differential diagnosis with aortic dissection. Performing a coronary angiography in case of aortic dissection can be potentially life-threatening so, when suspected, this diagnosis needs to be rule out. Furthermore, coronary vasculitis is a rare but devastating complication of giant cell arteritis. Methods and results We describe a case of 62-year-old man hospitalized for acute coronary syndrome with persistent ST segment elevation involving the inferior wall. Ha was a heavy smoker with familiar history of cardiovascular disease and recent suspicion of Horton arteritis with aortic involvement under investigation, no previous cardiological events. Presenting symptoms are chest pain, sweating, bradycardia, and hypotension. In the emergency department, due to the history of suspected arteritis, chest CT scan was performed in order to rule out the hypothesis of aortic dissection before proceeding to coronarography. No signs of aortic rupture but the presence of thickening of the aorta from the arch to the carrefour was found. The coronary angiography showed critical stenosis in the medial tract of the circumflex artery and thrombotic subocclusion in the middle segment of the right coronary (culprit lesion—Figure 1) that was treated with PCI using drug-eluting stent. The echocardiogram showed mild left ventricular disfunction (EF 53%) due to posterolateral hypokinesia, no other pathological findings. Blood tests revealed anaemia, elevated platelets, and an increase of inflammation markers. Peak Hs-troponin was 18 000 ng/L (n.v. &amp;lt; 0.02 ng/ml). After 2 days we performed elective revascularization of the circumflex artery using a drug-eluting stent. Considering the medical history, we performed temporal artery biopsy and a total body PET scan that showed accumulation of radioactive tracer from the aortic arch to the sub-renal abdominal aorta, with a thickened wall. After that empirical corticosteroid therapy was started and some days later the result of the temporal artery biopsy confirmed the diagnosis of Horton arteritis. The patient was discharged to a rehabilitation structure in good general condition with cardioactive and corticosteroid therapy after 9 days of hospitalization. Conclusions Horton arteritis usually involves the external carotid artery and its branches, but sometimes inflammation of the aorta occurs in a subgroup of patients and rarely can involve the coronary arteries. An acute coronary syndrome in patients with Horton arteritis can be very insidious because aortic dissection can be the hidden cause, so chest CT scan must be performed before coronary angiography to avoid acute complication associated with an elevated mortality. Furthermore, being the vasculitic inflammation the trigger of the coronary involvement immunosuppressive therapy could be helpful to prevent subsequent acute coronary events.

Radioembolization Dosimetry with Total-Body 90Y PET.

Transarterial radioembolization (TARE) is a locoregional radiopharmaceutical therapy based on the delivery of radioactive 90Y microspheres to liver tumors. The importance of personalized dosimetry to make TARE safer and more effective has been demonstrated in recent clinical studies, stressing the need for quantification of the dose-response relationship to ultimately optimize the administered activity before treatment and image it after treatment. 90Y dosimetric studies are challenging because of the lack of accurate and precise methods but are best realized with PET combined with Monte Carlo simulations and other image modalities to calculate a segmental dose distribution. The aim of this study was to assess the suitability of imaging 90Y PET patients with the total-body PET/CT uEXPLORER and to investigate possible improvements in TARE 90Y PET-based dosimetry. The uEXPLORER is the first commercially available ultra-high-resolution (171 cps/kBq) total-body digital PET/CT device with a 194-cm axial PET field of view that enables the whole body to be scanned at a single bed position. Methods: Two PET/CT scanners were evaluated in this study: the Biograph mCT and the total-body uEXPLORER. Images of a National Electrical Manufacturers Association (NEMA) image-quality phantom and 2 patients were reconstructed using our standard clinical oncology protocol. A late portal phase contrast-enhanced CT scan was used to contour the liver segments and create corresponding volumes of interest. To calculate the absorbed dose, Monte Carlo simulations were performed using Geant4 Application for Tomographic Emission (GATE). The absorbed dose and dose-volume histograms were calculated for all 6 spheres (diameters ranging from 10 to 37 mm) of the NEMA phantom, the liver segments, and the entire liver. Differences between the phantom doses and an analytic ground truth were quantified through the root mean squared error. Results: The uEXPLORER showed a higher signal-to-noise ratio at 10- and 13-mm diameters, consistent with its high spatial resolution and system sensitivity. The total liver-absorbed dose showed excellent agreement between the uEXPLORER and the mCT for both patients, with differences lower than 0.2%. Larger differences of up to 60% were observed when comparing the liver segment doses. All dose-volume histograms were in good agreement, with narrower tails for the uEXPLORER in all segments, indicating lower image noise. Conclusion: This patient study is compelling for the use of total-body 90Y PET for liver dosimetry. The uEXPLORER scanner showed a better signal-to-noise ratio than mCT, especially in lower-count regions of interest, which is expected to improve dose quantification and tumor dosimetry.

Total-Body PET Multiparametric Imaging of Cancer Using a Voxelwise Strategy of Compartmental Modeling.

Quantitative dynamic PET with compartmental modeling has the potential to enable multiparametric imaging and more accurate quantification than static PET imaging. Conventional methods for parametric imaging commonly use a single kinetic model for all image voxels and neglect the heterogeneity of physiologic models, which can work well for single-organ parametric imaging but may significantly compromise total-body parametric imaging on a scanner with a long axial field of view. In this paper, we evaluate the necessity of voxelwise compartmental modeling strategies, including time delay correction (TDC) and model selection, for total-body multiparametric imaging. Methods: Ten subjects (5 patients with metastatic cancer and 5 healthy volunteers) were scanned on a total-body PET/CT system after injection of 370 MBq of 18F-FDG. Dynamic data were acquired for 60 min. Total-body parametric imaging was performed using 2 approaches. One was the conventional method that uses a single irreversible 2-tissue-compartment model with and without TDC. The second approach selects the best kinetic model from 3 candidate models for individual voxels. The differences between the 2 approaches were evaluated for parametric imaging of microkinetic parameters and the 18F-FDG net influx rate, KiResults: TDC had a nonnegligible effect on kinetic quantification of various organs and lesions. The effect was larger in lesions with a higher blood volume. Parametric imaging of Ki with the standard 2-tissue-compartment model introduced vascular-region artifacts, which were overcome by the voxelwise model selection strategy. Conclusion: The time delay and appropriate kinetic model vary in different organs and lesions. Modeling of the time delay of the blood input function and model selection improved total-body multiparametric imaging.

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.

PROSTATE CANCER WITH ISOLATED LUNG METASTASIS: AN UNUSUAL PRESENTATION

TOPIC: Lung Pathology TYPE: Medical Student/Resident Case Reports INTRODUCTION: A solitary pulmonary nodule from metastatic prostate cancer without concurrent bone involvement is extremely rare. Although more than 40% of prostate cancer patients have pulmonary involvement on autopsy, less than 1% have isolated pulmonary metastasis [1]. Prostate cancer routinely metastasizes from prostate to bone before reaching the lungs and other organs at later stages [2]. We present a unique case of a solitary pulmonary nodule from metastatic prostate cancer in the absence of osseous, lymphatic, or other organ metastasis. To date, only 23 other similar cases have been reported throughout the world. CASE PRESENTATION: We present a case of a 78-year-old male diagnosed with prostate cancer in 2009 (Gleasons 6-Gleasons 8, PSA 13, T1CN0M0). Patient initially underwent definitive radiation therapy and androgen deprivation therapy (ADT) with bicalutamide. Total body CT and PET scans revealed no adenopathy and no other metastatic lesions. After multiple rounds of ADT and radiation, repeat prostate biopsies in 2012 and 2013 were both negative and PSA was undetectable. The patient was then placed on active surveillance. This uncovered a PSA elevation in 2014. At the time the patient was given treatment options, but he elected for conservative management by restarting ADT and undergoing further imaging. Chest CT scans were performed from 2014 to 2021 for surveillance. A chest CT scan in 2014 demonstrated no metastatic lesions, however in 2016 a solitary 11mm pulmonary nodule was discovered in the right upper lobe. This nodule enlarged to 16mm over the course of 4 years, which prompted further investigation. A primary pulmonary carcinoma was suspected due to a 15-pack-year smoking history and absence of metastatic lesions. However, CT-guided core biopsy of the right upper lobe revealed an adenocarcinoma consistent with prostate cancer metastasis. DISCUSSION: In patients with a solitary pulmonary nodule, primary lung carcinoma is much more likely (35%) than isolated lung metastasis from prostate cancer [3]. Isolated lung involvement in metastatic prostate cancer is extremely rare, with less than 1% found in autopsy [4]. We present a unique case of a solitary pulmonary nodule from metastatic prostate cancer in the absence of bone involvement. In a study with over 1,290 prostate cancer patients, 48 were found to have lung metastasis, while only 11 (0.86%) had pulmonary nodules [5]. CONCLUSIONS: Active surveillance with routine PSA checks and digital rectal exams are important for monitoring recurrence of prostate cancer. The addition of routine imaging and prostate biopsies may aid in earlier detection of recurrence and distant metastasis. Early detection of oligometastatic pulmonary nodules from prostate cancer may guide targeted therapy, such as with our patient that is undergoing targeted radiation. REFERENCE #1: Siegel RL, Miller KD, Jemal A. Cancer statistics, 2018. CA Cancer J Clin 2018;68:7-30. REFERENCE #2: Fornetti, J., Welm, A.L. and Stewart, S.A., 2018, Understanding the Bone in Cancer Metastasis. J Bone Miner Res, 33: 2099-2113. REFERENCE #3: Greenlee RT, Hill-Harmon MB, Murray T, et al. Cancerstatistics, 2001. CA Cancer J Clin 2001; 51:15–36 Reference #4: Saitoh H, Hida M, Shimbo T, et al. Metastatic patterns of prostatic cancer. Correlation between sites and number of organs involved. Cancer 1984;54:3078-84. Reference #5: Fabozzi SJ, Schellhammer PF, el-Mahdi AM. Pulmonary metastases from prostate cancer. Cancer 1995;75:2706-9. DISCLOSURES: No relevant relationships by Luke Dreisbach, source=Web Response No relevant relationships by Saad Fattouhi, source=Web Response No relevant relationships by Garo Kalfayan, source=Web Response No relevant relationships by Shahriyar Tavakoli, source=Web Response No relevant relationships by Vahe Zograbyan, source=Web Response

Simulating NEMA characteristics of the modular total-body J-PET scanner—an economic total-body PET from plastic scintillators

The purpose of the presented research is estimation of the performance characteristics of the economic total-body Jagiellonian-PET system (TB-J-PET) constructed from plastic scintillators. The characteristics are estimated according to the NEMA NU-2-2018 standards utilizing the GATE package. The simulated detector consists of 24 modules, each built out of 32 plastic scintillator strips (each with cross section of 6 mm times 30 mm and length of 140 or 200 cm) arranged in two layers in regular 24-sided polygon circumscribing a circle with the diameter of 78.6 cm. For the TB-J-PET with an axial field-of-view (AFOV) of 200 cm, a spatial resolutions (SRs) of 3.7 mm (transversal) and 4.9 mm (axial) are achieved. The noise equivalent count rate (NECR) peak of 630 kcps is expected at 30 kBq cc−1. Activity concentration and the sensitivity at the center amounts to 38 cps kBq−1. The scatter fraction (SF) is estimated to 36.2 %. The values of SF and SR are comparable to those obtained for the state-of-the-art clinical PET scanners and the first total-body tomographs: uExplorer and PennPET. With respect to the standard PET systems with AFOV in the range from 16 to 26 cm, the TB-J-PET is characterized by an increase in NECR approximately by factor of 4 and by the increase of the whole-body sensitivity by factor of 12.6 to 38. The time-of-flight resolution for the TB-J-PET is expected to be at the level of CRT = 240 ps full width at half maximum. For the TB-J-PET with an AFOV of 140 cm, an image quality of the reconstructed images of a NEMA IEC phantom was presented with a contrast recovery coefficient and a background variability parameters. The increase of the whole-body sensitivity and NECR estimated for the TB-J-PET with respect to current commercial PET systems makes the TB-J-PET a promising cost-effective solution for the broad clinical applications of total-body PET scanners. TB-J-PET may constitute an economic alternative for the crystal TB-PET scanners, since plastic scintillators are much cheaper than BGO or LYSO crystals and axial arrangement of the strips significantly reduces the costs of readout electronics and SiPMs.

Optimisation of the event-based TOF filtered back-projection for online imaging in total-body J-PET

We perform a parametric study of the newly developed time-of-flight (TOF) image reconstruction algorithm, proposed for the real-time imaging in total-body Jagiellonian PET (J-PET) scanners. The asymmetric 3D filtering kernel is applied at each most likely position of electron-positron annihilation, estimated from the emissions of back-to-back γ-photons. The optimisation of its parameters is studied using Monte Carlo simulations of a 1-mm spherical source, NEMA IEC and XCAT phantoms inside the ideal J-PET scanner. The combination of high-pass filters which included the TOF filtered back-projection (FBP), resulted in spatial resolution, 1.5 times higher in the axial direction than for the conventional 3D FBP. For realistic 10-minute scans of NEMA IEC and XCAT, which require a trade-off between the noise and spatial resolution, the need for Gaussian TOF kernel components, coupled with median post-filtering, is demonstrated. The best sets of 3D filter parameters were obtained by the Nelder-Mead minimisation of the mean squared error between the resulting and reference images. The approach allows training the reconstruction algorithm for custom scans, using the IEC phantom, when the temporal resolution is below 50 ps. The image quality parameters, estimated for the best outcomes, were systematically better than for the non-TOF FBP.

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.

Model Corrected Blood Input Function to Compute Cerebral FDG Uptake Rates From Dynamic Total-Body PET Images of Rats in vivo.

Recently, we developed a three-compartment dual-output model that incorporates spillover (SP) and partial volume (PV) corrections to simultaneously estimate the kinetic parameters and model-corrected blood input function (MCIF) from dynamic 2-[18F] fluoro-2-deoxy-D-glucose positron emission tomography (FDG PET) images of mouse heart in vivo. In this study, we further optimized this model and utilized the estimated MCIF to compute cerebral FDG uptake rates, Ki, from dynamic total-body FDG PET images of control Wistar–Kyoto (WKY) rats and compared to those derived from arterial blood sampling in vivo. Dynamic FDG PET scans of WKY rats (n = 5), fasted for 6 h, were performed using the Albira Si Trimodal PET/SPECT/CT imager for 60 min. Arterial blood samples were collected for the entire imaging duration and then fitted to a seven-parameter function. The 60-min list mode PET data, corrected for attenuation, scatter, randoms, and decay, were reconstructed into 23 time bins. A 15-parameter dual-output model with SP and PV corrections was optimized with two cost functions to compute MCIF. A four-parameter compartment model was then used to compute cerebral Ki. The computed area under the curve (AUC) and Ki were compared to that derived from arterial blood samples. Experimental and computed AUCs were 1,893.53 ± 195.39 kBq min/cc and 1,792.65 ± 155.84 kBq min/cc, respectively (p = 0.76). Bland–Altman analysis of experimental vs. computed Ki for 35 cerebral regions in WKY rats revealed a mean difference of 0.0029 min−1 (~13.5%). Direct (AUC) and indirect (Ki) comparisons of model computations with arterial blood sampling were performed in WKY rats. AUC and the downstream cerebral FDG uptake rates compared well with that obtained using arterial blood samples. Experimental vs. computed cerebral Ki for the four super regions including cerebellum, frontal cortex, hippocampus, and striatum indicated no significant differences.