18F-FDG PET/CT and PET/MRI Perform Equally Well in Cancer: Evidence from Studies on More Than 2,300 Patients

In situ labeling of pretargeted hyaluronan for PET/MR imaging of CD44+ tumors

BACKGROUND

Tumor-specific molecular probe-based imaging strategies have shown great potential for tumor diagnosis. However, the sensitivity and contrast of imaging may interfere with the complex labeling process and degradation of tumor-specific imaging probes. We sought to adapt a pretargeting strategy and an in vivo bioorthogonal reaction to improve hyaluronan (HA)-based tumor multimodal imaging diagnosis.

METHODS

Transcyclooctene-labeled HA (HA-TCO) and tetrazine-labeled NODA (NODA-Tz) were synthesized and purified. Probes Gd-NODA-Tz and [18F]AlF-NODA-Tz for magnetic resonance imaging (MRI) and positron emission tomography (PET) imaging were prepared. The bioorthogonal reaction of HA-TCO with NODA-Tz and the stability of the products were confirmed and analyzed. CD44 + A549 tumor-bearing mice were injected with HA-TCO via the tail vein, followed by Gd-NODA-Tz or [18F]AlF-NODA-Tz administration half an hour later, and subsequently imaged by MR or PET. The images were analyzed and tumor uptake was quantified.

RESULTS

HA-TCO efficiently bound to CD44-overexpressing A549 cells and selectively reacted with the Tz-imaging group. In vivo MR and PET images were obtained after probe injection and subsequent bioorthogonal labeling. The images showed a tumor mass with a high target background ratio (TBR) and clear boundaries.

CONCLUSION

In situ labeling of pretargeted HA-TCO enabled MRI and PET imaging of tumor tissues in mice with high sensitivity and improved TBR.

Inhibition of ACSS2 triggers glycolysis inhibition and nuclear translocation to activate SIRT1/ATG5/ATG2B deacetylation axis, promoting autophagy and reducing malignancy and chemoresistance in ovarian cancer

BACKGROUND

Metabolic reprogramming is a hallmark of cancer, characterized by a high dependence on glycolysis and an enhanced utilization of acetate as an alternative carbon source. ACSS2 is a critical regulator of acetate metabolism, playing a significant role in the development and progression of various malignancies. ACSS2 facilitates the conversion of acetate to acetyl-CoA, which participates in multiple metabolic pathways and functions as an epigenetic regulator of protein acetylation, thereby modulating key cellular processes such as autophagy. However, the roles and intrinsic connections of ACSS2, glycolysis, protein acetylation, and autophagy in ovarian cancer (OC) remain to be elucidated.

BASIC PROCEDURES

Utilizing clinical specimens and online databases, we analysed the expression of ACSS2 in OC and its relationship with clinical prognosis. By knocking down ACSS2, we evaluated its effects on the malignant phenotype, acetate metabolism, glycolysis, and autophagy. The metabolic alterations in OC cells were comprehensively analysed using Seahorse assays, transmission electron microscopy, membrane potential measurements, and stable-isotope labeling techniques. CUT&TAG and co-immunoprecipitation techniques were employed to explore the deacetylation of autophagy-related proteins mediated by ACSS2 via SIRT1. Additionally, through molecular docking, transcriptome sequencing, and metabolomics analyses, we validated the pharmacological effects of paeonol on ACSS2 and the glycolytic process in OC cells. Finally, both in vitro and in vivo experiments were performed to investigate the impact of paeonol on autophagy and its anti-OC effects mediated through the ACSS2/SIRT1 deacetylation axis.

MAIN FINDINGS

ACSS2 is significantly upregulated in OC and is associated with poor prognosis. Knockdown of ACSS2 inhibits OC cells proliferation, migration, invasion, angiogenesis, and platinum resistance, while reducing tumour burden in vivo. Mechanistically, inhibiting ACSS2 reduces acetate metabolism and suppresses glycolysis by targeting HXK2. This glycolytic reduction promotes the translocation of ACSS2 from the cytoplasm to the nucleus, leading to increased expression of the deacetylase SIRT1. SIRT1 mediates the deacetylation of autophagy-related proteins, such as ATG5 and ATG2B, thereby significantly activating autophagy in OC cells and exerting antitumor effects. Paeonol inhibits acetate metabolism and glycolysis in OC cells by targeting ACSS2. Paeonol activates autophagy through the ACSS2/SIRT1/ATG5/ATG2B deacetylation axis, demonstrating inhibition of OC in vitro and in vivo.

PRINCIPAL CONCLUSIONS

Pae can serve as an effective, low-toxicity, multi-targeted drug targeting ACSS2 and glycolysis. It activates autophagy through the ACSS2/SIRT1/ATG5/ATG2B deacetylation signalling cascade, thereby exerting anti-OC effects. Our study provides new insights into the malignant mechanisms of OC and offers a novel strategy for its treatment.

PET/MRI evaluation of hepatobiliary tumors

Positron-emission tomography magnetic resonance imaging (PET/MRI) has emerged as a powerful hybrid molecular imaging technique in clinical practice, overcoming initial technical challenges to provide comprehensive anatomic and metabolic information. This advanced modality combines the superior soft tissue contrast of MRI with the metabolic insights of PET, offering advantages in hepatobiliary imaging, including improved detection of small liver metastases and reduced radiation exposure. The evolution of PET/MRI technology has been marked by significant advancements, such as the development of MRI-compatible PET detectors and sophisticated motion compensation techniques. These innovations have enhanced image quality and co-registration accuracy, crucial for hepatobiliary imaging. The integration of time-of-flight capability and silicon photomultipliers has further improved spatial resolution and sensitivity. PET/MRI protocols for liver imaging typically involve a whole-body scan followed by a targeted liver examination, utilizing radiotracers like FDG and DOTATATE. This approach allows for comprehensive staging and detailed liver assessment in a single session, potentially altering management decisions in up to 30% of patients with intrahepatic cholangiocarcinoma. While PET/MRI excels in characterizing various hepatobiliary lesions, including hepatocellular carcinoma and cholangiocarcinoma, challenges remain in differentiating certain benign entities like small hemangiomas from metastases. Ongoing research and clinical experience continue to refine the role of PET/MRI in hepatobiliary imaging, promising improved diagnostic accuracy and patient care.

Advances and Prospects in Liquid Biopsy Techniques for Malignant Tumor Diagnosis and Surveillance

Liquid biopsy technology provides invaluable support for the early diagnosis of tumors and surveillance of disease course by detecting tumor-related biomarkers in bodily fluids. Currently, liquid biopsy techniques are mainly divided into two categories: biomarker and label-free. Biomarker liquid biopsy techniques utilize specific antibodies or probes to identify and isolate target cells, exosomes, or molecules, and these techniques are widely used in clinical practice. However, they have certain limitations including dependence on tumor markers, alterations in cell biological properties, and high cost. In contrast, label-free liquid biopsy techniques directly utilize physical or chemical properties of cells, exosomes, or molecules for detection and isolation. These techniques have the advantage of not needing labeling, not impacting downstream analysis, and low detection cost. However, most are still in the research stage and not yet mature. This review first discusses recent advances in liquid biopsy techniques for early tumor diagnosis and disease surveillance. Several current techniques are described in detail. These techniques exploit differences in biomarkers, size, density, deformability, electrical properties, and chemical composition in tumor components to achieve highly sensitive tumor component identification and separation. Finally, the current research progress is summarized and the future research directions of the field are discussed.

Hybrid FDG-PET/MRI for Diagnosis and Clinical Management of Patients with Suspected Perihilar Cholangiocarcinoma: A Feasibility Pilot Study

Purpose

Recently introduced hybrid 2-[18 F]-fluoro-2-deoxy-D-glucose (18 F-FDG) Positron Emission Tomography (PET) combined with Magnetic Resonance Imaging (MRI) may aid in proper diagnosis and staging of perihilar cholangiocarcinoma (pCCA). The aim of this study is to assess the effect of 18 F-FDG PET/MRI on diagnosis and clinical decision making in the pre-operative work up of pCCA.

Methods

In this single-centre pilot study patients with presumed resectable pCCA underwent state-of-the-art 18 F-FDG hybrid PET/MRI using digital silicone photomultiplier detectors integrated within a 3-Tesla bore. Data were collected on several baseline and imaging characteristics. The primary outcome measure was the added diagnostic information and the effect on clinical decision making. Secondary aim was to correlate quantitative PET signal intensity to patient- and tumour characteristics. High and low SUVmax subgroups related to the mean value were made. Significance of lesion- and patient characteristics with the high and low SUVmax subgroups, as well as TLR and TBR, was evaluated with Fisher's exact test or Mann-Whitney-U test.

Results

In total 14 patients were included (mean age 62.4 years, 64% male). Final diagnosis was pCCA in 10 patients (71.4%), follicular lymphoma in one patient (7.1%) and benign disease in the remaining three patients. FDG-PET/MRI added valuable diagnostic information in six (43%) patients and affected clinical decision making in two of these patients (14%) by increasing confidence for malignancy which lead to the decision for surgery on short term. High SUVmax values were seen in half of cases with pCCA and half of cases with non-cancerous lesions. In addition, high SUVmax values were directly associated with primary sclerosing cholangitis when present (p = 0.03).

Conclusion

Simultaneous 18 F-FDG-PET/MRI added diagnostic information in six of fourteen patients and influenced clinical decision making in two patients (14%) with presumed resectable pCCA.

Lung imaging methods: indications, strengths and limitations

Imaging methods are fundamental tools to detect and diagnose lung diseases, monitor their treatment and detect possible complications. Each modality, starting from classical chest radiographs and computed tomography, as well as the ever more popular and easily available thoracic ultrasound, magnetic resonance imaging and nuclear medicine methods, and new techniques such as photon counting computed tomography, radiomics and application of artificial intelligence, has its strong and weak points, which we should be familiar with to properly choose between the methods and interpret their results. In this review, we present the indications, strengths and main limitations of methods for chest imaging.

Comparison of PET/CT and PET/MRI in central nervous system tumors, a narrative review

BACKGROUND

PET/CT and PET/MRI are two useful imaging modalities in neuro-oncology. Our aim was to review the existing literature on the benefits and drawbacks of using PET/CT and PET/MRI in the diagnosis of central nervous system (CNS) tumors.

METHODS

A literature search was conducted using valid databases, limited to English-language articles published between 2010 and 2023, and independently reviewed by two reviewers. A standard data extraction form was used to extract data from the included papers. The results were condensed and narratively presented, accompanied by supporting data from the included investigations.

RESULTS

The study analyzed 28 articles, mostly from Europe. The results varied, with some studies comparing PET/CT and PET/MRI, examining specific types of brain tumors, pediatric tumors, or focusing on specific PET/CT or PET/MRI modalities. The synthesis aimed to provide a comprehensive overview of PET/CT and PET/MRI use in CNS malignancies.

CONCLUSIONS

PET/MRI offers promising advantages in neuro-oncology diagnosis and follow-up imaging, but its use should be prioritized in appropriate situations.

[18F]FDG PET/CT versus [18F]FDG PET/MRI in the evaluation of liver metastasis in patients with primary cancer: A head-to-head comparative meta-analysis

PURPOSE

This meta-analysis aimed to compare the diagnostic effectiveness of [18F]FDG PET/CT with that of [18F]FDG PET/MRI in terms of identifying liver metastasis in patients with primary cancer.

METHODS

PubMed, Embase, Web of Science, and the Cochrane Library were searched, and studies evaluating the diagnostic efficacy of [18F]FDG PET/CT and [18F]FDG PET/MRI in patients with liver metastasis of primary cancer were included. We used a random effects model to analyze their sensitivity and specificity. Subgroup analyses and corresponding meta-regressions focusing on race, image analysis, study design, and analysis methodologies were conducted. Cochrane Q and I2 statistics were used to assess intra-group and inter-group heterogeneity.

RESULTS

Seven articles with 343 patients were included in this meta-analysis. The sensitivity of [18F]FDG PET/CT was 0.82 (95 % CI: 0.63-0.96), and that of [18F]FDG PET/MRI was 0.91 (95 % CI: 0.82-0.98); there was no significant difference between the two methods (P = 0.32). Similarly, both methods showed equal specificity: 1.00 (95 % CI: 0.95-1.00) for [18F]FDG PET/CT and 1.00 (95 % CI: 0.96-1.00) for [18F]FDG PET/MRI, and thus, there was no significant difference between the methods (P = 0.41). Furthermore, the subgroup analyses revealed no differences. Meta-regression analysis revealed that race was a potential source of heterogeneity for [18F]FDG PET/CT (P = 0.01), while image analysis and contrast agent were found to be potential sources of heterogeneity for [18F]FDG PET/MRI (P = 0.02).

CONCLUSIONS

[18F]FDG PET/MRI has similar sensitivity and specificity to [18F]FDG PET/CT for detecting liver metastasis of primary cancer in both the general population and in subgroups. [18F]FDG PET/CT may be a more cost-effective option. However, the conclusions of this meta-analysis are tentative due to the limited number of studies included, and further research is necessary for validation.

Imaging and Metabolic Diagnostic Methods in the Stage Assessment of Rectal Cancer

Rectal cancer (RC) is a prevalent malignancy with significant morbidity and mortality rates. The accurate staging of RC is crucial for optimal treatment planning and patient outcomes. This review aims to summarize the current literature on imaging and metabolic diagnostic methods used in the stage assessment of RC. Various imaging modalities play a pivotal role in the initial evaluation and staging of RC. These include magnetic resonance imaging (MRI), computed tomography (CT), and endorectal ultrasound (ERUS). MRI has emerged as the gold standard for local staging due to its superior soft tissue resolution and ability to assess tumor invasion depth, lymph node involvement, and the presence of extramural vascular invasion. CT imaging provides valuable information about distant metastases and helps determine the feasibility of surgical resection. ERUS aids in assessing tumor depth, perirectal lymph nodes, and sphincter involvement. Understanding the strengths and limitations of each diagnostic modality is essential for accurate staging and treatment decisions in RC. Furthermore, the integration of multiple imaging and metabolic methods, such as PET/CT or PET/MRI, can enhance diagnostic accuracy and provide valuable prognostic information. Thus, a literature review was conducted to investigate and assess the effectiveness and accuracy of diagnostic methods, both imaging and metabolic, in the stage assessment of RC.

Fluorescent covalent organic frameworks - promising bioimaging materials

Fluorescent covalent organic frameworks (COFs) have emerged as promising candidates for imaging living cells due to their unique properties and adjustable fluorescence. In this mini-review, we provide an overview of recent advancements in fluorescent COFs for bioimaging applications. We discuss the strategies used to design COFs with desirable properties such as high photostability, excellent biocompatibility, and pH sensitivity. Additionally, we explore the various ways in which fluorescent COFs are utilized in bioimaging, including cellular imaging, targeting specific organelles, and tracking biomolecules. We delve into their applications in sensing intracellular pH, reactive oxygen species (ROS), and specific biomarkers. Furthermore, we examine how functionalization techniques enhance the targeting and imaging capabilities of fluorescent COFs. Finally, we discuss the challenges and prospects in the field of fluorescent COFs for bioimaging in living cells, urging further research in this exciting area.

SPECT/CT, PET/CT, and PET/MRI for Response Assessment of Bone Metastases

Recent developments in hybrid SPECT/CT systems and the use of cadmium-zinc-telluride (CZT) detectors have improved the diagnostic accuracy of bone scintigraphy. These advancements have paved the way for novel quantitative approaches to accurate and reproducible treatment monitoring of bone metastases. PET/CT imaging using [18F]F-FDG and [18F]F-NaF have shown promising clinical utility in bone metastases assessment and monitoring response to therapy and prediction of treatment response in a broad range of malignancies. Additionally, specific tumor-targeting tracers like [99mTc]Tc-PSMA, [68Ga]Ga-PSMA, or [11C]C- or [18F]F-Choline revealed high diagnostic performance for early assessment and prognostication of bone metastases, particularly in prostate cancer. PET/MRI appears highly accurate imaging modality, but has associated limitations notably, limited availability, more complex logistics and high installation costs. Advances in artificial intelligence (Al) seem to improve the accuracy of imaging modalities and provide an assistant role in the evaluation of treatment response of bone metastases.

MRI compatibility study of a prototype radiofrequency penetrable oval PET insert at 3 T

PURPOSE

To perform an MRI compatibility study of an RF field-penetrable oval-shaped PET insert that implements an MRI built-in body RF coil both as a transmitter and a receiver.

METHODS

Twelve electrically floating RF shielded PET detector modules were used to construct the prototype oval PET insert with a major axis of 440 mm, a minor axis of 350 mm, and an axial length of 225 mm. The electric floating of the PET detector modules was accomplished by isolating the cable shield from the detector shield using plastic tape. Studies were conducted on the transmit (B1) RF field, the image signal-to-noise ratio (SNR), and the RF pulse amplitude for a homogeneous cylindrical (diameter: 160 mm and length: 260 mm) phantom (NaCl + NiSO4 solution) in a 3 T clinical MRI system (Verio, Siemens, Erlangen, Germany).

RESULTS

The B1 maps for the oval insert were similar to the MRI-only field responses. Compared to the MRI-only values, SNR reductions of 51%, 45%, and 59% were seen, respectively, for the spin echo (SE), gradient echo (GE), and echo planar (EPI) images for the case of oval PET insert. Moreover, the required RF pulse amplitudes for the SE, GE, and EPI sequences were, respectively, 1.93, 1.85, and 1.36 times larger. However, a 30% reduction in the average RF reception sensitivity was observed for the oval insert.

CONCLUSIONS

The prototype floating PET insert was a safety concern for the clinical MRI system, and this compatibility study provided clearance for developing a large body size floating PET insert for the existing MRI system. Because of the RF shield of the insert, relatively large RF powers compared to the MRI-only case were required. Because of this and also due to low RF sensitivity of the body coil, the SNRs reduced largely.

Cancer diagnosis and treatment platform based on manganese-based nanomaterials

Cancer is a leading cause of death worldwide, and the development of new diagnostic and treatment methods is crucial. Manganese-based nanomaterials (MnNMs) have emerged as a focal point in the field of cancer diagnosis and treatment due to their multifunctional properties. These nanomaterials have been extensively explored as contrast agents for various imaging technologies such as magnetic resonance imaging (MRI), photoacoustic imaging (PAI), and near-infrared fluorescence imaging (NIR-FL). The use of these nanomaterials has significantly enhanced the contrast for precise tumor detection and localization. Moreover, MnNMs have shown responsiveness to the tumor microenvironment (TME), enabling innovative approaches to cancer treatment. This review provides an overview of the latest developments of MnNMs and their potential applications in tumor diagnosis and therapy. Finally, potential challenges and prospects of MnNMs in clinical applications are discussed. We believe that this review would serve as a valuable resource for guiding further research on the application of manganese nanomaterials in cancer diagnosis and treatment, addressing the current limitations, and proposing future research directions.

Case report: diagnosis and treatment of advanced high-grade serous ovarian carcinoma aided by 68Ga-FAPI PET/MR scan

High-grade serous ovarian cancer (HGSOC) is the most common type of epithelial ovarian cancer with insidious onset, rapid growth, and invasive spread. Here, we reported the diagnosis and treatment of a 53-year-old patient with a history of hysterectomy aided by the 68Ga-FAPI PET/MR scan. The patient was first presented to the local hospital with a lump on the left side of the neck with a biopsy suggesting metastatic cancer. Pelvic ultrasonography revealed two irregular masses. After admission, tumor markers, pathology consultation of the biopsy, and the 68Ga-FAPI PET/MR scan were administered. The biopsy of the lump suggested poorly differentiated adenocarcinoma and CA125 was elevated at 530.6 U/ml. The 68Ga-FAPI PET/MR scan showed several abnormal lymph nodes and two soft tissue masses with borders of dispersed restriction displaying internally uneven signals depicted by slightly elongated T1 and T2 signals within the pelvic cavity suggesting that pelvic mass could be the primary lesion. The patient received cytoreductive surgery including bilateral adnexectomy, omentectomy, and appendectomy. Post-surgical pathology suggested left and right HGSOC with left fallopian tube invasion. The patient completed six courses of first-line chemotherapy and remained progression-free for 14 months up to date. To conclude, 68Ga-FAPI PET/MR aids in primary tumor determination and tumor burden assessment and provides a guide for the management of late-stage HGSOC patients.

Significance of F-18 FDG PET/MRI in the search for the etiology of inflammation of unclear origin and fever of unknown origin

PURPOSE

To evaluate the contribution of F-18 FDG-PET/MRI in the search for the etiology of the inflammation of unknown origin (IUO) and fever of unknown origin (FUO).

MATERIAL AND METHODS

The study included 104 patients who underwent F-18 FDG-PET/MRI for IUO or FUO. The sensitivity, specificity, predictive values of the PET/MRI findings in relation to the final diagnosis of IUO/FUO were evaluated. A five-point Likert scale was used to semiquantitatively assess the probability of the cause of IUO/FUO based on PET/MRI finding. Furthermore, clinical (fever, arthralgia, weight loss, night sweats, age) and laboratory (C-reactive protein, leukocytes) parameters were monitored and compared with the true positivity rate of PET/MRI.

RESULTS

In patients with definitively identified etiology of FUO and IUO, FDG-PET/MRI achieved a sensitivity of 96 %, specificity of 82 %, and positive and negative predictive values of 92 and 90 %. The cause of the IUO was determined in 71 patients (68.3 %). In 33 (31.7 %) patients, the etiology of IUO/FUO remained unknown, while in 25 (75.8 %) of them the symptoms resolved spontaneously and in 8 (24.2 %) patients they persisted without explanation even after 12 months of the follow-up. The most significant parameter in relation to subsequent PET/MRI finding was increased level of CRP, which was present in 96 % of true positive PET/MRI and normal CRP level was present in 56 % of true negative PET/MRI.

CONCLUSION

Based on this study, FDG-PET/MRI is a suitable alternative for the investigation of IUO/FUO, this imaging technique has a very high sensitivity and negative predictive value.

Added value of regional 18F-FDG PET/MRI-assisted whole-body 18F-FDG PET/CT in malignant ascites with unknown primary origin

BACKGROUND

Comparing to PET/CT, integrative PET/MRI imaging provides superior soft tissue resolution. This study aims to evaluate the added value of regional delayed 18F-FDG PET/MRI-assisted whole-body 18F-FDG PET/CT in diagnosing malignant ascites patients.

RESULTS

The final diagnosis included 22 patients with ovarian cancer (n = 11), peritoneal cancer (n = 3), colon cancer (n = 2), liver cancer (n = 2), pancreatic cancer (n = 2), gastric cancer (n = 1), and fallopian tube cancer (n = 1). The diagnosis of the primary tumor using whole-body PET/CT was correct in 11 cases. Regional PET/MRI-assisted whole-body PET/CT diagnosis was correct in 18 cases, including 6 more cases of ovarian cancer and 1 more case of fallopian tube cancer. Among 4 cases that were not diagnosed correctly, 1 case had the primary tumor outside of the PET/MRI scan area, 2 cases were peritoneal cancer, and 1 case was colon cancer. The diagnostic accuracy of regional PET/MRI-assisted whole-body PET/CT was higher than PET/CT alone (81.8% vs. 50.0%, κ 2 = 5.14, p = 0.023). The primary tumor conspicuity score of PET/MRI was higher than PET/CT (3.67 ± 0.66 vs. 2.76 ± 0.94, P < 0.01). In the same scan area, more metastases were detected in PET/MRI than in PET/CT (156 vs. 86 in total, and 7.43 ± 5.17 vs. 4.10 ± 1.92 per patient, t = 3.89, P < 0.01). Lesion-to-background ratio in PET/MRI was higher than that in PET/CT (10.76 ± 5.16 vs. 6.56 ± 3.45, t = 13.02, P < 0.01).

CONCLUSION

Comparing to whole-body PET/CT alone, additional delayed regional PET/MRI with high soft tissue resolution is helpful in diagnosing the location of the primary tumor and identifying more metastases in patients with malignant ascites. Yet larger sample size in multicenter and prospective clinical researches is still needed.

Update on Positron Emission Tomography/Magnetic Resonance Imaging: Cancer and Inflammation Imaging in the Clinic

Hybrid PET/MRI is highly valuable, having made significant strides in overcoming technical challenges and offering unique advantages such as reduced radiation, precise data coregistration, and motion correction. Growing evidence highlights the value of PET/MRI in broad clinical aspects, including inflammatory and oncological imaging in adults, pregnant women, and pediatrics, potentially surpassing PET/CT. This newly integrated solution may be preferred over PET/CT in many clinical conditions. However, further technological advancements are required to facilitate its broader adoption as a routine diagnostic modality.

Long-axial field-of-view PET/CT: perspectives and review of a revolutionary development in nuclear medicine based on clinical experience in over 7000 patients

Recently introduced long-axial field-of-view (LAFOV) PET/CT systems represent one of the most significant advancements in nuclear medicine since the advent of multi-modality PET/CT imaging. The higher sensitivity exhibited by such systems allow for reductions in applied activity and short duration scans. However, we consider this to be just one small part of the story: Instead, the ability to image the body in its entirety in a single FOV affords insights which standard FOV systems cannot provide. For example, we now have the ability to capture a wider dynamic range of a tracer by imaging it over multiple half-lives without detrimental image noise, to leverage lower radiopharmaceutical doses by using dual-tracer techniques and with improved quantification. The potential for quantitative dynamic whole-body imaging using abbreviated protocols potentially makes these techniques viable for routine clinical use, transforming PET-reporting from a subjective analysis of semi-quantitative maps of radiopharmaceutical uptake at a single time-point to an accurate and quantitative, non-invasive tool to determine human function and physiology and to explore organ interactions and to perform whole-body systems analysis. This article will share the insights obtained from 2 years' of clinical operation of the first Biograph Vision Quadra (Siemens Healthineers) LAFOV system. It will also survey the current state-of-the-art in PET technology. Several technologies are poised to furnish systems with even greater sensitivity and resolution than current systems, potentially with orders of magnitude higher sensitivity. Current barriers which remain to be surmounted, such as data pipelines, patient throughput and the hindrances to implementing kinetic analysis for routine patient care will also be discussed.

[18F]FDG PET/CT versus [18F]FDG PET/MRI for the diagnosis of colorectal liver metastasis: A systematic review and meta-analysis

Purpose

The purpose of our meta-analysis and systematic review was to compare the diagnostic performance of [18F]FDG PET/CT and [18F]FDG PET/MRI in colorectal liver metastasis.

Methods

We searched PubMed, Embase, and Web of Science for eligible articles until November 2022. Studies focusing on the diagnostic value of [18F]FDG PET/CT or PET/MRI for colorectal liver metastasis were included. Using a bivariate random-effect model, the pooled sensitivity and specificity for [18F]FDG PET/CT and [18F]FDG PET/MRI were reported as estimates with 95% confidence intervals (CIs). Heterogeneity among pooled studies was assessed using the I² statistic. The Quality Assessment of Diagnostic Performance Studies (QUADAS-2) method was used to evaluate the quality of the studies that were included.

Results

There were a total of 2743 publications identified in the initial search, finally, a total of 21 studies comprising 1036 patients were included. The pooled sensitivity, specificity, and AUC of [18F]FDG PET/CT in were 0.86 (95% CI: 0.76-0.92), 0.89 (95% CI: 0.83-0.94), and 0.92(95% CI: 0.90-0.94). [18F]FDG PET/MRI were 0.84 (95% CI: 0.77-0.89), 1.00 (95% CI: 0.32-1.00), and 0.89(95% CI: 0.86-0.92), respectively.

Conclusion

[18F]FDG PET/CT shows similar performance compared to [18F]FDG PET/MRI in detecting colorectal liver metastasis. However, pathological results were not obtained for all patients in the included studies and PET/MRI results were derived from studies with small sample sizes. There is a need for additional, larger prospective studies on this issue.

Systematic review registration

https://www.crd.york.ac.uk/prospero/, identifier (CRD42023390949).

Current Update on PET/MRI in Gynecological Malignancies-A Review of the Literature

Early detection of gynecological malignancies is vital for patient management and prolonging the patient's survival. Molecular imaging, such as positron emission tomography (PET)/computed tomography, has been increasingly utilized in gynecological malignancies. PET/magnetic resonance imaging (MRI) enables the assessment of gynecological malignancies by combining the metabolic information of PET with the anatomical and functional information from MRI. This article will review the updated applications of PET/MRI in gynecological malignancies.

Optimized Whole-Body PET MRI Sequence Workflow in Pediatric Hodgkin Lymphoma Patients

¹⁸F-FDG PET/MRI might be the diagnostic method of choice for Hodgkin lymphoma patients, as it combines significant metabolic information from PET with excellent soft-tissue contrast from MRI and avoids radiation exposure from CT. However, a major issue is longer examination times than for PET/CT, especially for younger children needing anesthesia. Thus, a targeted selection of suitable whole-body MRI sequences is important to optimize the PET/MRI workflow. Methods: The initial PET/MRI scans of 84 EuroNet-PHL-C2 study patients from 13 international PET centers were evaluated. In each available MRI sequence, 5 PET-positive lymph nodes were assessed. If extranodal involvement occurred, 2 splenic lesions, 2 skeletal lesions, and 2 lung lesions were also assessed. A detection rate was calculated dividing the number of visible, anatomically assignable, and measurable lesions in the respective MRI sequence by the total number of lesions. Results: Relaxation time-weighted (T2w) transverse sequences with fat saturation (fs) yielded the best result, with detection rates of 95% for nodal lesions, 62% for splenic lesions, 94% for skeletal lesions, and 83% for lung lesions, followed by T2w transverse sequences without fs (86%, 49%, 16%, and 59%, respectively) and longitudinal relaxation time-weighted contrast-enhanced transverse sequences with fs (74%, 35%, 57%, and 55%, respectively). Conclusion: T2w transverse sequences with fs yielded the highest detection rates and are well suited for accurate whole-body PET/MRI in lymphoma patients. There is no evidence to recommend the use of contrast agents.

EANM practice guideline for quantitative SPECT-CT

PURPOSE

Quantitative SPECT-CT is a modality of growing importance with initial developments in post radionuclide therapy dosimetry, and more recent expansion into bone, cardiac and brain imaging together with the concept of theranostics more generally. The aim of this document is to provide guidelines for nuclear medicine departments setting up and developing their quantitative SPECT-CT service with guidance on protocols, harmonisation and clinical use cases.

METHODS

These practice guidelines were written by members of the European Association of Nuclear Medicine Physics, Dosimetry, Oncology and Bone committees representing the current major stakeholders in Quantitative SPECT-CT. The guidelines have also been reviewed and approved by all EANM committees and have been endorsed by the European Association of Nuclear Medicine.

CONCLUSION

The present practice guidelines will help practitioners, scientists and researchers perform high-quality quantitative SPECT-CT and will provide a framework for the continuing development of quantitative SPECT-CT as an established modality.

Imaging Techniques in Pharmacological Precision Medicine

Biomedical imaging is a powerful tool for medical diagnostics and personalized medicines. Examples of commonly used imaging modalities include Positron Emission Tomography (PET), Ultrasound (US), Single Photon Emission Computed Tomography (SPECT), and hybrid imaging. By combining these modalities, scientists can gain a comprehensive view and better understand physiology and pathology at the preclinical, clinical, and multiscale levels. This can aid in the accuracy of medical diagnoses and treatment decisions. Moreover, biomedical imaging allows for evaluating the metabolic, functional, and structural details of living tissues. This can be particularly useful for the early diagnosis of diseases such as cancer and for the application of personalized medicines. In the case of hybrid imaging, two or more modalities are combined to produce a high-resolution image with enhanced sensitivity and specificity. This can significantly improve the accuracy of diagnosis and offer more detailed treatment plans. In this book chapter, we showcase how continued advancements in biomedical imaging technology can potentially revolutionize medical diagnostics and personalized medicine.

Development of 89Zr-anti-CD103 PET imaging for non-invasive assessment of cancer reactive T cell infiltration

PURPOSE

CD103, an integrin specifically expressed on the surface of cancer-reactive T cells, is significantly increased during successful immunotherapy across human malignancies. In this study, we describe the generation and zirconium-89 (⁸⁹Zr) radiolabeling of monoclonal antibody (mAb) clones that specifically recognize human CD103 for non-invasive immune positron-emission tomography (PET) imaging of T cell infiltration as potential biomarker for effective anticancer immune responses.

EXPERIMENTAL DESIGN

First, to determine the feasibility of anti-CD103 immuno-PET to visualize CD103-positive cells at physiologically and clinically relevant target densities, we developed an ⁸⁹Zr-anti-murine CD103 PET tracer. Healthy, non-tumor bearing C57BL/6 mice underwent serial PET imaging after intravenous injection, followed by ex vivo biodistribution. Tracer specificity and macroscopic tissue distribution were studied using autoradiography combined with CD103 immunohistochemistry. Next, we generated and screened six unique mAbs that specifically target human CD103 positive cells. Optimal candidates were selected for ⁸⁹Zr-anti-human CD103 PET development. Nude mice (BALB/cOlaHsd-Foxn1nu) with established CD103 expressing Chinese hamster ovary (CHO) or CHO wild-type xenografts were injected with ⁸⁹Zr-anti-human CD103 mAbs and underwent serial PET imaging, followed by ex vivo biodistribution.

RESULTS

⁸⁹Zr-anti-murine CD103 PET imaging identified CD103-positive tissues at clinically relevant target densities. For human anti-human CD103 PET development two clones were selected based on strong binding to the CD103⁺ CD8⁺ T cell subpopulation in ovarian cancer tumor digests, non-overlapping binding epitopes and differential CD103 blocking properties. In vivo, both ⁸⁹Zr-anti-human CD103 tracers showed high target-to-background ratios, high target site selectivity and a high sensitivity in human CD103 positive xenografts.

CONCLUSION

CD103 immuno-PET tracers visualize CD103 T cells at relevant densities and are suitable for future non-invasive assessment of cancer reactive T cell infiltration.

Consistency and prognostic value of preoperative staging and postoperative pathological staging using 18F-FDG PET/MRI in patients with non-small cell lung cancer

OBJECTIVE

In recent years, positron emission tomography/magnetic resonance imaging (PET/MRI) has been clinically used as a method to diagnose non-small cell lung cancer (NSCLC). This study aimed to evaluate the concordance of staging and prognostic ability of NSCLC patients using thin-slice computed tomography (CT) and ¹⁸F-fluorodeoxyglucose (FDG) PET/MRI.

METHODS

This retrospective study was performed on consecutive NSCLC patients who underwent both diagnostic CT and ¹⁸F-FDG PET/MRI before surgery between November 2015 and May 2019. The cTNM staging yielded from PET/MRI was compared with CT and pathological staging, and concordance was investigated, defining pathological findings as reference. To assess the prognostic value of disease-free survival (DFS) and overall survival (OS), we dichotomized the typical prognostic factors and TNM classification staging (Stage I vs. Stage II or higher). Kaplan-Meier curves derived by the log-rank test were generated, and univariate and multivariate analyses were performed to identify the factors associated with DFS and OS.

RESULTS

A total of 82 subjects were included; PET/MRI staging was more consistent (59 of 82) with pathological staging than with CT staging. There was a total of 21 cases of CT and 11 cases of PET/MRI that were judged as cStage I, but were actually pStage II or pStage III. CT tended to judge pN1 or pN2 as cN0 compared to PET/MRI. There was a significant difference between NSCLC patients with Stage I and Stage II or higher by PET/MRI staging as well as prognosis prediction of DFS by pathological staging (P < 0.001). In univariate analysis, PET/MRI, CT, and pathological staging (Stage I or lower vs. Stage II or higher) all showed significant differences as prognostic factors of recurrence or metastases. In multivariate analysis, pathological staging was the only independent factor for recurrence (P = 0.009), and preoperative PET/MRI staging was a predictor of patient survival (P = 0.013).

CONCLUSIONS

In NSCLC, pathologic staging was better at predicting recurrence, and preoperative PET/MRI staging was better at predicting survival. Preoperative staging by PET/MRI was superior to CT in diagnosing hilar and mediastinal lymph-node metastases, which contributed to the high concordance with pathologic staging.

Diagnostic performance of [18F]-FDG PET/MR in evaluating colorectal cancer: a systematic review and meta-analysis

PURPOSE

To calculate the diagnostic performance of [¹⁸F]-FDG PET/MR in colorectal cancer (CRC).

METHODS

This study was designed following the PRISMA-DTA guidelines. To be included, published original articles (until December 31, 2021) that met the following criteria were considered eligible: (1) evaluated [¹⁸F]-FDG PET/MR as the diagnostic method to detect CRC; (2) compared [¹⁸F]-FDG PET/MR with histopathology as the reference standard, or clinical/imaging composite follow-up when pathology was not available; (3) provided adequate crude data for meta-analysis. The diagnostic pooled measurements were calculated at patient and lesion levels. Regarding sub-group analysis, diagnostic measurements were calculated in "TNM staging," "T staging," "N staging," "M staging," and "liver metastasis" sub-groups. Additionally, we calculated the pooled performances in "rectal cancer: patient-level" and "rectal cancer: lesion-level" sub-groups. A hierarchical method was used to pool the performances. The bivariate model was conducted to find the summary points. Analyses were performed using STATA 16.

RESULTS

A total of 1534 patients from 18 studies were entered. The pooled sensitivities in CRC lesion detection (tumor, lymph nodes, and metastases) were 0.94 (95%CI: 0.89-0.97) and 0.93 (95%CI: 0.82-0.98) at patient-level and lesion-level, respectively. The pooled specificities were 0.89 (95%CI: 0.84-0.93) and 0.95 (95%CI: 0.90-0.98) at patient-level and lesion-level, respectively. In sub-groups, the highest sensitivity (0.97, 95%CI: 0.86-0.99) and specificity (0.99, 95%CI: 0.84-1.00) were calculated for "M staging" and "rectal cancer: lesion-level," respectively. The lowest sensitivity (0.81, 95%CI: 0.65-0.91) and specificity (0.79, 95%CI: 0.52-0.93) were calculated for "N staging" and "T staging," respectively.

CONCLUSION

This meta-analysis showed an overall high diagnostic performance for [¹⁸F]-FDG PET/MR in detecting CRC lesions/metastases. Thus, this modality can play a significant role in several clinical scenarios in CRC staging and restaging. Specifically, one of the main strengths of this modality is ruling out the existence of CRC lesions/metastases. Finally, the overall diagnostic performance was not found to be affected in the post-treatment setting.

Value of FDG-PET/MR in Oral Focus Assessment in Head and Neck Cancer Patients-A Feasibility Study

FDG-PET/MR is a hybrid imaging modality used for the staging and restaging of advanced head & neck cancer (HNC) patients. Their treatment typically involves radiation therapy, which requires previous dental focus assessment. The aim of this study was to analyze if staging FDG-PET/MR is a valuable tool for oral focus assessment. For this purpose, FDG-PET/MR findings, such as metabolic activity of periapical radiolucencies and marginal periodontitis, were retrospectively compared with conventional standardized dental focus assessment, including dental radiographs and clinical assessment of 124 teeth in seven patients. Increased FDG uptake of periapical lesions was found in one out of 23 lesions. Increased FDG uptake of the marginal periodontium was recorded in one out of 34 lesions. In summary, standardized dental focus assessment by panoramic radiography and periapical radiographs may be enriched by information from FDG-PET/MR, showing active inflammation in dental foci. However, many dental foci have no correlate in FDG-PET/MR. The treatment decision for oral foci may benefit from the visualized presence or absence of metabolic activity on FDG-PET/MR.

Integrated PET/MRI With 68Ga-DOTATATE and 18F-FDG in Pheochromocytomas and Paragangliomas: An Initial Study

PURPOSE

Pheochromocytomas and paragangliomas (PPGLs) are rare neuroendocrine tumors with metastatic potential. Both 68Ga-DOTATATE and 18F-FDG PET/CT scans have been demonstrated to have important roles in imaging PPGLs, but less is known about the performance of PET/MRI for PPGLs. The study is aimed to investigate whether diffusion-weighted imaging-MRI (DWI-MRI) has an added value to PET imaging in the identification of PPGL lesions by means of integrated PET/MRI.

METHODS

Eleven patients who underwent both 18F-FDG and 68Ga-DOTATATE PET/MRI within 2 weeks were retrospectively included in the study. A total of 56 PPGL lesions were analyzed, and lesion-based detection rates of 68Ga-DOTATATE PET, 18F-FDG PET, DWI-MRI, and PET/MRI were calculated and compared, respectively.

RESULTS

68Ga-DOTATATE PET was superior to 18F-FDG PET and DWI-MRI in imaging PPGLs with a lesion-based detection rate of 96.4% (54/56) (95% confidence interval [CI], 87.7%-99.6%), 85.7% (48/56) (95% CI, 76.3%-95.2%), and 89.3% (50/56) (95% CI, 80.9%-97.6%), respectively. PET/MRI with DWI could improve the detection rate of 68Ga-DOTATATE and 18F-FDG PET alone up to 100% in metastatic PPGLs. Lesions of PPGL demonstrated markedly higher tracer uptake in 68Ga-DOTATATE PET than in 18F-FDG PET (P = 0.009 for primary lesion, P = 0.033 for metastases).

CONCLUSIONS

68Ga-DOTATATE PET showed a higher detection rate than 18F-FDG for PPGLs. In integrated PET/MRI, MRI had an added value to 18F-FDG PET but not much to 68Ga-DOTATATAE PET in identifying PPGL lesions.

Study on the RF transparency of electrically floating and ground PET inserts in a 3T clinical MRI system

PURPOSE

The positron emission tomography (PET) insert for a magnetic resonance imaging (MRI) system that implements the radiofrequency (RF) built-in body coil of the MRI system as a transmitter is designed to be RF-transparent, as the coil resides outside the RF-shielded PET ring. This approach reduces the design complexities (e.g., large PET ring diameter) related to implementing a transmit coil inside the PET ring. However, achieving the required field transmission into the imaging region of interest (ROI) becomes challenging because of the RF shield of the PET insert. In this study, a modularly RF-shielded PET insert is used to investigate the RF transparency considering two electrical configurations of the RF shield, namely the electrical floating and ground configurations. The purpose is to find the differences, advantages and disadvantages of these two configurations.

METHODS

Eight copper-shielded PET detector modules (intermodular gap: 3 mm) were oriented cylindrically with an inner-diameter of 234 mm. Each PET module included four-layer LYSO scintillation crystal blocks and front-end readout electronics. RF-shielded twisted-pair cables were used to connect the front-end electronics with the power sources and PET data acquisition systems located outside the MRI room. In the ground configuration, both the detector and cable shields were connected to the RF ground of the MRI system. In the floating configuration, only the RF shields of the PET modules were isolated from the RF ground. Experiments were conducted using two cylindrical homogeneous phantoms in a 3T clinical MRI system, in which the built-in body RF coil (a cylindrical volume coil of diameter 700 mm and length 540 mm) was implemented as a transceiver.

RESULTS

For both PET configurations, the RF and MR imaging performances were lower than those for the MRI-only case, and the MRI-system provided SAR values that were almost double. The RF homogeneity and field strength, and the SNR of the MR images were mostly higher for the floating PET configuration than they were for the ground PET configuration. However, for a shorter axial FOV of 125 mm, both configurations offered almost the same performance with high RF homogeneities (e.g., 76 ± 10%). Moreover, for both PET configurations, 56 ± 6% larger RF pulse amplitudes were required for MR imaging purposes. The increased power is mostly absorbed in the conductive shields in the form of shielding RF eddy currents; as a result, the SAR values only in the phantoms were estimated to be close to the MRI-only values.

CONCLUSIONS

The floating PET configuration showed higher RF transparency under all experimental setups. For a relatively short axial FOV of 125 mm, the ground configuration also performed well which indicated that an RF-penetrable PET insert with the conventional design (e.g., the ground configuration) might also become possible. However, some design modifications (e.g., a wider intermodular gap and using the RF receiver coil inside the PET insert) should improve the RF performance to the level of the MRI-only case. This article is protected by copyright. All rights reserved.

Evaluating the impact of different positron emitters on the performance of a clinical PET/MR system

PURPOSE

The positron range and prompt gamma emission are distinctive with different positron emitters. The performance assessment of an integrated PET/MR scanner with these positron emitters is required for related applications, as the magnetic field interferes with the positron propagation. Such an assessment is to be performed on the United Imaging uPMR 790 integrated PET/MR system.

METHODS

The performance measurement methods were modified based on NEMA NU 2-2012, involving ¹⁸ F, ⁶⁴ Cu, ⁶⁸ Ga, ⁸⁹ Zr, and ¹²⁴ I as positron emitters. The NEMA IEC phantom was used for evaluations of image qualities. An agarose cap was wrapped around the point source for tissue-simulating spatial resolution measurement. The count rate performance was assessed with selected positron emitters. Images of a 3D-printed Derenzo phantom and representative patients were also acquired.

RESULTS

The image quality measurement showed that all five positron emitters were suitable for the PET/MR system studied. However, due to the magnetic field, the image of the point source showed an elongated comet-tail feature, which could be eliminated by a tissue-simulating cap. This effect is more obvious in ¹²⁴ I and ⁶⁸ Ga, due to their long positron ranges. The imaging ability with various positron emitters was further validated with the count rate assessment, the Derenzo phantom, and the clinical images.

CONCLUSIONS

Different positron emitters could be effectively imaged by the PET/MR system tested. The resolution measurement strategy proposed could be applied to measure PET spatial resolution in the magnetic field. This article is protected by copyright. All rights reserved.

[177Lu]Lu-DOTA-TATE and [131I]MIBG Phenotypic Imaging-Based Therapy in Metastatic/Inoperable Pheochromocytomas and Paragangliomas: Comparative Results in a Single Center

PURPOSE

The aim of the study is to assess phenotypic imaging patterns and the response to treatment with [¹⁷⁷Lu]Lu-DOTA-TATE and/or [¹³¹I]MIBG in paragangliomas (PGLs) and pheochromocytomas (PHEOs), globally and according to the primary location.

METHODS

This is a 17-patient retrospective observational study, with 9 cases treated with [¹⁷⁷Lu]Lu-DOTA-TATE and 8 with [¹³¹I]MIBG (37 total treatments). Functional imaging scans and treatment responses were studied in order to choose the best therapeutic option and to define the progression-free survival (PFS) and disease control rate (DCR) according to treatment modality and primary location.

RESULTS

All patients were studied with phenotypic nuclear medicine images. Twelve of 17 patients were tested with both [¹²³I]MIBG and somatostatin receptor images, and 6/12 showed appropriate expression of both targets to treatment in the phenotypic images. The rest of the patients were tested with one of the image modalities or only showed suitable uptake of a single radiotracer and were treated with the corresponding therapeutic option. [¹⁷⁷Lu]Lu-DOTA-TATE PFS was 29 months with a DCR of 88.8%. [¹³¹I]MIBG PFS was 18.5 months with a 62.5% DCR. According to the primary location, the best PFS was in PHEOs treated with [¹⁷⁷Lu]Lu-DOTA-TATE. Although the series are small due to the low disease prevalence and do not allow to yield statistically significant differences, this first study comparing [¹⁷⁷Lu]Lu-DOTA-TATE and [¹³¹I]MIBG displays a trend to an overall longer PFS with [¹⁷⁷Lu]Lu-DOTA-TATE, especially in the adrenal primary location. When both radionuclide targets are expressed, the patients' comorbidity and treatment effectiveness should be valued together with the intensity uptake in the phenotypic image in order to choose the best therapeutic option. These preliminary retrospective results reinforce the need for a prospective, multicentric trial to be confirmed.

Clinical Use of PET/MR in Oncology: An Update

The combination of PET and MRI is one of the recent advances of hybrid imaging. Yet to date, the adoption rate of PET/MRI systems has been rather slow. This seems to be partially caused by the high costs of PET/MRI systems and the need to verify an incremental benefit over PET/CT or sequential PET/CT and MRI. In analogy to PET/CT, the MRI part of PET/MRI was primarily used for anatomical imaging. Though this can be advantageous, for example in diseases where the superior soft tissue contrast of MRI is highly appreciated, the sole use of MRI for anatomical orientation lessens the potential of PET/MRI. Consequently, more recent studies focused on its multiparametric potential and employed diffusion weighted sequences and other functional imaging sequences in PET/MRI. This integration puts the focus on a more wholesome approach to PET/MR imaging, in terms of releasing its full potential for local primary staging based on multiparametric imaging and an included one-stop shop approach for whole-body staging. This approach as well as the implementation of computational analysis, in terms of radiomics analysis, has been shown valuable in several oncological diseases, as will be discussed in this review article.

Adapting Imaging Protocols for PET-CT and PET-MRI for Immunotherapy Monitoring

Hybrid imaging with positron emission tomography (PET) in combination with computer tomography (CT) is a well-established diagnostic tool in oncological staging and restaging. The combination of PET with magnetic resonance imaging (MRI) as a clinical scanner was introduced approximately 10 years ago. Although MRI provides superb soft tissue contrast and functional information without the radiation exposure of CT, PET-MRI is not as widely introduced in oncologic imaging as PET-CT. One reason for this hesitancy lies in the relatively long acquisition times for a PET-MRI scan, if the full diagnostic potential of MRI is exploited. In this review, we discuss the possible advantages of combined imaging protocols of PET-CT and PET-MRI, within the context of staging and restaging of patients under immunotherapy, in order to achieve "multi-hybrid imaging" in one single patient visit.

Whole-body hybrid positron emission tomography imaging yields clinically relevant information in the staging and restaging of sinonasal tumors

Background

Whole‐body hybrid positron emission tomography (PET) imaging is increasingly used for sinonasal tumors. However, only empirical data exist on the additional, clinically relevant information derived from these techniques.

Methods

This study included 96 regionalized magnetic resonance imaging (MRI) of the sinonasal tract/neck and separate hybrid FDG‐PET/CT or FDG‐PET/MRI in 74 patients. Additional radiological information (ARI) obtained from each hybrid examination was analyzed and its clinically relevance was determined. Clinically relevant information (CRI) was categorized with regard to primary tumor site, regional lymph node metastases, distant metastases, second primary tumors, and non‐neoplastic findings.

Results

A total of 45/96 (46.9%) hybrid PET examinations revealed ARI. CRI was found in 32/96 (33.3%) examinations and concerned the primary tumor site (6.1%), regional lymph node metastases (4.1%), distant metastases (14.3%), second primary tumors (7.3%), and non‐neoplastic findings (5.1%).

Conclusions

Hybrid PET imaging yields additional radiological information translating into clinically relevant information in a substantial proportion of patients with sinonasal tumors.

Fully Integrated Quantitative Multiparametric Analysis of Non-Small Cell Lung Cancer at 3-T PET/MRI: Toward One-Stop-Shop Tumor Biological Characterization at the Supervoxel Level

INTRODUCTION

The aim of this study was to study the feasibility of a fully integrated multiparametric imaging framework to characterize non-small cell lung cancer (NSCLC) at 3-T PET/MRI.

PATIENTS AND METHODS

An 18F-FDG PET/MRI multiparametric imaging framework was developed and prospectively applied to 11 biopsy-proven NSCLC patients. For each tumor, 12 parametric maps were generated, including PET full kinetic modeling, apparent diffusion coefficient, T1/T2 relaxation times, and DCE full kinetic modeling. Gaussian mixture model-based clustering was applied at the whole data set level to define supervoxels of similar multidimensional PET/MRI behaviors. Taking the multidimensional voxel behaviors as input and the supervoxel class as output, machine learning procedure was finally trained and validated voxelwise to reveal the dominant PET/MRI characteristics of these supervoxels at the whole data set and individual tumor levels.

RESULTS

The Gaussian mixture model-based clustering clustering applied at the whole data set level (17,316 voxels) found 3 main multidimensional behaviors underpinned by the 12 PET/MRI quantitative parameters. Four dominant PET/MRI parameters of clinical relevance (PET: k2, k3 and DCE: ve, vp) predicted the overall supervoxel behavior with 97% of accuracy (SD, 0.7; 10-fold cross-validation). At the individual tumor level, these dimensionality-reduced supervoxel maps showed mean discrepancy of 16.7% compared with the original ones.

CONCLUSIONS

One-stop-shop PET/MRI multiparametric quantitative analysis of NSCLC is clinically feasible. Both PET and MRI parameters are useful to characterize the behavior of tumors at the supervoxel level. In the era of precision medicine, the full capabilities of PET/MRI would give further insight of the characterization of NSCLC behavior, opening new avenues toward image-based personalized medicine in this field.

[Positron emission tomography with computed tomography/magnetic resonance imaging for primary staging of prostate cancer]

CLINICAL/METHODOLOGICAL ISSUE

Prostate cancer is the most common malignancy and the second leading cause of cancer-related death in men. Accurate imaging diagnosis and staging are crucial for patient management and treatment. The role of nuclear medicine in the diagnosis of prostate cancer has evolved rapidly in recent years due to the availability of hybrid imaging with radiopharmaceuticals targeting the prostate-specific membrane antigen (PSMA).

STANDARD RADIOLOGICAL PROCEDURES

Hybrid imaging provides higher diagnostic accuracy compared to conventional imaging and has a significant impact on clinical management. Numerous radiotracers have been used in clinical applications, with PSMA ligands being the most commonly used.

METHODOLOGICAL INNOVATIONS

Hybrid imaging provides higher diagnostic accuracy for lymph node and bone metastases compared to conventional imaging and has a significant impact on clinical management.

PERFORMANCE

The high accuracy for primary staging in high-risk prostate cancer using PSMA ligands has led to the inclusion of PSMA positron emission tomography (PET)/computed tomography (CT) in the new German S3 guideline for primary staging of prostate cancer.

PURPOSE

The aim of this article is to provide an overview of the use of PET imaging in the primary diagnosis of prostate cancer, to present the most commonly used radiotracers, and to highlight the results of recent studies.

A novel model to assess disease activity in Takayasu arteritis based on 18F-FDG-PET/CT: a Chinese cohort study

OBJECTIVE

To investigate the utility of 18F-fluorodeoxyglucose positron emission tomography/computed tomography (18F-FDG-PET/CT) in assessing disease activity in Takayasu arteritis (TA).

METHODS

Ninety-one patients with TA, were recruited from a Chinese cohort. Clinical data, acute-phase reactants (APRs), and 18F-FDG-PET/CT findings were simultaneously recorded. The value of using 18F-FDG-PET/CT to identify active disease was evaluated, using erythrocyte sedimentation rate (ESR) as a reference. Disease activity assessment models were constructed and concordance index (C-index), net reclassification index (NRI), and integrated discrimination index (IDI) were evaluated to compare the benefits of the new modes with ESR and Kerr score.

RESULTS

In total, 64 (70.3%) cases showed active disease. Higher levels of ESR and CRP, and lower interleukin (IL)-2R levels, were observed in active cases. 18F-FDG-PET/CT parameters, including SUVmean, SUVratio1, SUVratio2, sum of SUVmean, and sum of SUVmax, were significantly higher in active disease groups. The C index threshold of ESR to indicate active disease was 0.78 (95% CI: 0.69-0.88). The new activity assessment model combining ESR, sum of SUVmean, and IL-2R showed significant improvement in C index over the ESR method (0.96 vs 0.78, p < 0.01; NRI 1.63, p < 0.01; and IDI 0.48, p < 0.01). The new model also demonstrated modest superiority to Kerr score assessment (0.96 vs 0.87, p = 0.03; NRI 1.19, p < 0.01; and IDI 0.33 p < 0.01).

CONCLUSIONS

A novel 18F-FDG-PET/CT-based method that involves combining the sum of SUVmean with ESR score and IL-2R levels demonstrated superiority in identifying active TA compared with conventional methods.

Whole-Body Integrated [68Ga]PSMA-11-PET/MR Imaging in Patients with Recurrent Prostate Cancer: Comparison with Whole-Body PET/CT as the Standard of Reference

PURPOSE

The aim of this study was to evaluate the detection rate of [⁶⁸Ga]prostate-specific membrane antigen ([⁶⁸Ga]PSMA-11) positron emission tomography (PET)/magnetic resonance imaging (MRI) and to compare it with [⁶⁸Ga]PSMA-11 PET/X-ray computed tomography (CT) in patients with recurrent prostate cancer (PC) after radical prostatectomy.

PROCEDURES

A total of 93 patients with biochemically recurrent prostate cancer underwent [⁶⁸Ga]PSMA-11 PET/CT and subsequently a whole-body integrated PET/MRI examination. Board certified nuclear medicine physicians and radiologists evaluated PET/CT and PET/MRI datasets regarding identification of tumor lesions ((i) lymph nodes, (ii) bone lesions, (iii) local recurrence, and (iv) parenchymal lesions) based on maximum [⁶⁸Ga]PSMA-11 uptake as well as morphological changes. Quality of PET images for both PET/CT and PET/MRI were rated using a 5-point scoring system by evaluating lesion homogeneity, contrast, contour, and delineation. Wilcoxon signed-rank tests were used to determine statistical differences.

RESULTS

PC relapse was detected in 62/93 patients. PET/MRI detected 148 out of 150 lesions described in PET/CT. In addition, PET/MRI detected 11 lesions not detected in PET/CT (5 lymph nodes, 6 local recurrences). The exact McNemar statistical test (one-sided) showed significant difference between PET/CT and PET/MRI for diagnosis of local recurrence (p value = 0.031). Diagnostic confidence for (iii) was higher in PET/MRI compared with PET/CT (PET/CT = 1.1; PET/MRI = 4.9). Diagnostic confidence for (i) (PET/CT = 4.9; PET/MRI = 4.6), (ii) (PET/CT = 4.9; PET/MRI = 4.6), and (iv) (PET/CT = 4.6; PET/MRI = 4.8) was equivalent between PET/MRI and PET/CT.

CONCLUSIONS

Integrated [⁶⁸Ga]PSMA-11 PET/MRI provides a similarly high diagnostic performance for localization of recurrent PC as PET/CT. For the detection of local recurrences [⁶⁸Ga]PSMA-11 PET/MRI is superior compared with [⁶⁸Ga]PSMA-11 PET/CT.

PET/MRI assessment of lung nodules in primary abdominal malignancies: sensitivity and outcome analysis

PURPOSE

To evaluate PET/MR lung nodule detection compared to PET/CT or CT, to determine growth of nodules missed by PET/MR, and to investigate the impact of missed nodules on clinical management in primary abdominal malignancies.

METHODS

This retrospective IRB-approved study included [18F]-FDG PET/MR in 126 patients. All had standard of care chest imaging (SCI) with diagnostic chest CT or PET/CT within 6 weeks of PET/MR that served as standard of reference. Two radiologists assessed lung nodules (size, location, consistency, position, and [18F]-FDG avidity) on SCI and PET/MR. A side-by-side analysis of nodules on SCI and PET/MR was performed. The nodules missed on PET/MR were assessed on follow-up SCI to ascertain their growth (≥ 2 mm); their impact on management was also investigated.

RESULTS

A total of 505 nodules (mean 4 mm, range 1-23 mm) were detected by SCI in 89/126 patients (66M:60F, mean age 60 years). PET/MR detected 61 nodules for a sensitivity of 28.1% for patient and 12.1% for nodule, with higher sensitivity for > 7 mm nodules (< 30% and > 70% respectively, p < 0.05). 75/337 (22.3%) of the nodules missed on PET/MR (follow-up mean 736 days) demonstrated growth. In patients positive for nodules at SCI and negative at PET/MR, missed nodules did not influence patients' management.

CONCLUSIONS

Sensitivity of lung nodule detection on PET/MR is affected by nodule size and is lower than SCI. 22.3% of missed nodules increased on follow-up likely representing metastases. Although this did not impact clinical management in study group with primary abdominal malignancy, largely composed of extra-thoracic advanced stage cancers, with possible different implications in patients without extra-thoracic spread.

Systematic imaging in medicine: a comprehensive review

Systematic imaging can be broadly defined as the systematic identification and characterization of biological processes at multiple scales and levels. In contrast to "classical" diagnostic imaging, systematic imaging emphasizes on detecting the overall abnormalities including molecular, functional, and structural alterations occurring during disease course in a systematic manner, rather than just one aspect in a partial manner. Concomitant efforts including improvement of imaging instruments, development of novel imaging agents, and advancement of artificial intelligence are warranted for achievement of systematic imaging. It is undeniable that scientists and radiologists will play a predominant role in directing this burgeoning field. This article introduces several recent developments in imaging modalities and nanoparticles-based imaging agents, and discusses how systematic imaging can be achieved. In the near future, systematic imaging which combines multiple imaging modalities with multimodal imaging agents will pave a new avenue for comprehensive characterization of diseases, successful achievement of image-guided therapy, precise evaluation of therapeutic effects, and rapid development of novel pharmaceuticals, with the final goal of improving human health-related outcomes.

Diagnostic Accuracy of Combined PET/CT with MRI, 18F-FDG PET/MRI, and 18F-FDG PET/CT in Patients with Oropharyngeal and Hypopharyngeal Squamous Cell Carcinoma: A Systematic Review and Meta-Analysis

Introduction

The aim of this paper is to compare the diagnostic accuracy of PET/CT, PET/MRI, and the combination of PET/CT and MRI for detecting synchronous cancer and distant metastasis in patients with oropharyngeal and hypopharyngeal squamous cell carcinomas (OHSCC).

Method

A large and growing body of literature has been conducted using the Preferred Reporting Items for Systematic Reviews (PRISMA). The researchers collected all accessible literature existing through Cochrane Library (John Wiley & Sons) electronic databases, Embase (Elsevier), PubMed (U.S. National Library of Medicine), Scopus, and Google Scholar up to June 2020. Analyses were conducted using Stata version 12.0 (StataCorp LP).

Results

A total of nine studies consisting of 1166 patients were included. The pooled sensitivity of combined PET/CT with MRI, 18F-FDG PET/MRI, and 18F-FDG PET/CT was 0.92, 0.80, and 0.79, respectively, and the corresponding specificities were 0.93, 0.91, and 0.88. The overall prevalence of distant metastases and synchronous cancer in patients with oropharyngeal and hypopharyngeal squamous cell carcinomas was 9.2% and 11.8%, respectively, with the esophagus (4.6%) being the most common site of synchronous cancer. The most common sites of distant metastases were lung (3%), bone (1.2%), and distant lymph nodes (1.2%), respectively.

Conclusion

Our study showed an approximately similar diagnostic performance for PET/CT, PET/MRI, and the combination of PET/CT and MRI for metastasis assessment in advanced oropharyngeal and hypopharyngeal squamous cell carcinomas.

A quantitative LC-MS/MS approach for monitoring 2'-fluoro-2'-deoxy-D-glucose uptake in tumor tissue

Purpose: Develop a quantitative LC-MS/MS method for FDG, FDG-monophosphate, glucose and glucose-monophosphate in mouse tumor models to assist in validating the use of [¹⁸F]FDG-positron emission tomography (PET) imaging for anticancer therapies in a clinical setting. Methodology/results: Analytes were isolated from tumors by protein precipitation and detected on a Sciex API-5500 mass spectrometer. Improved assay robustness and selectivity were achieved through chromatographic separation of FDG-monophosphate from glucose-monophosphate, selection of a unique ion transition and incorporation of stable isotope labeled internal standards. In a mouse JIMT-1 tumor model, FDG-monophosphate levels measured by LC-MS/MS correlated with [¹⁸F]FDG-PET imaging results. Conclusion: LC-MS/MS analysis of FDG-monophosphate accumulation in tumors is a cost-effective tool to gauge the translational potential of [¹⁸F]FDG-PET imaging as a noninvasive biomarker in clinical studies.

Abdominal and pelvic 18F-FDG PET/MR: a review of current and emerging oncologic applications

Positron emission tomography (PET) using fluorodeoxyglucose (¹⁸F-FDG) combined with magnetic resonance imaging (MR) is an emerging hybrid modality that has shown utility in evaluating abdominal and pelvic disease entities. Together, the high soft tissue contrast and metabolic/functional imaging capabilities make this modality ideal for oncologic imaging in many organ systems. Its clinical utility continues to evolve and future research will help solidify its role in oncologic imaging. In this manuscript, we aim to (1) provide an overview of the various PET/MR systems, describing the strengths and weaknesses of each system, and (2) review the oncologic applications for ¹⁸F-FDG PET/MR in the abdomen and pelvis.

Clinical utilization of whole-body PET/MRI in childhood sarcoma

Hybrid positron emission tomography (PET)/magnetic resonance imaging (MRI) has emerged as a useful tool that combines the superior tissue contrast of MRI with the targeted functional imaging of PET. In the assessment of sarcomas in children, PET/MRI has the potential to serve as a single point of service, allowing superior anatomical imaging and evaluation of metabolic uptake during one imaging session. In this pictorial essay, we review our preliminary experience with PET/MRI in the evaluation of pediatric sarcoma. The limitations and contraindications of PET/MRI are also discussed.

Initial experience with positron emission tomography/computed tomography in addition to computed tomography and magnetic resonance imaging in preoperative risk assessment of endometrial cancer patients

OBJECTIVE

Improved preoperative evaluation of lymph node status could potentially replace lymphadenectomy in women with endometrial cancer. PET/CT was routinely implemented in the preoperative workup of endometrial cancer at St Olav's University Hospital in 2016. Experience with PET/CT is limited, and there is no consensus about the use of PET/CT in the diagnostic workup of endometrial cancer. The aim of the study was to evaluate the diagnostic accuracy of PET/CT compared to standard CT/MRI in identifying lymph node metastases in endometrial cancer with histologically confirmed lymph node metastases as the standard of reference. We especially wanted to look at PET/CT as a supplement to the sentinel lymph node algorithm in the detection of paraaortic lymph nodes.

STUDY DESIGN

A retrospective study included all women undergoing surgery for endometrial cancer from January 2016 through July 2019 at St Olav's University Hospital. Clinical data, results of CT, MRI, and PET/CT, and histopathological results were analyzed.

RESULTS

Among 185 patients included, 27 patients (15 %) had lymph node metastases. 17 (63 %) had pelvic lymph node metastases, one (4 %) had isolated paraaortic lymph node metastases, and 9 (33 %) had lymph node metastases in both the pelvis and the paraaortic region. The sensitivity, specificity, positive predictive value, negative predictive value and accuracy of PET/CT for the detection of lymph node metastases were 63 %, 98 %, 85 %, 94 %, and 93 %, respectively. The sensitivity, specificity, positive predictive value, negative predictive value and accuracy of CT/MRI were 41 %, 98 %, 73 %, 91 %, and 90 %, respectively (p = 0.07). For the 26 pelvic lymph node metastases, PET/CT had a sensitivity of 58 %, compared to 42 % for CT/MRI (p = 0.22). PET/CT detected all 10 paraaortic lymph node metastases, for a sensitivity of 100 %, compared to 50 % for CT/MRI (p = 0.06).

CONCLUSIONS

PET is superior to CT/MRI for detection of lymph node metastases in endometrial cancer, particularly in detecting paraaortic lymph node metastases. The ability of preoperative PET to exclude paraaortic lymph node metastases may strengthen the credibility of the sentinel lymph node algorithm.

Expanding PET-applications in life sciences with positron-emitters beyond fluorine-18

Positron-emission-tomography (PET) has become an indispensable diagnostic tool in modern nuclear medicine. Its outstanding molecular imaging features allow repetitive studies on one individual and with high sensitivity, though no interference. Rather few positron-emitters with near favourable physical properties, i.e. carbon-11 and fluorine-18, furnished most studies in the beginning, preferably if covalently bound as isotopic label of small molecules. With the advancement of PET-devices the scope of in vivo research in life sciences and especially that of medical applications expanded, and other than "standard" PET-nuclides received increasing significance, like the radiometals copper-64 and gallium-68. Especially during the last decades, positron-emitters of other chemical elements have gotten into the focus of interest, concomitant with the technical advancements in imaging and radionuclide production. With known nuclear imaging properties and main production methods of emerging positron-emitters their usefulness for medical application is promising and even proven for several ones already. Unfortunate decay properties could be corrected for, and β+-emitters, especially with a longer half-life, provided new possibilities for application where slower processes are of importance. Further on, (bio)chemical features of positron-emitters of other elements, among there many metals, not only expanded the field of classical clinical investigations, but also opened up new fields of application. Appropriately labelled peptides, proteins and nanoparticles lend itself as newer probes for PET-imaging, e.g. in theragnostic or PET/MR hybrid imaging. Furthermore, the potential of non-destructive in-vivo imaging with positron-emission-tomography directs the view on further areas of life sciences. Thus, exploiting the excellent methodology for basic research on molecular biochemical functions and processes is increasingly encouraged as well in areas outside of health, such as plant and environmental sciences.

Measuring Glucose Uptake in Primary Invasive Breast Cancer Using Simultaneous Time-of-Flight Breast PET/MRI: A Method Comparison Study with Prone PET/CT

Purpose

To compare the measurement of glucose uptake in primary invasive breast cancer using simultaneous, time-of-flight breast PET/MRI with prone time-of-flight PET/CT.

Materials and Methods

In this prospective study, women with biopsy-proven invasive breast cancer undergoing preoperative breast MRI from 2016 to 2018 were eligible. Participants who had fasted underwent prone PET/CT of the breasts approximately 60 minutes after injection of 370 MBq (10 mCi) fluorine 18 fluorodeoxyglucose (18F-FDG) followed by prone PET/MRI using standard clinical breast MRI sequences performed simultaneously with PET acquisition. Volumes of interest were drawn for tumors and contralateral normal breast fibroglandular tissue to calculate standardized uptake values (SUVs). Spearman correlation, Wilcoxon signed ranked test, Mann-Whitney test, and Bland-Altman analyses were performed.

Results

Twenty-three women (mean age, 50 years; range, 33-70 years) were included. Correlation between tumor uptake values measured with PET/MRI and PET/CT was strong (r s = 0.95-0.98). No difference existed between modalities for tumor maximum SUV (SUVmax) normalized to normal breast tissue SUVmean (normSUVmax) (P = .58). The least amount of measurement bias was observed with normSUVmax, +3.86% (95% limits of agreement: -28.92, +36.64).

Conclusion

These results demonstrate measurement agreement between PET/CT, the current reference standard for tumor glucose uptake quantification, and simultaneous time-of-flight breast 18F-FDG PET/MRI.Keywords: Breast, Comparative Studies, PET/CT, PET/MR Supplemental material is available for this article. © RSNA, 2021See also the commentary by Mankoff and Surti in this issue.

Attenuation correction for human PET/MRI studies

Attenuation correction has been one of the main methodological challenges in the integrated positron emission tomography and magnetic resonance imaging (PET/MRI) field. As standard transmission or computed tomography approaches are not available in integrated PET/MRI scanners, MR-based attenuation correction approaches had to be developed. Aspects that have to be considered for implementing accurate methods include the need to account for attenuation in bone tissue, normal and pathological lung and the MR hardware present in the PET field-of-view, to reduce the impact of subject motion, to minimize truncation and susceptibility artifacts, and to address issues related to the data acquisition and processing both on the PET and MRI sides. The standard MR-based attenuation correction techniques implemented by the PET/MRI equipment manufacturers and their impact on clinical and research PET data interpretation and quantification are first discussed. Next, the more advanced methods, including the latest generation deep learning-based approaches that have been proposed for further minimizing the attenuation correction related bias are described. Finally, a future perspective focused on the needed developments in the field is given.