Added Value of Contrast-enhanced US for Evaluation of Female Pelvic Disease.

Since the first application of contrast-enhanced US (CEUS) in the late 1960s, the use of US contrast agents has grown tremendously, and this examination has proved to be a valuable adjunct to diagnostic US for detection and characterization of disease. Also, CEUS has emerged as an excellent option for evaluation of indeterminate lesions that require additional imaging, given its excellent safety profile, including that in patients with end-stage renal disease or allergies to contrast material who are unable to undergo contrast-enhanced CT or MRI. US traditionally has been considered the imaging modality of choice for evaluation of the female pelvis, followed by MRI and rarely fluoroscopy, CT, PET, or angiography. CEUS has the potential to add significant value in imaging gynecologic disease, and indications for its use in the female pelvis are expected to continue evolving. It can aid in evaluation of nonvascular structures, such as assessment of tubal patency, uterine cavity morphology, and pelvic fistulas. CEUS can help characterize poorly vascularized gynecologic tumors or tissues with slow flow by using qualitative and quantitative parameters and aid in image-guided interventions or biopsies by facilitating visualization of lesions that are difficult to see with other imaging modalities. The authors provide an overview of current applications of US contrast agents in the female pelvis and discuss associated factors such as technique, interpretation, and image optimization. They also discuss the limitations of CEUS and describe its utility in the evaluation of female pelvic disease by using an organ system case-based approach. © RSNA, 2024 Test Your Knowledge questions for this article are available in the supplemental material.

Metabolic Disruption Induced by mTOR Signaling Pathway Inhibition in Regulatory T-Cell Expansion for Clinical Application.

BACKGROUND: Regulatory T cell (Treg) therapy is considered an alternative approach to induce tolerance in transplantation. If successful, this therapy may have implications on immunosuppression minimization/withdrawal to reduce drug-induced toxicity in patients. The aim of this study was to assess the efficacy of the mTORC1/C2 inhibitor, AZD8055, in the manufacturing of clinically competent Treg cells and compare the effects with those induced by rapamycin (RAPA), another mTOR inhibitor commonly used in Treg expansion protocols. METHODS: Primary human Treg cells were isolated from leukapheresis product. Cell viability, expansion rates, suppressive function, autophagy, mitochondrial unfolded protein response (mitoUPR), and cell metabolic profile were assessed. RESULTS: We observed a stronger inhibition of the mTORC2 signaling pathway and downstream events triggered by Interleukin 2 (IL2)-receptor in AZD8055-treated cells compared with those treated with RAPA. AZD8055 induced progressive metabolic changes in mitochondrial respiration and glycolytic pathways that disrupted the long-term expansion and suppressive function of Tregs. Unlike RAPA, AZD8055 treatment impaired autophagy and enhanced the mitoUPR cell stress response pathway. CONCLUSIONS: A distinct pattern of mTOR inhibition by AZD, compared with RAPA, induced mitochondrial stress response and dysfunction, impaired autophagy, and disrupted cellular bioenergetics, resulting in the loss of proliferative potential and suppressive function of Treg cells.

Molecular and Therapeutic Insights of Alpha-Lipoic Acid as a Potential Molecule for Disease Prevention.

Alpha-lipoic acid is an organic, sulfate-based compound produced by plants, humans, and animals. As a potent antioxidant and a natural dithiol compound, it performs a crucial role in mitochondrial bioenergetic reactions. A healthy human body, on the other hand, can synthesize enough α-lipoic acid to scavenge reactive oxygen species and increase endogenous antioxidants; however, the amount of α-lipoic acid inside the body decreases significantly with age, resulting in endothelial dysfunction. Molecular orbital energy and spin density analysis indicate that the sulfhydryl (-SH) group of molecules has the greatest electron donating activity, which would be responsible for the antioxidant potential and free radical scavenging activity. α-Lipoic acid acts as a chelating agent for metal ions, a quenching agent for reactive oxygen species, and a reducing agent for the oxidized form of glutathione and vitamins C and E. α-Lipoic acid enantiomers and its reduced form have antioxidant, cognitive, cardiovascular, detoxifying, anti-aging, dietary supplement, anti-cancer, neuroprotective, antimicrobial, and anti-inflammatory properties. α-Lipoic acid has cytotoxic and antiproliferative effects on several cancers, including polycystic ovarian syndrome. It also has usefulness in the context of female and male infertility. Although α-lipoic acid has numerous clinical applications, the majority of them stem from its antioxidant properties; however, its bioavailability in its pure form is low (approximately 30%). However, nanoformulations have shown promise in this regard. The proton affinity and electron donating activity, as a redox-active agent, would be responsible for the antioxidant potential and free radical scavenging activity of the molecule. This review discusses the most recent clinical data on α-lipoic acid in the prevention, management, and treatment of a variety of diseases, including coronavirus disease 2019. Based on current evidence, the preclinical and clinical potential of this molecule is discussed. Supplementary Information: The online version contains supplementary material available at 10.1007/s43450-023-00370-1.

Anti-neoplastic sulfonamides alter the metabolic homeostasis and disrupt the suppressor activity of regulatory T cells.

Regulatory T cells (Tregs) are essential to maintain self-tolerance and immune homeostasis but, as components of the tumor microenvironment (TME), are also a major barrier to effective cancer immunosurveillance and immunotherapy. FH535 and its derivative Y3 are two N-aryl-benzene-sulfonamides (NABs) that inhibit HCC cell proliferation and tumor progression. However, the impact of NABs on the immune cells in the TME is not yet known. Analyses of explanted livers from patients with hepatocellular carcinoma (HCC) showed that high levels of tumor-infiltrating Tregs were associated with poor tumor differentiation. These results lead us to investigate the immunomodulatory effects of NABs in regulatory and effector T cells. Exposure of primary human Tregs to NABs induced a rapid but temporary increase of cell expansion, a gradual disruption of suppressor activity, and concomitant bioenergetics and autophagic flux dysregulations. In contrast to Tregs, no gross effects were observed in effector T cells. Addition of Rapamycin prevented the functional decay of Tregs and restored their metabolic profile, suggesting that NAB effects require the integrity of the mTOR pathway. This study revealed the immunomodulatory properties of NABs with a preferential impact on Treg activity and provided novel insights into the anti-tumor potential of sulfonamides.

Cell sorting microbeads as novel contrast agent for magnetic resonance imaging.

The success of several cell-based therapies and prevalent use of magnetic resonance imaging (MRI) in the clinic has fueled the development of contrast agents for specific cell tracking applications. Safe and efficient labeling of non-phagocytic cell types such as T cells nonetheless remains challenging. We developed a one-stop shop approach where the T cell sorting agent also labels the cells which can subsequently be depicted using non-invasive MRI. We compared the MR signal effects of magnetic-assisted cell sorting microbeads (CD25) to the current preclinical gold standard, ferumoxytol. We investigated in vitro labeling efficiency of regulatory T cells (Tregs) with MRI and histopathologic confirmation. Thereafter, Tregs and T cells were labeled with CD25 microbeads in vitro and delivered via intravenous injection. Liver MRIs pre- and 24 h post-injection were performed to determine in vivo tracking feasibility. We show that CD25 microbeads exhibit T2 signal decay properties similar to other iron oxide contrast agents. CD25 microbeads are readily internalized by Tregs and can be detected by non-invasive MRI with dose dependent T2 signal suppression. Systemically injected labeled Tregs can be detected in the liver 24 h post-injection, contrary to T cell control. Our CD25 microbead-based labeling method is an effective tool for Treg tagging, yielding detectable MR signal change in cell phantoms and in vivo. This novel cellular tracking method will be key in tracking the fate of Tregs in inflammatory pathologies and solid organ transplantation.

Interobserver Agreement Between Primary Sonographers and Secondary Overreaders for Screening and Surveillance Liver Ultrasounds Using Ultrasound Liver Imaging Reporting and Data System.

ABSTRACT: The authors aim to identify if primary sonographers and secondary reviewers, both radiologists and sonographers, are likely to assign the same Ultrasound Liver Imaging Reporting and Data System (US LI-RADS) scores for liver surveillance ultrasounds. Institutional review board approval was obtained. Sonographers were familiarized with US LI-RADS via radiologist-led lectures. Three sonographers prospectively scored 170 screening examinations using US LI-RADS recommendations. Scans were retrospectively rescored by a fourth sonographer and a radiologist, both of whom were blinded to the original scores. Results were analyzed with weighted and nonweighted Cohen kappa statistical analysis methods. There was near-perfect agreement between primary and secondary sonographers and primary sonographer and radiologist (kappa of 0.87 and 0.92, respectively) for US LI-RADS category (cat) scores. However, only substantial and moderate agreements were noted for visualization (vis) scores between primary and secondary sonographers and primary sonographer and radiologist (weighted kappa of 0.73 and 0.48, respectively). There was vis score disagreement between the primary sonographer and radiologist in 60 (35.3%) cases. In 35 (20%) cases, the radiologist assigned a lower/more conservative vis score. There was vis score disagreement between the primary and secondary reviewing sonographers in 30 (17.6%) cases. In 12 (7%) cases, the secondary sonographer assigned a more conservative vis score. Although a good degree of concordance was noted between the groups, radiologists will need to generate their own US LI-RADS scoring to accurately reflect their impression and appropriately steer management.

Light and moderate intensity physical activity are associated with better ambulation, quality of life, and vascular measurements in patients with claudication.

OBJECTIVE: We sought to determine whether patients with claudication who reported performing either light intensity physical activity (LPA) or moderate-to-vigorous intensity physical activity (MVPA) would have higher levels of objectively determined physical activity and better physical function, health-related quality of life (HRQoL), and vascular measures, consisting of exercise time to minimum calf muscle oxygen saturation (StO2) and high-sensitivity C-reactive protein, than patients who reported being physically sedentary. METHODS: A total of 269 patients were assessed using the Johnson Space Center physical activity scale. The patients were grouped according to whether they performed no physical activities (n = 75), LPAs (n = 140), or MVPAs (n = 54). The primary measurements were the total daily steps obtained from a step activity monitor worn for 1 week, peak walking time obtained from a treadmill test, physical function score on the Medical Outcomes Study short-form 36-item survey to assess HRQoL, and high-sensitivity C-reactive protein. RESULTS: The total daily steps was significantly different among the groups. Both the LPA group (mean ± standard deviation, 7878 ± 2808 steps/d) and the MVPA group (mean, 8551 ± 3365 steps/d) had taken more daily steps (P < .01) than had the sedentary group (mean, 3323 ± 986 steps/d). The treadmill peak walking time was significantly different among the three groups. Both the LPA group (433 ± 296 seconds) and the MVPA group (548 ± 300 seconds) had had a greater peak walking time (P < .01) than that of the sedentary group (302 ± 210 seconds). The physical function score was also significantly different among the groups. The LPA group (44% ± 20%) and MVPA group (58% ± 19%) both had had higher scores (P < .01) than the sedentary group (36% ± 20%). In addition, the exercise time to the minimum calf muscle StO2 was significantly different among the groups. Both the LPA group (215 ± 238 seconds) and the MVPA group (377 ± 351 seconds) had had greater values (P < .05 and P < .01, respectively) than the sedentary group (147 ± 172 seconds). Finally, the high-sensitivity C-reactive protein level was significantly different among the groups. Both the LPA group (4.8 ± 5.5 mg/L) and the MVPA group (3.5 ± 3.6 mg/L) had had lower values (P < .01) than the sedentary group (8.6 ± 8.4 mg/L). CONCLUSIONS: Patients with claudication who reported performing LPA had greater amounts of objectively determined physical activity levels and better physical function, HRQoL, and vascular measures than those who reported being physically sedentary. Furthermore, these favorable results associated with LPA were even more pronounced for the patients who performed MVPA compared with those who were sedentary. The clinical significance is that our results have shown that engaging in any physical activity, even at relatively light intensity, is associated with favorable health and vascular measures for patients with claudication.

Diagnostic Performance of 9 Quantitative Ultrasound Parameters for Detection and Classification of Hepatic Steatosis in Nonalcoholic Fatty Liver Disease.

BACKGROUND: Nonalcoholic fatty liver disease (NAFLD) is a leading cause of chronic liver disease worldwide. Quantitative ultrasound (QUS) parameters based on radiofrequency raw data show promise in quantifying liver fat. PURPOSE: The aim of this study was to evaluate the diagnostic performance of 9 QUS parameters compared with magnetic resonance imaging (MRI)-estimated proton density fat fraction (PDFF) in detecting and staging hepatic steatosis in patients with or suspected of NAFLD. MATERIALS AND METHODS: In this Health Insurance Portability and Accountability Act-compliant institutional review board-approved prospective study, 31 participants with or suspected of NAFLD, without other underlying chronic liver diseases (13 men, 18 women; average age, 52 years [range, 26-90 years]), were examined. The following parameters were obtained: acoustic attenuation coefficient (AC); hepatorenal index (HRI); Nakagami parameter; shear wave elastography measures such as shear wave elasticity, viscosity, and dispersion; and spectroscopy-derived parameters including spectral intercept (SI), spectral slope (SS), and midband fit (MBF). The diagnostic ability (area under the receiver operating characteristic curves and accuracy) of QUS parameters was assessed against different MRI-PDFF cutoffs (the reference standard): 6.4%, 17.4%, and 22.1%. Linearity with MRI-PDFF was evaluated with Spearman correlation coefficients (p). RESULTS: The AC, SI, Nakagami, SS, HRI, and MBF strongly correlated with MRI-PDFF (P = 0.89, 0.89, 0.88, -0.87, 0.81, and 0.71, respectively [P < 0.01]), with highest area under the receiver operating characteristic curves (ranging from 0.85 to 1) for identifying hepatic steatosis using 6.4%, 17.4%, and 22.1% MRI-PDFF cutoffs. In contrast, shear wave elasticity, shear wave viscosity, and shear wave dispersion did not strongly correlate to MRI-PDFF (P = 0.45, 0.38, and 0.07, respectively) and had poor diagnostic performance. CONCLUSION: The AC, Nakagami, SI, SS, MBF, and HRI best correlate with MRI-PDFF and show high diagnostic performance for detecting and classifying hepatic steatosis in our study population. SUMMARY STATEMENT: Quantitative ultrasound is an accurate alternative to MRI-based techniques for evaluating hepatic steatosis in patients with or at risk of NAFLD. KEY FINDINGS: Our preliminary results show that specific quantitative ultrasound parameters accurately detect different degrees of hepatic steatosis in NAFLD.

Review of Learning Tools for Effective Radiology Education During the COVID-19 Era.

Coronavirus disease 2019 (COVID-19) has significantly disrupted medical education around the world and created the risk of students missing vital education and experience previously held within actively engaging in-person activities by switching to online leaning and teaching activities. To retain educational yield, active learning strategies, such as microlearning and visual learning tools are increasingly utilized in the new digital format. This article will introduce the challenges of a digital learning environment, review the efficacy of applying microlearning and visual learning strategies, and demonstrate tools that can reinforce radiology education in this constantly evolving digital era such as innovative tablet apps and tools. This will be key in preserving and augmenting essential medical teaching in the currently trying socially and physically distant times of COVID-19 as well as in similar future scenarios.

Role of Ultrasound for Chronic Liver Disease and Hepatocellular Carcinoma Surveillance.

Ultrasound plays a vital role in the evaluation of patients with chronic liver disease and in hepatocellular carcinoma (HCC) surveillance in populations at risk for developing HCC. Semiannual ultrasound for HCC surveillance is universally recommended by all liver societies around the world. Advanced ultrasound techniques, such as elastography and contrast-enhanced ultrasound, offer additional benefits in imaging evaluation of chronic liver disease. Major benefits of ultrasound include its high safety profile and relatively low cost.

Correlation of placental MR imaging signs and pathologic diagnosis of placenta accreta spectrum: Retrospective single center case series.

INTRODUCTION: Alongside initial screening obstetric US, use of placental MRI has been increasing in the last few decades to aid with antenatal diagnosis and delivery planning in Placenta Accreta Spectrum (PAS). The aim of this study was to determine if the MRI pathophysiological sign subcategories described in the current literature can predict the severity of pathologic diagnosis. METHODS: Institutional imaging records were reviewed for placental MRIs performed for suspicion of PAS in the last decade. Electronic health records were searched for patient history and pathology. The 59 MRI studies were reviewed using the 11 MRI signs described by the SAR and ESUR joint consensus statement. Further breakdown of the signs was divided by underlying pathophysiologic subcategories including gross morphologic, interface and tissue architecture signs. RESULTS: Pathologic diagnosis yielded 34 cases: accreta 4/34, incerta 14/34, percreta 10/34 and normal 6/34. Of the accreta cases all of them demonstrated at least two interface and half of the cases had tissue architecture signs, 13/14 increta cases demonstrated interface signs and 12/14 demonstrated tissue architecture signs, 9/10 percreta cases had two interface and at least six demonstrated three tissue architecture signs. Statistical analysis showed significant difference between pathologic diagnosis and the number of positive interface signs with p = 0.02. DISCUSSION: Interface signs were the most objective and sensitive MRI subcategory. Statistical analysis determined there was a significant difference between PAS diagnosis and number of interface signs present. This subcategory has the most overlap with classic US signs which are traditionally used before MRI referral.

Review of MRI imaging for placenta accreta spectrum: Pathophysiologic insights, imaging signs, and recent developments.

Placenta Accreta Spectrum (PAS) refers to the range of abnormally adhesive and penetrative placental tissue at a uterine scar. PAS is divided into accreta, increta, and percreta based on degree of myometrial invasion. Its incidence has increased, and PAS is now the leading indication for emergency peripartum hysterectomy in the setting of catastrophic hemorrhage from a non-separating placenta. The recent release of the International Federation of Gynecology and Obstetrics (FIGO) guidelines in 2018 coupled with the joint consensus statement from the Society of Abdominal Radiology (SAR) and European Society of Urogenital Radiology (ESUR) in 2020 reflect decades worth of diagnostic and therapeutic advances in this field. Although the increasing role of MRI in PAS diagnosis is evident, the literature on PAS reveals several disparate but conceptually overlapping MRI signs. Identifying and differentiating between placenta increta and percreta on imaging may be quite challenging even with MRI and sometimes even on final pathology. In this review, we aim to (i) provide a clarified understanding of PAS pathophysiology, (ii) comprehensively review and classify MRI signs based on pathophysiologic underpinnings, (iii) highlight shortcomings in the current PAS literature; and (iv) highlight best practice guidelines for imaging diagnosis of PAS.

Mitochondrial uncoupling and the disruption of the metabolic network in hepatocellular carcinoma.

BACKGROUND: Hepatocellular Carcinoma (HCC) is the third most common cause of cancer related death worldwide. Adequate treatment options for patients with advanced HCC are currently limited. MATERIALS AND METHODS: We studied the anti-HCC effect of FH535 and a novel derivative Y3, on proliferation, mitochondrial function and cellular metabolism focusing on the three key substrates, glutamine, glucose, and fatty acids. RESULTS: FH535 and Y3 disrupted mitochondrial redox control in HCC cells that resulted from uncoupling mechanisms that increased proton leakage and decreased ATP production leading to apoptosis. The uncoupling effects of the sulfonamides in HCC cells were supported by the loss of activity of the methylated analogs. The accumulation of ROS significantly contributed to cell damage after the impaired autophagic machinery. These sulfonamides, FH535 and Y3, targeted glutamine and fatty acid metabolism and caused HCC cell reprograming towards the preferential use of glucose and the glycolytic pathway. CONCLUSIONS: FH535, and Y3, demonstrated potent anti-HCC activity by targeting OXPHOS, increasing dangerous levels of ROS and reducing ATP production. These sulfonamides target glutamine and FA metabolic pathways significantly increasing the cellular dependency on glycolysis.

Quantitative ultrasound approaches for diagnosis and monitoring hepatic steatosis in nonalcoholic fatty liver disease.

Nonalcoholic fatty liver disease is a major global health concern with increasing prevalence, associated with obesity and metabolic syndrome. Recently, quantitative ultrasound-based imaging techniques have dramatically improved the ability of ultrasound to detect and quantify hepatic steatosis. These newer ultrasound techniques possess many inherent advantages similar to conventional ultrasound such as universal availability, real-time capability, and relatively low cost along with quantitative rather than a qualitative assessment of liver fat. In addition, quantitative ultrasound-based imaging techniques are less operator dependent than traditional ultrasound. Here we review several different emerging quantitative ultrasound-based approaches used for detection and quantification of hepatic steatosis in patients at risk for nonalcoholic fatty liver disease. We also briefly summarize other clinically available imaging modalities for evaluating hepatic steatosis such as MRI, CT, and serum analysis.

Reporting of acute pancreatitis by radiologists-time for a systematic change with structured reporting template.

Acute pancreatitis has a wide array of imaging presentations. Various classifications have been used in the past to standardize the terminology and reduce confusing and redundant terms. We aim to review the historical and current classifications of acute pancreatitis and propose a new reporting template which can improve communication between various medical teams by use of appropriate terminology and structured radiology template. The standardized reporting template not only conveys the most important imaging findings in a simplified yet comprehensive way but also allows structured data collection for future research and teaching purposes.

Tumor Formation of Adult Stem Cell Transplants in Rodent Arthritic Joints.

PURPOSE: While imaging matrix-associated stem cell transplants aimed for cartilage repair in a rodent arthritis model, we noticed that some transplants formed locally destructive tumors. The purpose of this study was to determine the cause for this tumor formation in order to avoid this complication for future transplants. PROCEDURES: Adipose-derived stem cells (ADSC) isolated from subcutaneous adipose tissue were implanted into 24 osteochondral defects of the distal femur in ten athymic rats and two immunocompetent control rats. All transplants underwent serial magnetic resonance imaging (MRI) up to 6 weeks post-transplantation to monitor joint defect repair. Nine transplants showed an increasing size over time that caused local bone destruction (group 1), while 11 transplants in athymic rats (group 2) and 4 transplants in immunocompetent rats did not. We compared the ADSC implant size and growth rate on MR images, macroscopic features, histopathologic features, surface markers, and karyotypes of these presumed neoplastic transplants with non-neoplastic ADSC transplants. RESULTS: Implants in group 1 showed a significantly increased two-dimensional area at week 2 (p = 0.0092), 4 (p = 0.003), and 6 (p = 0.0205) compared to week 0, as determined by MRI. Histopathological correlations confirmed neoplastic features in group 1 with significantly increased size, cellularity, mitoses, and cytological atypia compared to group 2. Six transplants in group 1 were identified as malignant chondrosarcomas and three transplants as fibromyxoid sarcomas. Transplants in group 2 and immunocompetent controls exhibited normal cartilage features. Both groups showed a normal ADSC phenotype; however, neoplastic ADSC demonstrated a mixed population of diploid and tetraploid cells without genetic imbalance. CONCLUSIONS: ADSC transplants can form tumors in vivo. Preventive actions to avoid in vivo tumor formations may include karyotyping of culture-expanded ADSC before transplantation. In addition, serial imaging of ADSC transplants in vivo may enable early detection of abnormally proliferating cell transplants.

Evaluation of Virtual Reality for Detection of Lung Nodules on Computed Tomography.

Virtual reality (VR) systems can offer benefits of improved ergonomics, but their resolution may currently be limited for the detection of small features. For detection of lung nodules, we compared the performance of VR versus standard picture archiving and communication system (PACS) monitor. Four radiologists and 1 novice radiologist reviewed axial computed tomography (CTs) of the thorax using standard PACS monitors (SM) and a VR system (HTC Vive, HTC). In this study, 3 radiologists evaluated axial lung-window CT images of a Lungman phantom. One radiologist and the novice radiologist reviewed axial lung-window patient CT thoracic images (32 patients). This HIPAA-compliant study was approved by the institutional review board. Detection of 227 lung nodules on patient CTs did not result in different sensitivity with SM compared with VR. Detection of 23 simulated Lungman phantom lung nodules on CT with SM resulted in statistically greater sensitivity (78.3%) than with VR (52.2%, P = .041) for 1 of 3 radiologists. The trend was similar but not significant for the other radiologists. There was no significant difference in the time spent by readers reviewing CT images with VR versus SM. These findings indicate that performance of a commercially available VR system for detection of lung nodules may be similar to traditional radiology monitors for assessment of small lung nodules on CTs of the thorax for most radiologists. These results, along with the potential of improving ergonomics for radiologists, are promising for the future development of VR in diagnostic radiology.

Visualization of macrophage recruitment in head and neck carcinoma model using fluorine-19 magnetic resonance imaging.

PURPOSE: To evaluate the role of infiltrating macrophages in murine models of single and double mutation head and neck tumors using a novel fluorine-19 (19 F) MRI technology. METHODS: Tumor cell lines single-hit/SCC4 or double-hit/Cal27, with mutations of TP53 and TP53 & FHIT, respectively, were injected bilaterally into the flanks of (n = 10) female mice. With tumors established, perfluorocarbon nanoemulsion was injected intravenously, which labels in situ predominantly monocytes and macrophages. Longitudinal spin density-weighted 19 F MRI data enabled quantification of the macrophage burden in tumor and surrounding tissue. RESULTS: The average number of 19 F atoms within the tumors was twice as high in the Cal27 group compared with SCC4 (3.9 × 1019 and 2.0 × 101919 F/tumor, respectively; P = 0.0034) two days after contrast injection, signifying increased tumor-associated macrophages in double-hit tumors. The difference was still significant 10 days after injection. Histology stains correlated with in vivo results, exhibiting numerous perfluorocarbon-labeled macrophages in double-hit tumors and to a lesser extent in single-hit tumors. CONCLUSIONS: This study helps to establish 19 F MRI as a method for quantifying immune cells in the tumor microenvironment, allowing distinction between double and single-hit head and neck tumors. This technique would be extremely valuable in the clinic for pretreatment planning, prognostics, and post-treatment surveillance. Magn Reson Med 79:1972-1980, 2018. © 2017 International Society for Magnetic Resonance in Medicine.