Generative AI in oncological imaging: Revolutionizing cancer detection and diagnosis.

Generative AI is revolutionizing oncological imaging, enhancing cancer detection and diagnosis. This editorial explores its impact on expanding datasets, improving image quality, and enabling predictive oncology. We discuss ethical considerations and introduce a unique perspective on personalized cancer screening using AI-generated digital twins. This approach could optimize screening protocols, improve early detection, and tailor treatment plans. While challenges remain, generative AI in oncological imaging offers unprecedented opportunities to advance cancer care and improve patient outcomes.

Frequency and temporal evolution of COVID-19 vaccination rate among oncological patients undergoing 18F-FDG-PET.

PURPOSE: To evaluate the temporal evolution of vaccination against COVID-19 in a Swiss oncological cohort. METHODS: History of complete vaccination (i.e. at least two vaccine doses) against COVID-19 of patients undergoing oncological 18F-FDG PET/CT between February and September 2021 (n = 2613) was taken. Vaccination rate was compared with age-matched national data from the Swiss Federal Office of Public Health. Subgroup differences in temporal evolution of vaccination rate were analyzed by fitting a generalized linear model and determined by significant interaction between, sex, oncological diagnosis, and month of examination. RESULTS: Rate of complete vaccination against COVID-19 steadily increased and reached 81 % in September 2021. The fraction of vaccinated patients in the oncological cohort was higher in the beginning and approached the fraction in the age-matched general Swiss population at the end of the study period. Month of exam (p < 0.001) was the only significant predictor of the vaccination rate. CONCLUSION: Vaccination rate against COVID-19 in a Swiss oncological cohort increased steadily from February to September 2021. Compared to the age-matched general population it was higher in the beginning and similar by the end of the study period. Ethics approval: Trial registration: BASEC 2021-00444, Ethikkommission Zürich (Cantonal Ethics Committee Zurich), Switzerland, registered February 24th 2021.

Value of Clinical Information on Radiology Reports in Oncological Imaging.

Radiological reporting errors have a direct negative impact on patient treatment. The purpose of this study was to investigate the contribution of clinical information (CI) in radiological reporting of oncological imaging and the dependence on the radiologists' experience level (EL). Sixty-four patients with several types of carcinomas and twenty patients without tumors were enrolled. Computed tomography datasets acquired in primary or follow-up staging were independently analyzed by three radiologists (R) with different EL (R1: 15 years; R2: 10 years, R3: 1 year). Reading was initially performed without and 3 months later with CI. Overall, diagnostic accuracy and sensitivity for primary tumor detection increased significantly when receiving CI from 77% to 87%; p = 0.01 and 73% to 83%; p = 0.01, respectively. All radiologists benefitted from CI; R1: 85% vs. 92%, p = 0.15; R2: 77% vs. 83%, p = 0.33; R3: 70% vs. 86%, p = 0.02. Overall, diagnostic accuracy and sensitivity for detecting lymphogenous metastases increased from 80% to 85% (p = 0.13) and 42% to 56% (p = 0.13), for detection of hematogenous metastases from 85% to 86% (p = 0.61) and 46% to 60% (p = 0.15). Specificity remained stable (>90%). Thus, CI in oncological imaging seems to be essential for correct radiological reporting, especially for residents, and should be available for the radiologist whenever possible.

Undifferentiated Hepatic Sarcoma: A Rare Case.

Primary hepatic undifferentiated pleomorphic sarcoma (UPS) is a rare malignant mesenchymal tumor with a nonspecific clinical and radiologic presentation. Primary hepatic UPS is often a diagnosis of exclusion made by multiple immunohistological testing that rules out hepatic, hematologic, neural, and epithelial origin. Stains for mesenchymal origin are usually the only positive stain and do not demonstrate evidence of specific mesenchymal cell differentiation. We report a case of a 56-year-old male with no significant past medical history that presented with complaint of epigastric abdominal pain of six months duration. A computed tomography (CT) scan of the abdomen and pelvis exhibited numerous hepatic masses involving right and left hepatic lobe. A CT-guided core needle biopsy discovered undifferentiated/pleomorphic sarcoma. Histomorphology showed spindle cell neoplasm without recognizable hepatic tissue. Immunohistochemistry (IHC) stains were positive for smooth muscle actin (SMA) but failed to establish a more specific histogenesis. Furthermore, IHC stains revealed spindle neoplastic cells with focal and patchy positive h-caldesmon (approximately 10-15% of neoplastic cells), and negative for desmin. Given these results, the diagnosis of undifferentiated/pleomorphic sarcoma was established. It is imperative to consider UPS in the differential diagnosis of large liver lesions without evidence of differentiation. Early identification of this rare tumor can prevent the possibility of distant metastasis and improve survival among patients.

Weakly supervised segmentation of tumor lesions in PET-CT hybrid imaging.

Purpose: We introduce and evaluate deep learning methods for weakly supervised segmentation of tumor lesions in whole-body fluorodeoxyglucose-positron emission tomography (FDG-PET) based solely on binary global labels ("tumor" versus "no tumor"). Approach: We propose a three-step approach based on (i) a deep learning framework for image classification, (ii) subsequent generation of class activation maps (CAMs) using different CAM methods (CAM, GradCAM, GradCAM++, ScoreCAM), and (iii) final tumor segmentation based on the aforementioned CAMs. A VGG-based classification neural network was trained to distinguish between PET image slices with and without FDG-avid tumor lesions. Subsequently, the CAMs of this network were used to identify the tumor regions within images. This proposed framework was applied to FDG-PET/CT data of 453 oncological patients with available manually generated ground-truth segmentations. Quantitative segmentation performance was assessed for the different CAM approaches and compared with the manual ground truth segmentation and with supervised segmentation methods. In addition, further biomarkers (MTV and TLG) were extracted from the segmentation masks. Results: A weakly supervised segmentation of tumor lesions was feasible with satisfactory performance [best median Dice score 0.47, interquartile range (IQR) 0.35] compared with a fully supervised U-Net model (median Dice score 0.72, IQR 0.36) and a simple threshold based segmentation (Dice score 0.29, IQR 0.28). CAM, GradCAM++, and ScoreCAM yielded similar results. However, GradCAM led to inferior results (median Dice score: 0.12, IQR 0.21) and was likely to ignore multiple instances within a given slice. CAM, GradCAM++, and ScoreCAM yielded accurate estimates of metabolic tumor volume (MTV) and tumor lesion glycolysis. Again, worse results were observed for GradCAM. Conclusions: This work demonstrated the feasibility of weakly supervised segmentation of tumor lesions and accurate estimation of derived metrics such as MTV and tumor lesion glycolysis.

[Concepts of medical imaging in the work up and follow-up of cancer : oncological imaging at a glance]. / Concepts d'imagerie médicale dans la mise au point et le suivi des cancers : regard sur l'imagerie oncologique.

Oncological imaging is a subspecialty of medical imaging and focuses on the workup and the follow-up of cancer. Oncological imaging takes into account all the specificities of cancer diseases, which is a constantly evolving field, especially in the era of precision medicine, and plays a key role in the care of cancer patients. It permits reliable diagnosis and gives precious information concerning disease extension at diagnosis, which is essential for the treatment planning. Oncological imaging allows also followup of patients under treatment, using response evaluation scores. Interventional imaging, which provides minimally invasive procedures, is useful in order to obtain a histological diagnosis, to treat some tumour or to improve quality of life of cancer patients. Finally, numerous perspectives, among them the advent of artificial intelligence (radiomics), will further strengthen the role of oncologic imaging in the near future.

L'imagerie oncologique, qui est une sous-discipline de l'imagerie médicale, s'intéresse spécifiquement à la mise au point et au suivi des cancers. Elle prend en compte toutes les spécificités de la maladie oncologique, dont les traitements évoluent constamment à l'ère de la médecine de précision. Elle joue un rôle primordial à toutes les étapes du trajet de soin du patient. Elle permet la réalisation de diagnostics fiables et donne des informations sur l'étendue de la maladie au moment du diagnostic, nécessaires à l'établissement d'un plan de traitement. L'imagerie oncologique s'intéresse également au suivi des patients sous traitement, grâce notamment à l'utilisation de score d'évaluation de la réponse thérapeutique. L'imagerie interventionnelle, à travers la réalisation de procédures faiblement invasives, joue un rôle dans l'obtention du diagnostic, dans le traitement de certaines tumeurs ou dans l'amélioration de la qualité de vie du patient. Enfin, de nombreuses perspectives, et notamment l'avènement de l'intelligence artificielle (radiomique), ne vont faire que renforcer le rôle central de l'imagerie oncologique dans les prochaines années.

Radiotherapy in Follicular Lymphoma Staged by 18F-FDG-PET/CT: A German Monocenter Study.

This retrospective study examined the role of 18F-fluorodeoxyglucose-positron emission tomography/computed tomography (18F-FDG-PET/CT) in stage-related therapy of follicular lymphomas (FL). Twelve patients each in stages I and II, 13 in stage III and 11 in stage IV were treated in the Department of Radiation Oncology, University Hospital of Muenster, Germany from 2004 to 2016. Radiotherapy (RT), as well as additional chemoimmunotherapy were analyzed with a median follow-up of 87.6 months. Ultrasound (US), CT and 18F-FDG-PET/CT were used to determine progression-free survival (PFS), overall survival (OS) and lymphoma-specific survival (LSS) over 5- and 10- years. 23 of 24 patients with stage I/II (95.8%) had complete remissions (CR) and 17 of 24 patients with stages III/IV FL showed CR (70.8%). 5- and 10-year PFS in stages I/II was 90.0%/78.1% vs. 44.3%/28.5% in stages III/IV. 5- and 10-year OS rates in stages I/II was 100%/93.3% vs. 53.7%/48.4% in stages III/IV. 5- and 10-year LSS of stages I/II was 100%/93.8% vs. 69.2%/62.3% in stages III/IV. FL of stages I/II, staged by 18F-FDG-PET/CT, revealed better survival rates and lower risk of recurrence compared to studies without PET/CT-staging. Especially, patients with PET/CT proven stage I disease showed significantly better survival and lower relapses rates after RT.

Determining the axillary nodal status with four current imaging modalities including 18F-FDG PET/MRI in newly diagnosed breast cancer: A comparative study using histopathology as reference standard.

Purpose: To compare breast magnetic resonance imaging (MRI), thoracal MRI, thoracal 18F-fluorodeoxyglucose positron emission tomography (18F-FDG PET)/MRI and axillary sonography for the detection of axillary lymph node metastases in women with newly diagnosed breast cancer. Materials and Methods: This prospective double-center study included patients with newly diagnosed breast cancer between March 2018 and December 2019. Patients underwent thoracal (18F-FDG PET/)MRI, axillary sonography, and dedicated prone breast MRI. Datasets were evaluated separately regarding nodal status (nodal+ vs. nodal-). Histopathology served as reference standard in all patients. The diagnostic performance of breast MRI, thoracal MRI, thoracal PET/MRI and axillary sonography in detecting nodal positive patients was tested by creating receiver-operating-characteristic curves (ROC) with a calculated area under the curve (AUC). Sensitivity, specificity, positive predictive value, negative predictive value, and accuracy were calculated for all four modalities. A McNemar test was used to assess differences. Results: 112 female patients (mean age 53.04 ± 12.6 years) were evaluated. Thoracal PET/MRI showed the highest ROC-AUC with a value of 0.892. The AUC for breast MRI, thoracal MRI and sonography were 0.782, 0.814 and 0.834, respectively. Differences between thoracal PET/MRI and axillary sonography, thoracal MRI and breast MRI were statistically significant (PET/MRI vs. axillary sonography, P = 0.01; PET/MRI vs. thoracal MRI, P = 0.02; PET/MRI vs. breast MRI, P = 0.03). PET/MRI showed the highest sensitivity (81.8%, 36/44) (95%-CI: 67.29-91.81%) while axillary sonography had the highest specificity (98.5%, 65/66), 95%-CI: 91.84-99.96%). Conclusion: 18F-FDG PET/MRI outperforms axillary sonography, breast MRI and thoracal MRI in determining the axillary lymph node status. In a clinical setting, the combination of 18F-FDG PET/MRI and axillary sonography might be considered to provide even more accuracy in diagnosis.

Differences Between CT-Perfusion and Biphasic Contrast-enhanced CT for Detection and Characterization of Hepatocellular Carcinoma: Potential Explanations for Discrepant Cases.

AIM: To compare the diagnostic value of liver perfusion computed tomography (PCT) and biphasic contrast-enhanced CT (bpCECT) for detection and characterization of hepatocellular carcinoma (HCC), and to identify potential causes for inter-modal discrepancies. PATIENTS AND METHODS: In this retrospective study, 162 cases with a total of 325 HCC-typical lesions were evaluated using both PCT and bpCECT (mean time between examinations=15 days, range=0-13 days). HCC diagnosis was performed by multi-modality imaging including lesion growth at follow-up. For PCT, a total acquisition time of 40 s (26 measurements) each 1.5 s using 80 kV and 100 mAs, as well as 50 ml iodine contrast agent (at 5 ml/s) covering the entire liver was used. Mean arterial liver perfusion (ALP), portal venous perfusion (PVP) and hepatic arterial index (HPI) for both tumor and non-involved liver parenchyma; mean blood flow, blood volume and k-trans for tumor were quantified. Tumor localization, and size were registered. bpCECT consisted of unenhanced, arterial (30-33 s delay), and portal-venous (70-75 s) phases performed using 120 kV, 200-250 mAs, thin-slice reformates (<1 mm), 100 ml contrast agent (at 3 ml/s) followed by 50 ml saline flush. Finally, we divided the results according to detection by PCT only (i.e. missed by pbCECT), and by both PCT and pbCECT. RESULTS: PCT detected 272 lesions compared to 217 with bpCECT only. HCCs in liver segments 4 and 5 were significantly better detected by PCT (p<0.005). Furthermore, PCT detected significantly smaller HCCs than did bpCECT (p<0.001). Lesions detected by both methods had significantly higher mean ALP (p=0.03) and HPI (p=0.02), and lower mean PVP (p=0.01). Tumor blood flow, blood volume and k-trans proved not to be significant for lesion detection. The mean ALP, HPI, and PVP in inconspicuous cirrhotic liver were also not significant for lesion detection. The PVP(tumor)/HPI(liver) ratio of detected lesions was significantly higher for PCT alone (p=0.04). Pretreated, still vital lesions were better detected by bpCECT. CONCLUSION: Detection of smaller HCC lesions, lesions located in liver segments 4 and 5, as well as lesions presenting lower ALP and HPI, and higher PVP(tumor)/HPI(liver) ratio was better using both methods, emphasizing the important role of PCT.

PSMA PET/CT vs. CT alone in newly diagnosed biochemical recurrence of prostate cancer after radical prostatectomy: Comparison of detection rates and therapeutic implications.

OBJECTIVES: To compare prostate specific membrane antigen (PSMA) Positron Emission Tomography/Computed Tomography (PET/CT) and computed tomography (CT) alone for the detection of biochemical recurrence of prostate cancer (PCa) and effect on treatment. METHODS: This retrospective study included 59 patients with recently recorded biochemical recurrence of PCa (mean PSA 1.96 ± 1.64 ng/mL) after radical prostatectomy. Patients received PET/CT with either 68Ga-PSMA-11 (n = 36) or 18F-PSMA-1007 (n = 23). PET/CT and CT images were evaluated separately in regard to PCa lesion count, type, and localisation by two physicians. Histopathology, follow-up imaging and PSA levels after salvage irradiation served as reference standard. A McNemar test was used to compare detection rates. Changes in therapeutic approaches based on staging differences between CT alone and PET/CT were assessed in a virtual multidisciplinary tumour board. RESULTS: There were 142 lesions in 50 of 59 patients. PSMA PET/CT detected 141 lesions (99.3 %) in 50 patients (84.7 %), while CT detected 72 lesions (50.7 %) in 29 patients (49.2 %). A significantly higher detection rate of PSMA PET/CT was observed on a lesion-based analysis (p < 0.0001) and on a patient based analysis (p < 0.0001). Herein, both 68Ga- and 18F-PSMA PET/CT performed significantly better than CT alone (p < 0.0001, respectively). In 9 patients (15.3 %) no relapse was detectable by either modality. All lesions detected by CT were also detected by PSMA PET/CT. In 38 patients PSMA PET/CT detected more lesions than CT alone, altering the treatment approach in 22 of these patients. CONCLUSION: PSMA PET/CT is superior to CT alone in detecting biochemical recurrence in PCa patients after radical prostatectomy and offered additional therapeutic options in a substantial number of patients.

Current Perspectives on 89Zr-PET Imaging.

89Zr is an emerging radionuclide that plays an essential role in immuno-positron emission tomography (PET) imaging. The long half-life of 89Zr (t1/2 = 3.3 days) is favorable for evaluating the in vivo distribution of monoclonal antibodies. Thus, the use of 89Zr is promising for monitoring antibody-based cancer therapies. Immuno-PET combines the sensitivity of PET with the specificity of antibodies. A number of studies have been conducted to investigate the feasibility of 89Zr immuno-PET imaging for predicting the efficacy of radioimmunotherapy and antibody therapies, imaging target expression, detecting target-expressing tumors, and the monitoring of anti-cancer chemotherapies. In this review, we summarize the current status of PET imaging using 89Zr in both preclinical and clinical studies by highlighting the use of immuno-PET for the targets of high clinical relevance. We also present 89Zr-PET applications other than immuno-PET, such as nanoparticle imaging and cell tracking. Finally, we discuss the limitations and the ongoing research being performed to overcome the remaining hurdles.

The Economic Value of MR-Imaging for Uveal Melanoma.

OBJECTIVE: Uveal melanoma (UM) is the most common primary intra-ocular tumour. Treatment is determined by tumour size and location. Generally, smaller tumours are eligible for brachytherapy unless they are located close to posterior pole. Larger tumours are enucleated or undergo proton beam therapy (PBT), which is more expensive than brachytherapy and less available. Accuracy of tumour size determination is critical for accurate planning and delivery of treatment, particularly to ensure tumour coverage, critical structure sparing, and for the choice of treatment modality. This is particularly the case for tumour dimensions that are close to the cut-off point for a specific type of treatment: in the case of the brachytherapy protocol at our institution, 6-8 mm. Ultrasound is conventionally used, but magnetic resonance imaging (MRI) has recently become an additional available tool. Although more expensive, it enables more accurate measurements and is particularly useful in combination with clinical fundus examination, fundus photography and ultrasound. Our aim in this paper was to determine the economic value of MRI for UM treatment. METHODS: We retrospectively analysed 60 patients' MRI scans acquired as part of a study or for clinical care. For each patient, we assessed whether the extra cost of an MRI generated economic benefit or change in optimal treatment. RESULTS: MRI indicated a smaller tumour prominence than US in 10% of patients with intermediate tumour size, resulting in a change from PBT to brachytherapy. The costs of MRI, €200-€1000, are significantly lower than the higher costs of PBT compared to brachytherapy, €24,000 difference. In addition, the annual total economic burden of severe vision impairment associated with eye removal is €10,000. Furthermore, for patients where ultrasound was impossible due to previous surgery, MRI enabled eye-preserving treatment. CONCLUSION: An additional MRI for specific patients with UM improves economic value as it enables less expensive treatment in a sufficient percentage of patients to compensate for the MRI costs. Value is increased in terms of quality of care as it enables for some a treatment option which spares more vision.

[Diffusion-weighted imaging-diagnostic supplement or alternative to contrast agents in early detection of malignancies?] / Diffusionsbildgebung ­ diagnostische Erweiterung oder Ersatz von Kontrastmitteln in der Früherkennung von Malignomen?

Medical research in the field of oncologic imaging diagnostics using magnetic resonance imaging increasingly includes diffusion-weighted imaging (DWI) sequences. The DWI sequences allow insights into different microstructural diffusion properties of water molecules in tissues depending on the sequence modification used and enable visual and quantitative analysis of the acquired imaging data. In DWI, the application of intravenous gadolinium-containing contrast agents is unnecessary and only the mobility of naturally occurring water molecules in tissues is quantified. These characteristics predispose DWI as a potential candidate for emerging as an independent diagnostic tool in selected cases and specific points in question. Current clinical diagnostic studies and the ongoing technical developments, including the increasing influence of artificial intelligence in radiology, support the growing importance of DWI. Especially with respect to selective approaches for early detection of malignancies, DWI could make an essential contribution as an eligible diagnostic tool; however, prior to discussing a broader clinical implementation, challenges regarding reliable data quality, standardization and quality assurance must be overcome.

Radiolabeled bombesin derivatives for preclinical oncological imaging.

Despite efforts, cancer is still one of the leading causes of morbidity and mortality worldwide, with approximately 14 million new cases and 8.2 million cancer-related deaths each year, according to the World Health Organization. Among the strategies to reduce cancer progression and improving its management, implementing early detection technologies is crucial. Based on the fact that several types of cancer cells overexpress surface receptors, small molecule ligands, such as peptides, have been developed to allow tumor identification at earlier stages. Allied with imaging techniques such as PET and SPECT, radiolabeled peptides play a pivotal role in nuclear medicine. Bombesin, a peptide of 14 amino acids, is an amphibian homolog to the mammalian gastrin-releasing peptide (GRP), that has been extensively studied as a targeting ligand for diagnosis and therapy of GRP positive tumors, such as breast, pancreas, lungs and prostate cancers. In this context, herein we provide a review of reported bombesin derivatives radiolabeled with a multitude of radioactive isotopes for diagnostic purposes in the preclinical setting. Moreover, since animal models are highly relevant for assessing the potential of clinical translation of this radiopeptides, a brief report of the currently used GRP-positive tumor-bearing animal models is described.

Advanced abdominal imaging with dual energy CT is feasible without increasing radiation dose.

BACKGROUND: Dual energy CT (DECT) has proven its potential in oncological imaging. Considering the repeated follow-up examinations, radiation dose should not exceed conventional single energy CT (SECT). Comparison studies on the same scanner with a large number of patients, considering patient geometries and image quality, and exploiting full potential of SECT dose reduction are rare. Purpose of this retrospective study was to compare dose of dual source DECT versus dose-optimized SECT abdominal imaging in clinical routine. METHODS: One hundred patients (62y (±14)) had either contrast-enhanced SECT including automatic voltage control (44) or DECT (56). CT dose index (CTDIvol), size-specific dose-estimate (SSDE) and dose-length product (DLP) were reported. Image noise (SD) was recorded as mean of three ROIs placed in subcutaneous fat and normalized to dose by [Formula: see text] . For dose-normalized contrast-to-noise ratio (CNRD), mean attenuation of psoas muscle (CTmuscle) and subcutaneous fat (CTfat) were compared by CNRD = (CTmuscle - CTfat)/SDn. Statistical significance was tested with two-sided t-test (α = 0.05). RESULTS: There was no significant difference (p < 0.05) between DECT and SECT: Mean CTDIvol was 14.2 mGy (±3.9) (DECT) and 14.3 mGy (±4.5) (SECT). Mean DLP was 680 mGy*cm (±220) (DECT) and 665 mGy*cm (±231) (SECT). Mean SSDE was 15.7 mGy (±1.9) (DECT) and 16.1 mGy (±2.5) (SECT). Mean SDn was 42.2 (±13.9) HU [Formula: see text] (DECT) and 47.8 (±14.9) HU [Formula: see text] (SECT). Mean CNRD was 3.9 (±1.3) [Formula: see text]. (DECT) and 4.0 (±1.3) [Formula: see text] (SECT). CONCLUSION: Abdominal DECT is feasible without increasing radiation dose or deteriorating image quality, even compared to dose-optimized SECT including automatic voltage control. Thus DECT can contribute to sophisticated oncological imaging without dose penalty.

Contrast-enhanced PET/MR imaging versus contrast-enhanced PET/CT in head and neck cancer: how much MR information is needed?

UNLABELLED: Considering PET/MR imaging as a whole-body staging tool, scan time restrictions in a single body area are mandatory for the cost-effective clinical operation of an integrated multimodality scanner setting. It has to be considered that (18)F-FDG already acts as a contrast agent and that under certain circumstances MR contrast may not yield additional clinically relevant information. The concept of the present study was to understand which portions of the imaging information enhance the sensitivity and specificity of the hybrid examination and which portions are redundant. METHODS: One hundred fifty consecutive patients referred for primary staging or restaging of head and neck cancer underwent sequential whole-body (18)F-FDG PET with CT-based attenuation correction, contrast-enhanced (ce) CT, and conventional diagnostic MR imaging of the head and neck in a trimodality PET/CT-MR system. Assessed were image quality, lesion conspicuity, diagnostic confidence, and the benefit of additional coronal and sagittal imaging planes in cePET/CT, PET/MR imaging with only T2-weighted fat-suppressed images (T2w PET/MR imaging), and cePET/MR imaging. RESULTS: In 85 patients with at least 1 PET-positive lesion, 162 lesions were evaluated. Similar robustness was found for CT and MR image quality. T2w PET/MR imaging performed similarly to (metastatic lymph nodes) or better than (primary tumors) cePET/CT in the morphologic characterization of PET-positive lesions and permitted the diagnosis of necrotic or cystic lymph node metastasis without application of intravenous contrast medium. CePET/MR imaging yielded a higher diagnostic confidence for accurate lesion conspicuity (especially in the nasopharynx and in the larynx), infiltration of adjacent structures, and perineural spread. CONCLUSION: The results of the present study provide evidence that PET/MR imaging can serve as a legitimate alternative to PET/CT in the clinical workup of patients with head and neck cancers. Intravenous MR contrast medium may be applied only if the exact tumor extent or infiltration of crucial structures is of concern (i.e., preoperatively) or if perineural spread is anticipated. In early assessment of the response to therapy, in follow-up examinations, or in a whole-body protocol for non-head and neck tumors, T2w PET/MR imaging may be sufficient for coverage of the head and neck. The additional MR scanning time may instead be used for advanced MR techniques to increase the specificity of the hybrid imaging examination.