PET/MRI in head and neck cancer: initial experience

Positron Emission Tomography-Magnetic Resonance Imaging, a New Hybrid Imaging Modality for Dentomaxillofacial Malignancies-A Systematic Review

Background/Objectives: Emerging hybrid imaging modalities, like Positron Emission Tomography/Computed Tomography (PET/CT) and Positron Emission Tomography/Magnetic Resonance Imaging (PET/MRI), are useful for assessing head and neck cancer (HNC) and its prognosis during follow-up. PET/MRI systems enable simultaneous PET and MRI scans within a single session. These combined PET/MRI scanners merge MRI's better soft tissue contrast and the molecular metabolic information offered by PET. Aim: To review scientific articles on the use of hybrid PET/MRI techniques in diagnosing dentomaxillofacial malignancies. Method: The available literature on the use of PET/MRI for the diagnosis of dentomaxillofacial malignancies in four online databases (Scopus, PubMed, Web of Science, and the Cochrane Library) was searched. Eligible for this review were original full-text articles on PET/MRI imaging, published between January 2010 and November 2024, based on experimental or clinical research involving humans. Results: Out of the 783 articles retrieved, only twelve articles were included in this systematic review. Nearly half of the articles (5 out of 12) concluded that PET/MRI is superior to PET, MRI, and PET/CT imaging in relation to defining malignancies' size. Six articles found no statistically significant results and the diagnostic accuracy presented was similar in PET/MRI versus MRI and PET/CT images. Regarding the overall risk of bias, most articles had a moderate risk. Conclusions: The use of PET/MRI in HNC cases provides a more accurate diagnosis regarding dimensions of the tumor and thus a more accurate surgical approach if needed. Further prospective studies on a larger cohort of patients are required to obtain more accurate results on the application of hybrid PET/MRI.

PET/MR versus PET/CT for locoregional staging of oropharyngeal squamous cell cancer

Background

The value of fluorine-18-fluorodeoxyglucose positron emission tomography/computed tomography (FDG-PET/CT) for TN staging in head and neck cancer (HNC) has been proven in numerous studies. A few studies have investigated the value of FDG-PET/magnetic resonance imaging (MRI) in the staging of HNC; the combined results indicate potential for FDG-PET/MRI, but the scientific evidence remains weak.

Purpose

To compare performance of FDG-PET/CT and FDG-PET/MRI for locoregional staging in patients with oropharyngeal carcinomas.

Material and Methods

Two radiologists independently of each other retrospectively reviewed primary pre-therapeutic FDG-PET/CT and FDG-PET/MRI examinations from 40 individuals with oropharyngeal carcinomas. TN stage and primary tumor size were noted. The results were compared between observers and modalities and against TN stage set at a multidisciplinary conference.

Results

For nodal staging, PET/MRI had slightly higher specificity and accuracy than PET/CT for the most experienced observer. Both methods demonstrated excellent sensitivity (≥ 0.97 and 1.00, respectively), as well as high negative predictive values (≥ 0.95 and 1.00, respectively). No significant differences were found for tumor staging or measurement of maximum tumor diameter. There was a weak agreement (κ = 0.35–0.49) between PET/CT and PET/MRI for T and N stages for both observers. Inter-observer agreement was higher for PET/MRI than for PET/CT, both for tumor staging (κ = 0.57 vs. 0.35) and nodal staging (κ = 0.69 vs. 0.55). The agreement between observers was comparable to the agreement between methods.

Conclusion

PET/MRI may be a viable alternative to PET/CT for locoregional staging (TN staging) and assessment of maximal tumor diameter in oropharyngeal squamous cell cancer.

Diagnostic Accuracy of 18F-FDG-PET/CT and 18F-FDG-PET/MRI in Detecting Locoregional Recurrence of HNSCC 12 Weeks after the End of Chemoradiotherapy: Single-Center Experience with PET/MRI

Purpose

In head and neck squamous cell carcinoma (HNSCC), the early diagnosis and efficient detection of recurrences and/or residual tumor after treatment play a very important role in patient's prognosis. Positron emission tomography (PET) using 2-deoxy-2-¹⁸F-fluoro-D-glucose (¹⁸F-FDG) has become an established method for the diagnosis of suspected recurrence in head and neck carcinomas. In particular, integrated PET/MRI imaging that provides optimal soft tissue contrast and less dental implant artifacts compared to PET/CT is an intriguing technique for the follow-up imaging of HNSCC patients. The aim of this study was to evaluate the benefit of PET/MRI compared to PET/CT in post-treatment follow-up imaging of HNSCC patients.

Methods

This retrospective observational cohort study consists of 104 patients from our center with histologically confirmed HNSCC. All patients received chemoradiotherapy (CRT) and underwent ¹⁸F-FDG-PET/CT (n = 52) or ¹⁸F-FDG-PET/MRI (n = 52) scan 12 weeks after the end of treatment. Image analysis was performed by two independent readers according to a five-point Likert scale analysis.

Results

PET/MRI was more sensitive (1.00 vs. 0.77) than PET/CT in the detection of locoregional recurrence. PET/MRI also had better negative (1.00 vs. 0.87) predictive values. AUCs for PET/MRI and PET/CT on patient-based analysis were 0.997 (95% CI 0.989–1.000) and 0.890 (95% CI 0.806–0.974), respectively. The comparison of sensitivity, AUCs, and negative predictive values revealed a statistically significant difference, p < 0.05. In PET/CT, false-negative and positive findings were observed in the more advanced disease stages, where PET/MRI performed better. Also, false-negative findings were located in the oropharyngeal, laryngeal, and nasopharyngeal regions, where PET/MRI made no false-negative interpretations.

Conclusion

Based on these results, PET/MRI might be considered the modality of choice in detecting locoregional recurrence in HNSCC patients, especially in the more advanced stages in the oral cavity, larynx, or nasopharynx.

Relative clinical utility of simultaneous 18F-fluorodeoxyglucose PET/MRI and PET/CT for preoperative cervical cancer diagnosis

Objective

To investigate the utility of ¹⁸F-fluorodeoxyglucose (¹⁸F-FDG) positron emission tomography/magnetic resonance imaging (PET/MRI) for the preoperative diagnosis of cervical cancer.

Methods

We retrospectively analyzed 114 patients who were diagnosed with cervical cancer and underwent PET/MRI (n = 59) or PET/computed tomography (PET/CT) (n = 65) before surgery. The maximal standardized uptake value (SUV_max) and mean SUV (SUV_mean) were determined for regions of interest in the resultant radiographic images.

Results

Relative to PET/CT, ¹⁸F-FDG PET/MRI exhibited higher specificity and sensitivity in defining the primary tumor bounds and higher sensitivity for detection of bladder involvement. The SUV_max and SUV_mean of PET/MRI were remarkably higher than those of PET/CT as a means of detecting primary tumors, bladder involvement, and the lymph node status. However, no significant differences in these values were detected when comparing the two imaging approaches as a means of detecting vaginal involvement or para-aortic lymph node metastasis.

Conclusions

These outcomes may demonstrate the capability of ¹⁸F-FDG PET/MRI to clarify preoperative cervical cancer diagnoses in the context of unclear PET/CT findings. However, studies directly comparing SUVs in different lesion types from patients who have undergone both PET/MRI and PET/CT scans are essential to validate and expand upon these findings.

Value of 18F-FDG Hybrid PET/MR in Differentiated Thyroid Cancer Patients with Negative 131I Whole-Body Scan and Elevated Thyroglobulin Levels

Purpose

To evaluate the diagnostic performance of ¹⁸F-FDG PET/MR in detecting recurrent or metastatic disease in patients with differentiated thyroid cancer (DTC) who have increased thyroglobulin (Tg) levels but a negative ¹³¹I whole-body scan (WBS). The relationship between ¹⁸F-FDG PET/MR and serum Tg levels was explored. We also evaluated the therapeutic impact of PET/MR on patient clinical management.

Patients and Methods

Twenty-nine DTC patients with a negative ¹³¹I-WBS of the last post-therapeutic and increased Tg levels under thyroid-stimulating hormone suppression treatment who underwent ¹⁸F-FDG PET/MR examination were retrospectively analyzed.

Results

Of those 29 patients, ¹⁸F-FDG PET/MR findings were true positive, true negative, false positive, and false negative in 18, 7, 2, and 2 patients, respectively. The overall sensitivity, specificity, and accuracy were 90.0%, 77.8%, and 86.2%, respectively. We noticed significant differences in serum Tg levels between the PET/MR-positive and PET/MR-negative patient groups (P=0.049). Receiver operating characteristic curve analysis showed that a Tg level of 2.4 ng/mL was the optimal cut-off value for predicting PET/MR results. The sensitivity, specificity, and accuracy of PET/MR were higher in patients with Tg levels greater than 2.4 ng/mL than in patients with lower levels. By detecting recurrent or metastatic disease, ¹⁸F-FDG PET/MR altered the clinical management in 7 patients (24.1%) of the overall population.

Conclusion

¹⁸F-FDG PET/MR has high diagnostic accuracy for detecting recurrent or metastatic diseases in DTC patients and is useful for clinical management.

[18F]FDG PET/MRI versus contrast-enhanced MRI in detecting regional HNSCC metastases

OBJECTIVE

To compare the accuracy of contrast-enhanced MRI using established dimensional and morphological criteria versus integrated [¹⁸F]FDG PET/MRI in identifying regional lymph node metastases in patients with newly diagnosed head and neck squamous cell carcinoma (HNSCC). For this purpose, we compare MRI and PET/MRI using the histopathological findings in dissected lymph nodes as the gold standard.

METHODS

We retrospectively reviewed 26 patients with histologically proven HNSCC who underwent gadolinium-enhanced [¹⁸F]FDG PET/MRI as part of their staging. All neck lymph nodes were classified on MRI using dimensional and/or morphological criteria. Then, they were jointly assessed by a nuclear medicine physician and a radiologist using integrated [¹⁸F]PET/MR images. ROC curves were obtained to compare the techniques. Lymph node histopathology was considered as the reference standard.

RESULTS

Out of 865 lymph nodes, 35 were malignant at histopathology (3 with micro-metastases). Sensitivity and specificity were 48.6% and 99.5% for MRI using dimensional criteria; 60.0% and 99.6% for MRI using morphological criteria; 60.0% and 99.4% for MRI using both; and 74.3% and 97.6% for PET using MR as anatomic localization. The area under the ROC curve was higher for PET and MRI localization (0.859) than for MRI using dimensional (0.740; p < 0.05), or morphological (0.798; p < 0.05), or both criteria (0.797; p < 0.05). PET/MR using a PET SUVmax cutoff of 5.7 combined with MRI using dimensional and/or morphological criteria reached high values for accuracy (98.2%), NPV (98.2%), and PPV (95.2%).

CONCLUSIONS

Compared with traditional contrast-enhanced MRI or PET alone, integrated PET/MRI could improve diagnostic accuracy in detecting metastatic lymph nodes in patients with HNSCC.

Are Gadolinium-Enhanced MR Sequences Needed in Simultaneous 18F-FDG-PET/MRI for Tumor Delineation in Head and Neck Cancer?

BACKGROUND AND PURPOSE

PET/MRI with ¹⁸F-FDG has demonstrated the advantages of simultaneous PET and MR imaging in head and neck cancer imaging, MRI allowing excellent soft-tissue contrast, while PET provides metabolic information. The aim of this study was to evaluate the added value of gadolinium contrast-enhanced sequences in the tumor delineation of head and neck cancers on ¹⁸F-FDG-PET/MR imaging.

MATERIALS AND METHODS

Consecutive patients who underwent simultaneous head and neck ¹⁸F-FDG-PET/MR imaging staging or restaging followed by surgery were retrospectively included. Local tumor invasion and lymph node extension were assessed in 45 head and neck anatomic regions using ¹⁸F-FDG-PET/MR imaging by 2 rater groups (each one including a radiologist and a nuclear medicine physician). Two reading sessions were performed, one without contrast-enhanced sequences (using only T1WI, T2WI, and PET images) and a second with additional T1WI postcontrast sequences. The results were compared with the detailed histopathologic analysis, used as reference standard. The κ concordance coefficient between the reading sessions and sensitivity and specificity for each region were calculated.

RESULTS

Thirty patients were included. There was excellent agreement between the contrast-free and postgadolinium reading sessions in delineating precise tumor extension in the 45 anatomic regions studied (Cohen κ = 0.96, 95% CI = [0.94-0.97], P < .001). The diagnostic accuracy did not differ between contrast-free and postgadolinium reading sessions, being 0.97 for both groups and both reading sessions. For the 2 rater groups, there was good sensitivity for both contrast-free (0.83 and 0.85) and postgadolinium reading sessions (0.88 and 0.90, respectively). Moreover, there was excellent specificity (0.98) for both groups and reading sessions.

CONCLUSIONS

Gadolinium chelate contrast administration showed no added value for accurate characterization of head and neck primary tumor extension and could possibly be avoided in the PET/MR imaging head and neck workflow.

Diffusion-Weighted Imaging (DWI) derived from PET/MRI for lymph node assessment in patients with Head and Neck Squamous Cell Carcinoma (HNSCC)

BACKGROUND

To determine the usefulness of Diffusion Weighted Imaging (DWI) derived from PET/MRI in discriminating normal from metastatic lymph nodes and the correlation between the metastatic lymph nodes with the grade and the localization of the primary tumor.

METHODS

Retrospective study of 90 lymph nodes from 90 subjects; 65 patients who had proven histopathological metastatic lymph nodes from (HNSCC) who had undergone 18F- PET/MRI for clinical staging and assessment and twenty-five lymph nodes were chosen from 25 healthy subjects. Apparent Diffusion Coefficient (ADC) map was generated from DWI with b values (0 and 800 s/mm2). ADC values of the metastatic lymph nodes were calculated and compared to the normal lymph nodes ADC values, ROC was used to determine the best cut-off values to differentiate between the two group. Metastatic lymph nodes ADC mean values were compared to primary tumor grade and localization.

RESULTS

ADCmean value of the metastatic lymph nodes in the overall sample (0.899 ± 0.98*10- 3 mm2/sec) was significantly lower than the normal lymph nodes' ADCmean value (1.267 ± 0.88*10- 3 mm2/sec); (P = 0.001). The area under the curve (AUC) was 98.3%, sensitivity and specificity were 92.3 and 98.6%, respectively, when using a threshold value of (1.138 ± 0.75*10- 3 mm2/sec) to differentiate between both groups. Significant difference was found between metastatic lymph nodes (short-axis diameter < 10 mm), ADCmean (0.898 ± 0.72*10- 3 mm2/sec), and the benign lymph nodes ADCmean, (P = 0.001). No significant difference was found between ADCmean of the metastatic lymph nodes < 10 mm and the metastatic lymph nodes > 10 mm, ADCmean (0.899 ± 0.89*10- 3 mm2/sec), (P = 0.967). No significant differences were found between metastatic lymph nodes ADCmean values and different primary tumor grades or different primary tumor localization, (P > 0.05).

CONCLUSION

DWI-ADC is an effective and efficient imaging technique in differentiating between normal and malignant lymph nodes, and might be helpful to discriminate sub-centimeters lymph nodes.

TRIAL REGISTRATION

The trial is registered in clinical trials under ID: NCT04360993 , registration date: 17/04/2020.

Diagnostic Accuracy and Confidence of [18F] FDG PET/MRI in comparison with PET or MRI alone in Head and Neck Cancer

The usefulness of PET/MRI in head and neck malignancy has not been fully elucidated. The purpose of our study was to evaluate the diagnostic accuracy and confidence of PET/MRI in comparison with PET or MRI alone. This study included 73 consecutive patients who underwent [18F] FDG PET/MRI in head and neck under the suspicion of malignancy. A neuroradiologist and a nuclear medicine specialist reviewed MRI and PET images, respectively and independently, followed by a consensus review of PET/MRI one month later. For 134 lesions, accuracy and confidence were compared among PET, MRI, and PET/MRI. For lesion base, PET/MRI had a sensitivity of 85.7%, a specificity of 89.1%, a PPV of 89.6%, a negative predictive value of 85.1%, and an accuracy of 87.3%. AUCs of PET/MRI per lesion (0.926) and per patient (0.934) for diagnosing malignancy were higher than PET (0.847 and 0.747, respectively) or MRI (0.836 and 0.798, respectively) alone (P < 0.05). More than 80% of the cases (111/134) showed diagnostic concordance between PET and MRI. PPV of PET/MRI was higher in malignant concordant cases (93.2%, 55/59) than in discordant cases (62.5%, 5/8) (p = 0.040). Confident scoring rate in malignant concordant cases was higher on PET/MRI (96.6%, 57/59) than on MRI (76.3%, 45/59) (p = 0.003). In conclusion, compared with PET or MRI alone, PET/MRI presents better diagnostic performance in accuracy and confidence for diagnosis of malignancy. PET/MRI is useful in patients with head and neck cancer.

Application of integrated positron emission tomography/magnetic resonance imaging in evaluating the prognostic factors of head and neck squamous cell carcinoma with positron emission tomography, diffusion-weighted imaging, dynamic contrast enhancement and combined model

OBJECTIVES

This study was designed to investigate the distribution of the independent parameters of PET and MR in tumour differentiation and staging and to evaluate the diagnostic efficiency of the independent parameters and combined model of PET/MR in the tumour differentiation of head and neck squamous cell carcinoma (HNSCC).

METHODS

The patients with the preliminary diagnosis of HNSCC were included and underwent the integrated PET/MR The parameters included the diffusion-weighted imaging, dynamic contrast enhancement and PET. The correlations between different parameters and the distribution in groups of tumour differentiation and staging were analysed. The combined model was established with complementary PET/MR parameters. The diagnostic efficiency of the independent parameters and combined model in the tumour differentiation were analysed by receiver operating characteristic curve.

RESULTS

The correlations between the parameters of dynamic contrast enhancement and PET were most significant. There were significant differences between the well-differentiated group and the moderately/poorly differentiated group in terms of the mean values of apparent diffusion coefficient (ADC) and standardised uptake value (SUV) (p < 0.05). The distributions among different tumour stage groups were not statistically different in all the parameters. The diagnostic efficiency of tumour differentiation increased in the order of K_epmean, SUVmean, ADCmean, and the combined model.

CONCLUSIONS

Compared with the independent parameter, the combination of multiple parameters with PET/MR can further improve the diagnostic performance of tumour differentiation in HNSCC.

Usefulness of Hybrid PET/MRI in Clinical Evaluation of Head and Neck Cancer Patients

(1) Background: The novel hybrid of positron emission tomography/magnetic resonance (PET/MR) examination has been introduced to clinical practice. The aim of our study was to evaluate PET/MR usefulness in preoperative staging of head and neck cancer (HNC) patients (pts); (2) Methods: Thirty eight pts underwent both computed tomography (CT) and PET/MR examination, of whom 21 pts underwent surgical treatment as first-line therapy and were further included in the present study. Postsurgical tissue material was subjected to routine histopathological (HP) examination with additional evaluation of p16, human papillomavirus (HPV), Epstein-Barr virus (EBV) and Ki67 status. Agreement of clinical and pathological T staging, sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV) of CT and PET/MR in metastatic lymph nodes detection were defined. The verification of dependences between standardized uptake value (SUV value), tumor geometrical parameters, number of metastatic lymph nodes in PET/MR and CT, biochemical parameters, Ki67 index, p16, HPV and EBV status was made with statistical analysis of obtained results; (3) Results: PET/MR is characterized by better agreement in T staging, higher specificity, sensitivity, PPV and NPV of lymph nodes evaluation than CT imaging. Significant correlations were observed between SUVmax and maximal tumor diameter from PET/MR, between SUVmean and CT tumor volume, PET/MR tumor volume, maximal tumor diameter assessed in PET/MR. Other correlations were weak and insignificant; (4) Conclusions: Hybrid PET/MR imaging is useful in preoperative staging of HNC. Further studies are needed.

Diagnostic Capabilities of MRI Versus 18F FDG PET-CT in Postoperative Patients with Thyroglobulin Positive, 131I-negative Local Recurrent or Metastatic Thyroid Cancer

BACKGROUND

The detection of recurrence or metastasis might be challenging in patients, who underwent total thyroidectomy and radioactive iodine therapy for Differentiated Thyroid Carcinoma (DTC), with increased serum Thyroglobulin (Tg) levels and negative 131I whole body scan (131I-WBS) results.

AIMS

The purpose of this study was to compare the ability of Magnetic Resonance Imaging (MRI) and 18F-fluorodeoxyglucose Positron Emission Tomography/Computed Tomography (18F FDG PET-CT) to detect recurrence or cervical and upper mediastinal metastases in postoperative DTC patients who had negative 131I-WBS despite elevated serum Tg levels.

STUDY DESIGN

This study has a retrospective study design.

METHODS

We evaluated cervical and upper mediastinal MRI and 18F FDG PET-CT of 32 postoperative patients with DTC (26 patients with papillary thyroid carcinoma and 6 patients with follicular thyroid carcinoma).

RESULTS

We evaluated 44 lesions in 32 patients. For all lesions, the Positive Predictive Value, (PPV) Negative Predictive Value (NPV), sensitivity, specificity, and accuracy of MRI were 81.4%, 76.4%, 84.6%, 72.2%, and 79.5% respectively. The PPV, NPV, sensitivity, specificity, and accuracy of 18F FDG PET-CT were 100.0%, 85.7%, 88.4%, 100.0%, and 93.1%, respectively.

CONCLUSION

Although we could not replace 18F FDG PET-CT, MRI might be used as an adjunct to 18F FDG PET-CT for the evaluation of recurrent or cervical and upper mediastinal metastatic thyroid cancers; however, MRI is inadequate for the detection of metastases in small lymph nodes.

18F-FDG-PET/CT Imaging in Advanced Glottic Cancer: A Tool for Clinical Decision in Comparison with Conventional Imaging

This study assessed the role of ¹⁸F-FDG PET-CT (PET/CT) to detect the cartilage and paraglottic infiltration in advanced glottic cancer comparing the results with those of conventional imaging (CI) (contrast-enhanced computed tomography and/or magnetic resonance). In addition, we assessed the prognostic value of quantitative parameters, measured on baseline PET/CT, in terms of event-free survival (EFS) and overall survival (OS). We retrospectively analyzed 27 patients with glottic squamous cell carcinoma stage III and IVA, treated in our institute between 2010 and 2016, comparing PET/CT, performed for staging and radiotherapy planning, and CI findings. Cohen's K was used to compare concordance between PET/CT and CI. Imaging findings were correlated with endoscopic evaluation and histological reports (gold standard (GS)). All lesions shown by CI were also detected by PET/CT imaging, and in 5 cases, a better definition of local infiltration was achieved with PET/CT than CI (5 CT). Sensitivity, specificity, and accuracy of PET/CT and CT were 95%, 86%, and 93% and 70%, 86%, and 74% for, respectively. MRI showed sensitivity and specificity of 100%. One false-negative (FN) cases and 1 false-positive (FP) case were observed with PET/CT with no difference compared to MRI (10 cases). Six FN cases and 1 FP case were observed with CT. Cohen's K was 0.60 (PET vs. CI) and 0.80 (PET vs. GS). Patients were followed-up for at least 24 months to calculate EFS and OS. 13 local recurrence and 7 deaths were recorded. Among quantitative PET parameters, baseline MTV was the most powerful predictor of outcome. Our data suggest a reliable sensitivity and accuracy of PET/CT in the evaluation of local extension, proving a useful method for initial local staging in addition to the well-established role in lymph-node and distant sites assessment. Furthermore, pretreatment MTV provides better prognostic information than other PET/CT parameters.

PET/MRI vs PET/CT in Head and Neck Imaging: When, Why, and How?

The increasing availability of hybrid PET/MRI systems has led to a breadth of new publications and opportunities for use of PET/MRI. While PET/CT has been a valuable tool for oncologic staging, including head and neck malignancy, there are several theoretical and practical advantages a PET/MRI system would have over PET/CT in head and neck imaging. This review article discusses the established role of PET/CT, early evidence for the role of PET/MRI, and protocol considerations for both PET/CT and PET/MRI as they apply to head and neck imaging.

18 F-FDG PET/MRI vs MRI in patients with recurrent adenoid cystic carcinoma

OBJECTIVES

To evaluate and compare the diagnostic potential of ¹⁸ F-fluorodeoxyglucose positron emission tomography/magnetic resonance imaging (¹⁸ FDG-PET/MRI) and MRI for recurrence diagnostics after primary therapy in patients with adenoid cystic carcinoma (ACC).

METHODS

A total of 32 dedicated head and neck ¹⁸ F-FDG PET/MRI datasets were included in this analysis. MRI and ¹⁸ F-FDG PET/MRI datasets were analyzed in separate sessions by two readers for tumor recurrence or metastases.

RESULTS

Lesion-based sensitivity, specificity, positive predictive value, negative predictive value and diagnostic accuracy were 96%, 84%, 90%, 93%, and 91% for ¹⁸ F-FDG PET/MRI and 77%, 94%, 95%, 73%, and 84% for MRI, resulting in a significantly higher diagnostic accuracy of ¹⁸ F-FDG PET/MRI compared to MRI (P < .005).

CONCLUSION

¹⁸ F-FDG PET/MRI is superior to MRI in detecting local recurrence and metastases in patients with ACC of the head and neck. Especially concerning its negative predictive value, ¹⁸ F-FDG PET/MRI outperforms MRI.

FDG-PET/MRI in patients with pelvic recurrence of rectal cancer: first clinical experiences

OBJECTIVES

To determine the value of ¹⁸F-FDG-PET/MRI in the diagnosis and management of patients with pelvic recurrence of rectal cancer.

METHODS

Forty-four patients (16 women, 28 men) with a history of rectal cancer who received FDG-PET/MRI between June 2011 and February 2017 at our institution were retrospectively enrolled. Three patients received two FDG-PET/MRIs; thus a total of 47 examinations were included. Pelvic recurrence was confirmed either with histology (n = 27) or imaging follow-up (n = 17) (> 4 months). Two readers (one radiologist, one nuclear medicine physician) interpreted the images in consensus. Pelvic lesions were assessed regarding FDG uptake and morphology. Sensitivity, specificity, positive and negative predictive values as well as accuracy of PET/MRI in detecting recurrence were determined.

RESULTS

In 47 FDG-PET/MRIs 30 suspicious pelvic lesions were identified, 29 of which were malignant. Two patients underwent resection and had histologically proven pelvic recurrence without showing suspicious findings on FDG-PET/MRI. Changes in management due to FDG-PET/MRI findings had been implemented in eight patients. Eighty per cent (16/20) of resected patients had histologically negative resection margins (R0), one patient had uncertain resection margins. Sensitivity of FDG-PET/MRI in detecting recurrence was 94%, specificity 94%, positive/negative predictive value and accuracy were 97%, 90% and 94%, respectively.

CONCLUSIONS

FDG-PET/MRI is a valuable tool in the diagnosis and staging of pelvic recurrence in patients with rectal cancer.

KEY POINTS

• Metabolic information obtained from PET coupled with excellent soft tissue contrast from MRI could facilitate detection of rectal cancer recurrence and assist in treatment planning. • PET/MRI demonstrates high sensitivity and specificity for the diagnosis of local recurrence of rectal cancer • PET/MRI led to alterations in management in 18.2% of patients.

PET/MR Imaging in Head and Neck Cancer: Current Applications and Future Directions

Clinical PET/MR imaging is being implemented at institutions worldwide as part of the standard-of-care imaging for select oncology patients. This article focuses on oncologic applications of PET/MR imaging in cancers of the head and neck. Although current published literature is relatively sparse, the potential benefits of a hybrid modality of PET/MR imaging are discussed along with several possible areas of research. With the increasing number of PET/MR imaging scanners in clinical use and ongoing research, the role of PET/MR imaging in the management of head and neck cancer is likely to become more evident in the near future.

Hybrid PET/MRI-based delineation of gross tumor volume in head and neck cancer and tumor parameter analysis

OBJECTIVES

Accurate target delineation allows an increase in radiation dose to the target tumor while reducing damage to the surrounding normal tissue. However, there is currently no standard for evaluating volumes measured by different imaging modalities. The aim of this study is to evaluate the feasibility of contouring gross tumor volume (GTV) by PET/MRI in head and neck cancer, and to define an adaptive threshold level (aTL) for delineating the biological target volume (BTV).

PATIENTS AND METHODS

Eighteen head and neck cancer patients underwent time of flight PET/MRI before chemoradiotherapy. Different GTVs of primary tumors and metastatic lymph nodes were manually contoured on MRI (GTVMRI), PET (GTVVIS), and fused PET/MRI (GTVFUS). An MRI-based GTV contour was substituted for the pathologic GTV. The percentile threshold boundary of the maximum standardized uptake value (SUVmax) for the BTV was determined when the volume of BTV approached that of GTVMRI.

RESULTS

All GTVs were highly correlated (all Pearson's r>0.85, all P<0.001). Tumor diameter strongly correlated with GTVs (r=0.7-0.8 for all lesions and primary tumor; r=0.8-0.9 for lymph node metastases). aTL and SUVmax were moderately correlated for all lesions (r=-0.692, P<0.001) and were strongly correlated for primary tumors (r=-0.866, P<0.001).

CONCLUSION

Delineating GTV on hybrid PET/MRIs is feasible, and aTL, the threshold boundary of BTV, was correlated inversely with the SUVmax.

PET/CT and PET/MRI in head and neck malignancy

Combined 2-[18F]-fluoro-2-deoxy-d-glucose (FDG) positron-emission tomography (PET)/computed tomography (CT) has an established role in the staging of difficult cases of head and neck (HN) squamous cell carcinoma (SCC), looking for an unknown primary, assessing response post-chemotherapy at 3-6 months, and differentiating relapse from treatment effects in patients suspected to have tumour recurrence. The PET NECK trial, comparing PET/CT surveillance versus neck dissection in advanced head and neck cancer showed survival was similar among patients who underwent PET/CT-guided surveillance and those who underwent planned neck dissection, but surveillance was more cost-effective. There is growing interest in the use of hypoxia PET tracers, especially in targeting radiotherapy, where the radiotherapy dose can be boosted in regions of hypoxia; the use of 68Ga peptide tracers in neuroendocrine malignancy and also in the growing field of combined PET/magnetic resonance imaging (MRI). PET/MRI has the advantage of increased anatomical detail and radiation dose reduction combined with the molecular and metabolic data from PET, although PET/CT has the advantage in better sensitivity for imaging lung metastases. Thus far, there is good agreement between PET/CT and PET/MRI with high correlation between semi-quantitative measurements in primary, nodal, osseous, and soft-tissue lesions imaging. PET/MRI may indeed provide greater accuracy than the currently available imaging procedures in the staging and later treatment response evaluation in HNSCC.

PET/MRI: Where might it replace PET/CT?

Simultaneous positron emission tomography and MRI (PET/MRI) is a technology that combines the anatomic and quantitative strengths of MR imaging with physiologic information obtained from PET. PET and computed tomography (PET/CT) performed in a single scanning session is an established technology already in widespread and accepted use worldwide. Given the higher cost and complexity of operating and interpreting the studies obtained on a PET/MRI system, there has been question as to which patients would benefit most from imaging with PET/MRI versus PET/CT. In this article, we compare PET/MRI with PET/CT, detail the applications for which PET/MRI has shown promise and discuss impediments to future adoption. It is our hope that future work will prove the benefit of PET/MRI to specific groups of patients, initially those in which PET/CT and MRI are already performed, leveraging simultaneity and allowing for greater degrees of multiparametric evaluation.

LEVEL OF EVIDENCE

5 Technical Efficacy: Stage 5 J. Magn. Reson. Imaging 2017;46:1247-1262.

Chapter 8 On the Horizon: Advanced Imaging Techniques to Improve Noninvasive Assessment of Cervical Lymph Nodes

Conventional imaging modalities are limited in the evaluation of lymph nodes as they predominantly rely on size and morphology, which have suboptimal sensitivity and specificity for malignancy. In this review we will explore the role of "on the horizon" advanced imaging modalities that can look beyond the size and morphologic features of a cervical lymph node and explore its molecular nature and can aid in personalizing therapy rather than use the "one-size-fits-all" approach.

Predictors of Clinicopathologic Stage Discrepancy in Oropharyngeal Squamous Cell Carcinoma: A National Cancer Database Study

Objective To determine the frequency, associated factors, and prognosis of clinicopathologic stage discrepancy in oropharyngeal squamous cell carcinoma (OPSCC). Study Design Retrospective study using a national database. Setting National Cancer Database. Subjects and Methods Cases of OPSCC diagnosed between January 1, 2004, and December 31, 2013, with full clinical and pathologic staging information available were identified. Demographic, clinicopathologic, and treatment variables associated with overall stage discrepancy were identified by multivariate logistic regression analysis. Results In total, 7731 cases of OPSCC were identified. Overall stage discrepancy was present in 30.2% of cases (21.9% upstaging, 8.2% downstaging). A total of 13.1% of cases were T-upstaged, and 10.5% of cases were T-downstaged; 22.9% of cases were N-upstaged, and 8.6% of cases were N-downstaged. Upstaging by overall stage was associated with a high Charlson-Deyo score, high tumor grade, number of lymph nodes examined, and increasing tumor size. No factors were positively associated with downstaging. High tumor grade was negatively associated with downstaging. For stage II, III, and IVA tumors, upstaging was associated with poorer OS. Conclusion Clinicopathologic stage discrepancy is common in OPSCC and is likely attributable to insensitive clinical staging techniques as well as to intrinsic tumor biologic properties. Upstaging is associated with poorer prognosis, which is likely due to advancement of disease.

[Molecular imaging of head and neck cancers : Perspectives of PET/MRI]

BACKGROUND

The (18)F-fluorodeoxyglucose positron emission tomography-computed tomography ((18)F-FDG-PET/CT) procedure is a cornerstone in the diagnostics of head and neck cancers. Several years ago PET-magnetic resonance imaging (PET/MRI) also became available as an alternative hybrid multimodal imaging method.

OBJECTIVE

Does PET/MRI have advantages over PET/CT in the diagnostics of head and neck cancers?

MATERIAL AND METHODS

The diagnostic accuracy of the standard imaging methods CT, MRI and PET/CT is depicted according to currently available meta-analyses and studies concerning the use of PET/MRI for these indications are summarized.

RESULTS

In all studies published up to now PET/MRI did not show superiority regarding the diagnostic accuracy in head and neck cancers; however, there is some evidence that in the future PET/MRI can contribute to tumor characterization and possibly be used to predict tumor response to therapy with the use of multiparametric imaging.

CONCLUSION

Currently, (18)F-FDG-PET/CT is not outperformed by PET/MRI in the diagnostics of head and neck cancers. The additive value of PET/MRI due to the use of multiparametric imaging needs to be investigated in future research.

Reliability of 18F-FDG PET Metabolic Parameters Derived Using Simultaneous PET/MRI and Correlation With Prognostic Factors of Invasive Ductal Carcinoma: A Feasibility Study

OBJECTIVE

The objective of our study was to correlate semiquantitative PET parameters-standardized uptake value (SUV) and total lesion glycolysis (TLG)-derived in simultaneous PET/MRI using MRI-based attenuation correction with clinical and histopathologic prognostic factors in patients with breast cancer.

MATERIALS AND METHODS

Eighty-two invasive ductal carcinomas in 69 women were included in the study. All the subjects underwent whole-body (WB) PET/MRI (supine WB mode) and dedicated PET/MRI of the breast (prone breast imaging mode) for staging on a simultaneous PET/MRI system. The SUV and TLG values were calculated from ¹⁸F-FDG PET data using MRI-based attenuation correction (2-point Dixon sequence for tissue segmentation). Relationships between SUV and TLG values and clinical and histopathologic parameters (i.e., tumor size, tumor grade, Ki-67 status, and hormonal receptor expression status) were evaluated using Spearman correlation coefficient analysis.

RESULTS

A significant correlation was observed between mean SUV (SUV_mean) and maximum SUV (SUV_max) values derived with WB PET and regional PET of the breasts performed simultaneously with MRI (r = 0.88 and 0.89, respectively). A significant difference (p < 0.05) was observed in SUV_mean, SUV_max, and TLG values between the grades and molecular subtypes of breast cancer. High SUV_mean, SUV_max, and TLG values were found to correlate with larger tumor size (p < 0.01), higher proliferation index (p < 0.05), higher grade (p < 0.01), and triple-negative hormonal receptor status (p < 0.01, p < 0.05).

CONCLUSION

Semiquantitative FDG parameters derived with MRI-based attenuation correction in simultaneous PET/MRI are reliable and correlate with clinicopathologic features such as grade as well as subtype and thus could be used in the prognostication of breast cancer.

PET+MR versus PET/CT in the initial staging of head and neck cancer, using a trimodality PET/CT+MR system

PURPOSE

To compare the diagnostic accuracy of PET+MR with PET/CT in the initial staging of head and neck cancer.

MATERIALS AND METHODS

Contrast-enhanced PET/CT+MR was performed in 27 patients with newly diagnosed head and neck cancer. PET/CT and PET+MR were evaluated separately, and the TNM stage and factors influencing treatment were assessed.

RESULTS

The TNM staging by PET+MR was comparable to PET/CT (T: p=0.331, N: p=0.453, M: p=0.034). The sensitivity/specificity/accuracy of treatment-influencing factors by PET/CT and PET+MR were 0.68/0.99/0.97, and 1.00/1.00/0.99, respectively.

CONCLUSIONS

Whole-body staging with PET+MR yields at least equal diagnostic accuracy as PET/CT in head and neck cancer.

Feasibility of Multiparametric Imaging with PET/MR in Head and Neck Squamous Cell Carcinoma

The purpose of this study was to investigate and assess the correlation and reproducibility of multiparametric imaging in head and neck cancer patients.

METHODS

Twenty-one patients were included in this prospective scan-rescan study. All patients were scanned twice on an integrated PET and MRI scanner. Gross tumor volumes were defined on T2-weighted MR images, and volumes of interest were defined on diffusion-weighted MRI and 18F-FDG PET (VOIDWI, VOIPET). Overlap between volumes was assessed as a percentwise overlap. 18F-FDG uptake and diffusion were measured using SUV and apparent diffusion coefficient, and correlation was tested across and within patients and as a voxel-by-voxel analysis.

RESULTS

Seventeen patients were available for correlation analysis, and 12 patients were available for assessment of tumor overlap. The median tumor overlap between VOIDWI and VOIPET was 82% (VOIDWI in VOIPET) and 62% (VOIPET in VOIDWI) on scan 1 and scan 2, respectively. Across patients, the correlation between SUV and apparent diffusion coefficient was weak and nonsignificant. However, in individual patients a weak but significant correlation was identified on a voxel-by-voxel basis.

CONCLUSION

In multiparametric imaging with the integrated PET/MR scanner, the VOIs from DWI and 18F-FDG PET were both within the target volume for radiotherapy and overlapped substantially although not completely. No correlation between 18F-FDG uptake and DWI could be found across patients, but within individual patients a statistically significant, but weak, voxel-by-voxel correlation was found. The findings suggest that information on glucose uptake and diffusion coefficient carries complementary information of interest that may be relevant for radiotherapy treatment planning.

Impact of combined FDG-PET/CT and MRI on the detection of local recurrence and nodal metastases in thyroid cancer

Background

Suspected recurrence of thyroid carcinoma is a diagnostic challenge when findings of both a radio iodine whole body scan and ultrasound are negative. PET/CT and MRI have shown to be feasible for detection of recurrent disease. However, the added value of a consensus reading by the radiologist and the nuclear medicine physician, which has been deemed to be helpful in clinical routines, has not been investigated. This study aimed to investigate the impact of combined FDG-PET/ldCT and MRI on detection of locally recurrent TC and nodal metastases in high-risk patients with special focus on the value of the multidisciplinary consensus reading.

Materials and methods

Forty-six patients with suspected locally recurrent thyroid cancer or nodal metastases after thyroidectomy and radio-iodine therapy were retrospectively selected for analysis. Inclusion criteria comprised elevated thyroglobulin blood levels, a negative ultrasound, negative iodine whole body scan, as well as combined FDG-PET/ldCT and MRI examinations.

Neck compartments in FDG-PET/ldCT and MRI examinations were independently analyzed by two blinded observers for local recurrence and nodal metastases of thyroid cancer. Consecutively, the scans were read in consensus. To explore a possible synergistic effect, FDG-PET/ldCT and MRI results were combined. Histopathology or long-term follow-up served as a gold standard.

For method comparison, sensitivity, specificity, positive and negative predictive values, and diagnostic accuracy were calculated.

Results

FDG-PET/ldCT was substantially more sensitive and more specific than MRI in detection of both local recurrence and nodal metastases. Inter-observer agreement was substantial both for local recurrence (κ = 0.71) and nodal metastasis (κ = 0.63) detection in FDG-PET/ldCT. For MRI, inter-observer agreement was substantial for local recurrence (κ = 0.69) and moderate for nodal metastasis (κ = 0.55) detection. In contrast, FDG-PET/ldCT and MRI showed only slight agreement (κ = 0.21). However, both imaging modalities identified different true positive results. Thus, the combination created a synergistic effect. The multidisciplinary consensus reading further increased sensitivity, specificity, and diagnostic accuracy.

Conclusions

FDG-PET/ldCT and MRI are complementary imaging modalities and should be combined to improve detection of local recurrence and nodal metastases of thyroid cancer in high-risk patients. The multidisciplinary consensus reading is a key element in the diagnostic approach.

Electronic supplementary material

The online version of this article (doi:10.1186/s40644-016-0096-y) contains supplementary material, which is available to authorized users.

Potential Role of PET/MRI for Imaging Metastatic Lymph Nodes in Head and Neck Cancer

OBJECTIVE

This article explores recent developments in PET and MRI, separately or combined, for assessing metastatic lymph nodes in patients with head and neck cancer.

CONCLUSION

The synergistic role of PET and MRI for imaging metastatic lymph nodes has not been fully explored. To facilitate the understanding of the areas that need further investigation, we discuss potential mechanisms and evidence reported so far, as well as future directions and challenges for continued development and clinical research.

Multimodal nonlinear microscopy of head and neck carcinoma - toward surgery assisting frozen section analysis

BACKGROUND

Treatment of early cancer stages is deeply connected to a good prognosis, a moderate reduction of the quality of life, and comparably low treatment costs.

METHODS

Head and neck squamous cell carcinomas were investigated using the multimodal combination of coherent anti-Stokes Raman scattering (CARS), two-photon excited fluorescence (TPEF), and second-harmonic generation (SHG) microscopy.

RESULTS

An increased median TPEF to CARS contrast was found comparing cancerous and healthy squamous epithelium with a p value of 1.8·10(-10) . A following comprehensive image analysis was able to predict the diagnosis of imaged tissue sections with an overall accuracy of 90% for a 4-class model.

CONCLUSION

Nonlinear multimodal imaging is verified objectively as a valuable diagnostic tool that complements conventional staining protocols and can serve as filter in future clinical routine reducing the pathologist's workload. © 2016 Wiley Periodicals, Inc. Head Neck 38: First-1552, 2016.

PET/MR in cancers of the head and neck

One early application of PET/MRI in clinical practice may be the imaging of head and neck cancers. This is because the morphologic imaging modalities, CT and MR, are recognized as similarly effective tools in cross-sectional oncological imaging of the head and neck. The addition of PET with FDG is believed to enhance the accuracy of both modalities to a similar degree. However, there are a few specific scenarios in head and neck cancer imaging where MR is thought to provide an edge over CT, including perineural spread of tumors and the infiltration of important anatomical landmarks, such as the prevertebral fascia and great vessel walls. Here, hybrid PET/MR might provide higher diagnostic certainty than PET/CT or a separate acquisition of PET/CT and MR. Another advantage of MR is the availability of several functional techniques. Although some of them might enhance the imaging of head and neck cancer with PET/MR, other functional techniques actually might prove dispensable in the presence of PET. In this overview, we discuss current trends and potential clinical applications of PET/MR in the imaging of head and neck cancers, including clinical protocols. We also discuss potential benefits of implementing functional MR techniques into hybrid PET/MRI of head and neck cancers.

Positive and Negative Predictive Value of PET-CT in Skull Base Lesions: Case Series and Systematic Literature Review

Objectives To study positive (PPV) and negative predictive value (NPV) of positron emission tomography with computed tomography (PET-CT) scans in determining malignancy in skull base lesions and perform a systematic literature review for optimal PET-CT interpretation. Design Retrospective case series and systematic literature review of the current English literature. Setting Tertiary referral academic medical center. Participants All patients with skull base lesions that underwent PET-CT and tissue biopsy from 2010 to 2013. Main Outcome Measures PPV and NPV of radiologist's report and standardized uptake value (SUV) cutoff of 2.5 and 3, biopsy with pathologic interpretation, clinical follow-up. Results A total of 31 PET-CT scans of 16 patients were studied; 10 PET-CT were performed upfront for diagnostic purposes and 21 were post-treatment surveillance scans. The PPV of radiologist's interpretation, SUV cutoff of 2.5, and SUV cutoff of 3.0 was 80%, 60%, and 68.4%, with a NPV of 100%, 83.3%, and 75%, respectively. Literature search yielded 500 abstracts; 7 studies met inclusion criteria for detailed review. No consensus or guidelines for optimal SUV cutoff value was found. Conclusions PET-CT based on SUV cutoff criteria alone has high NPV but low PPV in determining malignancy in skull base lesions. Interpretation by a radiologist experienced in nuclear medicine and neuroradiology, synthesizing clinical, SUV, and radiologic data are of superior value.

Standardized Uptake Values from PET/MRI in Metastatic Breast Cancer: An Organ-based Comparison With PET/CT

Quantitative standardized uptake values (SUVs) from fluorine-18 (18F) fluorodeoxyglucose (FDG) positron emission tomography/computed tomography (PET/CT) are commonly used to evaluate the extent of disease and response to treatment in breast cancer patients. Recently, PET/magnetic resonance imaging (MRI) has been shown to qualitatively detect metastases from various primary cancers with similar sensitivity to PET/CT. However, quantitative validation of PET/MRI requires assessing the reliability of SUVs from MR attenuation correction (MRAC) relative to CT attenuation correction (CTAC). The purpose of this retrospective study was to assess the utility of PET/MRI-derived SUVs in breast cancer patients by testing the hypothesis that SUVs derived from MRAC correlate well with those from CTAC. Between August 2012 and May 2013, 35 breast cancer patients (age 37-78 years, 1 man) underwent clinical 18F-FDG PET/CT followed by PET/MRI. One hundred seventy metastases were seen in 21 of 35 patients; metastases to bone in 16 patients, to liver in seven patients, and to nonaxillary lymph nodes in eight patients were sufficient for statistical analysis on an organ-specific per patient basis. SUVs in the most FDG-avid metastasis per organ per patient from PET/CT and PET/MRI were measured and compared using Pearson's correlations. Correlations between CTAC- and MRAC-derived SUVmax and SUVmean in 31 metastases to bone, liver, and nonaxillary lymph nodes were strong overall (ρ = 0.80, 0.81). SUVmax and SUVmean correlations were also strong on an organ-specific basis in 16 bone metastases (ρ = 0.76, 0.74), seven liver metastases (ρ = 0.85, 0.83), and eight nonaxillary lymph node metastases (ρ = 0.95, 0.91). These strong organ-specific correlations between SUVs from PET/CT and PET/MRI in breast cancer metastases support the use of SUVs from PET/MRI for quantitation of 18F-FDG activity.

Common patterns of perineural spread in head-neck squamous cell carcinoma identified on fluoro-deoxy-glucose positron emission tomography/computed tomography

Perineural spread in HNSCC is associated with dismal prognosis and decreased overall survival. Clinical diagnosis of this relatively asymptomatic entity is usually delayed and made incidentally on imaging. MRI is gold standard imaging for early diagnosing of this condition owing to its excellent anatomic resolution. With the ever increasing use of PET/CT in commonly encountered cancer such as HNSCC for staging and re-staging, observing perineural spread on PET/CT is not infrequent. Through this pictorial essay we demonstrate the common patterns of perineural spread in HNSCC on PET/CT with the aim of improving reporting accuracy across readers.

Clinical applications of PET/MRI: current status and future perspectives

Fully integrated positron emission tomography (PET)/magnetic resonance imaging (MRI) scanners have been available for a few years. Since then, the number of scanner installations and published studies have been growing. While feasibility of integrated PET/MRI has been demonstrated for many clinical and preclinical imaging applications, now those applications where PET/MRI provides a clear benefit in comparison to the established reference standards need to be identified. The current data show that those particular applications demanding multiparametric imaging capabilities, high soft tissue contrast and/or lower radiation dose seem to benefit from this novel hybrid modality. Promising results have been obtained in whole-body cancer staging in non-small cell lung cancer and multiparametric tumor imaging. Furthermore, integrated PET/MRI appears to have added value in oncologic applications requiring high soft tissue contrast such as assessment of liver metastases of neuroendocrine tumors or prostate cancer imaging. Potential benefit of integrated PET/MRI has also been demonstrated for cardiac (i.e., myocardial viability, cardiac sarcoidosis) and brain (i.e., glioma grading, Alzheimer's disease) imaging, where MRI is the predominant modality. The lower radiation dose compared to PET/computed tomography will be particularly valuable in the imaging of young patients with potentially curable diseases.However, further clinical studies and technical innovation on scanner hard- and software are needed. Also, agreements on adequate refunding of PET/MRI examinations need to be reached. Finally, the translation of new PET tracers from preclinical evaluation into clinical applications is expected to foster the entire field of hybrid PET imaging, including PET/MRI.

In Vivo Correlation of Glucose Metabolism, Cell Density and Microcirculatory Parameters in Patients with Head and Neck Cancer: Initial Results Using Simultaneous PET/MRI

Objective

To demonstrate the feasibility of simultaneous acquisition of ¹⁸F-FDG-PET, diffusion-weighted imaging (DWI) and T1-weighted dynamic contrast-enhanced MRI (T1w-DCE) in an integrated simultaneous PET/MRI in patients with head and neck squamous cell cancer (HNSCC) and to investigate possible correlations between these parameters.

Methods

17 patients that had given informed consent (15 male, 2 female) with biopsy-proven HNSCC underwent simultaneous ¹⁸F-FDG-PET/MRI including DWI and T1w-DCE. SUV_max, SUV_mean, ADC_mean, ADC_min and K^trans, k_ep and v_e were measured for each tumour and correlated using Spearman’s ρ.

Results

Significant correlations were observed between SUV_mean and K^trans (ρ = 0.43; p ≤ 0.05); SUV_mean and k_ep (ρ = 0.44; p ≤ 0.05); K^trans and k_ep (ρ = 0.53; p ≤ 0.05); and between k_ep and v_e (ρ = -0.74; p ≤ 0.01). There was a trend towards statistical significance when correlating SUV_max and ADC_min (ρ = -0.35; p = 0.08); SUV_max and K^trans (ρ = 0.37; p = 0.07); SUV_max and k_ep (ρ = 0.39; p = 0.06); and ADC_mean and v_e (ρ = 0.4; p = 0.06).

Conclusion

Simultaneous ¹⁸F-FDG-PET/MRI including DWI and T1w-DCE in patients with HNSCC is feasible and allows depiction of complex interactions between glucose metabolism, microcirculatory parameters and cellular density.

Locoregional tumour evaluation of squamous cell carcinoma in the head and neck area: a comparison between MRI, PET/CT and integrated PET/MRI

PURPOSE

To evaluate the accuracy of integrated (18)F-FDG PET/MR imaging for locoregional tumour evaluation compared to (18)F-FDG PET/CT and MR imaging in initial tumour and recurrence diagnosis in histopathologically confirmed head and neck squamous cell carcinoma (HNSCC).

METHODS

(18)F-FDG PET/CT and integrated (18)F-FDG PET/MR imaging were performed for initial tumour staging or recurrence diagnosis in 25 patients with HNSCC. MR, fused (18)F-FDG PET/CT and fused (18)F-FDG PET/MR images were analysed by two independent readers in separate sessions in random order. In initial tumour staging, T and N staging was performed while individual lesions were analysed in patients with suspected cancer recurrence. In T and N staging, histopathological results after tumour resection served as the reference standard while histopathological sampling as well as cross-sectional and clinical follow-up were accepted in cancer recurrence diagnosis. The diagnostic accuracy of each modality was calculated separately for T and N staging as well as for tumour recurrence, and compared using McNemar's test. Values of p <0.017 were considered statistically significant after Bonferroni correction.

RESULTS

In 12 patients undergoing (18)F-FDG PET/CT and (18)F-FDG PET/MR for initial tumour staging, T staging was accurate in 50 % with MRI, in 59 % with PET/CT and in 75 % with PET/MR while N staging was accurate in 75 % with MRI, in 77 % with PET/CT and in 71 % with PET/MR in relation to the reference standard. No significant differences were observed in T and N staging among the three modalities (p > 0.017). In 13 patients undergoing hybrid imaging for cancer recurrence diagnosis, diagnostic accuracy was 57 % with MRI and in 72 % with (18)F-FDG PET/CT and (18)F-FDG PET/MR, respectively. Again, no significant differences were found among the three modalities (p > 0.017).

CONCLUSION

In this initial study, no significant differences were found among (18)F-FDG PET/MR, (18)F-FDG PET/CT and MRI in local tumour staging and cancer recurrence diagnosis.

PET/MRI in Oncological Imaging: State of the Art

Positron emission tomography (PET) combined with magnetic resonance imaging (MRI) is a hybrid technology which has recently gained interest as a potential cancer imaging tool. Compared with CT, MRI is advantageous due to its lack of ionizing radiation, superior soft-tissue contrast resolution, and wider range of acquisition sequences. Several studies have shown PET/MRI to be equivalent to PET/CT in most oncological applications, possibly superior in certain body parts, e.g., head and neck, pelvis, and in certain situations, e.g., cancer recurrence. This review will update the readers on recent advances in PET/MRI technology and review key literature, while highlighting the strengths and weaknesses of PET/MRI in cancer imaging.

Development of a multimodal imaging probe by encapsulating iron oxide nanoparticles with functionalized amphiphiles for lymph node imaging

Aim: We tried to develop a multimodal iron oxide nanoparticles (IO NP) imaging probe by an encapsulation method using specific amphiphiles for 68Ga-labeling and lymph node-targeting. Materials & methods: Nanoparticles (NPs) were encapsulated with a solution containing polysorbate 60 and the amphiphiles. The prepared NPs were labeled with 68Ga and tested in vitro and in vivo. Results: Prepared 1,4,7-triazacyclononane-1,4,7-triacetic acid-IO-Mannose (NOTA-IO-Man) showed a narrow size distribution, and no significant aggregation or degradation under harsh conditions. The relaxivity coefficient of 68Ga-NOTA-IO-Man was higher than that of ferumoxide. The accumulation of 68Ga-NOTA-IO-Man in the lymph node after injection into rat's footpad was confirmed by both positron emission tomography and MRI. Conclusion: We successfully developed PET/MRI dual-modality imaging probe targeting lymph nodes by using the facile encapsulation method.

Simultaneous PET/MR head-neck cancer imaging: Preliminary clinical experience and multiparametric evaluation

PURPOSE

To evaluate the role of simultaneous hybrid PET/MR imaging and to correlate metabolic PET data with morpho-functional parameters derived by MRI in patients with head-neck cancer.

METHODS

Forty-four patients, with histologically confirmed head and neck malignancy (22 primary tumors and 22 follow-up) were studied. Patients initially received a clinical exam and endoscopy with direct biopsy. Next patients underwent whole body PET/CT followed by PET/MR of the head/neck region. PET and MRI studies were separately evaluated by two blinded groups (both included one radiologist and one nuclear physician) in order to define the presence or absence of lesions/recurrences. Regions of interest (ROIs) analysis was conducted on the primary lesion at the level of maximum size on metabolic (SUV and MTV), diffusion (ADC) and perfusion (K(trans), Ve, kep and iAUC) parameters.

RESULTS

PET/MR examinations were successfully performed on all 44 patients. Agreement between the two blinded groups was found in anatomic allocation of lesions by PET/MR (Primary tumors: Cohen's kappa 0.93;

FOLLOW-UP

Cohen's kappa 0.89). There was a significant correlation between CT-SUV measures and MR (e.g., CT-SUV VOI vs.

MR-SUV VOI

ρ=0.97, p<0.001 for the entire sample). There was also significant positive correlations between the ROI area, SUV measures, and the metabolic parameters (SUV and MTV) obtained during both PET/CT and PET/MR. A significant negative correlation was observed between ADC and K(trans) values in the primary tumors. In addition, a significant negative correlation existed between MR SUV and ADC in recurrent tumors.

CONCLUSION

Our study demonstrates the feasibility of PET/MR imaging for primary tumors and recurrent tumors evaluations of head/neck malignant lesions. When assessing HNC, PET/MR allows simultaneous collection of multiparametric metabolic and functional data. This technique therefore allows for a more complete characterization of malignant lesions.

Dental artifacts in the head and neck region: implications for Dixon-based attenuation correction in PET/MR

Background

In the absence of CT or traditional transmission sources in combined clinical positron emission tomography/magnetic resonance (PET/MR) systems, MR images are used for MR-based attenuation correction (MR-AC). The susceptibility effects due to metal implants challenge MR-AC in the neck region of patients with dental implants. The purpose of this study was to assess the frequency and magnitude of subsequent PET image distortions following MR-AC.

Methods

A total of 148 PET/MR patients with clear visual signal voids on the attenuation map in the dental region were included in this study. Patients were injected with [¹⁸F]-FDG, [¹¹C]-PiB, [¹⁸F]-FET, or [⁶⁴Cu]-DOTATATE. The PET/MR data were acquired over a single-bed position of 25.8 cm covering the head and neck. MR-AC was based on either standard MR-AC_DIXON or MR-AC_INPAINTED where the susceptibility-induced signal voids were substituted with soft tissue information. Our inpainting algorithm delineates the outer contour of signal voids breaching the anatomical volume using the non-attenuation-corrected PET image and classifies the inner air regions based on an aligned template of likely dental artifact areas. The reconstructed PET images were evaluated visually and quantitatively using regions of interests in reference regions. The volume of the artifacts and the computed relative differences in mean and max standardized uptake value (SUV) between the two PET images are reported.

Results

The MR-based volume of the susceptibility-induced signal voids on the MR-AC attenuation maps was between 1.6 and 520.8 mL. The corresponding/resulting bias of the reconstructed tracer distribution was localized mainly in the area of the signal void. The mean and maximum SUVs averaged across all patients increased after inpainting by 52% (± 11%) and 28% (± 11%), respectively, in the corrected region. SUV underestimation decreased with the distance to the signal void and correlated with the volume of the susceptibility artifact on the MR-AC attenuation map.

Conclusions

Metallic dental work may cause severe MR signal voids. The resulting PET/MR artifacts may exceed the actual volume of the dental fillings. The subsequent bias in PET is severe in regions in and near the signal voids and may affect the conspicuity of lesions in the mandibular region.

Electronic supplementary material

The online version of this article (doi:10.1186/s40658-015-0112-5) contains supplementary material, which is available to authorized users.

Reproducibility of (18)F-FDG PET uptake measurements in head and neck squamous cell carcinoma on both PET/CT and PET/MR

OBJECTIVE

To investigate reproducibility of fluorine-18 fludeoxyglucose ((18)F-FDG) uptake on (18)F-FDG positron emission tomography (PET)/CT and (18)F-FDG PET/MR scans in patients with head and neck squamous cell carcinoma (HNSCC).

METHODS

30 patients with HNSCC were included in this prospective study. The patients were scanned twice before radiotherapy treatment with both PET/CT and PET/MR. Patients were scanned on the same scanners, 3 days apart and according to the same protocol. Metabolic tumour activity was measured by the maximum and peak standardized uptake value (SUVmax and SUVpeak, respectively), and total lesion glycolysis from the metabolic tumour volume defined from ≥50% SUVmax. Bland-Altman analysis with limits of agreement, coefficient of variation (CV) from the two modalities were performed in order to test the reproducibility. Furthermore, CVs from SUVmax and SUVpeak were compared. The area under the curve from cumulative SUV-volume histograms were measured and tested for reproducibility of the distribution of (18)F-FDG uptake.

RESULTS

24 patients had two pre-treatment PET/CT scans and 21 patients had two pre-treatment PET/MR scans available for further analyses. Mean difference for SUVmax, peak and mean was approximately 4% for PET/CT and 3% for PET/MR, with 95% limits of agreement less than ±20%. CV was small (5-7%) for both modalities. There was no significant difference in CVs between PET/CT and PET/MR (p = 0.31). SUVmax was not more reproducible than SUVpeak (p = 0.09).

CONCLUSION

(18)F-FDG uptake in PET/CT and PET/MR is highly reproducible and we found no difference in reproducibility between PET/CT and PET/MR.

ADVANCES IN KNOWLEDGE

This is the first report to test reproducibility of PET/CT and PET/MR.