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Imaging in head and neck squamous cell carcinoma: the potential role of PET/MRI.

Becker M, Zaidi H - Br J Radiol (2014)

Bottom Line: In head and neck oncology, the information provided by positron emission tomography (PET)/CT and MRI is often complementary because both the methods are based on different biophysical foundations.However, combining PET with MRI has proven to be technically and clinically more challenging than initially expected and, as such, research into the potential clinical role of PET/MRI in comparison with PET/CT, diffusion-weighted MRI (DW MRI) or the combination thereof is still ongoing.Feasibility and quantification issues, diagnostic pitfalls and challenges in clinical settings as well as ongoing research and potential future applications are also discussed.

View Article: PubMed Central - PubMed

Affiliation: Department of Imaging, Division of Radiology, Geneva University Hospital, Geneva, Switzerland.

ABSTRACT
In head and neck oncology, the information provided by positron emission tomography (PET)/CT and MRI is often complementary because both the methods are based on different biophysical foundations. Therefore, combining diagnostic information from both modalities can provide additional diagnostic gain. Debates about integrated PET/MRI systems have become fashionable during the past few years, since the introduction and wide adoption of software-based multimodality image registration and fusion and the hardware implementation of integrated hybrid PET/MRI systems in pre-clinical and clinical settings. However, combining PET with MRI has proven to be technically and clinically more challenging than initially expected and, as such, research into the potential clinical role of PET/MRI in comparison with PET/CT, diffusion-weighted MRI (DW MRI) or the combination thereof is still ongoing. This review focuses on the clinical applications of PET/MRI in head and neck squamous cell carcinoma (HNSCC). We first discuss current evidence about the use of combined PET/CT and DW MRI, and, then, we explain the rationale and principles of PET/MR image fusion before summarizing the state-of-the-art knowledge regarding the diagnostic performance of PET/MRI in HNSCC. Feasibility and quantification issues, diagnostic pitfalls and challenges in clinical settings as well as ongoing research and potential future applications are also discussed.

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This patient was a follow-up case of a squamous cell carcinoma of the oropharynx. (a) Axial positron emission tomography (PET)/CT shows metastatic mediastinal lymph nodes (dashed arrows) and metastatic lung nodules (arrows). (b) Corresponding hybrid PET/MRI (fused PET and gadolinium-enhanced water-only Dixon image and slice thickness of 2 mm) shows similar findings. Metastatic mediastinal nodes (dashed arrows). Lung metastases (arrows). Note that lung nodule conspicuity is slightly better on PET/CT than on PET/MRI.
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fig7: This patient was a follow-up case of a squamous cell carcinoma of the oropharynx. (a) Axial positron emission tomography (PET)/CT shows metastatic mediastinal lymph nodes (dashed arrows) and metastatic lung nodules (arrows). (b) Corresponding hybrid PET/MRI (fused PET and gadolinium-enhanced water-only Dixon image and slice thickness of 2 mm) shows similar findings. Metastatic mediastinal nodes (dashed arrows). Lung metastases (arrows). Note that lung nodule conspicuity is slightly better on PET/CT than on PET/MRI.

Mentions: One of the major potential disadvantages of PET/MRI over PET/CT in head and neck cancer patients is due to the fact that MRI is less sensitive than CT for the detection of pulmonary nodules.100 Appenzeller et al100 prospectively evaluated whether the performance of PET/MRI using the body coil is sufficient from a diagnostic point of view when compared with standard low-dose non-contrast-enhanced PET/CT regarding the overall diagnostic accuracy, lesion detectability, size and lesion conspicuity. The authors used an axial Dixon-based T1 weighted 3D gradient echo sequence with a slice thickness of 6.8 mm. Comparison of PET/MRI with PET/CT in 63 patients referred for a variety of malignant tumours revealed a statistically significant superiority of PET/CT over PET/MRI for the conspicuity of pulmonary lesions (p=0.016).100 The authors suggested that, for this reason, an additional chest CT will probably still remain necessary for most patients in the near future. Nevertheless recent data suggest that PET/MRI may perform somewhat better in this respect.82 Results from our institution have shown that in head and neck cancer patients PET/MRI may perform as well as PET/CT regarding lung nodule detection provided that a high-resolution Dixon sequence (voxel size 0.85 × 0.85 × 3 mm) is obtained.82 Nevertheless, the reported data are based on a small number of patients with a low prevalence of lung lesions; further studies in head and neck cancer patients are therefore required to confirm these findings. Our preliminary results in a larger patient series (unpublished data) also show that although the conspicuity of the lung lesions may be less good on PET/MRI than on PET/CT, FDG avid lung nodules are equally well detected with both modalities (Figure 7).


Imaging in head and neck squamous cell carcinoma: the potential role of PET/MRI.

Becker M, Zaidi H - Br J Radiol (2014)

This patient was a follow-up case of a squamous cell carcinoma of the oropharynx. (a) Axial positron emission tomography (PET)/CT shows metastatic mediastinal lymph nodes (dashed arrows) and metastatic lung nodules (arrows). (b) Corresponding hybrid PET/MRI (fused PET and gadolinium-enhanced water-only Dixon image and slice thickness of 2 mm) shows similar findings. Metastatic mediastinal nodes (dashed arrows). Lung metastases (arrows). Note that lung nodule conspicuity is slightly better on PET/CT than on PET/MRI.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4067029&req=5

fig7: This patient was a follow-up case of a squamous cell carcinoma of the oropharynx. (a) Axial positron emission tomography (PET)/CT shows metastatic mediastinal lymph nodes (dashed arrows) and metastatic lung nodules (arrows). (b) Corresponding hybrid PET/MRI (fused PET and gadolinium-enhanced water-only Dixon image and slice thickness of 2 mm) shows similar findings. Metastatic mediastinal nodes (dashed arrows). Lung metastases (arrows). Note that lung nodule conspicuity is slightly better on PET/CT than on PET/MRI.
Mentions: One of the major potential disadvantages of PET/MRI over PET/CT in head and neck cancer patients is due to the fact that MRI is less sensitive than CT for the detection of pulmonary nodules.100 Appenzeller et al100 prospectively evaluated whether the performance of PET/MRI using the body coil is sufficient from a diagnostic point of view when compared with standard low-dose non-contrast-enhanced PET/CT regarding the overall diagnostic accuracy, lesion detectability, size and lesion conspicuity. The authors used an axial Dixon-based T1 weighted 3D gradient echo sequence with a slice thickness of 6.8 mm. Comparison of PET/MRI with PET/CT in 63 patients referred for a variety of malignant tumours revealed a statistically significant superiority of PET/CT over PET/MRI for the conspicuity of pulmonary lesions (p=0.016).100 The authors suggested that, for this reason, an additional chest CT will probably still remain necessary for most patients in the near future. Nevertheless recent data suggest that PET/MRI may perform somewhat better in this respect.82 Results from our institution have shown that in head and neck cancer patients PET/MRI may perform as well as PET/CT regarding lung nodule detection provided that a high-resolution Dixon sequence (voxel size 0.85 × 0.85 × 3 mm) is obtained.82 Nevertheless, the reported data are based on a small number of patients with a low prevalence of lung lesions; further studies in head and neck cancer patients are therefore required to confirm these findings. Our preliminary results in a larger patient series (unpublished data) also show that although the conspicuity of the lung lesions may be less good on PET/MRI than on PET/CT, FDG avid lung nodules are equally well detected with both modalities (Figure 7).

Bottom Line: In head and neck oncology, the information provided by positron emission tomography (PET)/CT and MRI is often complementary because both the methods are based on different biophysical foundations.However, combining PET with MRI has proven to be technically and clinically more challenging than initially expected and, as such, research into the potential clinical role of PET/MRI in comparison with PET/CT, diffusion-weighted MRI (DW MRI) or the combination thereof is still ongoing.Feasibility and quantification issues, diagnostic pitfalls and challenges in clinical settings as well as ongoing research and potential future applications are also discussed.

View Article: PubMed Central - PubMed

Affiliation: Department of Imaging, Division of Radiology, Geneva University Hospital, Geneva, Switzerland.

ABSTRACT
In head and neck oncology, the information provided by positron emission tomography (PET)/CT and MRI is often complementary because both the methods are based on different biophysical foundations. Therefore, combining diagnostic information from both modalities can provide additional diagnostic gain. Debates about integrated PET/MRI systems have become fashionable during the past few years, since the introduction and wide adoption of software-based multimodality image registration and fusion and the hardware implementation of integrated hybrid PET/MRI systems in pre-clinical and clinical settings. However, combining PET with MRI has proven to be technically and clinically more challenging than initially expected and, as such, research into the potential clinical role of PET/MRI in comparison with PET/CT, diffusion-weighted MRI (DW MRI) or the combination thereof is still ongoing. This review focuses on the clinical applications of PET/MRI in head and neck squamous cell carcinoma (HNSCC). We first discuss current evidence about the use of combined PET/CT and DW MRI, and, then, we explain the rationale and principles of PET/MR image fusion before summarizing the state-of-the-art knowledge regarding the diagnostic performance of PET/MRI in HNSCC. Feasibility and quantification issues, diagnostic pitfalls and challenges in clinical settings as well as ongoing research and potential future applications are also discussed.

Show MeSH
Related in: MedlinePlus