**3.6 Other modalities**

PET-MRI is an examination modality where the metabolic phase of the study is performed using 18F-FDG/PET and the anatomical acquisition is performed by MRI. It has a good indication in tumors, such as lymphomas and sarcomas, but imaging protocols still need to be defined separately for each type of malignancy, both bone and soft tissue [30]. As advantages reduces radiation exposure, can optimize diagnostic accuracy, and is a good predictor of histological response. In addition, better delimitation of the primary tumor (invasion of soft tissues). As a disadvantage, there is still no diagnostic advantage in performing the staging of the patient by PET/ MRI in relation to conventional exams [30, 31], it presents several results similar to PET-CT [32] and still has limitations for the evaluation of nodules. Lungs smaller than 5 mm in size, and chest CT is still superior in this regard [32, 33]. PET-MRI can even be used for radiotherapy planning and detection of tissue damage by chemotherapy.

*Perspective Chapter: Bone Tumors – How to Make a Diagnosis? DOI: http://dx.doi.org/10.5772/intechopen.106673*

### **Figure 5.**

*Total body MRI. (A) patient with conventional osteosarcoma at the distal end of the femur, (B) patient with Ewing's sarcoma of the first metatarsal, observing metastasis in the proximal end of the tibia, and (C) patient with lung cancer and multiple bone metastases.*

Regarding specific diagnoses, for example, in osteosarcoma, PET/MRI can better define the anatomical location of the lesion, but the lesion detection rate is similar to PET/CT. In Ewing's sarcoma, it is superior to PET-CT in the evaluation of an organ with high metabolic activity, such as the brain, probably the PET/MRI will become the exam of choice in these patients [29]. In the investigation of metastases for prostate and breast carcinoma, PET/MRI is presented as a great tool in the evaluation of these patients, but still not statistically superior to conventional methods [34]. However, although PET/MRI proves to be valuable, it cannot replace conventional exams if it is not accessible to most cancer patients [35].

Whole body MRI is an imaging method that uses a core protocol with essential imaging contrasts and it can be completed with sequences to evaluate other specific regions as needed, is a modality under evaluation for its applications and usefulness in bone sarcomas, however, it is observed that is better than scintigraphy to the screening for metastases [36] and is a good screening for cancer in patients with genetic syndromes, such as Li-Fraumeni, especially after the second test (lower false positive value, [37]) (**Figure 5**). In patients with prostate cancer, multiple myeloma and melanoma, whole body MRI is already introduced in international protocols, while its usefulness in neoplasms, such as breast cancer, ovarian cancer, and lymphoma is on the rise [38, 39]. WB-MRI is an excellent test for detecting bone metastases, especially in the spine region [40].
