The purpose of the study is to compare the efficacy of 18F-FDG PET/CT and DWI WB-MRI in detection of distant metastasis of various cancers.

Metastasis is the leading cause of morbidity and mortality in patients with cancer, accounting for ~90% of cancer-associated deaths.

Distant metastasis (DM) is a crucial point in the management of malignant tumors. DM is always associated with poor survival. Conclusive diagnosis of DM is crucial for improving the prognosis, reduction of the recurrence rate and hence, elevation of the 5-year survival rate.

Positron emission tomography/computed tomography (PET/CT) allows the analysis of active tumor tissue in the whole body. So, it obtains improved sensitivity and specificity when compared to conventional imaging modalities.

18F-FDG PET/CT is a diagnostic imaging modality with good quantitative properties. It has proven its interest in diagnosing, staging, and evaluating tumor response.

Whole-body MRI (WB-MRI) has been proposed as another effective whole-body approach for assessing both local invasiveness and distant metastases in patients with newly diagnosed cancers providing several advantages.

WB-MRI primarily provides structural information (revealing a detailed image of the pathology or lesion) on tumor spread; however, the absence of functional datasets has been resolved by incorporating Whole-body Diffusion Weighted Imaging (WB-DWI) into medical practice. WB-DWI shortens examination interpretation times by directing the radiologist's attention to abnormalities, which may then be investigated on anatomic sequences. It enables early detection of skeletal metastases as well as spread to other sites (liver and brain).

DW-MRI measures the Brownian motion of water molecules within intra- and extracellular spaces. This occurs in highly cellular lesions or in environments in which tissue architecture is disrupted and can be quantified by calculating the apparent diffusion coefficient (ADC).

Inclusion Criteria:

• Only patients with malignancies proven by histology and patients with metastatic lesions proven by histopathology or cytology were included.

Exclusion Criteria:

• • As regard the PET/CT study, patients who have the general CT contraindications such as pregnancy, breast feeding, history of allergic reaction to the contrast medium, renal disease, etc.

  • As regard the MRI study, general contraindications including claustrophobia, MR-incompatible pacemakers and MR-incompatible heart valves.
  • Patients whose MRI sequences were incomplete, low-quality and/or had no histopathological evidence of metastatic lesions were eliminated from the study.
  • Low-quality or incomplete MRI included MRI exams with incomplete sequence(s), which is particularly common in elderly patients who are unable to tolerate the scan, or uncooperative patients who do not obey breathing instructions and motion artifacts that may impair images and lead to lower accuracy.
  • Declined consent.

adult patient, having present history of malignancy and referred from the general surgery or oncology clinics as having known metastatic lesions proven by histopathology or cytology. all Patients should be eligible to go through both modalities; PET-CT and MRI.