Role of Whole-body Diffusion MR in Detection of Metastatic lesions Prof. Dr. NAGUI M. ABDELWAHAB,M.D.; MARYSE Y. AWADALLAH, M.D. AYA M. BASSAM, Ms.C.
Cancer is a potentially life-threatening disease, and the development of skeletal or organ metastases is often not detected until clinical symptoms present. That is why radiological imaging such as plain film X- ray, Tc99m bone scintigraphy, computed tomography (CT), positron emission tomography (PET), magnetic resonance imaging (MRI), are the cornerstone for :- Detection and staging of metastatic lesions. Classifying their type, site and extent. Skeletal scintigraphy is the standard procedure for visualizing bone metastases, (50-70% of distant metstases).
DWI is a powerful imaging tool that provides unique information related to tumor cellularity, integrity of the cellular membrane, as well as the movement and functional status of the microenvironment of water in tissue. The technique can be applied widely for tumor detection, tumor characterization and monitoring of tumor response. Until recently, most sensitive radiological procedures were only limited to local coverage and could not interrogate the full body.
Diffusion-weighted sequence (DWI) of the entire body is a new promising technique feasible to evaluate multifocal disease. Technological advances and the development of the concept of diffusion-weighted whole-body imaging with background body signal suppression (DWIBS) have opened the path for routine clinical whole-body DWI, which allows detection and characterization of both oncological and non-oncological lesions throughout the entire body.
Several studies stated that; whole body magnetic resonance imaging (WB-MRI) has shown better results than skeletal scintigraphy. Practical implementation of whole body DWI, using the DWIBS concept, is relatively easy, since it can be performed on most modern MRI scanners and does not require any contrast agent administration. Furthermore, compared to SPECT/CT and PET CT, MRI scanners are more widely available and whole body DWI is less expensive.
To evaluate the value of WB DWI in detection of metastatic lesions, using bone scintigraphy for comparison.
Fifteen patients (5 males and 10 females), referred to the Radiology department of Kasr Al-Ainy Hospitals from the outpatient clinic of the Clinical Oncology department, their ages ranged between 34 to70 years, with known primary malignant tumor (confirmed histologically) underwent :- Whole body MRI including Diffusion weighted Whole body Imaging with Back ground body signal Suppression (DWIBS), Skeletal scintigraphy. Any other modality to detect extra-osseous metastases as computed tomography and ultrasound.
WB DWI Qualitative analysis was performed directly from the reformatted Malignant lesions images generally in the coronal exhibit considerably plane. Also, greater the source signal images intensities of DWI and were variability revised when on their required. profile than The benign lesions ones. were only categorized according to the subjectively WB T1-weighted, rated T2-weighted signal pattern, and signal STIR images intensity were and also morphology evaluated to without combine taking information, into account to accurately the apparent detect diffusion pathology coefficients, and rule out which artifacts were from not quantified. the diffusion-weighted sequence series.
The skeletal scintigrams were also analyzed; the increased uptake pattern of the identified lesions was rated according to the clinical experience. No quantitative measurements were considered.
RESULTS Breast carcinoma (53.3%) Prostatic carcinoma(13.3%) Bladder carcinoma(13.3%) Bronchogenic carcinoma(6.7%) Thyroid lymphoma(6.7%) Endometrial carcinoma(6.7%)
RESULTS Also, it showed the bony lesions detected by bone scan in the following sites: vertebra, sternum, femur, acetabulum, humerus, scapula, tibia, shoulder, pelvic bone, greater trochanter, clavicle, coracoid process & sacrum.
On the other hand, one rib lesion, lesions in skull & lateral condyle of femur were missed.
RESULTS The sensitivity of WB DWI in detecting metastatic bony lesions was 100% with positive predictive value = 94.7%. The sensitivity of WB DWI in detecting extraosseous lesions was 100% with positive predictive value = 100%.
Case 1 History and clinical data Female patient 33 years old who gave history of left modified radical mastectomy 3 years ago for breast carcinoma. Pathology: Invasive ductal carcinoma. Abdominal ultrasound: Multiple hepatic focal lesions.
CASES Case 1 Bone Scan Multiple metastatic osseous lesions involving sternum, head of left femur, bilateral acetabulum, DV8, LV2, 3, 4 & left 8th rib.
CASES Case 1 WB MRI A B C D E Bone metastases: Metastatic osseous lesion of sternum, bilateral acetabulum, head of left femur, DV8, LV2, 3, 4 & left 8th rib. Soft tissue metastases: Multiple liver metastases.
CASES Case 1 A WB MRI B The source axial images with the ADC=1.1 (malignant lesions).
CASES Case 2 History and clinical data 64 years old female patient with history of total thyroidectomy 1 year ago for thyroid malignancy. Pathology: Thyroid lymphoma. CT chest, abdomen & pelvis: Multiple metastatic lesions in the liver, both kidneys and right axillary LN.
Bone Scan Case 2 Multiple infiltrative osseous lesions at sacrum, DV2, 7 & 8 and posterior segment of left 7th rib.
CASES Case 2 WB MRI A B C D The source axial image (ADC=1.0) E Multiple metastatic lesions in sacrum, DV 2, 7 & 8, left 7th rib, right axillary lymph node, liver & bilaterally enlarged kidneys with multiple infiltrations.
CASES Case 3 History and clinical data 70 years old male patient with history of prostatic carcinoma. This patient was referred to us for follow up. CT chest, abdomen & pelvis: Right apical lung and bilateral suprarenal glands metastases.
Bone Scan Case 3 Multiple osseous lesions at right scapula, sternum, DV 10, right 9th & 10th ribs & its costovertebral junction and left greater trochanter.
CASES Case 3 WB MRI The primary malignant lesion is seen (prostatic carcinoma), in addition to multiple metastatic lesions in the right scapula, left humerus, sternum, DV 10 and its costovertebral junction & left 9th rib, &, left greater trochanter, AS WELL AS bilateral suprarenal glands metastases & right apical lung metastases & right 12 th rib.
A CASES WB MRI B C Case 3 D
CASES Case 3 Bone Scan
DISCUSSION In our study whole body diffusion MRI was capable to detect all extraosseous lesions (23 lesions) and most of bony lesions (107 lesions). The missed lesions were 4 lesions (two lesions in the skull, one in the rib & one in the lateral condyle of the femur).
DISCUSSION The limitation in detecting rib lesions is due to artifacts that are related to pulsation and breathing in the thorax, which make examination of the ribs, sternum and scapula more difficult. The reason for missed lesions in the skull is unclear, but may be induced by the interference of high signal in brain. Red marrow in patients (less than 40 years) causes high SI in DWI this may explain the missed lateral condyle metastatic lesion in our 38 years old female pateint by WB DWI.
LIMITATIONS The sample size was not large enough for powerful conclusion. We were unable to perform a biopsy of all skeletal metastases determined in routine examinations. The lack of a true gold standard. The standard of reference we chose was, however, the most effective method to determine lesions.
Recommendations The question of whether besides signal enhancement, quantitative assessment using the ADC values as well would further improve the results, possibly with threshold values between malignant and benign metastatic lesions, should be addressed in future studies. Larger studies using this WB DWI sequence should be performed. Comparing with other whole-body techniques such as PET/CT is recommended.
TAKE HOME MESSAGE WB-MRI WB-MRI that included DWI holds great promise, and has shown utility in the identification of both bony and visceral metastases. However, more optimization is required for WB-DWI to become a routine screening tool, and large-scale studies are needed to fully gauge its impact in oncology.