Bone PET/MRI : Diagnostic yield in bone metastases and malignant primitive bone tumors Lars Stegger, Benjamin Noto Department of Nuclear Medicine University Hospital Münster, Germany
Content From PET to PET/MRI General considerations Primary bone tumours Bone metastases, especially PCa
Content From PET to PET/MRI General considerations Primary bone tumours Bone metastases, especially PCa
PET - Milestones 1886 Detection of radioactivity Henri Becquerel (1852-1908) Noble price for physics 1903 1913 Invention of tracer method George de Hevesy (1885-1966) Noble price for chemistry 1943 1933 Detection of positron Carl D. Anderson (1905-1991) Noble price for physics 1936 1952 First clinical positron scanner Gordon L. Brownell, MGH 1970-71 First PET Gordon L. Brownell David Chesler Bilder: Wikipedia, G.L. Brownell
Hybrid imaging anatomy function chemistry X-ray computer tomographie (CT) ultrasound magnetic resonance imaging (MRI) planar scintigraphy single photon emission computer tomography (SPECT) positron emission tomography (PET) combination of devices
Hybrid imaging devices 2000 2001 2008 2010 SPECT/CT PET-CT small animal PET-MRI brain PET-MRI whole-body PET-MRI
Content From PET to PET/MRI General considerations Primary bone tumours Bone metastases, especially PCa
? PET-MRI PET-CT
PET-CT PET-CT has quickly replaced PET + CT because of favorable patient logistics because of integrated image interpretation not too difficult because of optimal spatial coregistration Sources: Pelc N, et al. J Med Imag. 4, 2017; Siemens Healthcare
PET-MRI Magnetic resonance imaging radiowaves interact with atomic nuclei such as 1 H in a magnetic field many different contrasts possible advantages PET-MRI vs. PET-CT more information less ionizing radiation temporal coregistration soft-tissue/liver/bone marrow contrast vessel imaging perfusion and diffusion metabolites (MRS), PET + diagnost. CT* 21,3 msv (7+14,3) PET + low dose-ct* 9,6 msv (7+2,6) intervention, motion correction, *370 MBq FDG, Brix G, et al. J Nucl Med 2005
Whole-body PET/MRI Source: Siemens Healthcare
PET/MRI typical PET study typical MRI study PET and MRI have different scales PET most often whole-body imaging (cancer, inflammation) less often organ imaging (brain, heart) MRI generally body-part imaging ( narrow but deep ) whole-body MRI with many compromises ( wide but shallow ) This means for PET/MRI protocols: for whole-body imaging significant compromises for brain and cardiac no compromises Source: Wikipedia
after PET with PET PET/MRI: standard whole-body sequences T1w native (3D GRE) T2w (fast SE) T1w contrast fat-sat T1w contrast fat-sat
PET/MRI: additional bone sequences e.g. after prostate carcinoma pelvis T1w TSE (high-res) T2w TIRM (high-res) lumbar spine T1w TSE (high-res) T2w TIRM (high-res)
PET/MRI: diffusion imaging Diffusion ADC map Ewing sarcoma, depiction of soft-tissue component Courtesy C. Franzius, Bremen
Bone malignancies primary bone cancer osteosarcoma Ewing sarcoma rare often in children and adolescents bone metastases prostate cancer breast cancer bronchial carcinoma common
Content From PET to PET/MRI General considerations Primary bone tumours Bone metastases, especially PCa
Primary bone tumors established roles of imaging Imaging modality X-ray MRI chest CT bone scintigraphy FDG-PET Aim diagnosis soft-tissue component, skip lesions lung metastases bone metastases whole-body staging For PET/MRI no studies available!! In order to estimate potential role look at role of PET look at role of whole-body MRI
Am J Roentgen 2015 64 patients (20 osteosarcoma, 44 Ewing sarcoma), 412 lesions Results Osteosarcoma (only follow-up) accuracy for bone lesions PET/CT 95%; CT 67%; MRI 86% Ewing sarcoma accuracy PET/CT 82%; CT 80%; MRI 83%; bone scan 53% PET/CT follow-up 85% vs. initial 69% diagnostic benefit: 9/20 osteosarcoma, 21/44 Ewing sarcoma PET/CT contributes at staging and during follow-up
Nuklearmedizin 2017;56:233-8 80 patients in follow-up Value of imaging during follow-up? Will imaging or symptoms lead to detection of recurrence?
Nuklearmedizin 2017;56:233-8 Imaging detects recurrence often
Nuklearmedizin 2017;56:233-8 PET/CT was the most effective
Pediatric Blood and Cancer 2018 data from register of CESS trial group multicenter with >70 centres in Germany, Switzerland, Austria 284 relapses, 160 with full information Scientific question: Is there a survival difference for imaging based vs. symptom based diagnosis of recurrent tumor?
Pediatric Blood and Cancer 2018 lung bone
39 children and young adults (2-19 years) initial staging gold standard: biopsy 21 patients had 51 bone metastases whole-body MRI is of value
Courtesy C. Franzius, Bremen Example PET/MRI in Ewing sarcoma 8 year old boy with first manifestation of Ewing sarcoma in the thorax Aim: Local staging and staging for metastases Comprehensive PET/MRI inclusive diffusion T2w Gd diffusion FDG-PET Fusion T1w Gd T2w TIRM MRI provides soft-tissue extension of tumour
Example PET/MRI in Ewing sarcoma 13 year old boy with several recurrences with Ewing sarcoma of pelvis at age 3 Aim: Staging for new manifestations FDG-PET Fusion T2w TIRM MRI identifies new bone metastasis in L2 Courtesy C. Franzius, Bremen
Content From PET to PET/MRI General considerations Primary bone tumours Bone metastases, especially PCa
67 patients CT: diagnostic, with contrast MRI: T1w +/- contrast, T2w,T2w fat-sat, DWI gold standard: histology or follow-up PET/MRI better for malignant than benign lesions
Diagnostic confidence 1 certainly benign 2 probably benign 3 indeterminate 4 probably malignant 5 certainly malignant PET/MRI better for malignant than benign lesions
prospective study in 117 patients (46 for PET/MRI) bone scan +/- SPECT/CT NaF-PET/CT NaF-PET/MRI in 46 patients Results bone metastases in 16 patients sensitivity highest for PET/MRI, specificity for PET/CT PET/MRI not significantly better than PET/CT
Letter to the editor response
Conclusion PET/MRI is slower to grab market share than PET/CT PET/MRI for imaging of primary and secondary bone tumours has potential This requires good protocols for whole-body coverage combined with high-resolution and diffusion MRI of relevant body parts. The scientific data so far is limited. It remains to be seen whether PET/MRI will be routinely chosen over PET/CT + MRI for bone tumours in the future. PET/MRI requires a multidisciplinary effort to unlock ist full potential. PET/MRI is a field that offers very interesting research opportunities.