PET-MRI in malignant bone tumours Lars Stegger Department of Nuclear Medicine University Hospital Münster, Germany
Content From PET to PET/MRI General considerations Bone metastases Primary bone tumours
Content From PET to PET/MRI General considerations Bone metastases Primary bone tumours
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 Bone metastases Primary bone tumours
? 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
Bone malignancies bone metastases prostate cancer breast cancer bronchial carcinoma primary bone cancer osteosarcoma Ewing sarcoma common rare often in children and adolescents
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 Courtesy C. Franzius, Bremen
Content From PET to PET/MRI General considerations Bone metastases Primary bone tumours
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
MRI may reveal metastases with little tracer afinity
J Nucl Med. 2014;55:191-7 98 bone lesions in 30/119 patients Low-dose-CT vs. MRI (T1w VIBE Dixon, T1w TSE) Anatomic location and delineation of PET-positive lesions with CT vs. with MRI higher means better MRI offers slightly better delineation than CT
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
retrospective study in 26 patients PET/CT versus PET/MRI MRI: T1w +/- contrast, T2w fat sat, DWI Results 28 bone lesions PET component: concordant in 100% LD-CT: 2 not found, MRI: all found MRI offers better delineation than low-dose CT
Non-expression of PSMA PSMA-PET/CT in patients with biochemical recurrence A high number of recurrent tumours do not show adequate tracer uptake Afshar-Oromieh A, et al. Eur J Nucl Med Mol Imaging 2017; 44: 1258-68
Non-expression of PSMA Example Primary Staging of Pat with bone metastases of PCA. ADC-Map 68 Ga-PSMA-11 PSMA MIP Tumour manifestations without PSMA uptake may be visible in MRI
Value of diffusion imaging Patient with elevated PSA values years after primary treatment. Metastases? MRI with additional diffusion imaging 68 Ga-PSMA-11 at1w native diffusion
Value of diffusion imaging Patient with elevated PSA values years after primary treatment. Metastases? MRI with additional diffusion imaging 68 Ga-PSMA-11 T1w native diffusion
Value of additional high-resolution imaging 74 yo patient with elevated PSA years after initial treatment Metastasis? MRI with additional high-resolution sequences of the pelvis and lumbar spine T1w TSE (high-res) Diffusion
Radionuclide imaging *and* therapy Prostate carcinoma with bone metastases 65 yo patient with castration-resistant, symptomatic bone metastases Evaluation for Radium-223 therapy Evaluation without PSMA-PET: for Radium-223 Indication therapy for Radium-223 therapy given with PSMA-PET: concordance with bone scintigraphy Performance of Radium-223 therapy as planned bone scintigraphy PSMA-PET/CT
Radionuclide imaging *and* therapy Prostate carcinoma with bone metastases 66 jähriger Patient mit bekannten Knochenmetastasen, nach Radiatio LWS jetzt schneller Tumormarkeranstieg unter antiandrogener Therapie Evaluation for Radium-223 therapy Vorstellung without PSMA-PET: zur Evaluation Indikation Radium-223-Therapie for Radium-223 therapy given with PSMA-PET: discrepancy between bone mineral turnover (target Ra- 223) and tumour in bone marrow Decision against Radium-223 therapy, instead experimental 177 Lu-PSMA therapy Advantage for PET/MRI instead of PET/CT? MRI may better show bone-marrow lesions. Still needs to be evaluated. Skelettszintigraphie PSMA-PET-CT Bräuer A, Rahbar K, Konnert J,..., Stegger L. Clin Nucl Med 2016 and Nuklearmedizin 2017
Radionuclide imaging *and* therapy 177 Lu-PSMA-Therapy in lymphnode metastases 80 yo patient, lymph node metastases 1st cycle 2nd cycle PSMA-PET/MRI whole-body 177 Lu-PSMA therapy scans
Content From PET to PET/MRI General considerations Metastases Primary bone tumours
Bone malignancies bone metastases prostate cancer breast cancer bronchial carcinoma primary bone cancer osteosarcoma Ewing sarcoma common rare often in children and adolescents
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 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-Nuclear Medicine, in-press 80 patients in follow-up Value of imaging during follow-up? Will imaging or symptoms lead to detection of recurrence?
Nuklearmedizin-Nuclear Medicine, in-press Imaging detects recurrence often
Nuklearmedizin-Nuclear Medicine, in-press PET/CT was the most effective
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
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.