What is PET-MRI?
MRI is a high-sensitivity imaging modality for cancer detection. PET can diagnose specific radioactive isotopes with a tumour, which increases accuracy in cancer diagnosis. PET-MRI is a state-of-the-art product that has high resolution PET detectors in a 3 Tesla high magnetic field MRI, which creates the most accurate imaging device for cancer diagnosis.
Simultaneous use of 3 Tesla MRI and PET detectors
Whole-body MRI with simultaneous PET data acquisition can be performed in a single PET-MRI scan.
The combination of the high tissue contrast of MRI together with functional MRI studies and molecular signals derived from PET detection allows multi-parametric cancer assessment.
Simultaneous data extraction from PET detectors and MRI requires high technology. High-resolution whole-body MRI coupled with PET detection provides a spatial 3D dataset that can image tumours as small as 5 mm.
With PET-MRI, cancer diagnosis, TNM staging and assessment of response to treatment can be performed in a single session. Although PET-MRI is mainly used for oncology imaging, the method is also used in imaging in the fields of cardiology and neurology.
Why choose PET-MRI?
- Better efficiency with one system, one examination
- No need to move patients between consulting rooms or multiple patient visits
- Less radiation, more information
- Comprehensive coverage of tumours and organs
- Greater certainty in tumour diagnosis
- Simultaneous imaging of morphology, function and metabolism
- Earliest assessment of response to tumour therapy
- Reduced investigation time by up to 50% with increased productivity
- Improved patient comfort with shorter and fewer investigations
PET-MRI can cover all cancers and organ systems with a single exam with low radiation exposure for patients.
PET-MRI - other differences in oncological diagnostics
MRI is the closest diagnostic imaging modality to pathomorphology because of its high resolution and imaging techniques against specific tissues.
When MR spectroscopy, diffusion MR imaging (DWI), perfusion imaging and BOLD (Detection of Tumour Hypoxia) studies are added, functional data are obtained, resulting in higher diagnostic sensitivity.
The key advantage of PET-MRI for the patient is the absence of radiation during MR imaging.
Specificity is increased in tumour imaging with the use of tumour-specific PET agents that take advantage of molecular imaging, providing metabolic, functional, and numerical information in cancer diagnostics in conjunction with multi-parameter MRI techniques.
PET-MRI compared with PET-CT
- Greater diagnostic accuracy in cases where tumours in soft tissue, central nervous system and bone marrow are evaluated.
- It differentiates tissue types, physiological and pathological organ content and further improves numerical analysis.
- Combined use of high-resolution PET detectors and 3 Tesla MRI allows detection of tumours much smaller in size with PET-MRI.
- Currently, whole-body CT is performed in determining the anatomical location of molecular images. However, with whole-body CT in PET-CT, patients are exposed to radiation caused by the CT.
- The patient is exposed to 70-80% less radiation with PET-MRI compared to PET-CT. The PET-MRI scanner does not emit radiation. The dose that the patient receives from the PET agents administered intravenously is very low compared to that from whole body CT. Thus, a more efficient diagnosis is achieved with a lower effective radiation dose.
- The benefits of the combined use of functional MRI and molecular imaging become apparent.
The benefits of PET-MRI in cancer staging
- Once a tumour is diagnosed, local and whole-body staging must be performed to achieve accurate treatment and prognosis.
- MRI is the most sensitive imaging modality for local tumour staging (T). Because the spatial resolution is enhanced with 3 Tesla MRI scan, local staging of rectal carcinoma, gynaecologic tumours, and head and neck tumours, as well as biliary liver neoplasms, can be performed with higher accuracy.
- Although lymph nodes (N) can be observed in terms of size with MRI, PET scanning is required to determine which lymph nodes contain tumour overlays. Lymph nodes that contain tumour cells can be detected with PET agents despite their normal size. The patient also undergoes a PET scan to detect distant metastases (M).
- Due to the fact FDG uptake is limited in tumours that are located in the central nervous system, liver, bone marrow, and in some certain tumour types, such as mucinous neoplasms and renal cell carcinoma, patients are referred for MRI after PET scan for further investigation.
- For accurate TNM staging, the patient should undergo both MRI and PET scans repeatedly and at different times. This is a difficult and expensive process.
- With PET-MRI, local staging is done very precisely; lymph nodes and distant metastases are evaluated completely and simultaneously, the two modalities complement each other in areas where one scan is better than the other and so no further study is required.
What is the benefit from PET-MRI in assessing response to tumour treatment in oncology?
Innovative targeted therapies are also being developed day by day, such as smart molecules that target signalling pathways and cytotoxic drugs in cancer treatment. The administration of targeted therapies is planned according to the genetic mutation of the tumour tissue. However, cancers may undergo new mutations other than the genetic structure they initially show.
With the rapid assessment of response from research, in cases of unsuccessful treatment, changing the therapy has a positive effect on the course of the disease.
With earlier evidence of a treatment response, or lack of such, treatment becomes less expensive.
Response to treatment can be assessed solely in terms of the observed change in the size of the tumour itself.
Using functional MRI, tumour perfusion (response to anti-angiogenic treatment), tumour cell density and metabolism (diffusion MRI, MR spectroscopy), as well as the PET scanner, the metabolic response of the tumour and the viability of tumour cells are assessed early.
PET-MRI provides the earliest and most accurate assessment of response to treatment by simultaneously demonstrating both changes in functional MRI and the involvement of PET agents. This allows accurate and rapid focus on the patients’ treatment plan.
The PET-MRI combination plays an important role in the imaging diagnosis of potentially curable children and adolescents. The effective radiation dose of PET-MRI is only 20% of that of a PET-CT scan.
What is the role of PET-MRI in cardiology?
PET-MRI shows features such as absolute anatomical location and volumetric confirmation in quantity, as well as molecular target detection, alongside other advantages such as radiation dose reduction compared to PET-CT.
PET-MRI plays an important role in imaging atherosclerotic plaques and assessing myocardial viability/hibernation. For example, it can show hemodynamic findings such as atherosclerotic plaque accumulation and ischemia.
Establishing the threshold for local glucose utilization on PET and transmurality from MRI in determining the amount of viable myocardial tissue represents a valid method for predicting improvement in wall motion in this area during the subacute period.
With the combination of PET and MRI, PET-MRI in cardiology provides rapid imaging without exposure to additional radiation.
What is the role of PET-MRI in neurology?
It is common for most patients with neuropsychiatric illness to undergo PET and MRI. The combination of these two examinations in one scanner provides greater comfort for the patient.
Better soft tissue contrast with less radiation administration is possible.
It is possible to perform multiple examinations with one scanner, which provides greater comfort for the patient.