E³ 118 - Liver, bile ducts and pancreas: improving your technique with advanced tools
E³ 118 - Liver, bile ducts and pancreas: improving your technique with advanced toolsWednesday, March 1, 08:30 - 10:00 Room: M 4 Session Type: E³ - ECR Academies: Tips and Tricks in Liver, Bile Ducts and Pancreas Imaging Topics: Nuclear Medicine, Imaging Methods, Abdominal Viscera Moderator: Y. Menu (Paris/FR) Add session to my schedule In your schedule (remove)
Optimal imaging technique is absolutely critical in abdominal studies, as many parameters may interfere in the production of final images. Despite technical advances, or may be as a consequence, settings and fine-tuning of machines is the only way to reach clinical relevance of images. The radiologist has to be familiar with the most important parameters that may influence image quality and relevance. In this session, the purpose is to learn the best and the most simple way to obtain optimized results with recent and advanced imaging technique, with a special interest on how to integrate it while driving these machines for clinical practice.
1. To learn about physiology of liver specific contrast media physiology, and to be able to optimise liver MRI protocols.
2. To understand why they are useful for the detection and characterisation of liver masses.
3. To learn and understand the limitations.
The so-called liver-specific (or hepatobiliary) contrast agents (gadobenate dimeglumine, Gd-BOPTA, and gadoxetic acid, Gd-EOB-DTPA), are characterised by a dual behaviour by exhibiting elimination through both renal and hepatic excretion pathways and thereby possessing both early perfusion information (renal elimination pathway) and, later, hepatocyte-selective information (hepatic excretion pathway) mediated through protein transporters, located in the canalicular or sinusoidal pole of the hepatocytes. As a basic rule of MR technique all non-blood pool gadolinium chelate-based contrast agents are suitable for dynamic liver MRI, but the use of liver-specific contrast agents is mandatory to obtain the hepatobiliary phase in addition to the dynamic phase. The workup of solid focal liver lesions should include: axial breath-hold heavily T2-weighted half-Fourier single-shot turbo spin-echo sequences; navigator triggered intermediate T2-weighted turbo spin-echo sequences, breath-hold T1-weighted two-dimensional dual gradient-echo in-phase and opposed-phase sequences, and dynamic contrast enhanced fat-suppressed three-dimensional spoiled gradient-echo breath-hold sequence, acquired before and during the late arterial, portal venous and late dynamic phase. Hepatocyte phase can be considered adequate when Gd-EOB is detected in the intrahepatic bile ducts and the vessels are definitely hypointense in comparison to the background parenchyma. Liver specific contrast agents improves the characterisation of benign liver lesions, malignant liver lesions in non-cirrhotic, focal lesions in cirrhotic patients; they are also helpful to to depict the degree of fibrotic changes in liver fibrosis.
1. To become familiar with the different acquisition techniques and to be able to adapt to a specific machine, including field strength.
2. To understand the role of DWI in the detection and characterisation of hepatobiliary and pancreatic diseases.
3. To learn about the potential technical future developments.
Diffusion-weighted MRI (DWI) is now routinely applied for the evaluation of abdominal diseases. The principles of optimising DWI are similar on both 1.5T and 3.0T, which includes maximising image signal to noise and minimising artefacts. In this regard, free-breathing DWI acquisition is most widely used to achieve the best image quality. DWI can be used to improve disease detection in the liver, hepatobiliary tract and the pancreas. It can be applied to support disease characterisation, but potential pitfalls should be appreciated. There is an increasing role for its deployment for the early evaluation of tumour response to treatment. Monoexponential DWI model to derive the apparent diffusion coefficient (ADC) of tissue is still the most widely used approach in the clinical setting. However, there is interest in applying non-monoexponential approaches including IVIM (intravoxel incoherent motion) and DKI (diffusion kurtosis imaging). These approaches should be utilised with full knowledge of their measurement repeatability so that it allows for meaningful data interpretation.
1. To understand why alternative tracers to FDG may be useful in exploring liver and pancreatic diseases.
2. To learn about the role of PET in the follow-up of tumours and quantification of tumour response.
3. To become familiar with the specific advantages of MR/PET over PET/CT in abdominal diseases.
In both PET/CT and MR/PET, radioactive tracers are used to detect primary tumours and metastases. During the lecture, we will discuss those tracers which are used for PET imaging of the abdomen and pelvis. By far the most commonly applied tracer is 18F-FDG which is used to study glucose metabolism in tumours and metastases. Increasingly, other more specific tracers, primarily marked with 68 Ga, are used for abdominal tumours such as DOTA-TATE and DOTA TOC. These tracers exhibit high affinity to somatostatin receptors and can be used to detect endocrine tumours (NET) with low or moderate proliferation rate (G1 and G2). To quantify tumour response to therapy, standard uptake values (SUV) can be calculated. Newer tracers like 68 Ga-PSMA-ligand are primarily used to diagnose prostate cancer (PCa) and its metastases to lymph nodes and bones. Furthermore, this tracer may be also useful to diagnose other tumours of the urinary tract. Bound to 90 Yttrium or 177 Lutetium, these carriers, i.e. DOTA-NOC and PSMA-ligand, can be used as so-called theranostics which are employed successfully to treat tumour metastases of certain cancers. All those markers can be used for PET/CT and MR/PET. While PET/CT is in clinical use already, MR/PET systems are still under evaluation. MR has better soft tissue contrast and radiation dose from MR/PET is substantially less than PET/CT. However, MR/PET takes longer than PET/CT and is only feasible in certain patients. Therefore, MR/PET is currently available for patients with selected indications and primarily used for clinical research studies.