Advanced imaging modalities of the liver


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New imaging modalities used in liver examination

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Advanced imaging modalities of the liver

  2. 2. Classification of liver diseases • Focal liver lesions • Diffuse liver diseases • Biliary diseases
  3. 3. Focal liver lesions         Hemangioma Focal Nodular Hyperplasia (FNH) Hepatocellular Adenoma (HCA) Focal fatty change (FFC) Cyst (Bile duct cyst) Abscess Metastasis Hepatocellular Carcinoma (HCC) Diffuse liver disease o o o o Steatosis Fibrosis Cirrhosis Irion overload (hemochromatosis)
  4. 4.  The role of diagnostic imaging in the assessment of liver disease continues to gain an importance. The classic techniques used for liver imaging are ultrasonography, CT and MRI.  New imaging modalities were developed to accurately characterized the hepatic lesions which is important in treatment plan and follow up process.
  5. 5. Contrast-enhanced Ultrasound (CEUS)  Microbubble contrast enhanced ultrasound (CEUS) is becoming an established technique with proven accuracy. CEUS has the advantage that it avoids the use of ionizing radiation, may be performed during the same patient visit as the B-mode scan and negates the need for more invasive investigations, such as formal angiography or biopsy. Advantages of CEUS are particularly relevant in cases where repeat follow-up imaging is required, for example, post-radiofrequency ablation, and there is a desire to reduce the patients’ exposure to ionizing radiation. The usual way of administration is an intravenous bolus injection.
  6. 6. Focal fatty sparing. (a) An area of low reflectivity (arrow) close to the lower aspect of the right lobe of the liver, close to the gall-bladder fossa; a common site for an area of focal fatty sparing. (b) Following the administration of microbubble contrast, imaging in the portal-venous phase (at 100 s), there is uniform enhancement of the area under investigation (arrow) indicating that this is ‘normal’ liver tissue.
  7. 7. Haemangioma. (a) A large mixed reflective lesion in the right lobe of the liver. (b) Following the administration of microbubble contrast, imaging in the arterial phase (at 20 s), there is peripheral nodular enhancement (arrows) with absence of enhancement in the centre of the lesion. (c) Imaging in the portal-venous phase (at 40 s), demonstrates gradual ‘in-filling’ of the lesion.
  8. 8. Liver abscess. (a) A large ‘solid’ predominantly low reflective lesion (arrows) occupies most of the right liver lobe, displacing the portal vein. (b) Imaging in the portalvenous phase (at 40 s), demonstrates multiple septum of a large abscess
  9. 9. Figure 6. (a) Focal nodular hyperplasia. An iso-reflective lesion (long arrow) in the right lobe of the liver with the suggestion of a ‘central scar’ (short arrow). (b) Following the administration of microbubble contrast, imaging in the arterial phase (at 15 s), demonstrates radial branches from the ‘central scar’. (c) Imaging in the portalvenous phase (at 45 s), clearly demonstrates the ‘central scar’ (arrow) with the lesion showing avid enhancement.
  10. 10. Hepatocellular carcinoma. (a) Two low reflective lesions (arrows) in the left lobe of the liver in a patient with hepatitis C. (b) Imaging in the arterial phase (16 s), both the lesions demonstrate marked enhancement (arrows) relative to the surrounding liver. (c) Imaging in the portal-venous phase (92 s), the central aspects of the lesions are demonstrating enhancement ‘washout’.
  11. 11. Multi-modality imaging (MMI) (Hybrid Imaging Modalities)  - A new standard of clinical care  - Diagnosis and staging  - Treatment planning  - Response assessment - Structural / morphological imaging  • CT  • MR -Functional / molecular imaging  • PET  • SPECT
  12. 12. PET/CT and SPECT/CT  Comparing the functional images of Nuclear Medicine with the more anatomical modalities like CT has been done in the past with side-by-side comparison techniques or by the use of software based fusion, overlaying the two sets of data information. Why Hybrid?  Hybrid PET/CT, and SPECT/CT can combine the functional imaging capabilities of PET and SPECT with the precise anatomical overlay of CT images, all performed in the one imaging session. The CT provides accurate anatomical localization of the functional information obtained from positron emission tomography (PET) and single photon emission computed tomography (SPECT) scan.
  13. 13. Justification of Dual Modality PET/CT • PET and CT images taken at different time on separate scanners can only be easily co-registered through rotation and translation with rigid structures, such as the brain or bones. • It is very difficult, if at all possible, to perfectly co-register soft, deformable or moving tissues, such as in the thorax and abdomen. • Acquisition of anatomic and functional images without having to move the patient from one scanner to another:  avoids patient repositioning and the inevitable anatomic variations resulting from motion of internal structures  provides automatically aligned images  avoids need for complex mathematical co-registration techniques to fuse images  enables exact localization of lesions and improved quantification.
  14. 14.  The obstacle to a wider dissemination of PET/CT and PET/MRI is the difficulty and cost of producing and transporting the radiopharmaceuticals used for PET imaging, which are usually extremely shortlived (for instance, the half life of radioactive fluorine18 used to trace glucose metabolism (using fluorodeoxyglucose, FDG) is two hours only. Its production requires a very expensive cyclotron as well as a production line for the radiopharmaceuticals.
  15. 15. SPECT/CT 16 slice CT machine with double detector Gamma Camera
  16. 16. Hybrid PET/CT scanner
  17. 17. Nuclear medicine fusion study. (A) Contrast-enhanced CT scan shows barely visible low attenuation lesions in the right lobe of the liver (arrows). (B) Hybrid fusion image from combined SPECT / CT scan shows two large lesions in the liver (arrows) that are not readily apparent on the contrastenhanced CT.
  18. 18. Differential uptake of FDG. Axial fused FDG PET–CT images of patient with colon cancer shows metastases to the liver. The metastases demonstrate differential FDG uptake in proportion to their metabolic activity. The necrotic centers of the metastases (straight solid arrow) show negligible uptake compared with their hypermetabolic peripheries (open arrows). Arrowheads represent physiologic FDG activity in the left kidney, wavy arrow is simple hepatic cyst without metabolic activity.
  19. 19. metastatic colorectal adenocarcinoma after multiple liver radiofrequency ablation procedures with recurrent/residual tumor delineated by PET/CT. A, Scan from unenhanced CT portion of examination shows multiple large and small, low- and mixed-density lesions throughout liver likely representing combination of ablation defects and recurrent/residual tumor. B, Fused PET/CT image from same examination shows three foci of increased 18FFDG uptake, clearly distinguishing tumor from ablation change and providing precise localization for radiofrequency ablation planning.
  20. 20. PET/MRI  Integrate the PET detectors into the MRI scanner which would allow simultaneous data acquisition, resulting in combined functional and morphological images with an excellent soft tissue contrast, very good spatial resolution of the anatomy and very accurate temporal and spatial image fusion. Additionally, since MRI provides also functional information, PET/MRI could even provide multifunctional information of physiological processes in vivo.
  21. 21. A separate MRI and PET scanners The patient turns 180° on a floor-based turntable to enter separate MRI and PET scanners
  22. 22. Hybrid PET/MRI scanner The PET detector and MR coils are built into the gantry of the new Siemens PET/MRI, allowing simultaneous acquisition of PET and MR data.
  23. 23. Hybrid PET/MRI
  24. 24. PET/MRI of patient has a hepatic tumor with left lung metastasis
  25. 25. Angiogenesis imaging of liver tumors  Hepatic CT perfusion Measures of permeability, blood flow, blood volume, and MTT can now be routinely acquired for tumors as part of clinical practice as well as for chronic liver disease. The development of modern, 128-slice CT hardware with accompanying software advances has allowed both whole organ and tumor perfusion analysis.
  26. 26. Hepatic CT Perfusion Normal liver perfusion image. A: Selection of ROI at aorta, portal vein and liver; B: Timedensity curve (TDC) for ROI (up left: aorta; up right: portal vein; down left: liver); C: Pseudo-color image of HBF.
  27. 27. CT perfusion functional maps of blood flow (BF), blood volume (BV), and mean transit Time (MTT) in a patient with hepatocellular carcinoma in the right lobe of the liver. Preferential arterial supply to the tumor results in higher BF, BV, and a lower MTT value.
  28. 28. Elastography: Imaging of Tommorow  Elastography is a method of imaging that produces a type of image, called an elastogram. It is a promising diagnostic, noninvasive technique used to evaluate the stiffness of soft tissues. It is done in correlation with a conventional sonogram or MRI.
  29. 29. Transient Elastography (Fibroscan) Transient elastography, commercially known as FibroScan®, uses a modified ultrasound probe to measure the velocity of a shear wave created by a vibratory source. It uses mechanical waves that are sent through the liver. The speed of these waves through tissue provides data about the condition and stiffness of the liver and thus can indicate a liver fibrosis. The velocity of the wave correlates with tissue stiffness: the wave travels faster through denser, fibrotic tissue
  30. 30. Fibroscan score A staging system for evaluating fibrosis in nonalcoholic liver disease categorized into five stages: no fibrosis (F0), perisinusoidal fibrosis (F1), perisinusoidal fibrosis plus periportal fibrosis (F2), bridging fibrosis (F3), and cirrhosis (F4). By TE  At a cut off point of ≥7 KPs, significant hepatic fibrosis could be predicted. At a cut off point of ≥ 16.5 kPa, hepatic cirrhosis could be predicted.
  31. 31. MR Elastography (MRE)  Magnetic resonance elastography appears more promising than ultrasound elastography. It uses a vibration device to induce a shear wave in the liver. The wave is detected by a modified magnetic resonance imaging machine, and a colorcoded image is generated that depicts the wave velocity, and hence stiffness, throughout the organ.
  32. 32. MRE Score for liver stiffness Malignant liver tumors had significantly greater mean shear stiffness than benign tumors with cut off value of 5 Kpa (kilopascals) . in the absence of focal mass, fibrotic and cirrhotic liver has a high shear stiffness more than 5 Kpa
  33. 33. Top row: Conventional MR images of two different patients. Middle row: Elastographic wave image. Bottom row: Wave images are processed to generate quantitative images showing stiffness of tissue (elastograms). Patient on right has markedly elevated liver stiffness, averaging 7 kPa (normal value 2 kPa seen in patient on left), indicating presence of moderate liver fibrosis.
  34. 34. MR elastography of HCV-related fibrosis. MR elastographic wave images (left) and color-coded elastograms (right), obtained at 3 T in three patients with chronic HCV infection, show biopsy-proved stage F1 (a), F2 (b), and F4 (c) .
  35. 35. Patient with hepatic adenoma. A, T2-weighted MR image (A) shows hyperintense 8-cm adenoma (arrow) in right lobe of liver. B, Gadolinium-enhanced MR image shows intense arterial phase enhancement (arrow). C, Axial MR elastographic wave image shows good illumination of tumor (circle). Waves in tumor have slightly longer wavelength than those in surrounding normal liver parenchyma. D, Elastogram with region of interest corresponding to tumor shows shear stiffness value of tumor is 3.1 kPa and of surrounding liver is 2.4 kPa.
  36. 36. Patient with liver cirrhosis and biopsy-proven hepatocellular carcinoma. A and B, Dynamic gadolinium-enhanced T1-weighted MR images show enhanced tumor (arrow) in right lobe of liver during arterial phase (A) with washout during portal venous phase (B). C, MR elastographic wave image shows shear waves with long wavelength (arrow) within tumor. Waves in surrounding liver also have longer wavelength than normal. D, Elastogram shows mean stiffness of tumor (arrow) is about 8 kPa.
  37. 37. Patient with metastatic colon cancer A, T2-weighted image shows single hyperintense lesion (arrow) in periphery of right lobe of liver. B, Wave image shows prolongation of shear wave through tumor (arrow) compared with surrounding normal liver parenchyma. C, Elastogram shows tumor (arrow) as hot spot with stiffness value of 6.2 kPa, suggestive of malignant tumor. Finding was confirmed at surgery to be metastasis from colon cancer.
  38. 38. Conclusion:  Contrast-enhanced ultrasound CEUS continues to grow in importance as a tool that may be used for the detection and characterization of focal liver lesions. As a general rule, benign lesions are characterized by the persistence of contrast enhancement during the late phase and a malignant lesion is characterized by loss of contrast enhancement in the late phase.
  39. 39. Conclusion: Indication to perform a HYBRID MMI (PET-SPECT/CT and PET/MRI) • High suspicion for active disease, or known structural pathology, as hybrid MMI may localize multiple sites and define extent of disease • Planning treatment (medical, surgical, or radiation therapy) • Monitoring response to treatment. • Absence of overt structural pathology in the presence of high clinical suspicion.
  40. 40. Conclusion: Fibroscan is a reliable screening tool for liver fibrosis or cirrhosis in high risk groups and it may be used in assessment of treatment response in liver fibrosis. fibroscan may replace invasive liver biopsies . MR elastography is a promising noninvasive technique for assessing hepatic fibrosis and cirrhosis as well as solid liver tumors.