الفهرس 
Anatomy of The LiverOnly 14 pages are availabe for public view
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Abstract
Hepatocellular carcinoma (HCC) is one of the most common types of malignancy in humans and is also one of the most difficult types of cancer to treat. Surgical resection can change the natural course of HCC at early stages
Unfortunately, because of tumor multifocality, portal venous thrombosis, and underlying advanced liver cirrhosis, surgical resection can be performed in only 20% of patients. Therefore, non surgical treatment is the only available option for the majority of patients with HCC
Several minimally invasive techniques have been used for the local ablation of liver lesions including laser, microwave, radiofrequency, cryotherapy and ethanol ablation. The main limitation of these techniques is the difficulty in ablating HCC more than 5cm in diameter. HIFU is an extracorporeal technology for the thermal ablation of tumors. HIFU can induce complete coagulation in large HCC lesions, ranging in size from 5-12 cm in diameter.
HIFU introduces a new concept into the field of interventional radiology. It is a shift from the minimal to completely non invasive era of image guided interventions. Such a complete non invasive approach is only applicable with radiotherapy, yet, a great difference between HIFU and radiotherapy exists.
In radiotherapy, the therapeutic radiation beam is directed towards the target lesion, yet, all the tissues in the path of the beam (before and after the target point) are flooded with radiation thus exposing healthy tissues to the hazardous radiation carrying the risk of inducing harm to already non diseased tissues. In HIFU, the harmless ultrasonic beam is focused with high accuracy into the focal point inducing lethal thermal damage only at the desired focus while the rest of normal tissues along the path of the beam are not exposed to such thermal changes but only exposed to low intensities of ultrasound that are essentially harmless.
HIFU is a trackless treatment, this means that resistant coagulopathies that may be encountered with advanced cirrhotic patients won’t be any more an absolute contraindication for intervention as there is no needle insertion so there is no chance for injury of the portal vein or biliary radicals as would be the case with needle introduction and there are no reports of iatrogenic bowel injury during the treatment sessions.
There is no fear of seedling of tumoural cells along the track or on the skin simply because there is no track .
There is no chance for injury of the portal vein or biliary radicals as would be the case with needle introduction and there are no reports of iatrogenic bowel injury during the treatment sessions.
HIFU provides a less painful treatment option for patients, no appreciable load on the hepatic reserve as compared to chemoembolization and no chance for skin wound infection.
In addition, ascites that is considered a relative contraindication for some other techniques e.g.: R.F won’t be an obstacle for HIFU , contrarily, ascites would provide good acoustic window for the focused ultrasonic beam in its way to the target lesion.
It is clear that until now HIFU treatment sessions take long time which may be problematic in patients with poor general condition as those with advanced cirrhosis. Specialized anesthesia teams and considering using epidural anesthesia instead of general anesthesia whenever possible would help to decrease the anesthesia risk in such patients.
Most of the current research is focused upon improving treatment guidance and monitoring. Guidance and monitoring of acoustic therapy is most important to ensure that the desired region is treated and to minimize damage to adjacent structures. Monitoring using real-time imaging, such as with sonography, ensures that the targeting of the HIFU beam is maintained on the correct area throughout the procedure. Currently, MRI and sonography are used for guidance and monitoring of HIFU therapy. Both methods have their advantages and disadvantages. MRI has the advantage of providing temperature data within seconds after HIFU exposure. However, MRI guidance is expensive and of lower spatial resolution in some cases, although it is superior to sonography in obese patients.
Sonographic guidance provides the benefit of imaging using the same form of energy that is being used for therapy. The significance of this is that the acoustic window can be verified with sonography. Therefore, if the target cannot be well visualized with sonography, then it is unlikely that HIFU therapy will be effective in the target region, and it may potentially cause thermal injury to unintended tissue.
Three-dimensional sonography is likely to better delineate a volume of tissue to be treated than just a single plane. Therefore, the application of 3D sonography techniques is an exciting area of future opportunity, especially for HIFU treatment planning and monitoring.
In conclusion, HIFU ablation is safe, effective and feasible in the treatment of patients with small and large HCCs. HIFU can improve the quality of life in patients with advanced-stage HCC, downgrade large HCC for subsequent hepatic resection, and establish the bridge between unresectable HCC and liver transplantation.