الفهرس 
Pathophysiology of Thoracic LymphomaOnly 14 pages are availabe for public view
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Abstract
Lymphomas are the malignant tumors of lymph nodes and considered as one of the most common primary hematopoietic malignancy. Non-Hodgkin lymphomas are morethan five times as common as Hodgkin disease. Both types of lymphoma are potentially curable, and treatment options varygreatly with the initial stage of the disease.
The primary therapeutic modalities for lymphoma are chemotherapyand radiotherapy. Treatmentprotocols for both Non-Hodgkin lymphomas and Hodgkin diseaseare predicated on the extent of tumor involvement. Staging of lymphoma is usually accomplished by using the Ann Arbor system.This scheme encompasses the number of sites of disease involved,the type of involvement (nodal or extranodal), and the distributionof disease. Because treatment protocols are designed aroundthis anatomic classification, accurate imaging is necessaryto determine the optimal therapeutic strategy.
Nuclear medicine techniques provide unique physiologic informationabout malignancies, including lymphomas. Positron emission tomography (PET) provides metabolic informationthat has been documented to be useful in patient care. The wide array of positron-emitting radiopharmaceuticals has been used to characterizemultiple physiologic and pathologic states. The major utilizationof PET clinically is in oncology and consists of imaging thedistribution of fluorine 18 fluorodeoxyglucose (FDG), ananalogue of glucose that accumulates in most tumors in a greateramount than it does in normal tissue. FDG PET is being usedin diagnosis, staging, restaging and follow-upof Hodgkin and Non-Hodgkin lymphomas.
With the increasing availability of FDG PET/CT for routine clinicalapplications, this modality was found to be highly sensitivein the detection of various malignancies, including lymphoma. FDG PET/CT has been found to be superior to CT and PET in initialstaging of both nodal and extra nodal Hodgkin disease and ofnon-Hodgkin lymphoma. It is also superior to CT and PET in monitoring response to treatmentand assessment of residual masses.
Differences between FDG PET/CT and Gallium-67 (Ga 67) scintigraphy are moreprominent in that FDG PET/CT helps correctlycharacterization of suspicious lesions in significantlymore sites than Ga 67 scintigraphy in both nodal and extra nodallocations and allows a significantly more accurate definitionof active disease compared with Ga 67 scintigraphy.
PET/CT is also preferred than MRI for its better detection of smaller parenchymal lesions and microscopic foci of residual disease which cannot be totally excluded by MRI.
Metabolic and anatomical imaging with FDG PET/CT is rapidly becoming an integralcomponent in the management of lymphomas disease. FDG PET/CT imaging playroles in allowing a more accurate overall evaluationof malignant processes. This is particularly valid in specificsituations, such as differential diagnosis of indeterminatelesions at CT, differentiation of post -treatment changes from recurrent tumor, and monitoring the response to therapy.
PET/CTdevices offer several potential advantages over PET scanneralone: better quality PET images, automatic registrationof CT (anatomic) and PET (metabolic) information, and shorterimaging times. The practical advantages and limitations of PET/CTscanners and the issue of cost versus benefit are currentlytopics of investigation.
In conclusion, FDG PET/CT is superior to other imaging modalities such as 67 Gallium scintigraphy, CT, MRI and US in characterization of suspicious lesions in lymphoma. It also plays an important role in diagnosis, staging and follow up response to treatment and recurrence of lymphoma by differentiation between residual viable tumor tissue versus fibrosis and necrosis, in addition to the technical advantages of FDG PET/CT, such as better contrast andresolution, lower dosimetry, shorter scanning time, as well as betterpatient compliance andcost-effectiveness, should also be considered.
The role of PET/CT in tumor imaging will continue to expand asmore indications are approved and newer more tumor-specific radiopharmaceutical agents are developed.