الفهرس 
ANATOMYOnly 14 pages are availabe for public view
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Abstract
Lung cancer is the leading cause of cancer related death in both men and woman. The overall mortality rate for lung cancer is high and early diagnosis provides the best chance for survival.
Lung cancer is divided into 2 categories: SCLC and NSCLC which accounts for approximately 80% of all lung cancers and is classified into different types, the most common types are Adenocarcinoma, Squamous cell carcinoma and Large cell carcinoma.
Diagnostic tests guide lung cancer management decisions and diagnostic imaging is increasingly being used in an effort to improve the clinical management of patients with lung cancer.
Pre-operative staging is essential and its goal is to identify patients who would not benefit from surgical resection thus avoiding the morbidity and mortality associated with major thoracic surgery.
Definitive diagnosis and staging have traditionally depended on invasive techniques. However even invasive procedures such as bronchoscopy and transbronchial or trans-thoracic biopsy have sensitivities of < 80% in certain settings and may be associated with significant complications.
Conventional imaging such as chest CT plays an important role in the detection of lung cancer but limited in staging of mediastinal lymph node involvement as it is assessed only on the basis of nodal size. False-negative CT scans have been reported related to the presence of metastasis in normal sized lymph nodes. Moreover, false positive CT findings have been related to lymph node enlargement due to benign processes. CT has also limited usefulness in the detection of chest wall and mediastinal invasion.
PET is an exciting imaging modality in patients with suspected lung cancer. It is more sensitive for the detection of early metastasis, because of its ability to demonstrate increased metabolic activity in normal sized lymph nodes.
A difficulty for the interpretation of FDG PET scans is the absence of identifiable anatomical structures in additional to the low contrast and low resolution anatomy visualized in the PET scan which makes it insufficient for precise anatomical localization of foci of abnormal uptake.
Also Increased glucose uptake in a benign node can be caused by either reactive hyperplasia or granulomatous inflammation, which may be indistinguishable from malignancy. Therefore, it is difficult to differentiate between benign lymph nodes and malignant lymph nodes with CT or FDG PET alone.
A lack of anatomic information could be overcomed by combining morphologic CT and metabolic PET data. By using only visual correlation between CT scans and PET scans, the precise location of lesions remained sometimes difficult to determine due to positional and motion induced miss-registrations and so this approach did not increase the accuracy of mediastinal staging over that obtained by PET alone.
Co-registration of PET scans (functional and morphologic information) with CT scans (anatomic information) using a combined PET/CT scanner improves the overall sensitivity and specificity of information provided by PET or CT alone. The unique advantage of PET/CT fusion imaging is the ability to correlate findings at two complementary imaging modalities in a comprehensive examination.
With integrated PET/CT, a diagnostic CT scan and a PET scan can be acquired sequentially with the patient lying on the imaging table and with simple translation between the 2 systems.
Integrated PET/CT enables anatomic correlation of the radionuclide uptake and this made possible a more precise delineation of the location of the primary tumor with improvement in the diagnosis of chest-wall infiltration and mediastinal invasion by the tumor.
Also it plays an important role in nodal staging due to its ability to reveal the exact location of metastatic lymph nodes (extrathoracic versus intrathoracic and mediastinal versus hilar lymph nodes). Accurate anatomic correlation may be of benefit for differentiating N1 from N2 disease.
Integrated PET/CT scanning has gained increasing application as a diagnostic and staging tool in the evaluation of lung cancer. It is not only useful in visualizing the solitary pulmonary nodule (SPN), but can also change patient management by accurate staging and detecting unsuspected nodal and metastatic disease, because of its high negative predictive value, PET/CT excludes malignancy correctly in the vast majority of cases. In these patients, thoracotomy can be avoided and follow up with X-ray or CT scan is advised.
Advantages of PET/CT over other imaging methods includes:
1. PET/CT is a safe noninvasive technique that frequently allows fast and accurate diagnosis of the SPN.
2. Metabolic and anatomic whole body staging of patients can be performed in one examination and much reduced scan times, thus increasing patient comfort.
3. Short acquisition time allows a better compliance of the patient, improving patient comfort and reducing possible errors due to movements.
4. Because of limited patient motion, near ideal fusion of metabolic and anatomic images can be achieved.
5. Differentiating benign from malignant lesions (based on both anatomical and metabolic information).
6. Better assessment of chest wall infiltration by precise delineation of the primary tumor.
7. Integrated PET/CT improves T staging and N staging of lung cancer in comparison with the other imaging methods.
8. Ability to demonstrate small neoplastic foci within normal sized nodes and differentiation of enlarged hyperplastic nodes from enlarged neoplastic nodes.
9. The ability of PET/CT to detect distant metastasis is high as it determines the exact localization and classification of a hot spot on PET, especially when no morphologic alterations are seen on CT images.
10. The use of whole body PET/CT scanning may be a reasonable alternative to multiple scans and thus facilitates the survey of a much larger area than is possible with commonly used radiographic methods to detect distant metastasis.