الفهرس 
Normal CT Anatomy Of The LungsOnly 14 pages are availabe for public view
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Abstract
Bronchogenic carcinoma is the leading cause of cancer-related mortality in both men and women throughout the world. 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, small-cell lung cancer and non–small cell lung cancer which accounts for approximately 80% of all bronchogenic carcinomas, and is typically classified into specific cell types. The most common types are adenocarcinoma, squamous cell carcinoma, and large cell carcinoma.
The optimal treatment of lung cancer depends on accurate disease staging, Which is based on tumour size, site, regional nodal involvement, and the presence of metastasis and thus accurate staging is necessary to determine resectability and overall prognosis
Conventional imaging methods, such as chest CT, continue to play important roles in the detection of lung cancer and in tumor staging, but they often fail to distinguish between malignant and nonmalignant tumors in the lung or metastasis to the mediastinum. Definitive diagnosis and staging have traditionally depended on invasive techniques. However, even invasive procedures such as bronchoscopy and transbronchial or transthoracic biopsy have sensitivities of < 80% in certain settings, and may be associated with significant complications.
Recently, positron emission tomography (PET) imaging has been used to evaluate pulmonary lesions. PET study using F-18-fluorodeoxyglucose (FDG), is very accurate in differentiating benign from malignant focal pulmonary lesions as small as 1 cm.
PET/CT imaging has been contributing widely to the patient treatment by its large advantages over anatomical imaging from screening to staging. PET images provide the functional activity inside the body while CT images demonstrate the anatomical information.
Lung cancer appears on PET-CT as nodule or mass with higher activity of FDG uptake (more intense) compared with normal mediastinum.
Advantages of PET/CT over other imaging methods include:
1- Differentiating benign from malignant lesions (based on both anatomical and metabolic information).
2- PET-CT is safe, noninvasive technique that frequently allows accurate diagnosis of SPN especially if lung nodule >1 cm because of its relatively low false negative rate.
3- PET-CT is not only useful in visualizing solitary pulmonary nodule, but can also change patient management by accurate staging and detecting unsuspected nodal and metastatic disease because of its high negative predictive value.
4- Selecting the region of a tumor most likely to yield diagnostic information for biopsy.
5- Better assessment of chest wall infiltration by precise delineation of the primary tumor.
6- FDG PET is a useful tool for the differentiation between tumor and peri-tumoral atelectasis.
7- Better differentiation between benign and malignant pleural effusion thereby preventing repeated thoracocentesis .
8- PET-CT is superior to CT scan in detecting mediastinal and distant metastases in non–small cell lung cancer
9- Ability to demonstrate small neoplastic foci within normal-sized nodes and differentiation of enlarged hyperplastic nodes from enlarged neoplastic nodes.
10- FDG PET/CT is superior to conventional staging in the detection of all involved metastastic sites. While PET/CT imaging currently remains a relatively expensive test, it is no more costly than multiple other scans. This would argue that PET/CT imaging may be a reasonable alternative to multiple scans.
11- PET-CT is more sensitive and specific imaging tool than CT in identifing lung tumors and mediastinal nodes as it differentiate tumor mass from adjacent consolidated lung tissue or atelectasis so enable radiotherapy target volumes to be reduced and minimizing irradiating uninvolved lung tissue.
12- Monitoring of the therapeutic response.
13- Ability to distinguish viable metabolically active tissue from scars.
14- Detecting local recurrence of malignancy even before anatomic changes are visible on conventional imaging.
The main Disadvantages of PET/CT in management of bronchogenic carcinoma include the following:-
1- False positive results as follow:
• Granulomatous disease and sarcoidosis.
• Inflammatory diseases and infection.
• Hamartomas, Adenoma and Neurofibromas.
• Pulmonary fibrosis.
• Physiological uptake.
2- False negative results as follow:
• Low metabolic activity tumors as broncho-alveolar carcinoma (BAC) and carcinoid tumors
• Scar adenocarinoma.
• Lesions that are too small <1cm.
• Hyperglycemia and hyper-insulinemia.
• Recent completion of chemotherapy or radiotherapy.
3- General:
• Radiation exposure.
• High Cost.
• Artifacts and limitations.