الفهرس 
Anatomy of the LungOnly 14 pages are availabe for public view
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Abstract
Bronchogenic carcinoma is the leading cause of cancer-related death in both men and women. 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.
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.
Preoperative 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
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.
Positron emission tomography (PET) is an exciting imaging modality in patients with suspected lung cancer. Other imaging studies rely primarily on a demonstration of altered anatomy, such as lymph node or adrenal enlargement, whereas the basis of PET imaging is a difference in metabolism between normal and malignant cells.
A difficulty for the interpretation of FDG PET scans is the absence of identifiable anatomical structures in addition 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.
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 scanning has gained increasing application as a diagnostic and staging tool in the evaluation of lung cancer
Advantages of PET/CT over other imaging methods includes:
1. Differentiating benign from malignant lesions (based on both anatomical and metabolic information).
2. Ideal for evaluation of indeterminate lung nodule if >1 cm because of its relatively low false negative rate.
3. Selecting the region of a tumor most likely to yield diagnostic information for biopsy.
4. Better assessment of chest wall infiltration by precise delineation of the primary tumor.
5. Better differentiation between benign and malignant pleural effusion thereby preventing repeated thoracocentesis owing to its high negative predictive value.
6. Ability to demonstrate small neoplastic foci within normal-sized nodes and differentiation of enlarged hyperplastic nodes from enlarged neoplastic nodes.
7. The ability of PET/CT to detect distant metastases is high, and the interpretation of a positive or negative PET result in an individual patient can be made with relative confidence.
8. 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.
9. Highly valuable tool for planning radiation treatment as it is useful for accurate target definition by reducing the probability of overlooking involved areas.
10. Monitoring of the therapeutic response.
11. Ability to distinguish viable metabolically active tissue from scars.
12. Detecting local recurrence of malignancy even before anatomic changes are visible on conventional imaging.
The main drawbacks of PET/CT in management of Bronchogenic carcinoma include the following:
I) General:
• Radiation exposure
• Cost
• Artifacts
II) False positive results:
• Physiological uptake.
• Inflammation (e.g., tuberculosis, sarcoidosis).
Because of the lower positive predictive value confirmation of 18FFDG PET–positive indeterminate lesion or lymph nodes by invasive means is required.
III) False negative results:
• Low spatial resolution.
• Low-metabolism neoplasms, such as primary pulmonary carcinoids and bronchioloalveolar cell carcinomas
• Recent completion of chemotherapy or radiotherapy.
• Physiologic movement (e.g. respiration) during emission scan, which is acquired during free breathing over several minutes.
• Hyperglycemia and hyperinsulinemia.