Chest CT Scan
I.
Clinical Indications for Procedure
a. Chest CT scan may be indicated for 1 or more of the following:
i. Abnormal chest x-ray findings, as indicated by 1 or more of the following:
1. Persistent atelectasis
2. Lung mass
3. Hilar adenopathy, or mediastinal mass or enlargement
4. Pleural thickening or pleural plaque
5. Pleural effusion poorly responsive to drainage and other conservative
treatments
6. Cystic or cavitary lesion
7. Interstitial or other systemic lung disease pattern (e.g., reticular, bronchial
wall thickening, honeycombing)
ii. Initial evaluation of solitary pulmonary nodule noted on plain chest x-ray
iii. Interval follow-up of benign-appearing solitary pulmonary nodule less than 10
mm in size
iv. Chest trauma
v. For anatomic guidance during percutaneous, pleural, lung, or mediastinal
biopsy
vi. Nonspecific chest x-ray finding in febrile neutropenic patient
vii. Suspected bronchopleural fistula
viii. Chest wall soft tissue mass
ix. Dyspnea (shortness of breath)
x. Esophageal trauma or perforation, suspected or known, and additional
information required beyond general clinical assessment and endoscopy
xi. Hemoptysis
xii. Pneumonia
xiii. Suspected or confirmed pulmonary tuberculosis
xiv. Interstitial lung disease
xv. Post bone marrow transplant
xvi. Post lung transplant
xvii. Suspected bronchiectasis signs or symptoms, as indicated by 1 or more of the
following:
1. Chronic cough
2. Fetid breath
3. Sputum production
4. Chronic respiratory infections
5. Hemoptysis
6. Cough-induced fracture of ribs
xviii. Collagen vascular disease
xix. Cystic fibrosis
xx. Pneumoconiosis
xxi. Lung cancer (primary)
xxii. Clinical suspicion of superior vena cava syndrome (i.e., venous obstruction by
tumor)
xxiii. Other cancer of adjacent structure, or metastatic or extending to lung
Chest CT Scan
xxiv. Estimation of postoperative pulmonary function reserve, prior to anticipated
resection, and nuclear medicine perfusion scanning indeterminate
xxv. Preoperative planning for patient with primary hyperparathyroidism, and
sestamibi nuclear scan positive for mediastinal location of adenoma
II.
Inappropriate Use
For lung cancer screening, a systematic review and consensus guidelines have concluded
that the role and benefits of screening for high-risk patients with low-dose CT scan
remains uncertain. The Early Lung Cancer Action Project, a nonrandomized study,
screened 31,567 asymptomatic patients age 40 years or older with risk factors, such as
cigarette smoking, exposure to secondhand smoke, or occupational exposure (asbestos,
beryllium, uranium, or radon), with low-dose CT scan; it detected lung cancer in 1.3% on
baseline CT screening, and in 0.3% on annual screening. The study authors estimated the
10-year survival rates for the 412 patients who were diagnosed with stage I lung cancer
and concluded that screening led to increased survival for patients diagnosed with early
disease. However, other large studies of CT screening of asymptomatic patients with
ascertainment of actual deaths due to lung cancer have concluded that, although
screening may increase the diagnosis and treatment of lung cancer, it may not reduce
mortality from lung cancer. These discordant conclusions are attributed to possible leadtime bias (disease is detected earlier, but death is not delayed), and length bias (CT
screening may identify indolent slowly progressive disease that may not otherwise have
been diagnosed). The goal of the US National Lung Screening Trial was to determine
whether screenings with low-dose helical CT reduced mortality from lung cancer relative
to screening with chest x-ray. Trial participants included more than 53,000 current and
former smokers with at least 30 pack-years of cigarettes randomized to screening with 3
annual plain chest x-rays or chest CT scans. They were then followed for up to another 5
years. The trial was stopped in October 2010 because the data necessary for inferring
effects on the primary end point of lung cancer-specific mortality had been collected. At
that point, it was noted that 354 deaths from lung cancer had occurred among participants
in the CT arm of the study as compared with 442 lung cancer deaths in the chest x-ray
arm. The mortality rate difference of 20.3% is statistically significant. Remaining issues
to be resolved include an assessment of risk regarding the cumulative effects of multiple
CT scans as well as cost-effectiveness of screening. Analysis of the data remains
incomplete and unpublished. Results of the largest European randomized trial
(NELSON) are still pending. The role of chest CT scan in screening for lung cancer
remains uncertain.
For asthma, studies of chest CT have demonstrated some correlation between degree of
airway remodeling and lung pathology; however, it is uncertain how such imaging may
improve clinical outcomes.
III.
Discussion
Chest CT scan is indicated for further evaluation of abnormal chest x-ray findings,
including lung nodules or masses, nonresolving pneumonia, pleural disease, interstitial
lung disease, and widened mediastinum or mediastinal masses.
Chest CT Scan
Chest CT scan is used for imaging mediastinal masses, such as thymoma or teratoma,
hilar adenopathy suspicious for sarcoidosis, or Hodgkin lymphoma.
CT scan is indicated for further characterization of a solitary pulmonary nodule found on
chest x-ray regarding size, shape, and type of opacity; higher rates of malignancy are
associated with increasing size, irregularities in shape (speculated or lobular), and
ground-glass appearance.
The frequency of CT scan for observation of benign-appearing nodules is guided by
nodule size, radiographic appearance, and patient risk factors for malignancy.
Chest CT scan is routinely used for staging and restaging primary lung cancer and for
post-treatment surveillance.
Chest CT is commonly used for cancer staging to detect pulmonary metastases secondary
to other types of cancer, most commonly head and neck cancer, melanoma, bone and soft
tissue sarcoma, and renal cell carcinoma.
IV.
Reference
Milliman Care Guidelines, “Ambulatory Care”, 15th Edition.