What are the essential components to include when writing a computed tomography (CT) scan request for a chest examination, considering factors such as clinical indication, medical history, and imaging protocol?

How to Write a CT Scan Request for the Chest

Essential Components of the Request

Your CT chest request must include the clinical indication, relevant medical history, specific imaging protocol requirements, and any special considerations to ensure appropriate acquisition and interpretation. 1

Clinical Indication

• State the specific clinical question clearly - this determines the imaging protocol and guides the radiologist's interpretation 1, 2
• Include whether you are evaluating for suspected malignancy, staging known cancer, assessing diffuse lung disease, evaluating pulmonary nodules, or investigating chronic symptoms 1
• Specify if the patient has high-risk features such as smoking history (quantify in pack-years), occupational exposures, or symptoms concerning for malignancy 1

Critical Medical History Elements

• Document smoking history in pack-years - this is essential for lung cancer risk stratification and determines screening eligibility 1
• List relevant symptoms with duration: chronic cough (>8 weeks), hemoptysis, chest pain, weight loss, dyspnea 1
• Include any known malignancy history, as 7-14% of patients with head and neck cancer have synchronous lung primaries 3, 4
• Note immunosuppression status, chronic lung disease, or connective tissue disorders if evaluating for diffuse lung disease 1
• Document occupational exposures (asbestos, silica, welding) that increase lung disease risk 1

Imaging Protocol Specifications

Specify whether contrast is needed based on your clinical question:

• For pulmonary nodule evaluation: request CT chest WITHOUT IV contrast - contrast does not improve nodule detection or characterization 3
• For suspected lung cancer staging: request CT chest WITH IV contrast - this improves detection of mediastinal/hilar lymphadenopathy and skeletal metastases 3, 4
• For diffuse lung disease: request high-resolution CT (HRCT) protocol WITHOUT contrast with thin sections (≤2.5 mm, preferably ≤1.0 mm) 1

Technical Requirements for Specific Indications

For lung cancer screening (if patient meets criteria):

• Low-dose protocol: 120-140 kVp, 40-80 mAs (approximately 1.5 mSv radiation exposure) 1
• Slice thickness ≤2.5 mm with 50% overlap for 3D reconstruction 1
• No oral or IV contrast 1
• Single breath-hold at maximum inspiration 1
• Requires ≥16 detector CT scanner 1

For nodule follow-up:

• Request comparison with ALL prior chest CTs (not just reports) - this is essential for assessing growth rate 1
• Specify series and image numbers of nodules if known 1
• Request volumetric measurement capability if available 1

For diffuse lung disease:

• Request HRCT protocol with thin sections (≤2.5 mm) 1
• Consider requesting expiratory and prone images for air trapping and dependent atelectasis evaluation 1
• Request multiplanar reconstructions (coronal reformats) 1

Common Pitfalls to Avoid

• Never request "routine chest CT" without specifying the clinical indication - this leads to inappropriate protocols and incomplete evaluation 2
• Do not request dual-phase CT (without and with contrast) for nodule evaluation - there is no supporting evidence for this approach 3
• Do not rely on chest radiography alone for lung cancer evaluation - sensitivity is only 28% compared to CT 1, 3, 4
• Do not order standard-dose CT when low-dose screening protocol is appropriate - this unnecessarily increases radiation exposure from 1.5 mSv to 5-8 mSv 1
• Do not forget to request comparison with prior imaging - failure to compare directly with previous studies (not just reports) is a major quality gap 1, 2

Sample Request Format

"CT chest [WITH/WITHOUT IV contrast] for [specific indication]. Patient is [age] with [pack-year] smoking history presenting with [symptoms and duration]. [Relevant medical history including prior malignancy, occupational exposures, chronic conditions]. Please compare with prior CT dated [date] if available. [Special protocol requests if applicable: low-dose screening protocol, HRCT with expiratory views, etc.]"

This structured approach ensures the radiologist receives all necessary information to select the appropriate protocol, interpret the study correctly, and provide guideline-concordant recommendations 1, 2.