Podcast
Questions and Answers
What is the primary indication for performing a CT of the neck?
What is the primary indication for performing a CT of the neck?
What is the recommended slice thickness for CT imaging of large lesions?
What is the recommended slice thickness for CT imaging of large lesions?
How long should a patient fast before a CT scan of the neck?
How long should a patient fast before a CT scan of the neck?
What is the appropriate patient position during a CT scan of the neck?
What is the appropriate patient position during a CT scan of the neck?
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What is the initial scanning technique performed before the actual axial CT scan?
What is the initial scanning technique performed before the actual axial CT scan?
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What is the recommended window level (WL) and width (WW) for optimal soft tissue imaging in CT?
What is the recommended window level (WL) and width (WW) for optimal soft tissue imaging in CT?
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Which of the following is NOT an indication for a CTA of the carotid artery?
Which of the following is NOT an indication for a CTA of the carotid artery?
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What advantage does spiral CT provide during chest scanning?
What advantage does spiral CT provide during chest scanning?
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What is the average dose of contrast media used for adults during the CT examination?
What is the average dose of contrast media used for adults during the CT examination?
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What is the primary purpose of using contrast media during a CT chest examination?
What is the primary purpose of using contrast media during a CT chest examination?
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Which parameter is optimal for demarcating the esophagus during a scan?
Which parameter is optimal for demarcating the esophagus during a scan?
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Which slice thickness is recommended for assessing pulmonary metastasis using a spiral CT?
Which slice thickness is recommended for assessing pulmonary metastasis using a spiral CT?
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What is the primary position for patients during chest HRCT scans?
What is the primary position for patients during chest HRCT scans?
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What is the recommended slice thickness for high-resolution CT scans of the chest?
What is the recommended slice thickness for high-resolution CT scans of the chest?
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What position should the patient be in during the CT chest examination?
What position should the patient be in during the CT chest examination?
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What is a characteristic of the low-dose high-resolution HR lung protocol?
What is a characteristic of the low-dose high-resolution HR lung protocol?
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What interval spacing should be maintained for adequate assessment during a CT chest examination?
What interval spacing should be maintained for adequate assessment during a CT chest examination?
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Which of the following is NOT an advantage of using contrast media in CT imaging?
Which of the following is NOT an advantage of using contrast media in CT imaging?
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What is the effect of using a low-dose HR CT scan compared to a standard dose?
What is the effect of using a low-dose HR CT scan compared to a standard dose?
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What is the recommended breathing technique during a CT chest scan?
What is the recommended breathing technique during a CT chest scan?
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What type of windowing is primarily used for lung HRCT scans?
What type of windowing is primarily used for lung HRCT scans?
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How important is clinical information before proceeding with a CT chest examination?
How important is clinical information before proceeding with a CT chest examination?
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Which scan technique allows for 3D visualization of the airways?
Which scan technique allows for 3D visualization of the airways?
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What specific action is recommended for prone scans in HRCT to enhance diagnostic capability?
What specific action is recommended for prone scans in HRCT to enhance diagnostic capability?
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Study Notes
Suprahyoid Neck Anatomy
- Suprahyoid neck is divided into nasopharynx, oropharynx, and oral cavity
CT of the Neck
- Indications include screening and staging of tumors/adenopathies, detecting parotid gland pathology, detecting carotid atheromatosis and obstruction, and evaluating congenital or post-traumatic abnormalities
- Patient preparation includes 4-6 hours of fasting, contrast material administration of 1-2 ml/kg of Urographin/Telebrix, and renal function tests.
- Anesthesia may be required for children and uncooperative patients.
Contrast Material Administration
- Contrast material may be used for masses, inflammation, and granulomas.
- It should be avoided in traumatic cases
Scanning Techniques
- Patient position is supine
- Scanogram from orbitometal line to vertex with gantry tilt
- Axial scans
- Scan intervals are 5mm
CT Procedure
- Patient is supine.
- Gantry is angled to prevent dental hardware artifact.
- Slice thickness is 3-5 mm or contiguous spiral, but may be more for large lesions.
- Window width (WW) and window level (WL) for optimal image display are:
- Soft tissue: WL:50, WW:400
- Bone: WL:300, WW:2000
- Patient should breathe quietly and avoid swallowing during data acquisition.
- IV contrast biphasic, 1ml/sec for 50ml followed by 0.4 ml/sec for 100 ml maximum injected volume, starting 1 min after injection.
CT of the Carotid Artery
- Indications include:
- Stenosis
- Occlusion
- Aneurysm
- Trauma
Advantages of Spiral CT Chest
- Allows scanning of major portions or entire chest during a single breath hold
- Eliminates motion artifacts
- High quality multiplanar and 3D image display
- Basis of virtual bronchoscope
Indications of Chest CT
-
Routine Chest CT:
- Evaluation of mediastinal or pleural mass
- Detection of pulmonary metastasis
- Hemoptysis
- Abscesses or cysts
- Guidance for FNA
-
HRCT Chest
- Suspected COPD (atelectasis, bronchitis, emphysema, asthma)
- Suspected infiltrative disease with normal or nonspecific CXR.
- Further characterizing diffuse disease
- CXR findings not matching clinical findings.
- Guiding type and site of biopsy
Patient Preparation and Contrast (Chest CT)
- Fasting for 3-4 hours before examination
- Contrast media is injected intravenously for mediastinal visualization.
- Specific type, volume and site of injection are determined by department protocols/radiologist preference.
- Average dose is 100 ml.
- Children receive 2 ml per kilogram body weight.
- Advantages of contrast media:
- Detecting lesions
- Distinguishing vessels from lesions
- Demonstrating vessels displacement by masses
- Demonstrating pathologies enhancement
CT Chest - Slice Spacing
- 10mm interval for adequate assessment of patient
- Improved spatial resolution allows better assessment of normal and abnormal findings
- Pulmonary metastasis requires spiral CT with 5 to 7 mm thick sections
- Trachea and central bronchi require 3 to 5 mm thick spiral CT
- Pulmonary parenchyma and peripheral bronchi require 1 to 2 mm sections
CT Chest Protocols
- Requires sufficient clinical information from the referring physician.
- Technologist selects the appropriate CT protocol based on patient history, clinical indications, and previous imaging.
CHEST (Lungs and Mediastinum)
- Assure patient understanding of the procedure and instructions
- Patient positioning: Supine with arms elevated above the head.
- Topogram: From lung apices to below diaphragm.
- Breathing: Breath hold in inspiration (single breath hold).
- Indications: General screening of pathology.
- Contrast: IV: 100 ml at 3ml/s. Imaging timing about 30-45 s.
- Technical Parameters: Slice thickness 7-10mm (3-5 mm for small lesions).
- Filming: Mediastinum window and Lung window.
- Parameters: Bone window if needed.
- Comments: For detection of lung nodules, a low dose protocol without contrast enhancement is recommended.
CHEST ( HRCT)
- Thin section and high spatial algorithm make structures sharper.
- Indications: Lung diseases: bronchiectasis, fibrosis, emphysema, etc.
- Patient position: Supine, arms elevated above head.
- Topogram: From lung apices to below diaphragm.
- Breathing: Breath hold in inspiration ( single breath hold).
- Contrast: N/A.
- Basic Technical Parameters: Slice thickness: 2-3 mm.
- Windowing: Lung window.
- Comments: Prone scans differentiate atelectasis. Expiratory scans show air trapping
CT of the Airways (key Concepts)
- [No content regarding key concepts of airway CT in the text]
Low-Dose High Resolution (HR) Lung Protocol
- Routine protocol for soft and lung window.
- Barium swallow optimizes esophagus delineation.
- Recommended for screening, detection, or exclusion of pulmonary nodes or infiltrates:
- Collimation: 4x2.5 mm
- Pitch factor 1.5
- Reconstruction: 3 mm
- Scanner setting: 120 kV, 10–20 mAs
- Rotation time: 0.5–0.75 s
- Kernel (algorithm): lung
- Window: lung window 1,500/–600
- Contrast material is not necessary.
- Reduces CT scan dose at the expense of more noise.
- Prone positioning recommended for detection or exclusion of asbestosis or orthostatic changes.
- ECG triggering may be used to minimize motion artifacts.
Advantages of Spiral CT Chest: Virtual Bronchoscopy
- Virtual Bronchoscopy (VB) is a 3D, computer-generated technique producing endobronchial images from spiral CT data.
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