Can you read a computed tomography (CT) scan?

Can You Read a CT Scan?

Yes, physicians can learn to read CT scans independently, but this requires formalized training with interpretation of at least 75 endoscopically or clinically correlated cases, followed by mentored supervision, with the primary determinant of accuracy being the skill and experience of the interpreting physician. 1, 2

Training Requirements for Independent CT Interpretation

Minimum Competency Standards

• Review at least 75 cases with endoscopic or clinical correlation to achieve minimal competence in detecting and characterizing findings on CT scans 1, 3
• Studies demonstrate that sensitivity improves after reading 50 cases, but optimal sensitivity (92% for target lesions) is achieved only after interpreting 75 cases 1, 3
• After initial training, participate in a mentored preceptorship lasting 4-6 weeks within 6 months, involving interpretation of at least 25-50 additional cases under supervision 3

Three Training Formats That Work

1. Formal hands-on interactive training on CT interpretation with structured teaching 1, 3
2. Supervision with a CT-trained physician acting as a double reader during your learning phase 1, 3
3. Correlation of CT findings with endoscopy or surgical findings in patients who undergo both procedures 1, 3

Essential Knowledge Base Required

Technical Understanding

• Master basic CT physics and parameters/acquisition techniques that affect radiation exposure and image quality 1, 3
• Learn to evaluate image quality, including adequacy of contrast enhancement and patient positioning 3
• Understand how to use CT workstations, including the ability to compare different views, generate 2D and 3D images, and examine CT attenuation values 3

Anatomical and Clinical Knowledge

• Develop thorough understanding of abdominal anatomy, including colon, rectal, appendiceal, and ileal anatomy 1, 3
• Learn to recognize the varied appearance of normal and pathological findings in abdominal structures 1, 3
• Understand indications for intravenous contrast, as well as contraindications and treatment of adverse reactions 1

Systematic Approach to Interpretation

Primary Search Methods

• Master both primary 2D and 3D search methods for optimal detection of abnormalities, as optimal performance likely involves both techniques 1, 3
• Follow a systematic approach such as the "4As, 3Bs, 2Cs and 1D" method to avoid missing pathology 4
• Use structured reporting templates to ensure comprehensive evaluation of all relevant structures 3

Critical Pitfalls to Avoid

• Inadequate oral contrast administration can cause normal bowel to remain unopacified and simulate tumors; repeat scanning with additional contrast material at selected levels often reveals the true nature of pseudotumors 5
• Volume averaging causes problems when section thicknesses are larger than lesions (e.g., small hepatic cysts); repeat CT with thinner sections is needed to obtain accurate attenuation values 5
• Lack of clinical information is a major contributor to misdiagnoses; always review available clinical history before interpreting 5, 2
• Reader variability is significant, with error rates ranging from 3.6-16.1% among faculty radiologists, demonstrating that the primary determinant of error rates is the skill of the interpreting radiologist 2

Extracolonic and Incidental Findings

Mandatory Evaluation Beyond Primary Focus

• Specific interpretation of extra-cardiac and extra-colonic fields should be performed to address significant incidental findings such as aortic disease, hilar adenopathy, large pulmonary nodules, and pulmonary emboli 1
• Training should include review of a dedicated teaching file of 25 cases featuring significant noncardiac or extracolonic pathology 1
• Approximately 50-61% of CT examinations reveal potentially significant cardiovascular findings when performed for other indications 6

When to Refer

• Cases with complex extracolonic findings require referral to a specialist or radiologist with expertise in chest or abdominal imaging 1
• The CT scout view should be systematically reviewed as it may contain important findings outside the scanned field of view, such as unsuspected lung cancer at the lung bases 7

Maintaining Competency

Ongoing Practice Requirements

• Interpret a minimum number of cases per year to maintain clinical expertise after formalized training 1, 3
• Participate in continuing medical education activities to stay updated on advances in the field 1, 3
• Collaborate with board-certified radiologists, especially when reviewing complex cases 3

Performance Variability

• Response to training is unpredictable, with some readers achieving competency faster than others despite similar training 1
• Prior experience in gastrointestinal or cardiovascular imaging enhances the ability to read CT, but competency cannot be assumed after training with only 50 cases 1
• Inexperienced readers who completed a structured training module performed better than experienced readers without formal training (70% vs 47% sensitivity for lesions ≥10 mm) 1