# Standard Operating Procedure: CT Imaging Protocol

| Document ID | SOP-RAD-001 |
|-------------|-------------|
| Title | Computed Tomography (CT) Imaging Protocol |
| Revision | 1.0 |
| Effective Date | [DATE] |
| Author | [AUTHOR] |
| Approved By | [APPROVER] |
| Department | Radiology/Diagnostic Imaging |

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## 1. Purpose

To establish standardized procedures for performing computed tomography (CT) examinations to ensure patient safety, optimal image quality, and regulatory compliance with ACR, state, and federal requirements.

## 2. Scope

This procedure applies to all CT examinations including:
- Non-contrast CT studies
- Contrast-enhanced CT studies
- CT angiography (CTA)
- CT-guided procedures
- Emergency/trauma CT

## 3. Responsibilities

### 3.1 CT Technologist
- Screen patients for contraindications
- Position patient properly
- Select and execute protocols
- Assess image quality
- Monitor patient during examination

### 3.2 Radiologist
- Approve protocols
- Supervise contrast administration
- Interpret studies and generate reports
- Manage contrast reactions

### 3.3 Radiology Nurse (if applicable)
- Assess IV access
- Administer contrast
- Monitor for reactions
- Provide patient care

### 3.4 Medical Physicist
- Establish dose optimization protocols
- Perform quality control
- Monitor radiation exposure

## 4. Definitions

| Term | Definition |
|------|------------|
| CTDI | CT Dose Index - measure of radiation output |
| DLP | Dose Length Product - total dose metric |
| HU | Hounsfield Units - density measurement |
| kVp | Kilovoltage peak |
| mAs | Milliampere-seconds |
| MPR | Multiplanar reconstruction |

## 5. Equipment and Materials

- CT scanner (accredited)
- Power injector
- Contrast media (iodinated)
- IV supplies
- Emergency equipment and medications
- Shielding devices
- Patient monitoring equipment

## 6. Procedure

### 6.1 Pre-Examination

#### 6.1.1 Order Verification
- [ ] Valid physician order present
- [ ] Appropriate indication documented
- [ ] Protocol selection appropriate for indication
- [ ] Prior imaging reviewed (if available)

#### 6.1.2 Patient Identification
- Verify using two identifiers
- Confirm exam matches order
- Review clinical history

#### 6.1.3 Safety Screening

**For all patients:**
- [ ] Pregnancy status (women of childbearing age)
- [ ] Previous CT studies (cumulative dose awareness)
- [ ] Ability to cooperate with positioning
- [ ] Metal implants/devices in scan field

**For contrast studies - additional screening:**

| Risk Factor | Check |
|-------------|-------|
| Previous contrast reaction | ☐ Yes ☐ No |
| Allergies (iodine, shellfish) | ☐ Yes ☐ No |
| Kidney disease/elevated creatinine | ☐ Yes ☐ No |
| Diabetes (metformin use) | ☐ Yes ☐ No |
| Thyroid disease | ☐ Yes ☐ No |
| Multiple myeloma | ☐ Yes ☐ No |
| Age >70 years | ☐ Yes ☐ No |
| Dehydration | ☐ Yes ☐ No |

**Renal Function Assessment:**
| eGFR Level | Risk | Action |
|------------|------|--------|
| ≥60 | Low risk | Proceed |
| 45-59 | Moderate risk | Hydration, consider alternatives |
| 30-44 | High risk | Alternative imaging preferred, radiologist approval |
| <30 | Very high risk | Avoid unless emergent, nephrology consult |

#### 6.1.4 Consent
- Explain procedure and risks
- Obtain informed consent for contrast (if applicable)
- Document consent

### 6.2 Patient Preparation

#### 6.2.1 Preparation by Exam Type

| Exam Type | Preparation Required |
|-----------|---------------------|
| Head CT | Remove metallic objects from head/neck |
| Chest CT | Breathing instructions, arms above head |
| Abdomen/Pelvis CT | Oral contrast (if ordered), full bladder (pelvic) |
| CT Angiography | IV access, contrast protocol |
| CT Colonography | Bowel preparation |

#### 6.2.2 IV Access for Contrast
- Assess vein suitability
- 20-gauge or larger preferred for power injection
- Verify patency with saline flush
- Secure catheter properly

### 6.3 Patient Positioning

#### 6.3.1 Standard Positions

| Body Part | Position | Gantry Entry |
|-----------|----------|--------------|
| Head | Supine, neutral | Head first |
| Neck | Supine, neck extended | Head first |
| Chest | Supine, arms up | Head or feet first |
| Abdomen | Supine, arms up | Head first |
| Pelvis | Supine, arms up | Feet first |
| Extremity | Per protocol | Varies |

#### 6.3.2 Positioning Considerations
- Center patient in gantry
- Use positioning aids as needed
- Apply shielding where appropriate
- Ensure patient comfort
- Remove all artifacts from scan field

### 6.4 Protocol Selection and Parameters

#### 6.4.1 Dose Optimization Principles
- ALARA (As Low As Reasonably Achievable)
- Use automatic exposure control (AEC)
- Size-appropriate protocols
- Limit scan range to clinical question

#### 6.4.2 Standard Protocol Parameters

| Protocol | kVp | mAs | Slice Thickness | Pitch |
|----------|-----|-----|-----------------|-------|
| Head routine | 120 | Auto | 5mm | N/A (axial) |
| Chest routine | 120 | Auto | 5mm/1.25mm | 1.0-1.5 |
| Abdomen routine | 120 | Auto | 5mm/2.5mm | 1.0-1.5 |
| CT Angiography | 100-120 | Auto | 0.625-1.25mm | 0.8-1.0 |
| Low-dose chest | 100-120 | Reduced | 1.25mm | 1.0-1.5 |

#### 6.4.3 Pediatric Considerations
- Reduce kVp and mAs based on weight/age
- Use pediatric-specific protocols
- Apply "Image Gently" principles
- Minimize number of phases

### 6.5 Contrast Administration

#### 6.5.1 Contrast Selection

| Indication | Contrast Type | Concentration |
|------------|---------------|---------------|
| Routine enhanced | Low-osmolar | 300-350 mgI/mL |
| CT Angiography | Low-osmolar | 350-370 mgI/mL |
| High-risk patients | Iso-osmolar | 270-320 mgI/mL |

#### 6.5.2 Contrast Volume and Rate

| Exam Type | Volume | Rate |
|-----------|--------|------|
| Head with contrast | 100 mL | 1-2 mL/sec |
| Chest with contrast | 100-125 mL | 2-3 mL/sec |
| Abdomen with contrast | 100-150 mL | 2-3 mL/sec |
| CT Angiography | 75-125 mL | 4-5 mL/sec |

#### 6.5.3 Timing Methods
- Fixed delay (empiric)
- Bolus tracking (threshold trigger)
- Test bolus (timing determination)

### 6.6 Image Acquisition

1. **Scout/Topogram**
   - Acquire scout images
   - Verify positioning and coverage
   - Set scan range

2. **Pre-Contrast (if applicable)**
   - Acquire non-contrast images
   - Assess for baseline findings

3. **Contrast Injection (if applicable)**
   - Verify IV patency
   - Program injector parameters
   - Monitor injection

4. **Post-Contrast Acquisition**
   - Acquire at appropriate phase(s)
   - Arterial: 25-35 seconds
   - Portal venous: 60-70 seconds
   - Delayed: 3-5 minutes (as needed)

5. **Image Review**
   - Review images for quality
   - Assess for artifacts
   - Repeat if technically inadequate

### 6.7 Post-Examination

#### 6.7.1 Patient Care After Contrast
- Monitor for 15-30 minutes
- Assess IV site
- Provide hydration instructions
- Advise on potential delayed reactions
- Metformin patients: follow institutional protocol

#### 6.7.2 Documentation
- Complete FRM-RAD-001 CT Procedure Log
- Document dose metrics (CTDIvol, DLP)
- Record contrast details
- Note any adverse events
- Submit images to PACS

### 6.8 Image Post-Processing

| Reconstruction | Application |
|----------------|-------------|
| Soft tissue | Routine interpretation |
| Bone | Skeletal evaluation |
| Lung | Pulmonary parenchyma |
| 3D/MPR | Vascular, complex anatomy |
| MIP | Angiography |

## 7. Contrast Reaction Management

### 7.1 Reaction Classification

| Severity | Symptoms | Action |
|----------|----------|--------|
| Mild | Nausea, urticaria (limited), warmth | Observe, treat symptoms |
| Moderate | Extensive urticaria, bronchospasm, hypotension | Medical treatment, monitor |
| Severe | Anaphylaxis, cardiac arrest, seizure | Emergency response, call code |

### 7.2 Emergency Equipment
Available in CT suite:
- Oxygen and suction
- Emergency medications (epinephrine, diphenhydramine, etc.)
- IV fluids
- Defibrillator/AED
- Crash cart

## 8. Radiation Safety

### 8.1 Dose Monitoring
- Record CTDIvol and DLP for each exam
- Compare to diagnostic reference levels
- Investigate outliers

### 8.2 Diagnostic Reference Levels

| Exam | CTDIvol (mGy) | DLP (mGy·cm) |
|------|---------------|--------------|
| Head | 60 | 1000 |
| Chest | 15 | 400 |
| Abdomen | 20 | 700 |
| Abdomen/Pelvis | 20 | 900 |

## 9. Quality Control

| Activity | Frequency |
|----------|-----------|
| Daily warm-up and calibration | Daily |
| Water phantom QC | Daily/Weekly |
| CT number accuracy | Weekly |
| Spatial resolution | Monthly |
| Physicist review | Annually |

## 10. Documentation

- FRM-RAD-001 CT Procedure Log
- FRM-RAD-002 Contrast Administration Record
- FRM-RAD-003 Adverse Reaction Report
- Dose reports
- QC logs

## 11. References

- ACR Practice Parameter for CT
- ACR Manual on Contrast Media
- Image Gently Campaign
- AAPM CT Protocols
- State radiation regulations

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## Revision History

| Rev | Date | Description | Author |
|-----|------|-------------|--------|
| 1.0 | [DATE] | Initial release | [AUTHOR] |