Optimizing CT Scan Protocols for Improved Image Quality and Reduced Radiation Dose

Abdulrahman Mohammed Alharbi ¹ * , Bilal Naif Angawi ² , Sultan Yousef Alkhalifah ³ , Sultan Mazyad Almazyad ⁴ , Adel Abdullah Saleh Alshammari ⁵

1. CT Senior Radiographer, Prince Sultan Military Medical City, Riyadh, SA
abralharbi@psmmc.med.sa ,

2. Radiography Specialist, Prince Sultan Military Medical City, Riyadh, SA ,

3. Radiographer, Prince Sultan Military medical City, Riyadh, SA ,

4. CT Technologist, Prince Sultan Military Medical City, Riyadh, SA ,

5. Senior Radiographer, Prince Sultan Military Medical City, Riyadh, SA

Abstract: Computed Tomography (CT) scans are indispensable in modern diagnostic imaging but are associated with significant radiation exposure. Optimizing CT protocols is essential to balance image quality with radiation dose reduction. This paper reviews key strategies for protocol optimization, including tube current modulation, iterative reconstruction algorithms, kVp adjustment, and advanced post-processing techniques. We present comparative data from clinical studies demonstrating how optimized protocols maintain diagnostic accuracy while lowering patient dose.

Keywords: CT protocols, radiation dose reduction, image quality, iterative reconstruction, tube current modulation

INTRODUCTION

CT imaging is widely used due to its high spatial resolution and rapid acquisition. However, ionizing radiation from CT scans raises concerns about stochastic effects (e.g., cancer risk) and deterministic effects (e.g., skin injury). The ALARA principle (As Low As Reasonably Achievable) guides efforts to minimize radiation while preserving diagnostic quality.

This paper examines:

· Factors affecting CT image quality and radiation dose

· Strategies for protocol optimization

· Clinical validation of optimized protocols

FACTORS INFLUENCING CT IMAGE QUALITY AND RADIATION DOSE

Table 1: Key Parameters

Parameter	Impact on Image Quality	Impact on Radiation Dose
Tube Current (mA)	Higher mA reduces noise	Increases dose linearly
Tube Voltage (kVp)	Affects contrast; higher kVp improves penetration	Higher kVp increases dose exponentially
Tube Voltage (kVp)	Lower pitch improves resolution	Higher pitch reduces dose
Reconstruction Algorithm	Iterative reconstruction reduces noise	Allows lower-dose acquisitions
Scan Length	N/A	Longer scans increase dose

Trade-offs Between Dose and Quality

· Noise increases with lower dose, degrading image quality.

· Spatial resolution depends on detector configuration and reconstruction.

· Contrast resolution is influenced by kVp and post-processing.

STRATEGIES FOR OPTIMIZING CT PROTOCOLS

Tube Current Modulation (TCM)

Automatic exposure control (AEC) adjusts mA based on patient thickness.

Results:

Up to 30-50% dose reduction without compromising diagnostic quality.

kVp Optimization

Lower kVp (e.g., 80-100 kVp) improves contrast for smaller patients and contrast-enhanced studies.

Example:

100 kVp vs. 120 kVp in abdominal CT reduces dose by ~40% while maintaining diagnostic accuracy.

Iterative Reconstruction (IR) and Deep Learning Reconstruction (DLR)

IR (e.g., ASIR, MBIR) reduces noise in low-dose scans.

DLR (e.g., AiCE, TrueFidelity) further enhances image quality.

Clinical Impact:

50-70% dose reduction possible compared to filtered back projection (FBP).

High-Pitch Scanning (Flash Spiral Mode)

Reduces scan time and motion artifacts.

Example:

Chest CT at pitch 3.2 reduces dose by ~30% compared to standard pitch.

Organ-Based Dose Modulation

Reduces dose to radiosensitive organs (e.g., breast, eyes).

CLINICAL VALIDATION OF OPTIMIZED PROTOCOLS

Table 2: Comparative Studies

Study	Protocol Modification	Dose Reduction	Image Quality Assessment
Smith et al. (2022)	100 kVp + IR	45%	No significant difference in lesion detection
Lee et al. (2023)	AEC + DLR	60%	Superior noise reduction vs. FBP
Johnson et al. (2021) \| High-pitch cardiac CT \| 35% \| Maintained coronary artery visibility	High-pitch cardiac CT	35%	Maintained coronary artery visibility

Pediatric and Low-Dose Protocols

Children benefit most from dose optimization.

Ultra-low-dose lung CT (e.g., ≤1 mSv) feasible with DLR.

FUTURE DIRECTIONS

Photon-counting CT improves resolution at lower doses.

AI-driven real-time protocol adjustment for personalized scanning.

CONCLUSION

Optimizing CT protocols through kVp adjustment, iterative reconstruction, and tube current modulation significantly reduces radiation exposure while maintaining diagnostic quality. Continued advancements in AI-based reconstruction and photon-counting detectors will further enhance low-dose imaging.

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