Tehran University of Medical Sciences Frontiers in Biomedical Technologies 2345-5837 0 0 2026 09 10 1585 1585 Abolhasan Divband Department of Pediatrics, Faculty of Medicine, Hormozgan University of Medical Sciences, Bandar Abbas, Iran Amir Ali Forghani School of Medicine, Shahid Beheshti University of Medical Sciences, Tehran, Iran Mohammad Reza Deevband Department of Biomedical Engineering and Medical Physics, School of Medicine, Shahid Beheshti University of Medical Sciences, Tehran, Iran Fatemeh zahra Nosrati Department of Biomedical Engineering and Medical Physics, School of Medicine, Shahid Beheshti University of Medical Sciences, Tehran, Iran somayeh Rashedi Department of Biomedical Engineering and Medical Physics, School of Medicine, Shahid Beheshti University of Medical Sciences, Tehran, Iran 2026 02 04 2026 04 24 Background: Head and neck CT examinations constitute more than 50% of all CT scans in Iran, and their utilization has dramatically increased in recent years, raising concerns about population radiation burden. Objectives: This study aimed to estimate organ doses, effective dose, and lifetime attributable risk (LAR) of cancer in Iranian patients undergoing routine head and neck CT using Monte Carlo-based dosimetry. Methods: In this retrospective cross-sectional study, 429 patients (215 females, 214 males; mean age 45.5 ± 17.2 years) from nine imaging centers (2020–2022) were evaluated. Organ and effective doses were calculated using NCICT software with size-specific dose estimate (SSDE) adjustment. LAR of cancer incidence and mortality was estimated using BEIR VII models, adjusted for Iranian life-tables. Results: Mean CTDIvol and DLP were 36.36 ± 17.17 mGy and 542.44 ± 292.56 mGy·cm, respectively. The mean effective dose was 1.23 ± 0.67 mSv. Proposed national diagnostic reference levels (75th percentile) were 48.31 mGy for CTDIvol and 752 mGy·cm for DLP. The highest organ doses were received by the brain (22.36 mGy) and salivary glands (19.84 mGy). The total LAR of cancer incidence was 181.82 per 100,000 (95% CI 174.13–189.51); females showed a 15.5% higher risk than males (p < 0.01). The "other cancers" category (mainly brain and salivary glands) contributed 98% of the total risk. Conclusion: Individual risk is low, but high CT frequency (>10 million/year) may cause thousands of radiation-induced cancers. Recommend ALARA adherence, protocol optimization, and national DRLs. https://fbt.tums.ac.ir/index.php/fbt/article/view/1585 https://fbt.tums.ac.ir/index.php/fbt/article/download/1585/581