Background: Computed tomography (CT) is an essential diagnostic tool, particularly for patients undergoing repeated procedures. Diagnostic Reference Levels (DRLs), introduced by the International Commission on Radiological Protection (ICRP), serve as reference values for monitoring radiation doses in radiological procedures. DRLs, based on parameters such as CTDIvol (Computed Tomography Dose Index volumetric) and DLP (Dose Length Product), do not represent absolute dose limits for individual patients but rather serve as benchmarks to assess the quality, efficacy, and safety of the administered dose during procedures. However, since these parameters are calculated using standard phantoms, they do not account for the specific anatomical characteristics of individual patients. To address this limitation, the Size-Specific Dose Estimate (SSDE) was introduced. SSDE incorporates the Water Equivalent Diameter (WED) to adjust the dose estimate to the patient's size and body composition, providing a more accurate, personalized, and safer assessment of the absorbed dose. Aim: The study aims to analyze the correlation between the dosimetric indices CTDIvol and SSDE in intensive care unit (ICU) patients undergoing CT examinations with automatic exposure control during their hospitalization. The role of WED (Water-Equivalent Diameter) and the number of CT scans performed were investigated to determine variations in the agreement between these parameters, highlighting the implications for optimal personalization of radiation dose. Materials and Methods: A total of 51 patients who underwent between 1 and 8 CT scans during their hospital stay were included. The cumulative CTDIvol was calculated as the sum of the CTDIvol values from all scans performed on each patient. This parameter measures the dose delivered per unit volume, providing a standardized estimate based on phantoms. Conversely, the cumulative SSDE was calculated by summing the SSDE values for each CT scan, taking into account the patient's specific size through the WED. Statistical analysis included Pearson and Spearman correlation coefficients, Lin’s concordance analysis, and the Bland-Altman plot. Results: The analysis revealed a strong correlation between cumulative CTDIvol and cumulative SSDE, with a Pearson correlation coefficient of r = 0.982 and a Concordance Correlation Coefficient (CCC) of 0.949, demonstrating that both parameters are valid indicators of overall dose in the general cohort. However, in patients with extreme WED values, a reduction in agreement between the two parameters was observed. Specifically, considering the cohort of patients with WED < 250 mm and WED > 350 mm, the CCC decreases to 0.825. Furthermore, when analyzing exclusively patients with WED < 250 mm, the CCC decreases further to 0.526, suggesting that WED is a determining factor influencing the agreement between the two parameters. This result highlights how WED variability plays a key role in determining the accuracy with which CTDIvol can estimate SSDE in subgroups characterized by atypical patient dimensions. Conclusions: The results emphasize the importance of WED and SSDE in personalizing radiological dose estimates, particularly for patients undergoing multiple CT scans. While CTDIvol serves as a useful standard parameter for dose monitoring, SSDE provides a more accurate and clinically relevant estimate, especially for patients with extreme body sizes. This study highlights the importance of assessing the potential integration of SSDE in optimization processes based on DRLs, especially for patients with WED values that deviate significantly from the norm, enhancing patient safety and ensuring higher diagnostic quality.
Presupposti dello studio: La tomografia computerizzata (TC) è uno strumento diagnostico indispensabile, in particolare per pazienti sottoposti a procedure ripetute. I Livelli Diagnostici di Riferimento (LDR), introdotti dalla Commissione Internazionale per la Protezione Radiologica (ICRP), rappresentano valori di riferimento per il monitoraggio della dose di radiazioni nelle procedure radiologiche. I LDR, basati su parametri come il CTDIvol (Computed Tomography Dose Index volumetrico) e il DLP (Dose Length Product), non rappresentano limiti di dose assoluti per il singolo paziente, ma piuttosto strumenti di confronto per valutare la qualità, l'efficacia e la sicurezza della dose somministrata durante le procedure. Tuttavia, essendo calcolati su fantocci standard, questi parametri non considerano le caratteristiche anatomiche specifiche dei pazienti. Per superare questa limitazione, è stato introdotto l’SSDE (Size-Specific Dose Estimate), che integra il Water Equivalent Diameter (WED) per adattare la stima della dose alle dimensioni e alla composizione corporea del paziente, offrendo così una valutazione più accurata, personalizzata e sicura della dose assorbita. Scopo: Lo studio si propone di analizzare la correlazione tra gli indici dosimetrici CTDIvol e SSDE nei pazienti ricoverati in terapia intensiva sottoposti ad indagine TC con controllo automatico della esposizione durante il periodo di ricovero. Si è indagato il ruolo del WED e del numero di TC effettuate nel determinare variazioni nell’accordo tra questi parametri, evidenziando le implicazioni per una personalizzazione ottimale della dose radiologica. Materiali e metodi: Sono stati inclusi 51 pazienti sottoposti a un numero di TC compreso fra 1 e 8 durante il periodo ricovero. L’analisi statistica ha incluso il coefficiente di correlazione di Pearson, Spearman, l’analisi di concordanza di Lin e il Bland-Altman plot. Risultati: L'analisi ha evidenziato una forte correlazione tra il CTDIvol cumulativo e l'SSDE cumulativo, con un coefficiente di correlazione di Pearson pari a r = 0,982 e un Concordance Correlation Coefficient (CCC) di 0,949, dimostrando che entrambi i parametri rappresentano validi indicatori di dose complessiva nella coorte generale. Tuttavia, nei pazienti con valori estremi di WED, si è osservata una riduzione dell'accordo tra i due parametri. In particolare, considerando la coorte di pazienti con WED < 250 mm e WED > 350 mm, il CCC si riduce a 0,825. Inoltre, analizzando esclusivamente i pazienti con WED < 250 mm, il CCC si riduce ulteriormente a 0,526, suggerendo che il WED rappresenta un fattore determinante nell'influenzare l'accordo tra i due parametri. Questo risultato sottolinea come la variabilità del WED giochi un ruolo chiave nel determinare la precisione con cui il CTDIvol può stimare l'SSDE in sottogruppi di pazienti caratterizzati da dimensioni atipiche. Conclusioni: I risultati sottolineano l’importanza del WED e dell’SSDE nella personalizzazione delle dosi radiologiche, specialmente in pazienti sottoposti a TC multiple. Sebbene il CTDIvol rappresenti un parametro standard utile per il monitoraggio delle dosi, l’SSDE fornisce una stima più accurata e clinicamente rilevante, particolarmente nei pazienti con taglie atipiche. Questo studio sottolinea l’importanza di valutare la potenziale integrazione di SSDE nei processi di ottimizzazione basati sui LDR, soprattutto nei pazienti con valori di WED che si discostano significativamente dalla norma, migliorando la sicurezza dei pazienti e garantendo una maggiore qualità diagnostica.
Correlazione tra CT dose index volumetrico (CTDIvol) e CT dose index normalizzato per la taglia del paziente (size specific dose estimate - SSDE - ) nei pazienti della terapia intensiva sottoposti ad indagine TC con controllo automatico della esposizione durante il periodo di ricovero
NACUCCHI, SALVATORE
2023/2024
Abstract
Background: Computed tomography (CT) is an essential diagnostic tool, particularly for patients undergoing repeated procedures. Diagnostic Reference Levels (DRLs), introduced by the International Commission on Radiological Protection (ICRP), serve as reference values for monitoring radiation doses in radiological procedures. DRLs, based on parameters such as CTDIvol (Computed Tomography Dose Index volumetric) and DLP (Dose Length Product), do not represent absolute dose limits for individual patients but rather serve as benchmarks to assess the quality, efficacy, and safety of the administered dose during procedures. However, since these parameters are calculated using standard phantoms, they do not account for the specific anatomical characteristics of individual patients. To address this limitation, the Size-Specific Dose Estimate (SSDE) was introduced. SSDE incorporates the Water Equivalent Diameter (WED) to adjust the dose estimate to the patient's size and body composition, providing a more accurate, personalized, and safer assessment of the absorbed dose. Aim: The study aims to analyze the correlation between the dosimetric indices CTDIvol and SSDE in intensive care unit (ICU) patients undergoing CT examinations with automatic exposure control during their hospitalization. The role of WED (Water-Equivalent Diameter) and the number of CT scans performed were investigated to determine variations in the agreement between these parameters, highlighting the implications for optimal personalization of radiation dose. Materials and Methods: A total of 51 patients who underwent between 1 and 8 CT scans during their hospital stay were included. The cumulative CTDIvol was calculated as the sum of the CTDIvol values from all scans performed on each patient. This parameter measures the dose delivered per unit volume, providing a standardized estimate based on phantoms. Conversely, the cumulative SSDE was calculated by summing the SSDE values for each CT scan, taking into account the patient's specific size through the WED. Statistical analysis included Pearson and Spearman correlation coefficients, Lin’s concordance analysis, and the Bland-Altman plot. Results: The analysis revealed a strong correlation between cumulative CTDIvol and cumulative SSDE, with a Pearson correlation coefficient of r = 0.982 and a Concordance Correlation Coefficient (CCC) of 0.949, demonstrating that both parameters are valid indicators of overall dose in the general cohort. However, in patients with extreme WED values, a reduction in agreement between the two parameters was observed. Specifically, considering the cohort of patients with WED < 250 mm and WED > 350 mm, the CCC decreases to 0.825. Furthermore, when analyzing exclusively patients with WED < 250 mm, the CCC decreases further to 0.526, suggesting that WED is a determining factor influencing the agreement between the two parameters. This result highlights how WED variability plays a key role in determining the accuracy with which CTDIvol can estimate SSDE in subgroups characterized by atypical patient dimensions. Conclusions: The results emphasize the importance of WED and SSDE in personalizing radiological dose estimates, particularly for patients undergoing multiple CT scans. While CTDIvol serves as a useful standard parameter for dose monitoring, SSDE provides a more accurate and clinically relevant estimate, especially for patients with extreme body sizes. This study highlights the importance of assessing the potential integration of SSDE in optimization processes based on DRLs, especially for patients with WED values that deviate significantly from the norm, enhancing patient safety and ensuring higher diagnostic quality.File | Dimensione | Formato | |
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https://hdl.handle.net/20.500.12608/80414