Patient-Specific Organ and Effective Dose Estimates in Adult Oncologic CT

Assessment of organ dose for adult undergoing CT examinations: Comparison of three software applications using Monte Carlo simulation

Understanding organ dose during CT scans is crucial due to cancer risks from low-level radiation exposure. This study aims to analyze and compare different methods for estimating CT organ doses in adult male and female patients, assessing the compatibility of NCICT with standard phantoms and NCICT with body size adjustment with GEANT4 simulations. It also evaluates the impact of different CT manufacturers on organ dose calculations. Previous research used various phantoms to represent organ doses across age groups. This study utilizes DICOM images from real adult patients undergoing CT scans to evaluate organ dose using the GEANT4 simulation toolkit. A retrospective analysis of 240 CT scans (head, chest, and abdomen-pelvis) compared GEANT4 dose estimates to the software tool NCICT. Data from Siemens and Philips CT scanners were included. Organ doses for 34 organs were calculated using Siemens patient DICOM data, while Philips estimates made using only NCICT with body size adjustment. Statistical analysis assessed differences in organ doses by gender and scanner type. Organ doses for the brain, spinal cord, and liver were higher in females (48.1, 4.9, and 6.7 mGy) compared to males (42.5, 4.4, and 6.3 mGy). NCICT with body size adjustment estimates were more consistent with GEANT4 (differences up to 18%) compared to NCICT with standard phantoms (differences up to 46%). Notable variations were found between Siemens and Philips scanners, despite identical detector rows. Accurate models and scanner-specific differences are critical for reliable radiation dose assessments, emphasizing the need for tailored dosimetry to enhance patient safety.

Representative Organ Doses from Computed Tomography (CT) Exams from a Large International Registry

Estimation of absorbed organ doses used in computed tomography (CT) using time-intensive Monte Carlo simulations with virtual patient anatomic models is not widely reported in the literature. Using the library of computational phantoms developed by the University of Florida and the National Cancer Institute, we performed Monte Carlo simulations to calculate organ dose values for 9 CT categories representing the most common body regions and indications for imaging (reflecting low, routine, and high radiation dose examinations), stratified by patient age (in children) and effective diameter (in adults, using "diameter" as a measure of patient size). Our sample of 559,202 adult and 103,423 pediatric CT examinations was prospectively assembled between 2015-2020 from 156 imaging facilities from 27 healthcare organizations in 20 U.S. states and 7 countries in the University of California San Francisco International CT Dose Registry. Organ doses varied by body region and exam type. For example, the mean brain dose associated with head CT was 20 mGy [standard deviation (SD) 14] for head low dose, 46 mGy (SD 21) for head routine dose, and 64 mGy (SD 31) for head high dose scan protocols. The mean colon doses associated with abdomen and pelvis CT were 19 mGy (SD 12), 32 mGy (SD 28), and 69 mGy (SD 42) for low, routine, and high dose examinations, respectively. Organ doses in general varied modestly by patient diameter, and for many categories the organ doses among the largest quartile of patients were no more than 10% higher than doses in the smallest quartile. For example, for abdomen and pelvis high dose, the colon dose increased from 67 to 74 mGy from the smallest to the largest patients (10% increase). With few exceptions, pediatric organ doses also varied relatively little by patient age, except for the youngest children who, on average, had higher organ doses. Thyroid dose, however, tended to increase with age in neck or cervical spine and chest CT. Overall, the highest organ doses were to the skin, thyroid, brain, and eye lens. Mean organ doses differ substantially by site. The organ dose values included in this report are derived from empirical clinical exams and offer useful, representative values. Large inter-site variations demonstrate areas for radiation dose reduction.

Improving outcomes in electromagnetic navigation bronchoscopy-guided transbronchial microwave ablation for pulmonary nodules: the role of cone-beam computed tomography

BACKGROUND

Studies have shown the potential of electromagnetic navigation bronchoscopy (ENB)-guided transbronchial microwave ablation (MWA) for treating pulmonary nodules. The role of cone-beam computed tomography (CBCT) in the procedure remains unknown.

OBJECTIVES

To investigate the efficacy and safety of employing CBCT during ENB-guided transbronchial MWA for pulmonary nodules.

DESIGN

Retrospective analysis of clinical records.

METHODS

Patients who underwent ENB-guided transbronchial MWA at the Department of Thoracic Surgery, Tongji Hospital. Patients were categorized into two groups: those who received CBCT during the procedure and those who did not. Technical and ablation success rates, complication rates, and patient characteristics were assessed.

RESULTS

A total of 283 patients with 371 nodules were included in the final analysis. The technical success rate was significantly higher in the CBCT group (97.0%) compared to the non-CBCT group (91.5%, p = 0.034). The overall ablation success rate was 88.1%, with the CBCT group demonstrating a higher rate (90.9% vs 81.5%, p = 0.018). Complication rates were similar between the two groups, with no significant differences.

CONCLUSION

The use of CBCT in ENB-guided transbronchial MWA significantly increases the technical and ablation success rates without raising complication rates. These findings underscore the potential advantages of CBCT in enhancing procedural outcomes for patients with pulmonary nodules. Further validation through larger, multi-center studies with longer follow-up is warranted.

The osteopontin expression and microvascular density in thyroid cancer, comparison of CT and ultrasound in diagnosis of thyroid cancer and correlations of CT features and thyroid cancer

BACKGROUND

The aim of this study was to explore the osteopontin expression and microvascular density in thyroid cancer, compare computed tomography (CT) and ultrasound in diagnosis of thyroid cancer and investigate the correlations of CT Features and thyroid cancer.

METHODS

A total of 80 patients with thyroid masses admitted to our hospital from April 2017 to August 2019 were selected, of which there were 40 with benign tumor and 40 with malignant tumor. All patients with thyroid cancer confirmed by pathological tissue biopsy were examined by ultrasound (ultrasound group) and CT (CT group). The expression of osteopontin was detected by PCR while microvascular density was tested by immunohistochemistry. Then univariate analysis and multivariate logistic regression analysis of risk factors were carried out for CT imaging diagnosis of thyroid cancer.

RESULTS

The levels of osteopontin and microvascular density in malignant group were significantly higher than those in benign group. The incidence rates of unclear boundary and peripheral lymph node enlargement in CT group were remarkably higher than those in ultrasound group. The diagnostic rate of masses ≥1 cm in diameter was notably higher than that of masses <1 cm in diameter in thyroid cancer patients in CT group and ultrasound group (P<0.05). In addition, the diagnostic rates of follicular carcinoma and papillary carcinoma were higher, whereas those of medullary carcinoma and undifferentiated carcinoma were lower in CT group and ultrasound group. There was no significant difference in the accuracy of thyroid cancer diagnosis between CT group and ultrasound group. Moreover, diameter ≥1 cm, irregular shape, unclear boundary, calcified foci, uneven density/echo and peripheral lymph node enlargement were related risk factors for the CT imaging diagnosis of thyroid cancer, in which irregular shape, unclear boundary, calcified foci and uneven density/echo were independent risk factors for the CT imaging diagnosis of thyroid cancer.

CONCLUSIONS

The levels of osteopontin and microvascular density were increased in thyroid cancer. CT examination may be of higher diagnostic value in diagnosis of thyroid cancer compared with ultrasound. Irregular shape, unclear boundary, calcified foci, and uneven density/echo were independent risk factors for the CT imaging diagnosis of thyroid cancer.

Assessment of organ and effective doses received by adult patients undergoing computed tomography in three hospitals in Brazzaville, Congo Republic

The present study aimed to evaluate adult patient data collected from three hospitals in Brazzaville, Congo Republic, for the purpose of estimating organ and effective doses for each included examination type. A total of 1277 adult patients (aged 16-97 years) who underwent head, chest, abdominopelvic (AP), chest-abdomen-pelvis (CAP), and lumbar spine computed tomography scans were considered. The organ and effective doses were estimated using a Monte Carlo-based method. The effective doses were also determined using k-factors. In general, the organ and effective doses estimated in this study were higher than those reported in the literature. The k-factor method underestimated the effective dose by up to 65.9%. This study demonstrates that urgent steps should be taken to reduce doses administered to patients to optimal levels. Such optimal levels may be achieved by adopting local diagnostic reference levels, together with the implementation of dose reduction strategies.

Dose quantities for measurement and comparison of doses to individual patients in computed tomography (CT)

The dose quantities displayed routinely on CT scanners, the volume averaged CT dose index (CTDI_vol) and dose length product, provide measures of doses calculated for standard phantoms. The American Association of Medical Physics has published conversion factors for the adjustment of CTDI_volto take account of variations in patient size, the results being termed size-specific dose estimate (SSDE). However, CTDI_voland SSDE, while useful in comparing and optimising doses from a set procedure, do not provide risk-related information that takes account of the organs and tissues irradiated and associated cancer risks. A derivative of effective dose that takes account of differences in body and organ sizes and masses, referred to here as size-specific effective dose (SED), can provide such information. Data on organ doses from NCICT software that is based on Monte Carlo simulations of CT scans for 193 adult phantoms have been used to compute values of SED for CT examinations of the trunk and results compared with corresponding values of SSDE. Relationships within ±8% were observed between SED and SSDE for scans extending over similar regions for phantoms with a wide range of sizes. Coefficients have been derived from fits of the data to estimate SED values from SSDEs for different regions of the body for scans of standard lengths based on patient height. A method developed to take account of differences in scan length gave SED results within ±5% of values calculated using the NCI phantom library. This approach could potentially be used to estimate SED from SSDE values, allowing their display at the time a CT scan is performed.

BENCHMARKING OF A NEW AUTOMATIC CT RADIATION DOSE CALCULATOR

Information on patient radiation dose is essential to meet the radiation protection regulations and the demands of dose optimization. Vendors have developed different tools for patient dose assessment for radiological purposes. In this study, estimated effective doses derived from a new image-based software tool (DoseWatch, GE Healthcare) was benchmarked against the corresponding doses from a dose calculator (CT-Expo, SASCRAD) and a conversion coefficient method. Dose data from 150 adult patients (66 male and 84 female), who underwent CT head, abdominopelvic or chest examinations, were retrospectively collected using DoseWatch. Effective dose estimated by DoseWatch was significantly lower than that of CT-Expo and DLP-E (k) (p ≤ 0.001). For the organ doses, DoseWatch resulted in lower dose than CT-Expo for all the organs with the exception of testis (p ≤ 001) and eye lenses (p ≤ 0.026).