Radiation exposures of cancer patients from medical X-rays: how relevant are they for individual patients and population exposure?

The role of pre-biopsy mpMRI in lymph node staging for prostate cancer

INTRODUCTION

Prostate cancer (PCa) staging is an integral part in the management of prostate cancer. The gold standard for diagnosing lymph node invasion is a surgical lymphadenectomy, with no superior imaging modality available at the clinician's disposal. Our aim in this study is to identify if a pre-biopsy multiparametric MRI (mpMRI) can provide enough information about pelvic lymph nodes in intermediate and high risk PCa patients, and whether it can substitute further cross sectional imaging (CSI) modalities of the abdomen and pelvis in these risk categories.

METHODS

Patients with intermediate and high risk prostate cancer were collected between January 2015 and June 2019, while excluding patients who did not undergo a pre-biopsy mpMRI or a CSI. Date regarding biopsy result, PSA, MRI results, CSI imaging results were collected. Using Statistical Package for the Social Sciences (SPSS) version 24.0, statistical analysis was conducted using the Cohen's Kappa agreement for comparison of mpMRI with CSI. McNemar's test and receiver operator curve (ROC) curve were used for comparison of sensitivity of both tests when comparing to the gold standard of lymphadenectomy.

RESULTS

A total of 143 patients fit the inclusion criteria. We further stratified our patients into according to PSA level and Gleason score. Overall, agreement between mpMRI and all CSI was 0.857. When stratifying patients based on Gleason score and PSA, the higher the grade or PSA, the higher agreement between mpMRI and CSI. The sensitivity of mpMRI (73.7%) is similar to CSI (68.4%). When comparing CSI sensitivity to that of mpMRI, no significant difference was present by utilizing the McNemar test and very similar receiver operating characteristic curve.

CONCLUSION

A pre-biopsy mpMRI can potentially substitute further cross sectional imaging in our cohort of patients. However, larger prospective studies are needed to confirm our findings.

[Frequency and doses of diagnostic and interventional X‑ray applications : Trends between 2007 and 2014]

BACKGROUND

In Germany, approximately 95% of man-made radiation exposure of the population results from diagnostic and interventional X‑ray procedures. Thus, radiation protection of patients in this field of application is of great importance.

OBJECTIVE

Quantification and evaluation of current data on the frequency and doses of X‑ray procedures as well as temporal trends for the years 2007-2014.

MATERIAL AND METHODS

For outpatients the frequency of X‑ray procedures was estimated using reimbursement data from health insurances and for inpatients by means of hospital statistics. For the years under review, representative values for the effective dose per X‑ray application were determined mainly from data reported by X‑ray departments to the competent authorities.

RESULTS

In 2014 approximately 140 million X‑ray procedures were performed in Germany with some 40% from dental examinations. On average 1.7 procedures per inhabitant and year were almost constantly carried out between 2007 and 2014. Besides dental diagnostics, X‑ray examinations of the skeleton and thorax were performed most frequently. The number of computed tomography (CT) examinations increased by approximately 40%. The increase in magnetic resonance imaging (MRI) was even more pronounced with approximately 55% but overall CT examinations were still performed more often than MRI. The doses per X‑ray procedure were only slightly reduced, despite the various dose reduction approaches established in recent years; therefore, the mean effective dose per inhabitant increased from approximately 1.4 mSv in 2007 to 1.6 mSv in 2014, mainly due to the increasing frequency of CT examinations.

CONCLUSION

The principles of justification and optimization of radiological procedures are to be consistently applied in each individual instance, especially in the case of CT examinations.

Unindicated multiphase CT scans in non-traumatic abdominal emergencies for women of reproductive age: a significant source of unnecessary exposure

PURPOSE

To determine the frequency of unindicated CT phases and the resultant excess of absorbed radiation doses to the uterus and ovaries in women of reproductive age who have undergone CT for non-traumatic abdomino-pelvic emergencies.

MATERIALS AND METHODS

We reviewed all abdomino-pelvic CT examinations in women of reproductive age (40 years or less), between 1 June 2012 and 31 January 2015. We evaluated the appropriateness of each CT phase on the basis of clinical indications, according to ACR appropriateness criteria and evidence-based data from the literature. The doses to uterus and ovaries for each phase were calculated with the CTEXPO software, taking into consideration the size-specific dose estimate (SSDE) after measuring the size of every single patient.

RESULTS

The final cohort was composed of 76 female patients with an average age of 30 (from 19 to 40 years). In total, 197 CT phases were performed with an average of 2.6 phases per patient. Out of these, 93 (47%) were unindicated with an average of 1.2 inappropriate phases per patient. Unindicated scans were most frequent for appendicitis and unlocalized abdominal pain. The excesses of mean radiation doses to the uterus and ovaries due to unindicated phases were, respectively, of 38 and 33 mSv per patient.

CONCLUSION

In our experience, unindicated additional CT phases were numerous with a significant excess radiation dose without an associated clinical benefit. This excess of radiation could have been avoided by widespread adoption of the ACR appropriateness criteria and evidence-based data from the literature.

X-ray irradiation has positive effects for the recovery of peripheral nerve injury maybe through the vascular smooth muscle contraction signaling pathway

INTRODUCTION

It is well known that moderate to high doses of ionizing radiation have a toxic effect on the organism. However, there are few experimental studies on the mechanisms of LDR ionizing radiation on nerve regeneration after peripheral nerve injury.

METHODS

We established the rats' peripheral nerve injury model via repaired Peripheral nerve injury nerve, vascular endothelial growth factor a and Growth associated protein-43 were detected from different treatment groups. We performed transcriptome sequencing focusing on investigating the differentially expressed genes and gene functions between the control group and 1Gy group. Sequencing was done by using high-throughput RNA-sequencing (RNA-seq) technologies.

RESULTS

The results showed the 1Gy group to be the most effective promoting repair. RNA-sequencing identified 619 differently expressed genes between control and treated groups. A Gene Ontology analysis of the differentially expressed genes revealed enrichment in the functional pathways. Among them, candidate genes associated with nerve repair were identified.

DISCUSSION

Pathways involved in cell-substrate adhesion, vascular smooth muscle contraction and cell adhesion molecule signaling may be involved in recovery from peripheral nerve injury.

Vessel Visibility Assessment of Low Tube Voltage Coronary Computed Tomography Angiography Determined with Contrast-to-Noise Ratio

PURPOSE

The purpose of this study was to investigate the association of vessel visibility and radiation dose using contrast-to-noise ratio (CNR) method with low tube voltage in coronary computed tomography angiography (c-CTA).

METHODS

We performed electrocardiogram-gated scan of 2.0-mm diameter simulated vessel in the center of the cardiac phantom by the use of a 64-detector CT scanner. Reference CNR was calculated from the target coronary CT number (CT_numberA; 350 Hounsfield units [HU]), epicardial fat CT number (CT_numberB; -100 HU), and target epicardial fat standard deviation (SD) number (SD_B; 25 HU) at the 120 kV. We obtained the tube current at low tube voltage (100 and 80 kV) to perform the similar reference CNR at 120 kV. The full widths at half maximum from axial images were evaluated with quantitative evaluation and three types of visualizations of the vessel phantom were evaluated with the qualitative evaluations.

RESULTS

CT_numberA of 100 and 80 kV were increased by 26% and 50%, respectively, compared with 120 kV (P<0.01). SD_B was also increased by a similar ratio (P<0.01). CTDI_vol of 100 and 80 kV were decreased by 39% and 51%, respectively, compared with 120 kV (P<0.05). There were no significant voltage differences among three tubes in quantitative and qualitative evaluations at the same CNR (P> 0.05).

CONCLUSION

In this phantom study, these results show that the CNR method with low tube voltage achieves radiation dose reduction without decreasing the image quality.

Temporal trends in the use of diagnostic imaging for inpatients with pancreatic conditions: How much ionizing radiation are we using?

BACKGROUND

Low-dose ionizing radiation from medical imaging has been indirectly linked with subsequent cancer and increased costs. Computed tomography (CT) is the gold standard for defining pancreatic anatomy and complications. Our primary goal was to identify the temporal trends associated with diagnostic imaging for inpatients with pancreatic diseases.

METHODS

Data were extracted from the Healthcare Cost and Utilization Project Nationwide Inpatient Sample (NIS) database from 2000 to 2008. Pancreas-related ICD-9 diagnostic codes were matched to all relevant imaging modalities.

RESULTS

Between 2000 and 2008, a significant increase in admissions (p < 0.001), but decrease in overall imaging procedures (p = 0.032), for all pancreatic disorders was observed. This was primarily a result of a reduction in the number of CT and endoscopic retrograde cholangiopancreatography examinations (i.e., reduced radiation exposure, p = 0.008). A concurrent increase in the number of inpatient magnetic resonance cholangiopancreatography/magnetic resonance imaging performed was observed (p = 0.040). Intraoperative cholangiography and CT remained the dominant imaging modality of choice overall (p = 0.027).

CONCLUSION

Inpatients with pancreatic diseases often require diagnostic imaging during their stay. This results in substantial exposure to ionizing radiation. The observed decrease in the use of CT may reflect an improved awareness of potential stochastic risks.

Common-mask guided image reconstruction (c-MGIR) for enhanced 4D cone-beam computed tomography

Compared to 3D cone beam computed tomography (3D CBCT), the image quality of commercially available four-dimensional (4D) CBCT is severely impaired due to the insufficient amount of projection data available for each phase. Since the traditional Feldkamp-Davis-Kress (FDK)-based algorithm is infeasible for reconstructing high quality 4D CBCT images with limited projections, investigators had developed several compress-sensing (CS) based algorithms to improve image quality. The aim of this study is to develop a novel algorithm which can provide better image quality than the FDK and other CS based algorithms with limited projections. We named this algorithm 'the common mask guided image reconstruction' (c-MGIR).In c-MGIR, the unknown CBCT volume is mathematically modeled as a combination of phase-specific motion vectors and phase-independent static vectors. The common-mask matrix, which is the key concept behind the c-MGIR algorithm, separates the common static part across all phase images from the possible moving part in each phase image. The moving part and the static part of the volumes were then alternatively updated by solving two sub-minimization problems iteratively. As the novel mathematical transformation allows the static volume and moving volumes to be updated (during each iteration) with global projections and 'well' solved static volume respectively, the algorithm was able to reduce the noise and under-sampling artifact (an issue faced by other algorithms) to the maximum extent. To evaluate the performance of our proposed c-MGIR, we utilized imaging data from both numerical phantoms and a lung cancer patient. The qualities of the images reconstructed with c-MGIR were compared with (1) standard FDK algorithm, (2) conventional total variation (CTV) based algorithm, (3) prior image constrained compressed sensing (PICCS) algorithm, and (4) motion-map constrained image reconstruction (MCIR) algorithm, respectively. To improve the efficiency of the algorithm, the code was implemented with a graphic processing unit for parallel processing purposes.Root mean square error (RMSE) between the ground truth and reconstructed volumes of the numerical phantom were in the descending order of FDK, CTV, PICCS, MCIR, and c-MGIR for all phases. Specifically, the means and the standard deviations of the RMSE of FDK, CTV, PICCS, MCIR and c-MGIR for all phases were 42.64  ±  6.5%, 3.63  ±  0.83%, 1.31%  ±  0.09%, 0.86%  ±  0.11% and 0.52 %  ±  0.02%, respectively. The image quality of the patient case also indicated the superiority of c-MGIR compared to other algorithms.The results indicated that clinically viable 4D CBCT images can be reconstructed while requiring no more projection data than a typical clinical 3D CBCT scan. This makes c-MGIR a potential online reconstruction algorithm for 4D CBCT, which can provide much better image quality than other available algorithms, while requiring less dose and potentially less scanning time.

Towards the clinical implementation of iterative low-dose cone-beam CT reconstruction in image-guided radiation therapy: cone/ring artifact correction and multiple GPU implementation

PURPOSE

Compressed sensing (CS)-based iterative reconstruction (IR) techniques are able to reconstruct cone-beam CT (CBCT) images from undersampled noisy data, allowing for imaging dose reduction. However, there are a few practical concerns preventing the clinical implementation of these techniques. On the image quality side, data truncation along the superior-inferior direction under the cone-beam geometry produces severe cone artifacts in the reconstructed images. Ring artifacts are also seen in the half-fan scan mode. On the reconstruction efficiency side, the long computation time hinders clinical use in image-guided radiation therapy (IGRT).

METHODS

Image quality improvement methods are proposed to mitigate the cone and ring image artifacts in IR. The basic idea is to use weighting factors in the IR data fidelity term to improve projection data consistency with the reconstructed volume. In order to improve the computational efficiency, a multiple graphics processing units (GPUs)-based CS-IR system was developed. The parallelization scheme, detailed analyses of computation time at each step, their relationship with image resolution, and the acceleration factors were studied. The whole system was evaluated in various phantom and patient cases.

RESULTS

Ring artifacts can be mitigated by properly designing a weighting factor as a function of the spatial location on the detector. As for the cone artifact, without applying a correction method, it contaminated 13 out of 80 slices in a head-neck case (full-fan). Contamination was even more severe in a pelvis case under half-fan mode, where 36 out of 80 slices were affected, leading to poorer soft tissue delineation and reduced superior-inferior coverage. The proposed method effectively corrects those contaminated slices with mean intensity differences compared to FDK results decreasing from ∼497 and ∼293 HU to ∼39 and ∼27 HU for the full-fan and half-fan cases, respectively. In terms of efficiency boost, an overall 3.1 × speedup factor has been achieved with four GPU cards compared to a single GPU-based reconstruction. The total computation time is ∼30 s for typical clinical cases.

CONCLUSIONS

The authors have developed a low-dose CBCT IR system for IGRT. By incorporating data consistency-based weighting factors in the IR model, cone/ring artifacts can be mitigated. A boost in computational efficiency is achieved by multi-GPU implementation.

The impact of an acute care surgery clinical care pathway for suspected appendicitis on the use of CT in the emergency department

BACKGROUND

The natural evolution of an acute care surgery (ACS) service is to develop disease-specific care pathways aimed at quality improvement. Our primary goal was to evaluate the implementation of an ACS pathway dedicated to suspected appendicitis on patient flow and the use of computed tomography (CT) in the emergency department (ED).

METHODS

All adults within a large health care system (3 hospitals) with suspected appendicitis were analyzed during our study period, which included 3 time periods: pre- and postimplementation of the disease-specific pathway and at 12-month follow-up.

RESULTS

Of the 1168 consultations for appendicitis that took place during our study period, 349 occurred preimplementation, 392 occurred postimplementation, and 427 were follow-up visits. In all, 877 (75%) patients were admitted to the ACS service. Overall, 83% of patients underwent surgery within 6 hours. The mean wait time from CT request to obtaining the CT scan decreased with pathway implementation at all sites (197 v. 143 min, p < 0.001). This improvement was sustained at 12-month followup (131 min, p < 0.001). The pathway increased the number of CTs completed in under 2 hours from 3% to 42% (p < 0.001). No decrease in the total number of CTs or the pattern of ultrasonography was noted (p = 0.42). Wait times from ED triage to surgery were shortened (665 min preimplementation, 633 min postimplementation, 631 min at the 12-month follow-up, p = 0.040).

CONCLUSION

A clinical care pathway dedicated to suspected appendicitis can decrease times to both CT scan and surgical intervention.

Current knowledge on tumour induction by computed tomography should be carefully used

Risks associated to ionising radiation from medical imaging techniques have focused the attention of the medical society and general population. This risk is aimed to determine the probability that a tumour is induced as a result of a computed tomography (CT) examination since it makes nowadays the biggest contribution to the collective dose. Several models of cancer induction have been reported in the literature, with diametrically different implications. This article reviews those models, focusing on the ones used by the scientific community to estimate CT detriments. Current estimates of the probability that a CT examination induces cancer are reported, highlighting its low magnitude (near the background level) and large sources of uncertainty. From this objective review, it is concluded that epidemiological data with more accurate dosimetric estimates are needed. Prediction of the number of tumours that will be induced in population exposed to ionising radiation should be avoided or, if given, it should be accompanied by a realistic evaluation of its uncertainty and of the advantages of CTs. Otherwise they may have a negative impact in both the medical community and the patients. Reducing doses even more is not justified if that compromises clinical image quality in a necessary investigation. Key Points • Predictions of radiation-induced cancer should be discussed alongside benefits of imaging. • Estimates of induced cancers have noticeable uncertainties that should always be highlighted. • There is controversy about the acceptance of the linear no-threshold model. • Estimated extra risks of cancer are close to the background level. • Patients should not be alarmed by potential cancer induction by CT examinations.

Influence of age, sex and calendar year on lifetime accumulated red bone marrow dose from diagnostic radiation exposure

Our aim is to evaluate the relevance of different factors influencing lifetime accumulated red bone marrow dose, such as calendar year, age and sex. The lifetime dose was estimated for controls interviewed in person (N = 2811, 37.5% women) of the population-based representative Northern Germany Leukemia and Lymphoma Study. Data were assessed in standardized computer-assisted personal interviews. The calculation of doses is based on a comprehensive quantification model including calendar year, sex, kind of examination, and technical development. In multivariate regression models the annual red bone marrow dose was analyzed depending on age, sex and calendar year to consider simultaneously temporal changes in radiologic practice and individual risk factors. While the number of examinations continuously rises over time, the dose shows two peaks around 1950 and after 1980. Men are exposed to higher doses than woman. Until 1970 traditional examinations like conventional and mass screening examinations caused the main dose. They were then replaced by technically advanced examinations mainly computed tomography and cardiac catheter. The distribution of the red bone marrow dose over lifetime depends highly on the technical standards and radiation protection survey. To a lesser extent it is influenced by age and sex of the subjects. Thus epidemiological studies concerning the assessment of radiation exposure should consider the calendar year in which the examination was conducted.

Low-dose ionising radiation from medical imaging in patients hospitalised in Internal Medicine

BACKGROUND

Medical imaging is responsible for increasing exposure to low-dose ionising radiation in the general population. The extent of exposure in specific patient populations remains to be determined.

AIM

We sought to determine the level of exposure in patients hospitalised in General Internal Medicine.

METHODS

In this retrospective cohort study, we searched the Centre Informatisé de Recherche Évaluative en Services et Soins de Santé database for adult patients hospitalised in General Internal Medicine from 1 January 2008 to 31 December 2008. We collected data on demographics, co-morbidities, and radiological and nuclear imaging. We used data from the literature to calculate an estimated annual effective dose for each patient and searched for factors associated with higher exposure.

RESULTS

One thousand one hundred eighty-seven (1187) patients were hospitalised at least once during the study period. The median age was 69 years (interquartile range 56-81) and 636 (53.6%) were men. The median annual effective dose of the whole cohort was 8.7 mSv/year. Patients aged between 55 and 80 years were exposed to a higher median effective dose compared with their younger and older counterparts (P < 0.001). Patients with cardiac, pulmonary, peripheral arterial and neoplastic disease were at higher risk of exposure to high and very high annual effective dose (P < 0.01). Patients with longer hospitalisations were at higher risk of exposure to high and very high annual effective dose (P < 0.01).

CONCLUSION

Patients hospitalised on a General Internal Medicine ward are exposed to three times more ionising radiation than the general population.

Ionizing radiation in abdominal CT: unindicated multiphase scans are an important source of medically unnecessary exposure

PURPOSE

CT radiation exposure has come under increasing scrutiny because of dramatically increased utilization. Multiphase CT studies (repeated scanning before and after contrast injection) are a potentially important, overlooked source of medically unnecessary radiation because of the dose-multiplier effect of extra phases. The purpose of this study was to determine the frequency of unindicated multiphase scanning and resultant excess radiation exposure in a sample referral population.

METHODS

Abdominal and pelvic CT examinations (n = 500) performed at outside institutions submitted for tertiary interpretation were retrospectively reviewed for (1) the appropriateness of each phase on the basis of clinical indication and ACR Appropriateness Criteria(®) and (2) per phase and total radiation effective dose.

RESULTS

A total of 978 phases were performed in 500 patients; 52.8% (264 of 500) received phases that were not supported by ACR criteria. Overall, 35.8% of phases (350 of 978) were unindicated, most commonly being delayed imaging (272 of 350). The mean overall total radiation effective dose per patient was 25.8 mSv (95% confidence interval, 24.2-27.5 mSv). The mean effective dose for unindicated phases was 13.1 mSv (95% confidence interval, 12.3-14.0 mSv), resulting in a mean excess effective dose of 16.8 mSv (95% confidence interval, 15.5-18.3 mSv) per patient. Unindicated radiation constituted 33.3% of the total radiation effective dose in this population. Radiation effective doses exceeding 50 mSv were found in 21.2% of patients (106 of 500).

CONCLUSIONS

The results of this study suggest that a large proportion of patients undergoing abdominal and pelvic CT scanning receive unindicated additional phases that add substantial excess radiation dose with no associated clinical benefit.

[Radiation hygiene in medical X-ray imaging. Part 3: radiation exposure of patients and risk assessment]

The frequency of X-ray examinations in Germany and the resulting radiation exposure is amongst the highest in comparison with other European countries. To reduce medical radiation exposure and to safeguard radiation protection regulations, the X-ray ordinance stipulates a justification of each individual X-ray application. The justification principle means that the X-ray application should produce sufficient health benefit to offset the radiation risk. Such a benefit-risk assessment needs an adequate estimation of radiation risk. The aim of this paper is to explain the principles of benefit-risk assessment for different situations (e.g. healthcare and screening). The basics and concepts of radiation effects and radiation epidemiology as well as examples of risk estimation and benefit-risk assessments are given.

Radiation exposure from CT examinations in Japan

Background

Computed tomography (CT) is the largest source of medical radiation exposure to the general population, and is considered a potential source of increased cancer risk. The aim of this study was to assess the current situation of CT use in Japan, and to investigate variations in radiation exposure in CT studies among institutions and scanners.

Methods

Data-sheets were sent to all 126 hospitals and randomly selected 14 (15%) of 94 clinics in Gunma prefecture which had CT scanner(s). Data for patients undergoing CT during a single month (June 2008) were obtained, along with CT scan protocols for each institution surveyed. Age and sex specific patterns of CT examination, the variation in radiation exposure from CT examinations, and factors which were responsible for the variation in radiation exposure were determined.

Results

An estimated 235.4 patients per 1,000 population undergo CT examinations each year, and 50% of the patients were scanned in two or more anatomical locations in one CT session. There was a large variation in effective dose among hospitals surveyed, particularly in lower abdominal CT (range, 2.6-19.0 mSv). CT examinations of the chest and upper abdomen contributed to approximately 73.2% of the collective dose from all CT examinations. It was estimated that in Japan, approximately 29.9 million patients undergo CT annually, and the estimated annual collective effective dose in Japan was 277.4 *10³ Sv person. The annual effective dose per capita for Japan was estimated to be 2.20 mSv.

Conclusions

There was a very large variation in radiation exposure from CT among institutions surveyed. CT examinations of the chest and upper abdomen were the predominant contributors to the collective dose.

Radiation dose from computed tomography in patients with necrotizing pancreatitis: how much is too much?

OBJECTIVES

Low-dose ionizing radiation from medical imaging has been indirectly linked with subsequent cancer. Computed tomography (CT) is the gold standard for defining pancreatic necrosis. The primary goal was to identify the frequency and effective radiation dose of CT imaging for patients with necrotizing pancreatitis.

METHODS

All patients with necrotizing pancreatitis (2003-2007) were retrospectively analyzed for CT-related radiation exposure.

RESULTS

Necrosis was identified in 18% (238/1290) of patients with acute pancreatitis (mean age = 53 years; hospital/ICU length of stay = 23/7 days; mortality = 9%). A median of five CTs/patient [interquartile range (IQR) = 4] were performed during a median 2.6-month interval. The average effective dose was 40 mSv per patient (equivalent to 2,000 chest X-rays; 13.2 years of background radiation; one out of 250 increased risk of fatal cancer). The actual effective dose was 63 mSv considering various scanner technologies. CTs were infrequently (20%) followed by direct intervention (199 interventional radiology, 118 operative, 12 endoscopic) (median = 1; IQR = 2). Magnetic resonance imaging did not have a CT-sparing effect. Mean direct hospital costs increased linearly with CT number (R = 0.7).

CONCLUSIONS

The effective radiation dose received by patients with necrotizing pancreatitis is significant. Management changes infrequently follow CT imaging. The ubiquitous use of CT in necrotizing pancreatitis raises substantial public health concerns and mandates a careful reassessment of its utility.