Image Gently: toward optimizing the practice of pediatric CT through resources and dialogue

Radiation dose in cardiac CT for preoperative diagnosis of children with congenital heart disease

Background

One of the most common congenital conditions detected globally, congenital heart diseases, and CT techniques provide a high-quality and thorough presentation of heart anatomy, thoracic vasculature, and extracardiac structures, and hence, it is becoming a more popular non-invasive diagnostic imaging method for congenital heart disease. The drawbacks with CT imaging are the radiation exposure from repeated scans is also rising, especially in young patients. The present study is aimed to evaluate the radiation dose in gated and non-gated cardiac CT for preoperative diagnosis of pediatric patients with congenital heart diseases.

Results

A total of 111 pediatric patients with mean age of 7.47 years were prospectively included in the study. The mean value of “Effective dose (E)” for gated CT at $$100\;{\text{kV}}_{{\text{p}}}$$ 100 kV p was found to be $$4.71\;{\text{mSv}}$$ 4.71 mSv which is higher than mean “E” of $$3.95\;{\text{mSv}}$$ 3.95 mSv observed for gated CT at $$80\;{\text{kV}}_{{\text{p}}}$$ 80 kV p . The average value of “E” for non-gated technique was observed less than that of gated technique at both $$100\;{\text{kV}}_{{\text{p}}}$$ 100 kV p and $$80\;{\text{kV}}_{{\text{p}}}$$ 80 kV p . The multiple regression analysis shows that “E” is significantly dependent on $${\text{DLP}}\left( {{\text{mGy}}\;{\text{cm}}} \right)$$ DLP mGy cm for both gated and non-gated techniques at 95% level of significance $$\left( {p < 0.05} \right)$$ p < 0.05 . The Student’s t-test verifies that the mean value of “E” for both the techniques at $$100\;{\text{kV}}_{{\text{p}}}$$ 100 kV p and $$80\;{\text{kV}}_{{\text{p}}}$$ 80 kV p are significantly different at 95% level of significance $$\left( {p < 0.05} \right)$$ p < 0.05 .

Conclusions

The effective dose received by pediatric patients is much higher when using ECG-gated acquisition with an average value of $$4.71\;{\text{mSv}}$$ 4.71 mSv and $$3.95\;{\text{mSv}}$$ 3.95 mSv at $$100\;{\text{kV}}_{{\text{p}}}$$ 100 kV p , and at $$80\;{\text{kV}}_{{\text{p}}}$$ 80 kV p respectively. Because low-voltage X-rays are more sensitive to high atomic number iodinated contrast media, the mean “E” for non-gated cardiac CT imaging at $$80\;{\text{kV}}_{{\text{p}}}$$ 80 kV p   is $$2.26\;{\text{mSv}}$$ 2.26 mSv , and results in significant reduction of effective dose.

Comparison of the different imaging modalities used to image pediatric oncology patients: A COG diagnostic imaging committee/SPR oncology committee white paper

Diagnostic imaging is essential in the diagnosis and management, including surveillance, of known or suspected cancer in children. The independent and combined roles of the various modalities, consisting of radiography, fluoroscopy, ultrasonography (US), computed tomography (CT), magnetic resonance imaging (MRI), and nuclear medicine (NM), are both prescribed through protocols but also function in caring for complications that may occur during or subsequent to treatment such as infection, bleeding, or organ compromise. Use of a specific imaging modality may be based on situational circumstances such as a brain CT or MR for a new onset seizure, chest CT for respiratory signs or symptoms, or US for gross hematuria. However, in many situations, there are competing choices that do not easily lend themselves to a formulaic approach as options; these situations depend on the contributions of a variety of factors based on a combination of the clinical scenario and the strengths and limitations of the imaging modalities. Therefore, an improved understanding of the potential influence of the imaging decision pathways in pediatric cancer care can come from comparison among the individual diagnostic imaging modalities. The purpose of the following material to is to provide such a comparison. To do this, pediatric imaging content experts for the individual modalities of radiography and fluoroscopy, US, CT, MRI, and NM will discuss the individual modality strengths and limitations.

Zero TE MRI for Craniofacial Bone Imaging

Zero TE MR imaging is a novel technique that achieves a near-zero time interval between radiofrequency excitation and data acquisition, enabling visualization of short-T2 materials such as cortical bone. Zero TE offers a promising radiation-free alternative to CT with rapid, high-resolution, silent, and artifact-resistant imaging, as well as the potential for "pseudoCT" reconstructions. In this report, we will discuss our preliminary experience with zero TE, including technical principles and a clinical case series demonstrating emerging applications in neuroradiology.

Radiation Exposure Associated With Computed Tomography in Childhood and the Subsequent Risk of Cancer: A Meta-Analysis of Cohort Studies

Background:

Computed tomography (CT) is used worldwide; however, recent studies suggest that CT radiation exposure during childhood may be a risk factor for cancer, although the data are inconsistent.

Methods:

A comprehensive search of electronic databases including PubMed, SpringerLink, Embase, Cochrane Library, Elsevier/ScienceDirect, Medline, Orbis, and Web of Science databases from January 1990 to November 2018 for observational epidemiologic studies reporting associations between radiation exposure from CT in childhood and the subsequent risk of cancer was conducted. A linear model was used to explore the dose–response relationship.

Results:

Seven studies with 1180 987 children enrolled were included. The risk of later cancer was 1.32-fold higher for children exposed to CT than those without exposure. Compared to those not exposed to pediatric CT, the relative risk (RRs) were larger for the higher doses but with wider CIs (RR for 5-10 mGy: 0.90, 95% CI: 0.69-1.12; RR for 10-15 mGy: 1.02, 95% CI: 0.86-1.18; RR for >15 mGy: 1.13, 95% CI: 0.97-1.30), the leukemia risk was higher in exposed children (RR: 1.23, 95% CI: 1.10-1.36), and brain cancer risk was higher in exposed children (RR: 1.54, 95% CI: 0.84-2.45).

Conclusions:

Our analysis suggested that radiation exposure from CT during childhood is associated with a subsequently elevated risk of cancer. However, caution is needed when interpreting these results because of the heterogeneity among the studies. The findings should be confirmed in further studies with longer follow-up periods.

Necessity of Intracranial Imaging in Infants and Children With Macrocephaly

BACKGROUND

Macrocephaly is frequently encountered in pediatrics and often leads to imaging. There are no recommendations from the American Academy of Pediatrics or the American College of Radiology providing imaging guidelines for macrocephaly. The goal of this study is to identify risk factors for pathologic macrocephaly and to aid the clinician in identifying patients that would benefit from imaging.

METHODS

We conducted a medical record review throughout a multistate health care system, Sanford Health, from January 1, 2012 to December 31, 2016. Patients with macrocephaly were identified by problem list in children aged less than 36 months. Data collection included basic demographics, imaging modality, developmental delay, prematurity, seizures, focal neurological symptoms, family history of macrocephaly, sedation used, and sedation complications.

RESULTS

A total of 169 patients were included in the analysis. Imaging modalities included 39 magnetic resonance imagings (23.1%), 47 cranial computed tomographies (27.8%), and 83 head ultrasounds (49.1%). Imaging results demonstrated 13 abnormal studies with five of those studies being abnormal with high clinical yield. Patients with abnormal studies were more likely to have developmental delay (P = 0.04) or neurological symptoms (P = 0.015). Positive family history of macrocephaly was predictive of normal imaging (P = 0.004). There were no sedation complications.

CONCLUSIONS

Intracranial imaging does not appear to be necessary in children with no risk factors and or a positive family history of macrocephaly. Risk factors such as developmental delay or neurological symptoms could identify children at risk for imaging abnormalities that require further management.

Dose Optimization to Minimize Radiation Risk for Children Undergoing CT and Nuclear Medicine Imaging Is Misguided and Detrimental

A debate exists within the medical community on whether the linear no-threshold model of ionizing radiation exposure accurately predicts the subsequent incidence of radiogenic cancer. In this article, we evaluate evidence refuting the linear no-threshold model and corollary efforts to reduce radiation exposure from CT and nuclear medicine imaging in accord with the as-low-as-reasonably-achievable principle, particularly for children. Further, we review studies demonstrating that children are not, in fact, more radiosensitive than adults in the radiologic imaging dose range, rendering dose reduction for children unjustifiable and counterproductive. Efforts to minimize nonexistent risks are futile and a major source of persistent radiophobia. Radiophobia is detrimental to patients and parents, induces stress, and leads to suboptimal image quality and avoidance of imaging, thus increasing misdiagnoses and consequent harm while offering no compensating benefits.

Consistent low-contrast detectability for variable patient sizes and corresponding dose in abdominal CT

PURPOSE

For CT dose optimization, one needs to address two important questions. The first is how various lesion-specific detection tasks demand different patient doses for the same patient. The second is how the variation of the patient size requires different patient doses for the same lesion detection task. In this study, we attempted to find quantitative solutions to these questions by utilizing a wide range of abdomen phantoms.

METHODS

A simplified model with a monochromatic fan beam passing through a bowtie-filter and an elliptical object was proposed. The model relates the minimum detectable contrast (MDC) to the size-specific dose by power index of -1/2 and to the lesion size by power index of -1 with a patient size dependence function (PSDF) as the proportionality factor. The experimental validation was performed using seven abdomen phantoms (lateral ranges: 10 cm-39 cm) scanned with helical modes at various dose levels on two 64-slice scanners (Siemens mCT and GE HD 750). Noise images were obtained using subtractions among adjacent slices in the images reconstructed with filtered backprojection. It was verified that the mean pixel value distributions from various small regions (1.8 mm-10 mm) are Gaussian, thus the concept of the statistically defined minimum detectable contrast (SD-MDC), defined as distribution's standard deviation multiplied by 3.29, can be applied. The impact of the helical pitch and the high-definition (HD) acquisition was also studied.

RESULTS

The experimental data from all phantoms were found to fit the power law well (R²  ≥ 0.983). The PSDF was found to be scanner dependent - modeled with a Gaussian amplifier (R²  = 0.983) for one manufacturer and with an exponential function for the other (R²  = 0.990). The MDC relationship was not found to be impacted by different pitches or by HD acquisition. The results were used to find the size-specific doses and corresponding acquisition techniques required by consistent low-contrast detectability for variable patient sizes. Visual comparisons on the low-contrast insert images demonstrated that the derived techniques delivered consistent low-contrast detectability.

CONCLUSIONS

We have modeled and verified the relationship of the minimum detectable contrast to the patient size, the patient dose, and the lesion size from the images reconstructed with filtered backprojection. The findings can be useful for task-specific dose modulation on abdomen CT studies.

Don't forget the dose: Improving computed tomography dosing for pediatric appendicitis

BACKGROUND

A pediatric computed tomography (CT) radiation dose reduction program was implemented throughout our children's associated hospital system in 2010. We hypothesized that the CT dose received for evaluation of appendicitis in children would be significantly higher among the 40 referral, nonmember hospitals (NMH) than the 9 member hospitals (MH).

METHODS

Preoperative CTs of pediatric (<18years) appendectomy patients between April 2012 and April 2015 were reviewed. Size specific dose estimate (SSDE), an approximation of absorbed dose incorporating patient diameter, and Effective Dose (ED) were calculated for each scan.

RESULTS

1128 (65%) of 1736 appendectomy patients underwent preoperative CT. 936 patients seen at and 102 children evaluated at NMH had dosing and patient diameter data for analysis. SSDE and ED were significantly higher with greater variance at NMH across all ages (all p<0.05, Figure). NMH's SSDE and ED also exceeded reference levels.

CONCLUSION

Radiation exposure in CT scans for evaluation of pediatric appendicitis is significantly higher and more variable in NMH. A proactive approach to reduce dose, in addition to frequency, of CT scans in pediatric patients is essential.

LEVEL OF EVIDENCE

Level III.

Subjecting Radiologic Imaging to the Linear No-Threshold Hypothesis: A Non Sequitur of Non-Trivial Proportion

Radiologic imaging is claimed to carry an iatrogenic risk of cancer, based on an uninformed commitment to the 70-y-old linear no-threshold hypothesis (LNTH). Credible evidence of imaging-related low-dose (<100 mGy) carcinogenic risk is nonexistent; it is a hypothetical risk derived from the demonstrably false LNTH. On the contrary, low-dose radiation does not cause, but more likely helps prevent, cancer. The LNTH and its offspring, ALARA (as low as reasonably achievable), are fatally flawed, focusing only on molecular damage while ignoring protective, organismal biologic responses. Although some grant the absence of low-dose harm, they nevertheless advocate the "prudence" of dose optimization (i.e., using ALARA doses); but this is a radiophobia-centered, not scientific, approach. Medical imaging studies achieve a diagnostic purpose and should be governed by the highest science-based principles and policies. The LNTH is an invalidated hypothesis, and its use, in the form of ALARA dosing, is responsible for misguided concerns promoting radiophobia, leading to actual risks far greater than the hypothetical carcinogenic risk purportedly avoided. Further, the myriad benefits of imaging are ignored. The present work calls for ending the radiophobia caused by those asserting the need for dose optimization in imaging: the low-dose radiation of medical imaging has no documented pathway to harm, whereas the LNTH and ALARA most assuredly do.

Relationship between paediatric CT scans and subsequent risk of leukaemia and brain tumours: assessment of the impact of underlying conditions

BACKGROUND

We previously reported evidence of a dose-response relationship between ionising-radiation exposure from paediatric computed tomography (CT) scans and the risk of leukaemia and brain tumours in a large UK cohort. Underlying unreported conditions could have introduced bias into these findings.

METHODS

We collected and reviewed additional clinical information from radiology information systems (RIS) databases, underlying cause of death and pathology reports. We conducted sensitivity analyses excluding participants with cancer-predisposing conditions or previous unreported cancers and compared the dose-response analyses with our original results.

RESULTS

We obtained information from the RIS and death certificates for about 40% of the cohort (n∼180 000) and found cancer-predisposing conditions in 4 out of 74 leukaemia/myelodysplastic syndrome (MDS) cases and 13 out of 135 brain tumour cases. As these conditions were unrelated to CT exposure, exclusion of these participants did not alter the dose-response relationships. We found evidence of previous unreported cancers in 2 leukaemia/MDS cases, 7 brain tumour cases and 232 in non-cases. These previous cancers were related to increased number of CTs. Exclusion of these cancers reduced the excess relative risk per mGy by 15% from 0.036 to 0.033 for leukaemia/MDS (P-trend=0.02) and by 30% from 0.023 to 0.016 (P-trend<0.0001) for brain tumours. When we included pathology reports we had additional clinical information for 90% of the cases. Additional exclusions from these reports further reduced the risk estimates, but this sensitivity analysis may have underestimated risks as reports were only available for cases.

CONCLUSIONS

Although there was evidence of some bias in our original risk estimates, re-analysis of the cohort with additional clinical data still showed an increased cancer risk after low-dose radiation exposure from CT scans in young patients.