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Published on: September 11, 2011
Analysis of limited-sequence head computed tomography for children with shunted hydrocephalus: potential to reduce
Jonathan Pindrik1, Thierry A G M Huisman, Mahadevappa Mahesh
1Department of Neurosurgery, Johns Hopkins University School of Medicine;
Insights
A new limited head CT sequence effectively diagnoses children with shunted hydrocephalus, significantly reducing radiation exposure. This method maintains diagnostic accuracy while prioritizing patient safety by lowering effective dose (ED).
Area of Science:
- Radiology
- Pediatric Neuroradiology
- Medical Imaging
Background:
- Head CT scans are crucial for diagnosing shunt-treated hydrocephalus in children.
- Children with shunted hydrocephalus face increased radiation risks due to immature tissues and frequent scanning.
- Existing dose reduction methods involve modifying CT scanner parameters.
Purpose of the Study:
- To evaluate a novel limited sequence of axial head CT slices for diagnosing children with shunted hydrocephalus.
- To assess the potential for significant radiation dose reduction using this limited sequence.
- To determine if the limited sequence maintains diagnostic adequacy and accuracy compared to standard head CT.
Main Methods:
- Retrospective review of 7-slice limited head CT sequences extracted from standard scans of 50 children with shunted hydrocephalus.
- Blind review by pediatric neuroradiologists and a neurosurgeon to assess ventricular system portrayal, size changes, and catheter visualization.
- Comparison of limited-sequence CT adequacy and accuracy against gold-standard full head CT series; effective dose (ED) comparison using descriptive statistics and Mann-Whitney test.
Main Results:
- The limited-sequence CT adequately visualized the ventricular system in all cases.
- Clinically relevant inaccuracy rate for assessing ventricular size changes was low (4%).
- High sensitivity (100%) and specificity (91%) for ventricular caliber changes; proximal catheter visualized in 91.7% of scans.
- Significant reduction in effective dose (ED): median ED50 of 0.284 mSv for limited-sequence vs. 4.27 mSv for standard head CT (91.8% mean reduction).
Conclusions:
- Limited-sequence head CT provides adequate and accurate diagnostic information for children with shunted hydrocephalus.
- Minimizing slice quantity and modifying CT parameters significantly reduces radiation dose.
- This approach balances diagnostic utility with enhanced patient safety.
Object:
Despite its diagnostic utility, head CT scanning imparts risks of radiation exposure. Children with shunt-treated hydrocephalus exhibit increased risks of radiation toxicity due to the higher vulnerability of developing, immature tissues and frequent scanning. Several methods have been used to achieve dose reduction, including modifications of CT scanner tube current and potential. This retrospective study explores the use of a newly defined limited sequence of axial head CT slices to evaluate children with shunted hydrocephalus and decrease radiation exposure from diagnostic CT scans.
Methods:
Consistent sequences of 7 axial slices were extracted from previously performed standard head CT scans in children with shunted hydrocephalus. Chronologically distinct limited sequences of each patient were blindly, retrospectively reviewed by 2 pediatric neuroradiologists and 1 pediatric neurosurgeon. Limited-sequence CT evaluation focused on the adequacy of portraying the ventricular system, changes in ventricular size, and visualization of the proximal catheter. Reviewers assessed all original full series head CT scans at least 4 months later for comparison. Adequacy and accuracy of the limited-sequence CT compared with the gold standard head CT was investigated using descriptive statistics. Effective dose (ED) estimates of the limited-sequence and standard head CT scans were compared using descriptive statistics and the Mann-Whitney test.
Results:
Two serial head CT scans from each of 50 patients (age range 0-17 years; mean age 5.5 years) were reviewed both in standard and limited-sequence forms. The limited-sequence CT adequately portrayed the ventricular system in all cases. The inaccuracy rate for assessing changes in ventricular size by majority assessment (2 of 3 reviewers evaluating inaccurately) was 3 (6%) of 50. In 1 case, the inaccurate assessment would not have altered clinical management, corresponding to a 2 (4%) of 50 clinically relevant inaccuracy rate. As compared with the gold standard complete head CT series, the limited-sequence CT exhibited high sensitivity (100%) and specificity (91%) for portraying changes in ventricular caliber. Additionally, the limited-sequence CT displayed the ventricular catheter in 91.7% of scans averaged across 3 observers. Among all scans reviewed, 97 pairs of standard head CT and complementary limited-sequence CT scans contained adequate dosing information to calculate the effective dose (ED). The ED50 of the limited-sequence CT (0.284 mSv) differed significantly from the ED50 of the standard head CT (4.27 mSv) (p < 0.0001). The limited-sequence CT reflected a median absolute reduction of 4.10 mSv and a mean percent reduction of 91.8% in ED compared with standard head CT.
Conclusions:
Limited-sequence head CT scanning provided adequate and accurate diagnostic information in children with shunted hydrocephalus. Techniques including minimization of axial slice quantity and modification of CT scanner parameters can achieve significant dose reduction, maintaining a balance between diagnostic utility and patient safety.
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