Radiation Dose Reduction in Scoliosis Patients: Low-Dose Full-Spine Radiography with Digital Flat Panel Detector and Image Stitching System

Reduction of radiation exposure in scoliosis monitoring using flat detector and pulsed fluoroscopy technology

A new flat detector and pulsed fluoroscopy technology is available to further reduce radiation exposure in radiological monitoring during scoliosis treatment in children and adolescents. The aim of this study is to compare different settings of the system (opening area(OA) and image quality settings (IQS)) in order to find the optimal parameters with high image quality and the lowest possible radiation exposure. Therefore, we examined four cadaver spines (T1 to sacrum) with the flat detector technique using digital pulsed fluoroscopy and simulated the abdominal soft tissues. The images were merged and evaluated by three different investigators using an established scoring system. For comparison, we used digital radiography images of the cadaver spines. The values for the DAP increased from the small OA (33% ; 0.56 µGy·m²) to the maximum OA (100% ; 0.82 µGy·m²) by 45% (p = .003) and from the low image quality setting (0.57 µGy·m²) to the high setting (0.84 µGy·m²) by 48% (p = .028). Despite the low DAP, the setting 33% OA achieved the best point values for image quality, therefore this setting is clearly preferred. Using a digital fluoroscopy system allows a significant reduction of radiation exposure by a factor of 7.5 (3.88µGy·m² to 0.5µGy·m²) compared to slot- scanning x-ray (EOS). Due to this success, the flat detector and pulsed fluoroscopy technology can be an alternative to established methods such as X-ray and EOS in clinical use.

Case of the Missing Vertebra: A Report of a Radiographic Stitching Error in a Scoliosis Patient

CASE

A 14-year-old girl with adolescent idiopathic scoliosis underwent imaging in preparation for scoliosis surgery. Posteroanterior traction radiographs showed 4 lumbar vertebrae, while the standing film showed 5. Reconciliation with the component radiographs used for the traction showed the discrepancy was caused by a software error. She underwent surgical correction, and her recovery has been uncomplicated.

CONCLUSION

Image stitching errors can lead to false depiction of structural abnormalities. Radiology technicians and clinicians should be cautious when reviewing digitally stitched images. We recommend that technicians label stitched images and indicate the overlapping region to assist with radiographic assessment.

A phantom study on dose efficiency for orthopedic applications: Comparing slot-scanning radiography using ultra-small-angle tomosynthesis to conventional radiography

PURPOSE

This paper studies the abilities of a twin-robotic x-ray slot-scanning system for orthopedic imaging to reduce dose by scatter rejection compared to conventional digital radiography.

METHODS

We investigate the dose saving capabilities, especially in terms of the signal- and the contrast-to-noise ratio, as well as the scatter-to-primary ratio of the proposed slot-scanning method in comparison to the state-of-the-art method for length-extended imaging. As a baseline, we use x-ray parameters of two clinically established acquisition protocols that provide the same detector entrance dose but are profoundly different in patient dose. To obtain an estimate of the photon-related noise directly from an x-ray image, we implement a Poisson-Gaussian noise model. This model is used to compare the dose efficiency of two settings and combined with the well-known K SNR to determine the transmission parameters. We present a method with an associated measurement protocol, utilizing the robotic capabilities of the used system to automatically obtain quasi-scatter-free ground-truth data with exact geometric correspondence to full-field and slot acquisitions. In total, we investigate two body regions (thoracic spine and lumbar spine) in anterior-posterior view with two patient sizes (BMI = 22 and 30) in two acquisition modes (conventional and slot scan with a flat-panel detector) with and without anti-scatter grid using an anthropomorphic upper-body phantom.

RESULTS

We have shown that it is feasible to combine the proposed approach with the K SNR for the determination of scatter rejection parameters. The use of an anti-scatter grid is indicated for full-field acquisitions allowing for dose savings up to 46% compared to their gridless counterparts. When changing the acquisition mode to the investigated slot scan, the use of an anti-scatter grid has no major impact on the image quality in terms of dose efficiency, in particular for patients with a BMI of 22. However, an increased contrast improvement factor was found. For normal-sized patients, up to 53% of dose can be saved additionally in comparison to full-field acquisitions with grid. Moreover, we could demonstrate that a slot size of 5 cm and air gap of 10 cm is sufficient to achieve scatter-to-primary ratios, which are equal or better compared to those of the full-field acquisitions with a grid.

CONCLUSIONS

We have shown, that the slot-scanning approach is always superior to the conventional full-field acquisition in terms of signal-to-noise and scatter-to-primary ratios. Compared to the state-of-the-art acquisition protocols with a grid, dose savings up to 53% are possible due to the scatter rejection without compromising the SNR. Hence, the use of the slot-scanning method is indicated, especially when it comes to regularly carried-out follow-up acquisitions, for example, in the case of scoliosis monitoring.

Radiographic Resource Utilization in the Initial Referral and Evaluation of Patients With Adolescent Idiopathic Scoliosis

INTRODUCTION

The dangers of radiation exposure in children have been well studied, with assessment of adolescent idiopathic scoliosis (AIS) documented as having the potential for notable patient exposure. The purposes of this study were to evaluate a consecutive series of patients referred to a tertiary care pediatric hospital for AIS and to assess the type and quality of imaging obtained before referral for specialist evaluation.

METHODS

We performed a prospective study of consecutive patients referred over a 6-month period to a pediatric orthopaedic practice at a large, free-standing, urban children's hospital for evaluation of AIS. We assessed prereferral radiographic exposure, evaluating the utilization and adequacy of these radiographs.

RESULTS

Of a total of 131 patients enrolled in the study, 79 had received radiographs before the visit; of these, only 59 patients (75%) brought the previously obtained radiographs to the specialist consultation, and 45 patients (76%) of this subset were found to be adequate for evaluation of AIS. Of the total cohort, 56 patients (43%) required repeat radiographs because of missing or inadequate radiographs.

DISCUSSION

We found a large number of missing or inadequate radiographs, leading to repeat radiation exposure in this cohort. Improvements in the utilization of radiographs before orthopaedic referral could decrease unnecessary patient radiation exposure.

Radiation dose reduction in plain radiography of the full-length lower extremity and full spine

OBJECTIVE

To compare the diagnostic performance of standard- and low-dose radiographs of the full-length lower extremity and spine.

METHODS

This study included 223 patients who visited our hospital and received full-length lower extremity standing radiographs and full-spine radiographs. We determined the dose area product (DAP) of each image, and effective doses (ED, mSv) were calculated based on the DAP. Subjective evaluation of the full-length radiographs was based on image quality, which was assessed by bony cortex and trabecula evaluation, and on diagnostic performance, which was assessed by leg length measurement. Subjective evaluation of the full-spine radiographs was based on image quality, which was assessed by viewing the vertebral endplate, pedicle and lateral border of vertebral body, and on diagnostic performance from measurement of Cobb's angle.

RESULTS

For the full-length view and the full-spine view both the mean DAP and ED values of the standard-dose group were significantly higher than those of the low-dose group (p < 0.05). Mean scores for subjective values did not significantly differ based on the radiation dosage (p-values, 0.15-0.99). The subjective value scores for the full-length view were 2.94-2.98 in the standard-dose group and 2.91-3.00 in the low-dose group. Of note, both groups had very high scores. Additionally, the diagnostic performance scores between the two groups were also very high (range from 2.92 to 3.00).

CONCLUSION

Reducing mAs by 50% of the standard dose does not affect the radiograph image quality or its clinical validity. Advances in knowledge: Radiation dose reduction (50% of the standard dose of mAs) in plain radiography of the full-length lower extremity and full spine do not affect the clinical validity and the image quality.

Radiography of scoliosis: Comparative dose levels and image quality between a dynamic flat-panel detector and a slot-scanning device (EOS system)

PURPOSE

To compare radiation dose and image quality between a slot-scanning system (SSS) and a dynamic flat-panel detector (DFD) in assessing scoliosis in children.

METHODS

An experimental study was first performed with a phantom to assess the quality of each device. The clinical part included a prospective observational dosimetric and qualitative comparative study with acquisition of whole-spine X-ray: SSS (31 children), DFD (26 children). Institutional review board approval and informed consent were obtained. Dosimetric statistical analysis was performed from dose area product (DAP) and entrance skin dose measured by thermo-luminescent dosimeters localized in the cervical, thoracic and sacral areas. Assessment of the diagnostic quality (phantom and clinical) was realized by independent evaluation by 3 observers, using statistical analysis of quality score and inter-observer reproducibility.

RESULTS

DAP was equivalent with the 2 systems. Entrance skin dose was significantly higher with DFD in thoracic and pelvic regions (P<0.05). Image quality scores of the SSS were significantly better than DFD for a majority of criteria, in both phantom and clinical evaluations.

CONCLUSION

For scoliosis evaluation, the SSS, compared to the DFD system, offers enhanced image quality while reducing the entrance skin dose in the most radiosensitive areas.

Radiation exposure during scoliosis surgery: a prospective study

BACKGROUND CONTEXT

The present literature on the cancer risks related to radiation exposure in patients and surgeons during scoliosis surgery is sparse.

PURPOSE

To assess the radiation exposure in patients and surgeons during scoliosis surgery and estimate the increased cancer risk of both groups.

STUDY DESIGN

Over a 6-month period, we conducted a prospective study to monitor the intraoperative radiation dose received by both patients and surgeons during scoliosis cases.

PATIENT SAMPLE

It included 30 consecutive patients undergoing scoliosis surgery by a team of two surgeons (S1 and S2).

OUTCOME MEASURES

We measured the radiation exposure to the eyes, thyroid, and hands for each surgeon; measured the difference of radiation exposure between the two surgeons; the difference in radiation exposure with respect to the proximity of the surgeon to the X-ray tube, and the radiation exposure for each patient.

METHODS

An electronic dosimeter was attached over the thyroid guard and a thermoluminescent dosimeter ring on both hands of each surgeon. The patients were monitored using the dose area product (DAP) measurements from the image intensifier, and their radiation exposure was calculated with the Monte Carlo calculation.

RESULTS

The mean eye dose per procedure for the two surgeons S1 and S2 was 0.8 μSv and 1.3 μSv, respectively. The mean thyroid dose for S2 and S1 was 1.2 μSv and 1.4 μSv, respectively. The dose recorded by the surgeon on the same side of the patient as the X-ray tube was significantly higher than for the surgeon on the far side (p<.05). Mean DAP per procedure was 91.3 cGycm(2) and the mean radiation dose for patients was 252.9 μSv. The increase in cancer risk for patients and surgeons was 0.001% and 0.0005%, respectively, for each year of exposure.

CONCLUSIONS

A significantly higher dose of radiation during scoliosis surgery was received by the surgeon standing on the same side as the X-ray tube. However, both surgeons received a total radiation dose of less than 1% of the recommended dose limit per year and, therefore, the total radiation exposure in both surgeons and patients was well within the recommended safe limits.

Quality-controlled dose reduction of full-leg radiography in patients with knee malalignment

OBJECTIVE

Digital plain radiographs of the full leg are frequently performed examinations of children and young adults. Thus, the objective of this work was to reduce the radiation exposure dependent on specific indications, and to determine objective quality-control criteria to ensure accurate assessment.

MATERIALS AND METHODS

Institutional review board approval and informed consent of all participants were obtained. In this prospective, randomized controlled, blinded, two-armed single-center study, 288 evaluable patients underwent plain radiography of the full leg with standard and reduced doses. The evaluation of the plain radiographs was conducted using the following criteria: mechanical axis, leg length, and maturation of the epiphyseal plate. Two blinded radiologists evaluated these criteria using a score ranging from 1 (definitely assessable) to 4 (not assessable). If a single criterion had been evaluated with a score of 3 or more points or all criteria with 2 points, the radiograph was scored as "not assessable". The study was designed as a non-inferiority trial.

RESULTS

Eleven (3.8%) examined X-rays were scored as not assessable. The rate of non-assessable radiographs with 33% reduced dose was significantly not inferior to the rate of non-assessable radiographs with standard dose. The evaluation of the quality criteria was dose independent.

CONCLUSIONS

Full-leg plain radiography in patients with knee malalignment can be performed at 33% reduced dose without loss of relevant diagnostic information.

Are routine postoperative radiographs necessary during the first year after posterior spinal fusion for idiopathic scoliosis? A retrospective cohort analysis of implant failure and surgery revision rates

BACKGROUND

Radiographs are routinely obtained at postoperative visits during the first year after posterior spinal fusion (PSF) for idiopathic scoliosis (IS). The goal of this study was to determine how often radiographic findings change postoperative care.

METHODS

A total of 227 consecutive patients aged 10 to 21 years who underwent surgery for IS at our institution from 2004 to 2010 were identified. Charts were reviewed to determine the frequency of the following clinical symptoms during the first year after surgery: pain greater than expected, implant prominence, and sensory/motor disturbance. Radiographs were reviewed to identify implant failure and curve change. Logistic regression analysis was used to identify clinical symptoms associated with treatment deviation.

RESULTS

During the first year after surgery, an average of 6 (range, 2 to 12) radiographs were obtained from patients during an average of 3 (range, 2 to 10) follow-up visits. Pain (14%) was the most common symptom. Neurologic symptoms (13%) and implant prominence (4%) were less common. Implant failure was identified in 4 subjects (2%), of which 3 required revision surgery. The incidence of revision surgery was 2.9/1000 radiographs (95% confidence interval, 0.6-8.3). Curve progression >5 degrees in the uninstrumented curve occurred in 2 patients (0.9%). Curve progression did not result in a change in treatment for any of the patients. Pain was the only clinical symptom associated with implant failure (P=0.0047). 169/227 patients did not have any symptoms and only one of these underwent revision surgery. The sensitivity of a clinical test, which uses the presence of pain to guide the need for radiographic evaluation and rule out implant failure, was 75%, specificity 87%, positive predictive value 10%, and negative predictive value 99.5%.

CONCLUSIONS

After obtaining baseline postoperative radiographs, additional radiographs during the first year after surgery for IS may not be required in the absence of clinical symptoms. Reducing the number of radiographs taken during the first year after surgery for IS in patients without symptoms can reduce radiation exposure to patients and health care costs without affecting treatment.

LEVEL OF EVIDENCE

Level II, Diagnostic Study.