Patient skin dose measurements using a cable free system MOSFETs based in fluoroscopically guided percutaneous vertebroplasty, percutaneous disc decompression, radiofrequency medial branch neurolysis, and endovascular critical limb ischemia

Comparison of operator and patient radiation exposure during fluoroscopy-guided vertebroplasty and kyphoplasty: a systematic review and meta-analysis

OBJECTIVE

Percutaneous vertebroplasty (PV) and balloon kyphoplasty (BK) are two minimally invasive techniques used to treat mechanical pain secondary to spinal compression fractures. A concern for both procedures is the radiation exposure incurred by both operators and patients. The authors conducted a systematic review of the available literature to examine differences in interventionalist radiation exposure between PV and BK and differences in patient radiation exposure between PV and BK.

METHODS

The authors conducted a search of the PubMed, Ovid Medline, Cochrane Reviews, Embase, and Web of Science databases according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. Full-text articles in English describing one of the primary endpoints in ≥ 5 unique patients treated with PV or BK of the mobile spine were included. Estimates of mean operative time, radiation exposure, and fluoroscopy duration were reported as weighted averages. Additionally, annual occupational dose limits provided by the United States Nuclear Regulatory Commission (USNRC) were used to determine the number needed to harm (NNH).

RESULTS

The meta-analysis included 27 articles. For PV, the mean fluoroscopy times were 4.9 ± 3.3 minutes per level without protective measures and 5.2 ± 3.4 minutes with protective measures. The mean operator radiation exposures per level in mrem were 4.6 ± 5.4 at the eye, 7.8 ± 8.7 at the neck, 22.7 ± 62.4 at the torso, and 49.2 ± 62.2 at the hand without protective equipment and 0.3 ± 0.1 at the torso and 95.5 ± 162.5 at the hand with protection. The mean fluoroscopy times per level for BK were 6.1 ± 2.5 minutes without protective measures and 6.0 ± 3.2 minutes with such measures. The mean exposures were 31.3 ± 39.3, 19.7 ± 4.6, 31.8 ± 34.2, and 174.4 ± 117.3 mrem at the eye, neck, torso, and hand, respectively, without protection, and 1, 9.2 ± 26.2, and 187.7 ± 100.4 mrem at the neck, torso, and hand, respectively, with protective equipment. For protected procedures, radiation to the hand was the limiting factor and the NNH estimates were 524 ± 891 and 266 ± 142 for PV and BK, respectively. Patient exposure as measured by flank-mounted dosimeters, entrance skin dose, and dose area product demonstrated lower exposure with PV than BK (p < 0.01).

CONCLUSIONS

Operator radiation exposure is significantly decreased by the use of protective equipment. Radiation exposure to both the operator and patient is lower for PV than BK. NNH estimates suggest that radiation to the hand limits the number of procedures an operator can safely perform. In particular, radiation to the hand limits PV to 524 and BK to 266 procedures per year before surpassing the threshold set by the USNRC.

Flexible film dosimeter for in vivo dosimetry

PURPOSE

The aims of this study were to develop a flexible film dosimeter applicable to the irregular surface of a patient for in vivo dosimetry and to evaluate the device's dosimetric characteristics.

METHODS

A flexible film dosimeter with active layers consisting of radiochromic-sensitive films and flexible silicone materials was constructed. The dose-response, sensitivity, scanning orientation dependence, energy dependence, and dose rate dependence of the flexible film dosimeter were tested. Irradiated dosimeters were scanned 24 h post-irradiation, and the region of interest was 5 mm × 5 mm. Biological stability tests ensured the safety of application of the flexible film dosimeter for patients. A preliminary clinical study with the flexible film dosimeter was implemented on four patients.

RESULTS

The red channel demonstrated the highest sensitivity among all channels, and the response sensitivity of the dosimeter decreased with the applied dose, which were the same as the characteristics of GAFCHROMIC EBT3 radiochromic films. The flexible film dosimeter showed no significant energy dependence for photon beams of 6 MV, 6 MV flattening filter-free (FFF), 10 MV, and 15 MV. The flexible film dosimeter showed no substantial dose rate dependence with 6 or 6 MV FFF. In terms of biological stability, the flexible film dosimeter demonstrated no cytotoxicity, no irritation, and no skin sensitization. In the preliminary clinical study, the dose differences between the measurements with the flexible film dosimeter and calculations with the treatment planning system ranged from -0.1% to 1.2% for all patients.

CONCLUSIONS

The dosimeter developed in this study is a flexible film capable of attachment to a curved skin surface. The biological test results indicate the stability of the flexible film dosimeter. The preliminary clinical study showed that the flexible film dosimeter can be successfully applied as an in vivo dosimeter.

Measurement of skin surface dose distributions in radiation therapy using poly(vinyl alcohol) cryogel dosimeters

In external beam radiation therapy (EBRT), skin dose measurement is important to evaluate dose coverage of superficial target volumes. Treatment planning systems (TPSs) are often inaccurate in this region of the patient, so in vivo measurements are necessary for skin surface dose estimation. In this work, superficial dose distributions were measured using radiochromic translucent poly(vinyl alcohol) cryogels. The cryogels simultaneously served as bolus material, providing the necessary buildup to achieve the desired superficial dose. The relationship between dose to the skin surface and dose measured with the bolus was established using a series of oblique irradiations with gantry angles ranging from 0° to 90°. EBT-2 Gafchromic film was placed under the bolus, and the ratio of bolus-film dose was determined ranging from 0.749 ± 0.005 to 0.930 ± 0.002 for 0° and 90° gantry angles, respectively. The average ratio over 0-67.5° (0.800 ± 0.064) was used as the single correction factor to convert dose in bolus to dose to the skin surface. The correction factor was applied to bolus measurements of skin dose from head and neck intensity-modulated radiation therapy (IMRT) treatments delivered to a RANDO phantom. The resulting dose distributions were compared to film measurements using gamma analysis with a 3%/3 mm tolerance and a 10% threshold. The minimum gamma pass rate was 95.2% suggesting that the radiochromic bolus may provide an accurate estimation of skin surface dose using a simple correction factor. This study demonstrates the suitability of radiochromic cryogels for superficial dose measurements in megavoltage photon beams.

Translucent poly(vinyl alcohol) cryogel dosimeters for simultaneous dose buildup and monitoring during chest wall radiation therapy

Chest wall radiation therapy treatment delivery was monitored using a 5 mm thick radiochromic poly(vinyl alcohol) cryogel that also provided buildup material. The cryogels were used to detect positioning errors and measure the impact of shifts for a chest wall treatment that was delivered to a RANDO phantom. The phantom was shifted by ± 2, ± 3, and ± 5 mm from the planned position in the anterior/posterior (A/P) direction; these shifts represent setup errors and the uncertainty associated with lung filling during breath-hold. The two-dimensional absolute dose distributions measured in the cryogel at the planned position were compared with the distributions at all shifts from this position using gamma analysis (3%/3 mm, 10% threshold). For shifts of ± 2, ± 3, and ± 5 mm the passing rates ranged from 94.3% to 95.6%, 74.0% to 78.8%, and 17.5% to 22.5%, respectively. These results are consistent with the same gamma analysis performed on dose planes calculated in the middle of the cryogel and on the phantom surface using our treatment plan-ning system, which ranged from 94.3% to 95.0%, 76.8% to 77.9%, and 23.5% to 24.3%, respectively. The Pinnacle dose planes were then scaled empirically and compared to the cryogel measurements. Using the same gamma metric, the pass rates ranged from 97.0% to 98.4%. The results of this study suggest that cryogels may be used as both a buildup material and to evaluate errors in chest wall treat-ment positioning during deep-inspiration breath-hold delivery. The cryogels are sensitive to A/P chest wall shifts of less than 3 mm, which potentially allows for the detection of clinically relevant errors.