Ann Surg Oncol DOI 10.1245/s10434-014-3822-3

ORIGINAL ARTICLE – ENDOCRINE TUMORS

Surgeon and Staff Radiation Exposure During Radioguided Parathyroidectomy at a High-Volume Institution Sarah C. Oltmann, MD1, Andrew V. Brekke1, Jose D. Macatangay, MS2, David F. Schneider, MD, MS1, Herbert Chen, MD1, and Rebecca S. Sippel, MD1 Section on Endocrine Surgery, Department of Surgery, University of Wisconsin, Madison, WI ; 2Department of Safety, University of Wisconsin Hospital and Clinics, Madison, WI

1

ABSTRACT Introduction. Radioguided parathyroidectomy (RGP) uses technetium-99 m sestamibi causing gamma ray emission during RGP to aid dissection and confirm parathyroid excision. Source (the patient) proximity and exposure duration determine degree of exposure. The purpose of this study was to quantify surgeon and staff radiation exposure during RGP. Methods. Surgeons and assistants wore radiation dosimeters during RGP procedures at a high-volume endocrine surgery practice. Area dosimeters measured personnel potential exposure. Data were prospectively collected. Provider exposures were corrected for both duration of exposure and case volume. Institutional safety requirements uses 100 mrem/year as an indicator for radiation safety training, 500 mrem/year for personal monitoring, and a maximum allowed exposure of 4,500 mrem/year. Results. A total of 120 RGP were performed over 6 months. Badges were worn in 82 cases (68 %). Three faculty and four assistants were included. Primary hyperparathyroidism was the diagnosis for 95 %. Median case volume per provider was 13 cases (range 6–45), with median exposure of 18 h (range 9–70). Mean provider deep dose exposure (DDE) was 22 ± 10 mrem. Corrected for exposure duration, mean DDE was 0.6 ± 0.2 mrem/h. Corrected for case volume, mean DDE was 0.8 ± 0.2 mrem/case. Anesthesia exposure was minimal, while mayo

Poster Presentation at Society of Surgical Oncology, Phoenix, AZ, March 12-15, 2014. Ó Society of Surgical Oncology 2014 First Received: 12 May 2014 S. C. Oltmann, MD e-mail: [email protected]

stand exposure was half to two thirds that of the surgeon and assistant. Based on institutional guidelines and above data, 125 RGP/year warrants safety training, 625 RGP/year warrants monitoring, whereas [5,600 RGP/year may result in maximum allowed radiation exposure to the surgeon. Conclusions. Surgeon and staff radiation exposure during RGP is minimal. However, high-volume centers warrant safety training. Primary hyperparathyroidism is a common endocrine disorder resulting in hypercalcemia, as well as a wide range of symptomatology.1 Surgical excision of the offending gland(s) remains the only curative option. Because roughly 80 % of patients will have single gland disease, surgical practice has moved towards a targeted dissection.2 Multiple tools aid the surgeon in gland localization. These tools include preoperative imaging modalities, intraoperative parathyroid hormone (ioPTH) monitoring, and injection of Technetium-99 m (Tc-99 m) Sestamibi with detection of gamma ray emission.3,4 The later, referred to as radioguided parathyroidectomy (RGP), relies on the mitochondrial uptake of Tc-99 m within the parathyroid gland, similar to its use during preoperative imaging.5 The gamma probe then detects emitted gamma rays during surgery to guide dissection and provides immediate confirmation that the resected tissue is parathyroid in origin.6 This avoids waiting for frozen-section analysis if there is uncertainty regarding the etiology of the excised tissue. RPG is routinely used in 11 % of the current North American endocrine surgery fellowship programs.2 Although RPB is not common practice for endocrine surgeons, the vast majority of parathyroid surgery is performed by low-volume surgeons across the country, many of which have adopted this technique.7,8 Radiation sources in various formats have existed in both the operating room and other intervention based areas for decades. Fluoroscopy is an integral component of

S. C. Oltmann et al.

numerous urologic, orthopedic, neurosurgical, vascular, cardiology, gastroenterology, interventional radiology, and even general surgery procedures.9–15 Safety practices based off the ‘‘As Low As Reasonably Achievable (ALARA)’’ principle are well known and understood regarding the use of radiation.16 In addition, equipment geared to protect providers is readily accessible in the form of lead aprons, skirts, glasses, and movable barriers. While these physician-controlled radiation sources are now commonly recognized and protected against, less attention or thought is paid to another radiation source: the patient.5,17 Techniques of using radiolabeled tracers and/or materials for intraoperative identification of target tissues are critical to sentinel node biopsies for breast cancer and malignant melanoma, and seed localization during lumpectomy.18–20 Due to concern regarding radiation exposure to the operative treatment team during these procedures, extensive study measured exposures to the extremities, eyes, and whole body during these procedures to be minimal.21,22 While some data exist regarding surgeon and staffing exposures during RGP, they are sparse.23,24 Significant extrapolation was used to calculate levels during prolonged and/or multiple exposures, as well as potential exposure to the remaining operating room staff and anesthesia providers. As RGP requires familiarity with the technique from both a surgeon and a systems standpoint, the routine practice of this methodology optimizes its usefulness. This raises the question of surgeon and staffing safety in a high-volume center. The purpose of this study was to quantify radiation exposure prospectively to the operative surgeon and operating room staff during RGP. METHODS This prospective study was approved by the institutional review board at a high-volume endocrine surgery practice. All parathyroid procedures within the study institution are performed as RGP with the use of ioPTH monitoring. Patients exempt from this technique are either pregnant or with Tc-99 m dose limitations.5 Patients are intravenously injected with 10 mCi of Tc-99 m sestamibi roughly 90 min before surgery.5 At the time of operation, an 11-mm collimated gamma probe (Neoprobe 2000; Ethicon EndoSurgery Breast-Care, Cincinnati, OH) is used to detect emitted radiation. Measurements of in vivo background (over the thyroid isthmus) versus ex vivo specimen formulate a ratio to indicate if resected tissue is parathyroid tissue.25,26 Ratios [20 % of background is confirmatory of resected parathyroid tissue.6 No specific radiation precautions are taken during the course of RPGs. Surgeons (faculty, fellows, and residents) wore dosimetry badges utilizing optical stimulated luminescence (Luxel ? , Landauer, Inc, Glenwood, IL) clipped to their

A

B

FIG. 1 Location of area monitors during radioguided parathyroidectomy. Hexagon represents where the radiation monitor was placed on the anesthesia machine (a) and on the mayo stand (b) during course of the study. On the mayo stand, monitors were placed in a similar fashion on each side of the stand. In this image, only the monitor on the patient’s left can be seen. The monitor on the patient’s right is in a similar location on the opposite side of the mayo stand

left chest scrub pocket on consecutive RGPs. The faculty surgeon stood opposite the targeted parathyroid gland(s), and in cases of bilateral exploration, the faculty and trainee switched sides as needed. Area dosimeters were placed along the mayo stand under the sterile drape and on the anesthesia machine to estimate relative radiation exposures to scrubbed operating room personnel and anesthesia providers during RPG (Fig. 1). The mayo stand monitors captured potential exposure to the scrub tech and medical student. They stand adjacent to, and further down, the patient’s torso compared to the surgeon and assistant. Because consistent operating room staff and anesthesia team were not available, area dosimeters were used in place of personal monitors. This allowed for cumulative exposure measurements through the duration of the procedure, which would not be influenced by breaks or shift changes. All badges were assessed on a monthly basis with

Exposure During Radioguided Parathyroidectomy

reports generated per badge, providing the lens dose exposure (LDE), shallow dose exposure (SDE), and deep dose exposure (DDE) in mrem. A control monitor was kept in the storage location to account for background exposures. A prospective record was maintained regarding provider and/or area monitor duration of exposure. Additional patient demographics, time of injection, injection dose, and procedure details were collected. Total duration of exposure was calculated per provider or monitor, as were the total number of cases. For the area monitors, time of exposure represents the total time the patient was within the operating room suite. For provider measurements, time of exposure represents the total time the provider was in the operating room with the patient. It is not indicative of actual operative duration, as surgeons were involved in preinduction safety checks, patient positioning, and performed an ultrasound for confirmation of gland localization. Institutional safety requirements are based on the U.S. Nuclear Regulatory Commission regulations and the Wisconsin Department of Health Services regulations regarding standards for protection against radiation.16,27 Individuals anticipated to have a minimum deep-dose exposure of 100 mrem per year are required to undergo radiation safety training, whereas an exposure of 500 mrem per year warrants provider radiation exposure monitoring. A total of 375 mrem per month (4,500 mrem per year) is noted to be the maximum allowed deep-dose exposure within the institution, in efforts to avoid the regulation limits set by the federal and state government of 5,000 mrem per year.16,27 Maximum allowable annual exposures to the eyes (lens) and extremities are 15,000 and 50,000 mrem respectively. IBM SPSS Statistics v. 21(Armonk, NY) was used to calculate descriptive statistics. Data are expressed as mean ± standard error of the mean, or median (minimum to maximum) as appropriate. RESULTS Between November 2012 and April 2013, a total of 120 RGP were performed. Badges and monitors were in place for 82 cases (68 %). Mean patient age was 60 ± 1.3 years, and 76 % were female. Patient body mass index was 29.9 ± 0.8 kg/m2. Most cases were for a diagnosis of primary hyperparathyroidism (n = 78, 95 %), with few for secondary (n = 1, 1 %) or tertiary (n = 3, 4 %) hyperparathyroidism. Patients were given 10.8 ± 0.2 mCi of Tc-99 m 115 ± 16 min before surgery. A directed, unilateral surgical approach was performed for 52 cases (63 %), whereas 30 (37 %) required bilateral exploration.

TABLE 1 Mean radiation exposures reported as per hour of exposure and as per case exposed. Because only one location for the anesthesia monitor was used throughout the study, reported number represents the data from the single location Provider or area

Exposure (mrem) per hour

Exposure (mrem) per case

Surgeon Deep dose equivalent

0.60 ± 0.17

0.80 ± 0.24

Lens dose equivalent

0.60 ± 0.17

0.80 ± 0.24

Surface dose equivalent

0.66 ± 0.17

0.88 ± 0.24

Anesthesia area monitor Deep dose equivalent

0.08

0.11

Lens dose equivalent

0.09

0.13

Surface dose equivalent

0.1

0.15

Deep dose equivalent Lens dose equivalent

0.29 ± 0.08 0.31 ± 0.09

0.46 ± 0.12 0.48 ± 0.14

Surface dose equivalent

0.33 ± 0.1

0.51 ± 0.15

Mayo stand area monitor

Three faculty endocrine surgeons, one endocrine surgery fellow, and three general surgery residents participated. Median case volume per provider was 13 procedures and ranged from 6 to 45 cases. This equated to median exposure duration of 18 h, ranging from 9 to 70 h. Total provider exposure levels were calculated as a sum of all exposures. To account for the variation in exposure duration for each provider, total exposure levels were divided by total duration of provider exposure in hours (Table 1). This resulted in a mean DDE of 0.6 ± 0.2 mrem, LDE of 0.6 ± 0.2 mrem, and SDE of 0.7 ± 0.2 mrem for every hour the provider was exposed. Exposure per case was calculated in a similar fashion, with a mean DDE of 0.8 ± 0.2 mrem, LDE of 0.8 ± 0.2 mrem, and SDE of 0.9 ± 0.2 mrem per RGP case. Corrected exposures between trainees and faculty were equivalent. Anesthesia and mayo area exposures were collected (Table 1). Data provided by these monitors represented a total of 50 cases or 74 ± 4 h of total operating room time. Anesthesia exposures per hour of patient contact was DDE 0.08 mrem, LDE 0.09 mrem, and SDE 0.1 mrem, and when corrected per case, were a DDE of 0.11 mrem, LDE 0.13 mrem, and a SDE of 0.15 mrem. Mayo stand monitors were averaged together (right and left). Mayo stand levels measured per hour of exposure had a DDE of 0.29 ± 0.08 mrem, LDE 0.31 ± 0.09 mrem, and SDE of 0.33 ± 0.1 mrem. When adjusted on a per case basis, the DDE was 0.46 ± 0.12 mrem, LDE 0.48 ± 0.14 mrem, and SDE 0.51 ± 0.15 mrem. The control badge repeatedly returned with undetected levels of exposure.

S. C. Oltmann et al. TABLE 2 Calculated number of cases required to reach radiation exposure thresholds to warrant safety training and monitoring, as well as to reach maximum allowed exposure per institutional safety regulations. Institutional safety regulations developed based off U.S. Nuclear Regulatory Commission regulations, as well as the Wisconsin Department of Health Services regulations 16,27 Provider/area

Number of cases to reach safety training threshold (100 mrem)

Number of cases to reach monitoring threshold (500 mrem)

Number of cases to reach annual maximum deep dose exposure (4,500 mrem)

Surgeon/trainee

125

625

5,625

Anesthesia

217

4,545

9,783

Scrub nurse/medical student

909

1 087

40,909

Based on these mean exposures per case, a surgeon performing more than 125 RGPs a year would likely reach the institutional threshold exposure of 100 mrem a year to warrant safety training, whereas 625 RGPs would require radiation exposure monitoring (Table 2). The scrubbed operating room nurse would meet threshold exposure for safety training after 215 RGPs and require monitoring after over a thousand cases. An anesthesia provider would meet the training threshold exposure after 900 RGPs and require monitoring after 4,500 RGPs. To reach the maximum allowed annual whole body exposure of 4,500 mrem, a surgeon would need to perform more than 5,600 RGPs a year, whereas the scrubbed operating room nurse would reach maximum exposure after nearly 10,000 RGPs and the anesthesia provider after roughly 41,000 RGPs. DISCUSSION We have described and documented in a prospective fashion the cumulative measured exposures to the operating surgeon, anesthesia provider, and operating room personnel during RGP. These data provide information on the number of cases required to meet thresholds for radiation safety training, monitoring, as well as the extreme volume of cases required to potentially reach maximum allowed radiation exposure. Previous descriptions of radiation exposure during RGP were either limited in the number of observations and/or extrapolated from single measurements to calculate theoretical exposures.23,24 These data represent 6 months of repeated exposures at a highvolume endocrine surgery practice, with three attending surgeons, trainee assistants, and the full gamut of hyperparathyroidism pathophysiology and operative findings. Previous studies concluded that radiation exposure during RGP was minimal and that the operating surgeon had the highest potential exposure. Bekis et al. concluded this from study only two RGPs.23 Before the beginning of the operation, single measurements were taken with a handheld Geiger counter at 50-cm intervals from the patient, out to 200 cm away from the patient. The operation was then video recorded, and the time each provider spent at each distance was used to calculate the whole body dose

to the staff. Norman et al. used radiation dosimeters on the chest and fingers of the operative surgeon and accumulated data over 15 RGPs.24 They concluded that over the course of 15 cases, the operative surgeon was exposed to 50 mrem, and this was felt to be an insignificant exposure by the authors. However, at that exposure level it would only take 30 cases for the surgeon to reach levels that warrant radiation safety training, and 150 cases to warrant radiation monitoring per the US Nuclear Regulatory Commission.16 Subsequent publications by Norman et al. 28 reference the use of a lead blanket to completely cover the body of the patient to shield the operative team from any emitted radiation, indicating that the earlier conclusion that it was an ‘‘insignificant exposure’’ may have changed. These previous studies used over twice the Tc-99 m sestamibi than that used within this study. The gamma probe is routinely used in both breast and melanoma surgery.18–20 Albumin colloid is labeled with Tc-99 m for localization of sentinel lymph nodes, although it is given at much lower doses for these procedures than that for RGP.21,22 Localization of nonpalpable breast lesions with implanted titanium seeds containing 0.1–0.25 mCi of 125 iodine is gaining popularity as a replacement for wire localization during breast conservation surgery.19 Extensive study into surgeon and operating staff exposures during these procedures concluded that whole body exposures are minimal during these procedures, and even extremity exposures (measured by multiple small dosimeters placed on various locations on the hands) would require thousands of procedures a year to reach maximal allowed exposure.21,22 Because the majority of surgeons performing parathyroid surgery are not endocrine specialists, their practices are likely to include breast and melanoma procedures.7,8,29 It is important for surgeons to be aware of all potential radiation exposures that they may encounter in the operating room. In particular, women who are pregnant or are considering becoming pregnant need to have access to information regarding the potential level of exposure RPG may cause. As the number of women within the field of surgery continues to grow, this information allows for critical assessment of the risk of participation in cases involving radiation exposure.

Exposure During Radioguided Parathyroidectomy

This study has its limitations. There was not 100 % capture of all RGPs performed during the study period. This was influenced by several factors: simultaneous cases, loss of badges, and forgetfulness when new trainees came onto service. However, 68 % of cases during the study period were included, which still allows for meaningful analysis. The surgeon and assistant stood on both sides of the table throughout the study period, and therefore no conclusions can be drawn as to variation in exposure based on proximity to the liver, which is known to have a high uptake of sestamibi.23 Likewise, conclusions regarding patient body mass index and renal function, which may influence degree of exposure, cannot be drawn. Conclusions from this study are based on exposures from 10 to 12 mCi of Tc-99 m sestamibi; however, different dosing protocols exist.26,28,30 Differing doses and time interval from injection to surgery will influence the potential exposure to the operative team, as will the overall duration of the case. Higher doses, shorter intervals, and/or longer cases result in greater exposure to the operative team. Finally, this study was performed at a high-volume endocrine surgery practice, with well-established institutional protocols in place for RGP. These last limitations may result in the underrepresentation of exposures on a case-bycase basis if performed at a lower-volume institution, or while an institutional protocol is initially being established.29 CONCLUSIONS Radioguided parathyroidectomy can be performed safely with minimal risk to the surgeon and operating room team. Based on the protocol presented within, at a highvolume center, surgeons performing more than 625 RGPs per year may warrant routine radiation exposure monitoring. Scrubbed operating room personnel had lower exposures and would require roughly double the cases to equate the surgeon’s exposure; however, scrubbed personnel often cover a variety of cases where radiation exposures also occur, either by use of fluoroscopy or patient emitted sources, and therefore should be considered for monitoring. Anesthesia providers had the lowest exposures, and do not warrant monitoring based on this procedure alone. Using a lead blanket to shield the patient is a reasonable means to further minimize exposures at very high-volume centers; however, further study is needed. REFERENCES 1. Murray SE, Pathak PR, Pontes DS, et al. Timing of symptom improvement after parathyroidectomy for primary hyperparathyroidism. Surgery. 2013;154(6):1463–9.

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