Jean St. Germain

Comparing Strategies for Operator Eye Protection in the Interventional Radiology Suite

PURPOSE To evaluate the impact of common radiation-shielding strategies, used alone and in combination, on scattered dose to the fluoroscopy operators eye. MATERIALS AND METHODS With an operator phantom positioned at the groin, upper abdomen, and neck, posteroanterior low-dose fluoroscopy was performed at the phantom patients upper abdomen. Operator lens radiation dose rate was recorded with a solid-state dosimeter with and without a leaded table skirt, nonleaded and leaded (0.75 mm lead equivalent) eyeglasses, disposable tungsten-antimony drapes (0.25 mm lead equivalent), and suspended and rolling (0.5 mm lead equivalent) transparent leaded shields. Lens dose measurements were also obtained in right and left 15° anterior obliquities with the operator at the upper abdomen and during digital subtraction angiography (two images per second) with the operator at the patients groin. Each strategys shielding efficacy was expressed as a reduction factor of the lens dose rate compared with the unshielded condition. RESULTS Use of leaded glasses alone reduced the lens dose rate by a factor of five to 10; scatter-shielding drapes alone reduced the dose rate by a factor of five to 25. Use of both implements together was always more protective than either used alone, reducing dose rate by a factor of 25 or more. Lens dose was routinely undetectable when a suspended shield was the only barrier during low-dose fluoroscopy. CONCLUSIONS Use of scatter-shielding drapes or leaded glasses decreases operator lens dose by a factor of five to 25, but the use of both barriers together (or use of leaded shields) provides maximal protection to the interventional radiologists eye.

Incidence of secondary cancer development after high-dose intensity-modulated radiotherapy and image-guided brachytherapy for the treatment of localized prostate cancer.

PURPOSE To report the incidence and excess risk of second malignancy (SM) development compared with the general population after external beam radiotherapy (EBRT) and brachytherapy to treat prostate cancer. METHODS AND MATERIALS Between 1998 and 2001, 1,310 patients with localized prostate cancer were treated with EBRT (n = 897) or brachytherapy (n = 413). We compared the incidence of SMs in our patients with that of the general population extracted from the National Cancer Institutes Surveillance, Epidemiology, and End Results data set combined with the 2000 census data. RESULTS The 10-year likelihood of SM development was 25% after EBRT and 15% after brachytherapy (p = .02). The corresponding 10-year likelihood for in-field SM development in these groups was 4.9% and 1.6% (p = .24). Multivariate analysis showed that EBRT vs. brachytherapy and older age were the only significant predictors for the development of all SMs (p = .037 and p = .030), with a trend for older patients to develop a SM. The increased incidence of SM for EBRT patients was explained by the greater incidence of skin cancer outside the radiation field compared with that after brachytherapy (10.6% and 3.3%, respectively, p = .004). For the EBRT group, the 5- and 10-year mortality rate was 1.96% and 5.1% from out-of field cancer, respectively; for in-field SM, the corresponding mortality rates were 0.1% and 0.7%. Among the brachytherapy group, the 5- and 10-year mortality rate related to out-of field SM was 0.8% and 2.7%, respectively. Our observed SM rates after prostate RT were not significantly different from the cancer incidence rates in the general population. CONCLUSIONS Using modern sophisticated treatment techniques, we report low rates of in-field bladder and rectal SM risks after prostate cancer RT. Furthermore, the likelihood of mortality secondary to a SM was unusual. The greater rate of SM observed with EBRT vs. brachytherapy was related to a small, but significantly increased, number of skin cancers in the EBRT patients compared with that of the general population.

Fears, feelings, and facts: interactively communicating benefits and risks of medical radiation with patients.

OBJECTIVE As public awareness of medical radiation exposure increases, there has been heightened awareness among patients and physicians of the importance of holistic benefit-and-risk discussions in shared medical decision making. CONCLUSION We examine the rationale for informed consent and risk communication, draw on the literature on the psychology of radiation risk communication to increase understanding, examine methods commonly used to communicate radiation risk, and suggest strategies for improving communication about medical radiation benefits and risk.

Safety and efficacy of radioactive seed localization with I-125 prior to lumpectomy and/or excisional biopsy

PURPOSE To evaluate the safety and efficacy of pre-operative I-125 radioactive seed localization (RSL) as an alternative to wire localization (WL). METHODS A waiver was granted by the institutional review board for this HIPAA compliant study. Review of 356 consecutive single site nonpalpable mammographic and ultrasound guided I-125 RSLs done between November 2011 and April 2012 was conducted. Preoperative mammograms and specimen radiographs were reviewed for seed-target distance, lesion location, and target/seed removal. During a brief surgical training period, 35 of 356 women had both RSL and wire localization (WL) of the same lesion. Chi-square and single sample t-tests were used to compare margin status and duration of procedures. RESULTS Of the 356 RSLs, 303 (85.1%) were performed ≥ 1 day before surgery. Mammographic guidance was used in 330 (93%) and ultrasound in 26 (7%). Mean seed to target distance was 1mm (range 0-20mm); all targeted lesions were retrieved. In 31 women in whom mammographic guidance was used for both RSL and WL, median procedure time was not significantly different (RSL 9.0 min; WL 7.0 min; p=0.91), and median seed migration distance was <1mm (range 0-15 mm). No difference was detected between margin status with RSL alone versus WL (p=0.40 and p=0.65 for positive and <1mm margins, respectively). Two adverse events occurred requiring an additional wire/surgery. CONCLUSION RSL ≥ 1 day before surgery is a safe effective procedure for pre-operative localization, with few adverse events and surgical outcomes comparable to those achieved with wire localization.

Unprotected operator eye lens doses in oncologic interventional radiology are clinically significant: estimation from patient kerma-area-product data.

PURPOSE To correlate operator lens dose to patient-delivered kerma-area-product (P(KA)) to evaluate the usefulness of P(KA) as a surrogate for operator eye dose if collar monitor readings are unavailable or deemed unreliable, and to evaluate if unprotected lens dose is clinically significant. MATERIALS AND METHODS A retrospective review of peak skin doses for consecutive interventional radiology procedures performed during 2006 that had P(KA) estimates recorded was performed. Unshielded operator lens dose equivalents (LDE) were obtained from dosimetry monitors worn outside the collar shield of operating interventional radiologists. Operator LDE were correlated with patient P(KA). RESULTS Average LDE for 2006 was 35.7 mSv ± 32.7 (range 5.2-89.9 mSv). Patient-delivered P(KA) correlated directly with LDE, where 1 Gy cm(2) to the patient resulted in an average of 4.2 μSv to the unprotected eyes of the primary operator (r(2) = 0.7). CONCLUSIONS P(KA) may be useful as a surrogate measure of operator LDE if collar monitor readings are unavailable or deemed unreliable. For this study, the dose-effect threshold for cataract formation could be surpassed for some physicians within 11 years if lens dose-mitigating strategies are not routinely employed.

RADIATION SAFETY CONSIDERATIONS FOR THE USE OF 223RaCl2 DE IN MEN WITH CASTRATION-RESISTANT PROSTATE CANCER

AbstractThe majority of patients with late stage castration-resistant prostate cancer (CRPC) develop bone metastases that often result in significant bone pain. Therapeutic palliation strategies can delay or prevent skeletal complications and may prolong survival. An alpha-particle based therapy, radium-223 dichloride (223RaCl2), has been developed that delivers highly localized effects in target areas and likely reduces toxicity to adjacent healthy tissue, particularly bone marrow. Radiation safety aspects were evaluated for a single comprehensive cancer center clinical phase 1, open-label, single ascending-dose study for three cohorts at 50, 100, or 200 kBq kg−1 body weight. Ten patients received administrations, and six patients completed the study with 1 y follow-up. Dose rates from patients administered 223Ra dichloride were typically less than 2 &mgr;Sv h−1 MBq−1 on contact and averaged 0.02 &mgr;Sv h−1 MBq−1 at 1 m immediately following administration. Removal was primarily by fecal excretion, and whole body effective half-lives were highly dependent upon fecal compartment transfer, ranging from 2.5–11.4 d. Radium-223 is safe and straightforward to administer using conventional nuclear medicine equipment. For this clinical study, few radiation protection limitations were recommended post-therapy based on facility evaluations. Specific precautions are dependent on local regulatory authority guidance. Subsequent studies have demonstrated significantly improved overall survival and very low toxicity, suggesting that 223Ra may provide a new standard of care for patients with CRPC and bone metastases.

Operational radiation safety for PET-CT, SPECT-CT, and cyclotron facilities.

Positron emission tomography (PET) and single-photon emission computed tomography (SPECT) are well- established and indispensable imaging modalities in modern medicine. State-of-the-art computed tomography (CT) scanners have now been integrated into multi-modality PET-CT and SPECT-CT devices, and these devices, particularly PET-CT scanners, are dramatically impacting clinical practice. 18F-fluorodeoxyglucose (FDG), by far the most widely used radiopharmaceutical for clinical PET imaging in general and oncologic PET imaging in particular, is highly accurate in detecting (approximately 90%) and staging many types of tumors, monitoring therapy response, and differentiating benign from malignant lesions. Several factors, including the relatively high administered activities [e.g., 370-740 MBq (10-20 mCi) of FDG], the high patient throughput (up to 30 patients per d), and in particular, the uniquely high energies (for a diagnostic setting) of the 511-keV positron-negatron annihilation photons, make shielding requirements, workflow, and other radiation protection issues important considerations in the design of a PET or PET-CT facility. The Report of Task Group 108 of the American Association of Physicists in Medicine (AAPM) provides a comprehensive summary of shielding design and related considerations, along with illustrative calculations. Whether in the form of a PET-CT or a SPECT-CT device, the introduction of CT scanners into a nuclear medicine setting has created new and complex radiation protection issues concerning the radiation burden and attendant risks accrued by patients undergoing such multi-modality procedures (especially in those instances in which higher-dose, diagnostic-quality CT studies are done as part of the PET-CT or SPECT-CT exam). In addition, because PET is dependent on the availability of short-lived 18F (Tp = 110 min) primarily in the form of FDG, and other short-lived positron emitters such as 11C (20 min), 13N (10 min), and 15O (2 min), cyclotrons for production of medically applied radionuclides and associated radiochemistry facilities are now widespread (well over 100 worldwide) and present their own radiation safety issues. In addition to the radioactive product, sources of exposure include neutrons and radioactive activation products in the various cyclotron components and surrounding shielding. Nonetheless, published studies have shown that the radiation doses to personnel working in cyclotron and associated radiochemistry facilities, as well as in PET or PET-CT and SPECT or SPECT-CT facilities, can be maintained below, and generally well below, the pertinent regulatory limits. This presentation will review the basic radiation safety aspects, including shielding and workflow, of these increasingly important and increasingly numerous facilities. The radiation burden accrued by the patients undergoing PET-CT or SPECT-CT exams will be considered as well.

Organ and effective dose estimates for patients undergoing hepatic arterial embolization for treatment of liver malignancy

PURPOSE Effective dose (E) is useful as a dose index for patient exposures in interventional radiology; therefore, the authors estimated E from the kerma-area product (P(KA)) utilized during hepatic embolization interventional radiology cases performed at a cancer center and determined the variation of such doses over a representative patient population. METHODS A single-center, IRB-approved retrospective study was performed to estimate doses from consecutive hepatic embolization procedures performed during 2006. Organ doses E and E/P(KA) were determined from patient height, weight, P(KA), procedure geometry factors, beam quality, the PCXMC Monte Carlo model, and the International Commission on Radiological Protection organ weighting factors. RESULTS One hundred thirteen patients were included in the study population, 72 males and 41 females, with a median age of 63 yr (29-89 yr), weight of 79 kg (42-111 kg), height of 170 cm (147-188 cm), and P(KA) of 233 Gy cm2 (9-1020 Gy cm2). E was directly correlated with P(KA) r2 = 0.8 (p < 0.01), with a median E/P(KA) of 0.18 mSv Gy(-1) cm(-2) (0.12-0.33 mSv Gy(-1) cm(-2)). The E/P(KA) ratio was inversely and exponentially correlated with weight r2 = 0.9 (p < 0.001). The median E (mSv) for the study patient population was 44 mSv (2.0-255 mSv). CONCLUSIONS Values of E can be estimated utilizing patient-specific and procedure-specific parameters. The strong inverse correlation of E/P(KA) with patient weight allows simple estimation of E from P(KA) and patient weight. There is a wide variation in effective dose in oncologic hepatic embolizations with doses up to an order of magnitude higher than diagnostic imaging of the abdomen by CT radiology. Variation is likely due to patient geometry, clinical technique factors, and procedure complexity.

Let's image gently: Reducing excessive reliance on CT scans

To the Editor: Meyer et al. [1] recommend imaging guidelines for children with Ewing sarcoma and osteosarcoma based on a report from the Children’s Oncology Group Bone Tumor Committee. The International Commission on Radiological Protection [2] and the National Council on Radiation Protection &Measurements [3] apply the principle of justification, that is, there is a need to justify any activity that involves radiation exposure on the basis that the expected benefits exceed the overall risk. We believe that the recommendation for frequent and repeated CT scans of the chest during surveillance post-chemotherapy for osteosarcoma is not adequately justified. While the authors included some risk and benefit considerations, their arguments for choosingCTappear to be unsupported. To justify their recommendation, the authors state that ‘‘early detection of lung metastases is important, as up to 25% of patients with lung metastases may become long-term survivors with multiple thoracotomies.’’ However, the largest series to evaluate survival after relapse of osteosarcoma estimates overall survival at 15%, and only 11% for patients whose recurrence is detected less than 18 months following completion of primary therapy [4]. Far more importantly, there is a significant lack of anydata to support the concept that detecting pulmonary metastases from osteosarcoma at 4 mm size on a CT scan leads to a higher probably of survival than detecting the same metastatic lesion at 1 cm on a plain radiograph. Indeed, the authors themselves state that this ‘‘is uncertain and could be a question for future research.’’ In the discussion of CT risks, the authors fail to quantify or compare radiation dose risks between CT scans and alternative AP/ lateral chest radiographs. ForCT scans, considerations unique to the pediatric population include increased radiosensitivity of certain tissues, a longer lifetime for radiation-related cancer to occur, and typically a lack of size-based adjustments in the technique [5]. Because of the large variability in CT scan protocols as well as patient age and size, estimates of effective dose for pediatric chest CT typically vary from about 2 mSv up to 10mSv [6,7]. An average effective dose of 6 mSv with appropriately adjusted pediatric settings [8] is up to 40 times higher than the combined dose fromAP and lateral chest radiographs totalling 0.16 mSv [8]. The guideline recommends chest CT during surveillance postchemotherapy and calls for 12 chest CTs with effective doses totaling approximately 72 mSv. An alternative schedule of AP and lateral chest radiographs monthly 12, then every 2 months 6, then every 3 months 4, followed by every 6 months 4 would increase the frequency of overall surveillance and reduce the cumulative dose risk by a factor of 17 down to 4 mSv. We concur with the recommendation of the Alliance for Radiation Safety in Pediatric Imaging [9] who suggest that we continue our efforts to reduce radiation dose to children by carefully evaluating the need for CT scans and minimizing CT doses whenever they are absolutely necessary.

The radioactive patient

Patients containing diagnostic or therapeutic amounts of radionuclides present exposure problems for medical and technical personnel. It is essential that personnel be aware of the magnitude of exposure expected and the methods available for its reduction. The design of a nuclear medicine facility should consider patients as sources of exposure. The size of imaging areas may be increased to reduce exposure to attending personnel. Patients containing radioactivity should be segregated from other patients and their families. Hospitalized patients given therapeutic amounts of radionuclides represent sources of exposure and contamination to personnel providing care. The use of disposable materials and the monitoring of these materials for contamination will reduce contamination of the hospital environment. Adequate instruction of personnel is essential to programs using therapeutic amounts of radionuclides so that patients are not made to feel isolated because of the form of treatment they are receiving.