Purpose: The aim of our study was to compare whole-body diffusion-weighted MRI (WB-DWI-MRI) to fluoro-2-deoxyglucose positron emission tomography/computed tomography (FDG-PET/CT) in the assessment of initial staging and treatment response in pediatric patients with Hodgkin lymphoma. Materials and Methods: This prospective study comprised 11 children with Hodgkin lymphoma. Whole-body DWI-MRI and FDG-PET/CT were obtained at baseline and after 2 cycles of chemotherapy. Two radiologists measured the apparent diffusion coefficient (ADC) values of the sites of involvement agreed upon in consensus and 1 nuclear medicine physician assessed the PET/CT. Reliability of radiologists' ratings was assessed by intraclass correlation coefficients (ICC2,1). The sensitivity and positive predictive value (PPV) of DW-MRI relative to PET/CT were calculated for nodal and extranodal sites. The patients were staged according to both modalities. Association of treatment responses was assessed through the Pearson correlation between the ADC ratios and the change standardized uptake value (SUV) between baseline and follow-up. Results: There was good agreement between the raters for nodal and extranodal ADC measurements. The sensitivity and PPV of DW-MRI relative to PET/CT of nodal disease was 0.651 and 1.0, respectively, at baseline, and 0.697 and 0.885 at follow-up. The sensitivity and PPV of extranodal disease were 0.545 and 0.6 at baseline, and 0.167 and 0.333 at follow-up. Diffusion-weighted MRI determined correct tumor stage in 8 of 11 examinations. There was poor correlation between the ADC ratios and the absolute change in SUV between baseline and follow-up (0.348). Conclusion: Our experience showed that WB-DWI-MRI is inferior to PET/CT for initial staging and assessment of treatment response of Hodgkin lymphoma in pediatric patients.

223Ra is an effective therapeutic radiopharmaceutical for the treatment of prostate cancer metastatic to bone. As an institutional participant in the ALSYMPCA trial, and early adopter of Xofigo as a clinical modality, our facility has accrued over 10 years’ experience in the regulatory-compliant use of this radiopharmaceutical. Because 223Ra is a pure alpha emitter, there is negligible concern regarding external exposure from injected patients. However, several radiation safety related factors still need to be considered when treating patients with 223Ra. Our presentation will discuss a number of these concerns, based on first-hand experience gained from navigating several specific scenarios and additional information gathered from the medical literature, to provide guidance on the safe usage of 223Ra in the treatment of patients with boney metastases. Personnel involved in the clinical care and radiation safety oversight of patients treated with 223Ra were canvassed to recall cases with radiation safety concerns. By drawing upon our institution’s experience, and reviewing the relevant world-wide literature, we have provided guidance for various scenarios in the radiation-safety compliant treatment of patients with 223Ra. Physical, biological and regulatory aspects of 223Ra form the basis of understanding radiation safety concerns. We describe the potential of internal contamination from patient excreta, body fluids, and tissue samples based on a number of clinical scenarios, and the ensuing exposures that may result. Adherence to Universal Precautions is paramount in avoiding internal contamination. Of particular interest is our first-hand experience with a patient who underwent hip replacement surgery following 223Ra therapy, including the proper handling and storage of radioactive bone fragments. Handling of a deceased patient, and the associated guidelines regarding 223Ra decedents, is a potential outcome that should be familiar to physicians administering 223Ra therapy. While the lack of a gamma emission greatly reduces exposure and radiation concerns when treating patients with therapeutic levels of 223Ra activity, there are still several regulatory and safety concerns that need to be addressed in the course of potential patient scenarios. We will review appropriate solutions to these scenarios in a radiation-safety compliant manner.

Radium 223Ra dichloride (223RaCl2) is an effective therapeutic radiopharmaceutical presently approved for the treatment of prostate cancer metastatic to bone. It is unique by virtue of being the first alpha-emitting radiopharmaceutical to achieve approval for use in the clinic, reaching this status both in the United States and Europe in 2013. In over ten years of research and approved clinical usage, the authors have encountered very few radiation-safety incidents of concern with 223RaCl2; in this review, they relate their first-hand experience with this radiopharmaceutical and share some lessons learned, including situations of bleeding, surgery and patient demise. The authors first provide a basic review of the relevant physical properties of 223Ra and aspects of its radiobiology, followed by a discussion of the biodistribution of 223RaCl2, the radiopharmaceutical presently approved for clinical use. As would be expected from a primarily alpha emitter, external exposures to staff and family members from patients administered 223Ra are typically low in comparison with exposure from patients who have undergone other nuclear medicine procedures. There still remains potential for health care workers and family members to receive a significant internal exposure, through the ingestion of even minute amounts of activity, so proper handling practices are paramount.

1252 Learning Objectives 1. Present a case of V/Q scan findings of absent perfusion in the right upper lobe in a young adult with history of repaired ASD and PAPVC. 2. Review types of PAPVC and possible complications leading to perfusion defects. 3. Provide a list of common and uncommon differential diagnosis of mismatched perfusion defects on V/Q scan. The presence of partial anomalous pulmonary venous connection (PAPVC) is probably under diagnosed as most patients are asymptomatic. Depending on the severity of the condition, definitive treatment for PAPVC is surgical repair, which may lead to complications such as baffled obstruction. In this poster we present an incidental finding of a mismatched perfusion defect with normal ventilation on V/Q scan in a patient with history of PAPVC. The patient is a 31 year old female 14 weeks pregnant who presented with sudden onset of left sided pleuritic chest pain. Chest X-ray is normal. A V/Q scan shows a mismatched perfusion defect involving the entire right upper lobe. On the follow up chest CT, no identifiable venous drainage of the right upper lobe to the left atrium is identified. The heart is normal in size.The patient has a history of ASD and PAPVC, which was surgically repaired 10 years prior to the V/Q scan, with the right upper pulmonary vein sacrificed. The mechanism of perfusion defect will be discussed. The most common form of PAPVC is one in which a right upper pulmonary vein connects to the right atrium or the superior vena cava. This form is almost always associated with a sinus venosus type of ASD. Other types of PAPVC will be discussed. The types and the seririty of PAPVC may have varied findings on V/Q scan. A V/Q scan is primarily used to evaluate pulmonary embolism. The diagnosis is based on mismatched perfusion defects, which could also be seen with other causes, including the uncommon cause presented in this poster. Knowledge of common and uncommon causes of mismatched perfusion defects is important to trainees in nuclear medicine and radiology. The differential for mismatched perfusion defects on V/Q scan will be presented in this poster.