Citations

Radioactive seed localization (RSL) using 125 I is widely employed for the surgical resection of nonpalpable breast lesions due to its precision and scheduling flexibility. Although clinical experience supports its safety, quantifying radiation dose to surrounding healthy breast tissue remains important for establishing conservative operational guidelines, including acceptable implant duration prior to surgery. In this study, cumulative dose to healthy breast tissue from an implanted 125 I localization seed was evaluated using two independent computational approaches: a simplified hemispherical breast model implemented in MATLAB and a Monte Carlo simulation developed in Mathematica. Both models incorporated dosimetric parameters from AAPM Task Group 43, including the dose-rate constant, radial dose function, and two-dimensional anisotropy function, along with tissue properties consistent with International Commission on Radiological Protection recommendations. Results from both models demonstrated that cumulative dose decreases rapidly with increasing distance from the seed and increases slowly with implantation time due to the low dose rate and long half-life of 125 I. At a distance of 1 cm, cumulative dose reached approximately 3–4 cGy after 5 d and approximately 50 cGy only after extended implantation times exceeding 200 d. Agreement between the MATLAB and Monte Carlo models was within expected limits given differences in deterministic and stochastic modeling approaches. These findings indicate that radiation dose to healthy breast tissue from RSL remains well below thresholds associated with deterministic effects for clinically relevant implantation times. The results support the use of a conservative “no later than” removal date while reaffirming the radiological safety and practical advantages of 125 I seed localization in breast cancer surgery.

SUMMARY Chromosomally integrated human herpesvirus 6 (ciHHV‐6) is a condition in which the complete HHV‐6 genome is integrated into the host germ line genome and is vertically transmitted in a Mendelian manner. The condition is found in less than 1% of controls in the USA and UK, but has been found at a somewhat higher prevalence in transplant recipients and other patient populations in several small studies. HHV‐6 levels in whole blood that exceed 5.5 log10 copies/ml are strongly suggestive of ciHHV‐6. Monitoring DNA load in plasma and serum is unreliable, both for identifying and for monitoring subjects with ciHHV‐6 due to cell lysis and release of cellular DNA. High HHV‐6 DNA loads associated with ciHHV‐6 can lead to erroneous diagnosis of active infection. Transplant recipients with ciHHV‐6 may be at increased risk for bacterial infection and graft rejection. ciHHV‐6 can be induced to a state of active viral replication in vitro . It is not known whether ciHHV‐6 individuals are put at clinical risk by the use of drugs that have been associated with HHV‐6 reactivation in vivo or in vitro . Nonetheless, we urge careful observation when use of such drugs is indicated in individuals known to have ciHHV‐6. Little is known about whether individuals with ciHHV‐6 develop immune tolerance for viral proteins. Further research is needed to determine the role of ciHHV‐6 in disease. Copyright © 2011 John Wiley & Sons, Ltd.