John K. Ma

Effect of postmortem delay on imidazoline receptor-binding proteins in human and mouse brain.

Abstract: Immunoreactive proteins of 45‐kD and 29/30‐kD doublet bands are candidate imidazoline receptor binding proteins (IRBP) based on associations with I1 or I2 binding sites, respectively. It was reported that the density of cortical membrane 29/30‐kD I2 protein is diminished whereas a 45‐kD I1 protein is increased in depressed suicide victims versus controls. IRBP immunoreactive bands of similar size have been suggested to be breakdown products of the 170‐kD protein known as IRAS (putative full‐length I1 receptor). This study compares nonpathologic human brains collected and frozen after postmortem delays of 13.4 hours 6 1.7 (SEM) with brains of longer postmortem delays (26.1 hours 6 1.2). The fresher human brains possessed more full‐length IRAS (P5 0.05). In another study, the postmortem decay of IRBP bands in mouse brain was shown to be linear over time. The results are relevant to previous studies of IRBP bands in postmortem brains of depressed suicide victims.

Short-term clinical outcome and dosimetric comparison of tandem and ring versus tandem and ovoids intracavitary applicators.

Purpose To compare the short-term toxicity and dosimetry of tandem and ring (TR), and tandem and ovoid (TO) applicators in treatment of gynecologic malignancy. Material and methods Following pelvic external beam radiation therapy (EBRT), a total of 52 computed tomography-based plans from 13 patients with cervical cancer (FIGO IB2-IIIB) were evaluated for HDR brachytherapy. Prescription was 7 Gy to the ICRU point A for four weekly fractions. Gastrointestinal and genitourinary toxicities were evaluated. Clinical target volume (CTV) and organs at risk were delineated on CT scans. Bladder, rectum, and sigmoid mean doses and D2cc were calculated. Treatment time and irradiated tissue volume were compared. Percent of CTV receiving 100% (CTV100%) of the prescribed dose as well as the percent of the prescription dose covering 90% of the CTV (D90) were evaluated. Results Gastrointestinal and genitourinary toxicities were not different between TO and TR applicators. No significant differences in the dose to the right and left point A, or the left point B were observed. TO delivered a higher dose to right point B. Organs at risk doses were similar between the two applicators, except mean rectal dose was lower for TO applicator. Overall, TO treats a larger tissue volume than TR. Mean treatment time was shorter for TR. Tumor coverage (D90 and CTV100%) was equivalent between TO and TR applicators. Conclusion Although TO treats a larger tissue volume than TR, short-term toxicities and tumor coverage are similar. Long-term clinical outcomes will be elucidated with longer follow up period.

SU‐E‐T‐414: TG‐129 Implementation On BrachyvisionTM

PURPOSE To outline the steps taken to clinically implement TG-129 on Brachyvision™ Treatment Planning System and to show the dosimetric differences that can be expected from the original COMS Eye Plaque model. METHODS The original COMS-Eye Plaque protocol was based on the following simplification: point source model in infinite water medium, 1D geometric function, 1D radial dose function and no anisotropy. Recently, AAPM Task Group 129 had made two specific recommendations: 1> Upgrade to TG-43U1 line source model; and 2> Report the heterogeneity corrected dose. Upgrading to line TG-43U1 line source model was done by a creating a seed collection in Brachyvision (version 11) for each plaque size. For each seed in the collection, both end coordinates had to be entered into the software. Full line source model was followed to compute the homogeneous dose at the prescription point. This homogeneous dose was converted to heterogeneous dose using a conversion table. Dose to prescription points for five different plaque sizes, including one customized notched plaque, was calculated using the implemented TG-129 model and compared against actual COMS derived doses from previously treated patient plans. Conversion to heterogeneous doses was done based on table 2 of TG-129 report. RESULTS As expected, dose difference between COMS and TG-129 was relatively minor, ranging from -0.15% to 1.91% at the prescription point. On the other hand, heterogeneous dose, which should be used for reporting purpose only, can be up to ∼17% lower than the corresponding homogeneous dose. CONCLUSION Conversion to TG-129 can be rapidly accomplished in 1-2 weeks. The initial time investment can be quickly recouped since the TPS plans created can be modified for different patient cases. Dosimetric difference between TG-129 and the original COMS model is small, generally less than 2%.

Computerized tomography-based radiotherapy improves heterotopic ossification outcomes☆

PURPOSE To report the impact of computerized tomography (CT) based radiotherapy (RT) on heterotopic ossification (HO) outcomes. METHODS This is a single institution, retrospective study of 532 patients who were treated for traumatic acetabular fractures (TAF). All patients underwent open-reduction internal-fixation (ORIF) of the TAF followed by RT for HO prophylaxis. Postoperative RT was delivered within 72h, in a single fraction of 7Gy. The patients were divided into 2 groups based on RT planning: CT (A) vs. clinical setup (B). RESULTS At a median follow up of 8years the incidence of HO was 21.6%. Multivariate regression analysis revealed that group (A) vs. (B) had HO incidence of 6.6% vs. 24.6% (p<0.001), respectively. Furthermore, HO Brooker grade ≥3 was observed in 2.2% vs. 10.8% (p=0.007) in group (A) vs. (B), respectively. Thus, the odds of developing HO and Brooker grades ≥3 were 4.7 and 4.5 times higher, respectively, in patients who underwent clinical setup. CONCLUSION Our data suggest that using CT based RT allowed more accurate delineation of the tissues and better clinical outcomes. Although CT-based RT is associated with additional cost the efficacy of CT-based RT reduces the risk of HO, thereby decreasing the need for additional surgical interventions.