Brent D. Weinberg

Theoretical analysis and experimental evaluation of a CsI(Tl) based electronic portal imaging system

This article discusses the design and analysis of a portal imaging system based on a thick transparent scintillator. A theoretical analysis using Monte Carlo simulation was performed to calculate the x-ray quantum detection efficiency (QDE), signal to noise ratio (SNR) and the zero frequency detective quantum efficiency [DQE(0)] of the system. A prototype electronic portal imaging device (EPID) was built, using a 12.7 mm thick, 20.32 cm diameter, Csl(Tl) scintillator, coupled to a liquid nitrogen cooled CCD TV camera. The system geometry of the prototype EPID was optimized to achieve high spatial resolution. The experimental evaluation of the prototype EPID involved the determination of contrast resolution, depth of focus, light scatter and mirror glare. Images of humanoid and contrast detail phantoms were acquired using the prototype EPID and were compared with those obtained using conventional and high contrast portal film and a commercial EPID. A theoretical analysis was also carried out for a proposed full field of view system using a large area, thinned CCD camera and a 12.7 mm thick CsI(TI) crystal. Results indicate that this proposed design could achieve DQE(0) levels up to 11%, due to its order of magnitude higher QDE compared to phosphor screen-metal plate based EPID designs, as well as significantly higher light collection compared to conventional TV camera based systems.

Injectable polymer depot combined with radiofrequency ablation for treatment of experimental carcinoma in rat.

Objective:The purpose of this study was to investigate whether an intralesional chemotherapy depot with or without a chemosensitizer could improve the efficacy of radiofrequency (RF) ablation in treatment of experimental carcinoma in rats. Materials and Methods:Eighteen BD-IX rats were inoculated with bilateral subcutaneous tumors via injection of DHD/K12TRb rat colorectal carcinoma cells in suspension. Four weeks after inoculation, one tumor in each rat was treated with RF ablation at 80°C for 2 minutes and the other with RF ablation followed by intralesional chemotherapy with carboplatin. The drug was administered via 2 different in situ-forming poly(D,L-lactide-coglycolide) (PLGA) depot formulations either with or without a chemosensitizer. Treatment efficacy was assessed by comparing the change in tumor diameter compared with control, percent of coagulation necrosis and a rating of treatment completeness. Results:Tumors treated with ablation and carboplatin + sensitizer (n = 9) showed a diameter decrease of 49.4 ± 24.5% at the end point relative to ablation control, while those treated with ablation and carboplatin only (n = 8) showed a 7.1 ± 12.6% decrease. Use of sensitizer also showed increased tissue necrosis (81.9 ± 9.7% compared with 68.7 ± 26.7% for ablation only) and double the number of complete treatments (6/9 or 66.7%) compared with ablation control (3/9 or 33.3%). Conclusions:From these results, we conclude that intralesional administration of a carboplatin and sensitizer-loaded polymer depot after RF ablation has the potential to improve the outcome of ablation by increasing effectiveness of local adjuvant chemotherapy in preventing progression of tumor unaffected by the ablation treatment.

Sub-acute changes in lesion conspicuity and geometry following MR-guided radiofrequency ablation

To evaluate MR signal and lesion zone volume evolution through the sub‐acute phase following image‐guided radiofrequency (RF) thermal ablation.

Combination of Sensitizing Pretreatment and Radiofrequency Tumor Ablation: Evaluation in Rat Model

PURPOSE To prospectively determine, in an animal tumor model, if the block copolymer Pluronic P85 (BASF, Shreveport, La) sensitizes cancer cells to hyperthermia and if intratumorally or intravenously administered copolymer improves the therapeutic outcome of radiofrequency (RF) ablation tumor treatment. MATERIALS AND METHODS The effects of Pluronic P85 and mild hyperthermia in vitro were tested in DHD/K12/TRb rat colorectal carcinoma cells. Cells were incubated at 37 degrees C or 43 degrees C for 15-60 minutes with 0%, 7%, or 10% wt/wt Pluronic P85, and cell viability was assessed by using a mitochondrial enzyme assay. In vivo experiments were performed as approved by the Institutional Animal Care and Use Committee at Case Western Reserve University and according to all applicable guidelines on animal use. Bilateral subcutaneous tumors in rats were treated with either intratumoral (13 tumors) or intravenous (15 tumors) Pluronic P85 followed by ablation or with ablation alone (14 tumors) and were monitored for 14 days by using volumes estimated from caliper measurements of tumor diameter. Acute effects of Pluronic P85 on the size of ablation-induced coagulation were measured after 24 hours in additional tumors (six tumors each treated according to the protocol for the ablation-only, intratumoral injection, and intravenous injection groups). Statistical testing was performed by using linear regression analysis and two-sided t tests with a significance level of .05. RESULTS At 43 degrees C, 7% and 10% Pluronic P85 reduced in vitro cell viability by 22% +/- 5 (standard error of the mean) (P < .001) and 28% +/- 5 (P < .001), respectively, compared with the viability of control cells. At day 14, the volume of tumors ablated after local and systemic Pluronic P85 pretreatment changed by -55% +/- 14 (P = .03) and -59% +/- 14 (P = .02), respectively, compared with an increase of 16% +/- 28 for tumors treated with ablation alone. Coagulation area at 24 hours was reduced by 44% relative to that in control tumors (P = .03) after intratumoral Pluronic P85 but was unchanged after systemic Pluronic P85. CONCLUSION Tumor pretreatment with Pluronic P85 improved the outcome of RF ablation by decreasing the tumor volume and residual tumor in an experimental carcinoma model.

Effect of Intratumoral Injection of Carboplatin Combined with Pluronic P85 or L61 on Experimental Colorectal Carcinoma in Rats

Pluronic, a poly(ethylene oxide)-poly(propylene oxide)-poly (ethylene oxide) block copolymer, has been shown to enhance the cytotoxic activity of anticancer drugs in various cell lines. In the current study the effect of Pluronic P85 (P85) and Pluronic L61 (L61) on the intratumoral chemotherapy of an experimental adenocarcinoma in rats was examined. A total of 120 subcutaneous tumors (4 per rat) were inoculated in 30 BDIX rats and were treated weekly for 4 weeks with intratumoral injection of carboplatin (CPt) alone or with either P85 or L61. Tumors were monitored weekly and were excised at the endpoint for histologic evaluation. The effect of Pluronic on levels of intracellular ATP was explored as a possible mechanism of sensitization. Results showed that tumors treated with low-dose CPt (2.8 mg/kg) and P85 or L61 exhibited significant reductions in tumor volume after 28 days relative to Day 0 (112.7% ± 34.4%, n = 15; 131.3% ± 55.6%, n = 8) compared with tumors treated with free drug (339.4% ± 75.0%, n = 16). Control tumors treated with either P85 or L61 alone or with saline showed volume increases of 1079.4% ± 143.6% (n = 16), 729.4% ± 202.2% (n = 7), and 1119.2% ± 6.1% (n = 16), respectively. Treatment with high-dose CPt (20.7 mg/kg) led to a 79.3% ± 4.2% reduction in tumor volume, and no differences were noted with addition of P85 or L61. In vitro ATP measurements showed that 28.0 mg/kg of P85 significantly reduced levels of intracellular ATP to 44.7% ± 1.5% of controls, whereas L61 at this concentration depleted ATP levels completely. Results confirm that Pluronic P85 and L61 act as potent sensitizers to carboplatin chemotherapy of the experimental colorectal carcinoma, leading to a significant reduction of tumor growth compared to carboplatin alone. ATP depletion is a possible mechanism for these observed differences.

Radiology Resident Preliminary Reporting in an Independent Call Environment: Multiyear Assessment of Volume, Timeliness, and Accuracy

PURPOSE The objective of this paper is to assess the volume, accuracy, and timeliness of radiology resident preliminary reports as part of an independent call system. This study seeks to understand the relationship between resident year in training, study modality, and discrepancy rate. METHODS Resident preliminary interpretations on radiographs, ultrasound, CT, and MRI from October 2009 through December 2013 were prospectively scored by faculty on a modified RADPEER scoring system. Discrepancy rates were evaluated based on postgraduate year of the resident and the study modality. Turnaround times for reports were also reviewed. Differences between groups were compared with a chi-square test with a significance level of 0.05. Institutional review board approval was waived as only deidentified data were used in the study. RESULTS A total of 416,413 studies were reported by 93 residents, yielding 135,902 resident scores. The rate of major resident-faculty assessment discrepancies was 1.7%. Discrepancy rates improved with increasing experience, both overall (PGY-3: 1.8%, PGY-4: 1.7%, PGY-5: 1.5%) and for each individual modality. Discrepancy rates were highest for MR (3.7%), followed by CT (2.4%), radiographs (1.4%), and ultrasound (0.6%). Emergency department report turnaround time averaged 31.7 min. The average graduating resident has been scored on 2,746 ± 267 reports during residency. CONCLUSIONS Resident preliminary reports have a low rate of major discrepancies, which improves over 3 years of call-taking experience. Although more complex cross-sectional studies have slightly higher discrepancy rates, discrepancies were still within the range of faculty report variation.

Portal imaging with a CsI(Tl) transparent scintillator x-ray detector

In a previous paper, a portal imaging system was described that used a 101 mm diameter, 3 mm thick CsI (Tl) transparent scintillating screen coupled to a liquid-nitrogen-cooled slow- scan CCD-TV camera with a 40 mm f1.0 macro lens with a 5:1 demagnification. Meanwhile, improved images have been acquired using a 50 mm f1.1 macro lens with a 7:1 demagnification. These images were presented at an AAPM International Symposium on Electronic Portal Imaging in Detroit, MI, in May, 1997. Since the Detroit meeting, a 203 mm diameter, 13 mm thick CsI(Tl) crystal has been purchased from Bicron. This transparent screen has been used with a Nikkor 35 mm f1.4 lens to show the whole 203 mm circular field at 0.53 mm pixel size with the existing Astromed liquid nitrogen cooled CCD TV camera system. The geometry of the imaging system has been optimized to achieve high spatial resolution (1 lp/mm) in spite of the increased thickness of the screen. This increased thickness allows the high image quality achieved with the older screen at 72 MU to be maintained with the newer screen while reducing the dose to 1 MU. Images have been acquired with the new screen of lead bar patterns, low-contrast hole patterns in Lucite blocks, and anthropomorphic phantoms.

Radiofrequency ablation: post-ablation assessment using CT perfusion with pharmacological modulation in a rat subcutaneous tumor model.

RATIONALE AND OBJECTIVES Inflammatory reaction surrounding the ablated area is a major confounding factor in the early detection of viable tumor after radiofrequency (RF) ablation. A difference in the responsiveness of normal and tumor blood vessels to vasoactive agents may be used to distinguish these regions in post-ablation follow-up. The goal of this study was to examine longitudinal perfusion changes in untreated viable tumor and the peripheral hyperemic rim of RF-ablated tumor in response to a vasoconstrictor (phenylephrine) or vasodilator (hydralazine) in a subcutaneous rat tumor model. MATERIALS AND METHODS Bilateral subcutaneous shoulder tumors were inoculated in 24 BDIX rats and evenly divided into two groups (phenylephrine and hydralazine groups). One tumor in each animal was completely treated with RF ablation (at 90 +/- 2 degrees C for 3 minutes), and the other remained untreated. Computed tomographic perfusion scans before and after phenylephrine (10 microg/kg) or hydralazine (5 mg/kg) administration were performed 2, 7, and 14 days after ablation. Four rats per group were euthanized on each scan day, and pathologic evaluation was performed. The changes of blood flow in the peripheral rim of ablated tumor and untreated viable tumor in response to phenylephrine or hydralazine at each time point were compared. The diagnostic accuracy of viable tumor using the percentage change of blood flow in response to phenylephrine and hydralazine was compared using receiver-operating characteristic analysis. RESULTS The peripheral rim of ablated tumor presented with a hyperemic reaction with dilated vessels and congestion on day 2 after ablation, numerous inflammatory vessels on day 7, and granulation tissue formation on day 14. Phenylephrine significantly decreased the blood flow in the peripheral hyperemic rim of ablated tumor on days 2, 7, and 14 by 16.3 +/- 9.7% (P = .001), 24.0 +/- 22.6% (P = .007), and 31.1 +/- 25.4% (P = .045), respectively. In untreated viable tumor, the change in blood flow after phenylephrine was irregular and insignificant. Hydralazine decreased the blood flow in the peripheral rim of both ablated tumor and untreated viable tumor. Receiver-operating characteristic analysis showed that reliable tumor diagnosis using the percentage change of blood flow in response to phenylephrine was noted on days 2 and 7, for which the areas under the curve were 0.82 (95% confidence interval, 0.64-1.00) and 0.81 (95% confidence interval, 0.56-1.00), respectively. However, tumor diagnosis using the blood flow change in response to hydralazine was unreliable. CONCLUSION Phenylephrine markedly decreased blood flow in the peripheral hyperemic rim of ablated tumor but had little effect on the untreated viable tumor. Computed tomographic perfusion with phenylephrine may be useful in the long-term treatment assessment of RF ablation.

Dynamics of MRI-Guided Thermal Ablation of VX2 Tumor in Paraspinal Muscle of Rabbits

This study combines fast magnetic resonance imaging (MRI) and model simulation of tissue thermal ablation for monitoring and predicting the dynamics of lesion size for tumor destruction. In vivo experiments were conducted using radiofrequency (RF) thermal ablation in paraspinal muscle of rabbit with a VX2 tumor. Before ablation, turbo-spin echo (TSE) images visualized the 3-D tumor (necrotic core and tumor periphery) and surrounding normal tissue. MR gradient-recalled echo (GRE) phase and magnitude images were acquired repeatedly in 3.3 s at 30-s intervals during and after thermal ablation to follow tissue temperature distribution dynamics and lesion development in tumor and surrounding normal tissue. Final lesion sizes estimated from GRE magnitude, post-ablation TSE, and stained histologic images were compared. Model simulations of temperature distribution and lesion development dynamics closely corresponded to the experimental data from MR images in tumor and normal tissue. The combined use of MR image monitoring and model simulation has the potential for improving pretreatment planning and real-time prediction of lesion-size dynamics for guidance of thermal ablation of tumors.

Entorhinal Cortex: Antemortem Cortical Thickness and Postmortem Neurofibrillary Tangles and Amyloid Pathology

BACKGROUND AND PURPOSE: The entorhinal cortex, a critical gateway between the neocortex and hippocampus, is one of the earliest regions affected by Alzheimer disease–associated neurofibrillary tangle pathology. Although our prior work has automatically delineated an MR imaging–based measure of the entorhinal cortex, whether antemortem entorhinal cortex thickness is associated with postmortem tangle burden within the entorhinal cortex is still unknown. Our objective was to evaluate the relationship between antemortem MRI measures of entorhinal cortex thickness and postmortem neuropathological measures. MATERIALS AND METHODS: We evaluated 50 participants from the Rush Memory and Aging Project with antemortem structural T1-weighted MR imaging and postmortem neuropathologic assessments. Here, we focused on thickness within the entorhinal cortex as anatomically defined by our previously developed MR imaging parcellation system (Desikan-Killiany Atlas in FreeSurfer). Using linear regression, we evaluated the association between entorhinal cortex thickness and tangles and amyloid-β load within the entorhinal cortex and medial temporal and neocortical regions. RESULTS: We found a significant relationship between antemortem entorhinal cortex thickness and entorhinal cortex (P = .006) and medial temporal lobe tangles (P = .002); we found no relationship between entorhinal cortex thickness and entorhinal cortex (P = .09) and medial temporal lobe amyloid-β (P = .09). We also found a significant association between entorhinal cortex thickness and cortical tangles (P = .003) and amyloid-β (P = .01). We found no relationship between parahippocampal gyrus thickness and entorhinal cortex (P = .31) and medial temporal lobe tangles (P = .051). CONCLUSIONS: Our findings indicate that entorhinal cortex–associated in vivo cortical thinning may represent a marker of postmortem medial temporal and neocortical Alzheimer disease pathology.