Metabolic Tumor Width Parameters as Determined on PET/CT Predict Disease-free Survival and Treatment Response in Squamous Cell Carcinoma of the Esophagus

Materials and Methods  We investigated the utility of metabolic tumor width parameters in predicting response to chemoradiotherapy and in predicting disease-free survival in patients with esophageal cancer. Furthermore, we evaluated the possible confounding effect of therapy-induced esophagitis on the evaluation of treatment response. Forty-nine patients with squamous cell carcinoma, who had undergone positron emission tomography/computed tomography (PET/CT) exams before and after neoadjuvant chemoradiotherapy, were included in the study. In the slice with the maximum 2-deoxy-2-[F-18]fluoro-d-glucose (FDG) uptake of the tumor, the following metabolic tumor width parameters were measured: Area of the tumor, maximum diameter of the tumor, maximum and mean standardized uptake value (SUV). Furthermore, the “diameter-SUV index” was calculated by multiplying the tumor diameter by the mean SUV. Results  The decrease of the metabolic tumor diameter between pre- and post-treatment PET/CT scans was the single best predictor of treatment response and tumor-free survival. However, the accuracy of predicting response and survival was even higher when using the decrease of the “diameter-SUV index” as the metabolic criterion for treatment response. A decrease by more than 55% of the diameter-SUV index identified pathologic responders (n = 22) with a sensitivity of 91% and a specificity of 93%. Radiation esophagitis was found to have a significant impact on the assessment of treatment response when evaluating therapy response based on the maximum SUV, whereas no confounding effect of radiation esophagitis was seen when evaluating therapy response based on the tumor diameter or the diameter-SUV index. Conclusion  The present study shows that tumor width parameters, especially the tumor diameter or the combination of diameter and SUV in the “diameter-SUV index”, are valuable for predicting tumor-free survival and treatment response independent from the presence of radiation esophagitis.     

64-Slice multidetector row CT angiography of the abdomen: comparison of low versus high concentration iodinated contrast media in a porcine model

Objective

In this study we aimed to assess the image quality and degree of vascular enhancement using low-concentration contrast media (LCCM) (300 mg I ml^–1) and high-concentration contrast media (HCCM) (370 mg I ml^–1) on 64-slice multidetector row CT (MDCT) abdominal CT angiography (CTA). In addition, we aimed to study the feasibility of using HCCM with a reduced total iodine dose.

Methods

CTA of the abdomen on a 64-slice MDCT was performed on 15 anaesthetised pigs. Study pigs were divided into three groups of five each based on the iodine concentration and dose received: Group A (LCCM; 300 mg I ml^–1), Group B (HCCM; 370 mg I ml^–1) and Group C HCCM with 20% less iodine dose. The total iodine injected was kept constant (600 mg kg^–1) in Groups A and B. Qualitative and quantitative analyses were performed to study and compare each group for image quality, visibility of the branch order of the superior mesenteric artery (SMA), artefacts, degree of enhancement in the aorta and main stem arteries and uniformity of enhancement in the aorta. Groups were compared using the analysis of variance test.

Results

The image quality of 64-slice MDCT angiography was excellent with a mean score of 4.63 and confident visualisation of the third to fifth order branches of the SMA in all groups. Group B demonstrated superior vascular enhancement, as compared with Groups A and C (p≤0.05). Uniform aortic enhancement was achieved with the use of LCCM and HCCM with 20% less iodine dose.

Conclusion

64-slice MDCT angiography of the abdomen was of excellent quality. HCCM improves contrast enhancement and overall CTA image quality and allows the iodine dose to be reduced.CT angiography (CTA) has rapidly emerged as a non-invasive imaging modality of choice to evaluate vasculature and vascular conditions in the abdomen [1-4]. Multidetector row CT (MDCT) has played a crucial role in the widespread acceptance of CTA as a non-invasive alternative to catheter angiography. Technical advances with the addition of more detector rows have significantly improved the spatial resolution and scanning speed of MDCT. CTA is evolving to adapt to these changes in MDCT technology. A marked reduction in scan duration with the newer 64-slice MDCT requires optimisation of scan timing to catch the bolus of enhancement for vascular and multiphasic organ imaging. Therefore, contrast administration strategies and scanning protocols need to be optimised either by increasing the rate of contrast injection or through the use of contrast media (CM) with a higher iodine concentration to adapt to a shorter scan duration. Increasing the rate of CM injection is limited, as it requires a relatively large-bore intravenous cannula for injection and could potentially increase the risk of extravasation [5]. By contrast, increasing the iodine concentration in CM not only improves contrast enhancement by increasing iodine flux, but could also help to reduce the volume of CM; the use of reduced volumes is highly desirable to match the shorter acquisition times on 16-slice and higher MDCT [6]. Use of high-concentration CM (HCCM) has been shown to provide superior vascular enhancement as compared with low-concentration CM (LCCM) on either 4- or 16-slice MDCT [7-11].In this study, we assessed the performance of abdominal CTA on 64-slice MDCT and compared the degree of enhancement and image quality using LCCM (300 mg I ml^–1) with HCCM (370 mg I ml^–1) in a porcine model. In addition, the potential of reducing the contrast volume or total iodine dose with the use of HCCM for CTA was assessed and compared with a regular dose of LCCM and HCCM.     

Depth-dependent temporal response properties in core auditory cortex

The computational role of cortical layers within auditory cortex has proven difficult to establish. One hypothesis is that interlaminar cortical processing might be dedicated to analyzing temporal properties of sounds; if so, then there should be systematic depth-dependent changes in cortical sensitivity to the temporal context in which a stimulus occurs. We recorded neural responses simultaneously across cortical depth in primary auditory cortex and anterior auditory field of CBA/Ca mice, and found systematic depth dependencies in responses to second-and-later noise bursts in slow (1-10 bursts/s) trains of noise bursts. At all depths, responses to noise bursts within a train usually decreased with increasing train rate; however, the rolloff with increasing train rate occurred at faster rates in more superficial layers. Moreover, in some recordings from mid-to-superficial layers, responses to noise bursts within a 3-4 bursts/s train were stronger than responses to noise bursts in slower trains. This non-monotonicity with train rate was especially pronounced in more superficial layers of the anterior auditory field, where responses to noise bursts within the context of a slow train were sometimes even stronger than responses to the noise burst at train onset. These findings may reflect depth dependence in suppression and recovery of cortical activity following a stimulus, which we suggest could arise from laminar differences in synaptic depression at feedforward and recurrent synapses.