Evaluating the Role of Tc99m Sestamibi Scan in Parathyroid Surgery: A 10-Year Institutional Experience

(RSNA 2018, Wed Nov 28 2018 3:50PM – 4:00PM ROOM Z44)

PURPOSE

In this study we aim to evaluate the (99mTc) sestamibi parathyroid scan as a single localizing modality, and we also assess its relation to the weight of the gland and to the preoperative parathyroid hormone (PTH) levels.

METHOD AND MATERIALS

We reviewed 744 patients from our hospital from 2007 to 2017, with a mean age of 56.6 years and a female to male ratio of 3.3:1. With primary hyperparathyroidism, all of them had (99mTc) sestamibi parathyroid scan for the localization of the parathyroid adenoma. Preoperative and postoperative PTH levels were recorded. The histopathology reports confirmed the diagnosis and weight of the diseased gland, which were recorded every time. The results were analyzed and correlated with the sestamibi results, to evaluate its accuracy.

RESULTS

506 patients (68%) of the 744 had an exact match (EM) sestamibi results, 227 (30.5%) had a partial match, and only 11 patients were reported as mismatch. Analyzing the mean weight of the gland in each group between matching (EM, PM) versus mismatch resulted in a mean difference of 0.823 g (1.05 and 0.247 g, respectively) P = 0.045. Hyperplasia to adenoma ratio was more in the partial matching group (18.5%) versus the exact matching group (7.6%). Finally the mean PTH level was higher in the EM group (36.8 pmol/L) compared to the mismatch group (10.1 pmol/L) P = 0.02. Overall sensitivity and specificity for the (99 mTc) sestamibi in our data was 98.1 and 97%, respectively.

CONCLUSION

(99mTc) sestamibi is a highly accurate test that can be employed as a single localizing modality for identifying a hypersecreting parathyroid, a parathyroid adenoma, or a parathyroidectomy. The weight of the gland plays an important role in the accuracy of the test, as also the preoperative PTH levels.

CLINICAL RELEVANCE/APPLICATION

(99mTc) sestamibi is a highly accurate test that can be employed as a single localizing modality for identifying a parathyroid adenoma.

A Comparative Analysis of Myocardial Perfusion on Gated SPECT versus Coronary Atherosclerosis and Calcium Score on 64-Slice CT

(RSNA 2018, Sun Nov 25 2018 11:05AM – 11:15AM ROOM Z44)

PURPOSE

The aim of the current study was to compare the results of 64-slice CT and gated SPECT on a regional basis (per vessel distribution territory) in patients with known or suspected CAD.

METHOD AND MATERIALS

Three hundred and seventy five patients underwent both gated SPECT for myocardial perfusion imaging and 64-slice CT for coronary calcium scoring and coronary angiography. The coronary calcium score was determined for each coronary artery. Coronary arteries on multislice CT angiography were classified as having no CAD, insignificant stenosis (<50% luminal narrowing),significant stenosis, or total or subtotal occlusion (>90% luminal narrowing).Gated SPECT findings were classified as normal or abnormal (reversible or fixed defects) and were allocated to the territory of one of the various coronary arteries.

RESULTS

In coronary arteries with a calcium score of 10 or less, the corresponding myocardial perfusion was normal in 96 %. In coronary arteries with extensive calcifications (score > 400), the percentage of vascular territories with normal myocardial perfusion was lower, 48%. Similarly, in most of the normal coronary arteries on 64-slice CT angiography, the corresponding myocardial perfusion was normal on SPECT in >94%. In contrast, the percentage of normal SPECT findings was significantly lower in coronary arteries with obstructive lesions (<57%) or with total or subtotal occlusions (<10%) (P < 0.01). Nonetheless, only 42% of vascular territories with normal perfusion corresponded to normal coronary arteries on multislice CTangiography, whereas insignificant and significant stenosis were present in, respectively, 40% and 18% of corresponding coronary arteries. CONCLUSION Although a relationship exists between the severity of CAD on multislice CT and myocardial perfusion abnormalities on SPECT, analysis on a regional basis showed only moderate agreement between observed atherosclerosis and abnormal perfusion. Accordingly, 64-slice CT and gated SPECT provide complementary rather than competitive information, and further studies should address how these two modalities can be integrated to optimize patient management. CLINICAL RELEVANCE/APPLICATION Accordingly, 64-slice CT and gated SPECT provide complementary rather than competitive information.

Evaluating Variability in Knee CartiGram MRI – A Quantitative Study

(RSNA 2018, Thu Nov 29 2018 11:50AM – 12:00PM ROOM Z15)

PURPOSE

MRI cartilage assessment using CartiGram is a widely used T2 mapping sequence to non-invasively detect changes in cartilage. We tested the robustness of the technique by quantitatively measuring intra- and inter-scanner variability of T2 values.

METHOD AND MATERIALS

Our study had two parts. First, a phantom containing NaCl, GdCl3 and Agarose was created to mimic human meniscus, muscles, cartilage and synovium. A T2 CartiGram (test) and T1w IR-TSE (gold standard) were performed on a 3.0T (750W, GE Healthcare) and 1.5T (HDxt, GE Healthcare) MRI scanners. A phantom integrity test was performed at the end. Obtained data was evaluated by creating T2 maps and calculation of T2 mean±SD. Second, in two healthy volunteers, a T2 CartiGram was performed twice, at an interval of 10 minutes with subject lying still in the scanner, each on both the scanners on the same day. T2 maps were created and mean±SD and Relative Percentage Difference (RPD) calculated. Additional 2-D wear maps were created to check for anatomical variability.

RESULTS

Phantom: 3.0T MRI showed T2 values of 26.5±1.4 in meniscus, 61±3.5 in muscles and 56±2.9, 71.4±3.8 and 78±5.5 in three cartilage samples. The 1.5T MRI showed T2 values of 28±1.2 in meniscus, 62.3±3.4 in muscles and 52.9±2.9, 77.5±5.4 and 89±7.3 in the three cartilage samples.
Healthy Volunteers: The RPDs on the same scanner for subject 1 were 3.5% (on 3.0T) and 3.8% (on 1.5T) on the medial femoral cartilage and -1.7% (on 3.0T) and -1% (on 1.5T) on the lateral, and for subject 2, they were -0.4% (on 3.0T) and 4.8% (on 1.5T) on the medial and 1.2% (on 3.0T) and 5.5% (on 1.5T) on the lateral. The 1.5T scanner reported a lower overall T2 value than the 3.0T, in contrast to the phantom results. Visual inspection of the 2D wear maps by a musculoskeletal radiologist revealed variability of T2 signal with no observable pattern.

CONCLUSION

There exists variability in T2 values of CartiGram when performed in healthy volunteers across both, different time points and different field-strengths. Further studies are needed to re-evaluate the threshold of 40ms for cartilage pathology and define MRI machine-specific guidelines.

CLINICAL RELEVANCE/APPLICATION

Significant differences in T2 values on CartiGram can lead to difficulty in diagnoses of borderline cases in clinical practice.

T2 Nerve Imaging of the Brachial Plexus Using Compressed-SENSE Effect on Image Quality and Acquisition Time

(RSNA 2018, Wed Nov 28 2018 3:40PM – 3:50PM ROOM Z17)

PURPOSE

In this study, compressed sensing is combined with the parallel-imaging or SENSE infrastructure, i.e., Compressed-SENSE (CSENSE), for accelerating anatomical MR data acquisition by exploiting the multi-element receiver coil sensitivity variation and sparsity constraining. We quantitatively evaluate the dual role of CSENSE imaging in reducing scan time without loss in resolution and in improving resolution with minimal increase in scan time.

METHOD AND MATERIALS

Ten healthy volunteers were scanned on a 3.0T MRI (Ingenia, Philips) using a proprietary “3D NerveView Sequence” (NVS), a T2W TSE isotropic sequence (TR 2200, TE 170, 2 mm slice thickness). Three versions of NVS were developed, SEQ1 (no CSENSE), SEQ2 (CSENSE factor = 9) and SEQ3 (CSENSE factor = 9) with acquisition times 6:16, 3:22 and 8:19 minutes respectively. SEQ1 and SEQ2 had the same acquisition and recon matrix of 252X325 and 640X640 while SEQ3 had a higher resolution having acquisition and recon matrix of 316X414 and 720X720 respectively. Contrast-to-Noise Ratio (CNR) was measured in all at the levels of the nerve roots (C5 to T1 levels), trunks and cords using Shinkei’s formula of CNR = (SI-Nerve – SI-Muscle)/ (SI-Nerve + SI-Muscle) where SI is average Signal Intensity in the region.

RESULTS

There was no significant difference in CNR for roots in all three sequences, i.e. SEQ1 – 0.7102±0.102, SEQ2 – 0.7040±0.044 and SEQ3 – 0.7253±0.035. In the trunks, SEQ3 performed as well as SEQ1 with a CNR of 0.567±0.10 against 0.5497±0.09. SEQ2 had a lower CNR of 0.4843±0.11. At the level of cords, SEQ1 outperformed both SEQ2 and SEQ3 with a CNR of 0.4248±0.17 against 0.3079±0.11 and 0.3505±0.19 respectively. We note that CSENSE performs better in areas where average CNR is on the higher side.

CONCLUSION

While CSENSE gives radiologists flexibility of reducing time or increasing resolution, the decision of when and how to use CSENSE depends on the clinical context. It can be used to reduce scan time when root lesions are suspected and improve resolution when lesions of the trunks and cords are suspected.

CLINICAL RELEVANCE/APPLICATION

Compressed Sensing for nerve imaging should be part of every radiologist and technologists’ arsenal to conduct patient-specific personalised scanning. Lower scan time leads to improved patient comfort and hence less motion artefacts, and higher resolution improves diagnostic accuracy of the scan.

Acceleration of MR Imaging of Spine Using Compressed-SENSE: A Comparison with Existing Standard of Care Clinical Acquisition Methods

(RSNA 2018, Wed Nov 28 2018 11:30AM – 11:40AM ROOM Z41)

PURPOSE

To objectively evaluate the impact of Compressed-SENSE (CSENSE), a novel acquisition technique that combines compressed sensing with parallel imaging (or SENSE), on acquisition time and image quality in MR imaging of the spine.

METHOD AND MATERIALS

Current standard of care clinical axial T1 and T2-weighted acquisitions of the cervical and lumbo-sacral spine were modified to obtain higher acceleration with CSENSE (CSENSE factor 1.3999). Twenty-six patients were scanned both, with and without CSENSE, on a 3.0 T wide-bore MRI (Ingenia, Philips Healthcare). The images were anonymised and shared with three specialist MRI radiologists blinded to the acquisition type. Both sets of images were rated on a scale of 1 to 5 for image quality and delineation of specific structures including vertebral bodies, lateral recess, neural foramina, facet joints, cauda equina, nerve roots, spinal cord and paraspinal muscles. Disc abnormalities, foraminal stenosis, nerve root compression and facet joint degeneration were also rated. Dicom metadata was analysed to assess scan time acceleration (ratio of original time to CSENSE time).

RESULTS

Interrater agreement on image quality was compared between the Normal and CSENSE scans via a multivariate non-parametric Hotelling\’s T2 test. There was no statistically significant difference between Normal and CSENSE scans in the 12 measures evaluated by each radiologist (alpha < 0.001 level). Further, the mean percentage observed agreement between Normal and CSENSE scans for all three measures across the radiologists was 93%. The average time acceleration achieved using CSENSE on axial T1 was 1.41 and on axial T2 was 1.36 and the average time saved was 58 seconds (29%) and 50 seconds (26%) respectively.

CONCLUSION

There is no difference in image quality between current standard of care and CSENSE-based T1 and T2 axial MRI scans of the spine. Compressed-SENSE in the spine can reliably replace current axial T1 and T2 acquisitions without loss in image quality and with significant reduction in scan time.

CLINICAL RELEVANCE/APPLICATION

The potential for CSENSE to accelerate MRI acquisition without hampering image quality will increase patient throughput and patient compliance in MR scanning.

Correlation of 99mTc-TRODAT-1 SPECT Imaging Findings and Clinical Staging of Parkinson’s Disease

(Accepted Poster at RSNA 2018, Tue Nov 27 2018 12:45PM – 1:15PM)

PURPOSE

Parkinson’s disease (PD) in a progressive neurodegenerative disorder that results in loss of dopaminergic neurons in the striatum. Its clinical diagnosis relies on the presence of cardinal motor symptoms of bradykinesia, rigidity, resting tremors and postural instability. 99mTc-TRODAT-1 is a sensitive diagnostic test for early detection of PD. We evaluate 99mTc-TRODAT-1 SPECT imaging patterns and assess their correlation with disease severity in clinically diagnosed patients of Parkinson’s disease.

METHOD AND MATERIALS

The study included 241 diagnosed patients of clinically probable PD who underwent 99mTc-TRODAT-1 SPECT scan. Binding ratios (BR) were calculated for each striatum, caudate, and putamen individually, by drawing region of interest (RoI). Occipital cortex was taken for background correction. Correlation of binding ratio with increasing clinical stage was derived.

RESULTS

Median binding ratio (BR) was the least in the contralateral putamen for all stages of Modified Hoehn and Yahr. A statistically significant negative correlation was found between increasing disease severity and BR in all sub-regions of striatum. Significant decline was noted in the binding ratio of the putamen as compared to caudate. Patients were further clinically categorized into postural-instability gait disorder (PIGD) group, and tremor-dominant PD (TD) group. No significant asymmetry was found between the left and right striatum in patients belonging to PIGD group and in those with bilateral tremors without lateralization. Significant correlation was found between decline in striatal binding on both the sides, even in early stages when patients presented with unilateral symptoms.

CONCLUSION

99mTc-TRODAT-1 SPECT can successfully detect and assess disease severity of PD.

CLINICAL RELEVANCE/APPLICATION

99mTc-TRODAT-1 SPECT should be used for early detection and assessment disease severity of PD and thereby guide treatment.

Synthetic PET Generator: A Novel Method to Improve Lung Nodule Detection by Combining Outputs from a Pix2pix Conditional Adversarial Network and a Convolutional Neural Network Based Malignancy Probability Estimator

(Accepted Poster at RSNA 2018, Tue Nov 27 2018 12:15PM – 12:45PM)

BACKGROUND

Assessment of malignancy of lung nodules on CT scans is a subjective and arduous task for radiologists with low reported accuracy rates, especially for small nodules. We propose a novel method to generate a synthetic PET image of the lung from CT images using Conditional Generative Adversarial Networks (cGAN) that can improve the sensitivity of the radiologist in the detection of malignant lung nodules.

EVALUATION

We used a combination of a PET Generator combined with a Malignancy Probability Estimator to generate a synthetic PET image from Lung CT scan. The PET Generator is a conditional adversarial network (pix2pix) trained on slices containing the Lung from 100 PET-CT scans which were acquired on patients suspected or diagnosed with Lung Cancer. The model performed at a mean squared error of 0.08 when compared in SUV units. The malignancy probability estimator is a 20-layer deep residual convolutional neural network trained on a dataset of 1595 scans from the NLST trial. The model performed produced a ROC of 0.89 when tested on 822 patients. The outputs of the PET Generator provides a background for overlaying outputs of the Malignancy Probability Estimator which together produce the synthetic PET image.

DISCUSSION

When tested on a dataset of 30 images, the synthetic PET model performed at a mean squared error of 0.08 when compared in SUV units. The malignancy model was independently tested on 350 scans and produced an AUC of 0.89.

A dataset of 22 malignant scans is used to benchmark performance of malignancy detection. Using the CT scan alone, three radiologists had sensitivities of 86%, 81% and 72% in detecting malignant studies. Using the synthetic PET as an additional modality, an increased sensitivity of 95% can be obtained. However, it is important to note that the SUV values detected on the nodules were not correlated with the actual SUV values.

CONCLUSION

Synthetic PET images can potentially increase the sensitivity of malignant nodule detection from Lung CT images. Such a modality can be easier for radiologists to understand than naive probability heatmaps. Further research is required to investigate the effect of potential biases and investigate appropriate clinical application.

Neuroimaging Evidence of Structural and Functional Brain Plasticity After Sight Onset Late in Childhood

(RSNA 2018, Mon Nov 26 2018 3:00PM – 3:10PM ROOM Z21)

PURPOSE

Direct data from human subjects on the validity of the “critical period” of brain development and the permanent detrimental impact of sensory deprivation during this period is lacking. We present evidence for neural plasticity in congenitally blind children following sight restoration.

METHOD AND MATERIALS

Pre- and post-treatment scans of 15 participants (8 to 24 years) who had been treated for bilateral congenital blindness were done on a 3.0T MRI (750w, GE Healthcare) using a 32 channel brain coil. A high-resolution T1-weighted fast spoiled gradient echo anatomical scan was acquired for each participant. To measure blood oxygen level dependent (BOLD) contrast, 35 slices parallel to the AC/PC were acquired using standard T2 weighted gradient-echo echoplanar imaging. A diffusion-weighted scan (40 direction + 5 b0; 74.4 ms TE; 13.7s TR; 2×0.86×0.86 mm3; FOV: 256 x 256 x 72; b = 1000 nm/s2) was performed for diffusion tensor tractography.

RESULTS

Using functional connectivity analyses, we find marked changes in the functional organization of the visual cortex. There is a significant enhancement of cortical decorrelation as a function of time following sight onset. The fusiform facial area (FFA) and occipital facial area (OFA) develop rapidly. Structural imaging demonstrates increase in both volume and thickness of grey matter compared to controls, especially in the fusiform. Analysis of the optic tract in the same participants revealed no change in mean diffusivity (MD) and fractional anisotropy (FA) during the post-treatment period, while the FA of the optic radiation decreased steeply over 2 years.

CONCLUSION

Contrary to our expectation of limited neural plasticity late in the developmental timeline, we find strong evidence of brain malleability using both functional and structural imaging. Our findings help explain the behaviourally observed gains in visual proficiency congenitally blind individuals exhibit as a function of time after sight restoring surgery.

CLINICAL RELEVANCE/APPLICATION

Our study presents evidence for brain plasticity and hence opens up treatment avenues for conditions such as late-diagnosed congenital blindness.

Posterior Cortical Variant Alzheimer’s Disease and Lew Body Dementia: Similarities and Differences on FDG PET Scan

(RSNA 2018, Mon Nov 26 2018 3:30PM – 3:40PM ROOM Z44)

PURPOSE

Posterior cortical atrophy (PCA) is a form of dementia considered to be an atypical variant of Alzheimer\’s disease (AD) and Dementia with Lewy bodies (DLB) is a type of posterior dementia characterized by fluctuating levels of cognition, changes in behavior, visual hallucinations with accompanying extrapyamidal motor symptoms. We attempt to identify specific core areas on FDG PET imaging which are common to both and also establish the differences which may be helpful to differentiating the two.

METHOD AND MATERIALS

We retrospectively analysed of 30 patients with clinically suspected posterior dementia. All the subjects underwent F-18 FDG PET CT scan of the brain and the studies were analyzed both qualitatively (visually) and semi-quantitatively. The subjects had undergone dopamine transporter imaging with Tc 99 m TRODAT 1 on a prior date. The subjects were divided into possible PCA with TRODAT scan normal (n=10) and possible DLB with abnormal (n=20). The FDG uptake patterns were recorded and areas of cortical hypometabolism in the cerebral cortex that were two standard deviations from the mean were considered as abnormal.

RESULTS

All the subjects had an abnormal pattern of F-18 FDG uptake on PET scan, both on visual inspection and semiquantitative analysis. Bilateral parieto-occipital hypometabolism was consistently found in all the subjects. Hypometabolism in precuneus, posterior cingulate and the cortex around the angular gyrus was present in all the subjects of PCA with relative sparing of the medial occipital cortices. DLB subjects showed variable degrees of involvement of the medial occipital cortices with relative sparing of posterior cingulate and precuneus.

CONCLUSION

FDG PET scan can act as a non-invasive diagnostic modality in differentiating the two posterior cortical dementias despite significant clinical and imaging overlap.

CLINICAL RELEVANCE/APPLICATION

We present features based on which FDG-PET can be used to diagnose and differentiate Posterior Cortical Atrophy (PCA) and Dementia with Lewy Bodies (DLB) in the clinical practice.

Hepatic Shear Wave Elastography: Correlation Between Liver Stiffness and Esophagogastric Varices

(RSNA 2018, Mon Nov 26 2018 11:40AM – 11:50AM ROOM Z10)

PURPOSE

To evaluate the role of liver stiffness measurement (LSM) measured by shear wave elastography (SWE) in predicting the presence of esophagogastric varices (EGV) in patients with portal hypertension and to determine the correlation between the LSM and endoscopic grade of EGV.

METHOD AND MATERIALS

This study included 331 patients with chronic liver disease being evaluated for portal hypertension and planned for esophagogastroduodenoscopy. SWE was performed in the right lobe of the liver by using a convex broadband probe on GE LOGIQ E9 ultrasound machine. The shear wave liver stiffness (in kPa) was recorded at ten locations and the median values calculated. Endoscopic findings were interpreted with reference to the presence of varices and grade of the varices. Correlation between LSM and grade of varices was analyzed with the Pearson correlation coefficient. Multiclass Receiver operating characteristic (ROC) curves were constructed, and the area under the ROC curves (AUC) was calculated to determine the discriminating power between the grades of the varices.

RESULTS

LSM and variceal grade showed no significant correlation (R = 0.351286, P <0001). The AUC for detection of the presence of varices was 0.7259. The AUC for differentiating between various grades of the varices was 0.6470, 0.5802, 0.6259 and 0.7692. Box plot of the LSM and grade of varices revealed no discrimination power. Hepatic shear wave stiffness was marginally useful in predicting the presence of varices. But the discriminating power of LSM among the grades of varices was poor.

CONCLUSION

We found marginal utility of LSM in predicting the presence of EGV. However, contrary to the existing knowledge, in our study, we found no correlation between liver stiffness measurement and grade of EGV. The liver stiffness measurement is not a reliable predictor of portal hypertension.

CLINICAL RELEVANCE/APPLICATION

In advanced fibrosis, liver stiffness measurements in isolation does not seem to predict the clinical severity of portal hypertension. The additional assessment of splenic stiffness should be considered.