Building contrast-enhanced CT-based models for preoperatively predicting malignant potential and Ki67 expression of small intestine gastrointestinal stromal tumors (GISTs)

PURPOSE

To assess contrast-enhanced computed tomography (CE-CT) features for predicting malignant potential and Ki67 in small intestinal gastrointestinal stromal tumors (GISTs) and the correlation between them.

METHODS

We retrospectively analyzed the pathological and imaging data for 123 patients (55 male/68 female, mean age: 57.2 years) with a histopathological diagnosis of small intestine GISTs who received CE-CT followed by curative surgery from May 2009 to August 2019. According to postoperatively pathological and immunohistochemical results, patients were categorized by malignant potential and the Ki67 index, respectively. CT features were analyzed to be associated with malignant potential or the Ki67 index using univariate analysis, logistic regression and receiver operating curve analysis. Then, we explored the correlation between the Ki67 index and malignant potential by using the Spearman rank correlation.

RESULTS

Based on univariate and multivariate analysis, a predictive model of malignant potential of small intestine GISTs, consisting of tumor size (p < 0.001) and presence of necrosis (p = 0.033), was developed with the area under the receiver operating curve (AUC) of 0.965 (95% CI, 0.915-0.990; p < 0.001), with 91.53% sensitivity, 96.87% specificity, 96.43% PPV, 92.54% NPV, 94.31% diagnostic accuracy. For high Ki67 expression, a model made up of tumor size (p = 0.051), presence of ulceration (p = 0.054) and metastasis (p = 0.001) may be the best predictive combination with an AUC of 0.785 (95% CI, 0.702-0.854; p < 0.001), 63.33% sensitivity, 76.34% specificity, 46.34% PPV, 86.59% NPV, 73.17% diagnostic accuracy. Ki67 index showed a moderate positive correlation with mitotic count (r = 0.578, p < 0.001), a weak positive correlation with tumor size (r = 0.339, p < 0.001) and with risk stratification (r = 0.364, p < 0.001).

CONCLUSION

Features on CE-CT could preoperatively predict malignant potential and high Ki67 expression of small intestine GISTs, and Ki67 index may be a promising prognostic factor in predicting the prognosis of small intestine GISTs, independent of the risk stratification system.

Neuromuscular neutral zones associated with viscoelastic hysteresis during cyclic lumbar flexion

STUDY DESIGN

The reflexive EMG from the L3-L4 to L5-L6 multifidus of the in vivo feline was recorded during application of single passive flexion-extension cycle of the lumbar spine.

OBJECTIVE

To determine the effect of viscoelastic hysteresis associated with a single-cycle flexion-extension and of increasing cycle frequency on the initiation and cessation displacement and tension thresholds of reflexive EMG from the multifidus muscles.

SUMMARY OF BACKGROUND DATA

It is known that reflexive EMG can be recorded from some paraspinal muscles as a result of mechanical stimulation of lumbar ligaments and other viscoelastic structures. It is also known that mechanical neutral zones exist in the spine, that viscoelastic hysteresis is associated with a stretch-release cycle, and that the rate of stretch and release has a profound impact on viscoelastic tissue responses. It is unknown what are the neurologic neutral zones of the spine within which reflexive EMG does not exist, as well as the dependence of such neurologic neutral zones on viscoelastic hysteresis and increasing frequency of a flexion-extension cycle.

METHODS

Single passive flexion-extension cycles of frequencies ranging from 0.1 to 1.0 Hz were applied to the lumbar spine of the feline while recording intramuscular EMG from the L3-L4 to L5-L6 multifidus. The displacement and tension thresholds associated with the initiation and cessation of EMG activity during the cycle were analyzed with respect to the cycles' viscoelastic hysteresis and frequency. The peak EMG discharge was tested for relationships with cycle frequency.

RESULTS

The displacement and tension thresholds during the flexion phase of the cycle were significantly lower than the corresponding thresholds in the extension phase of the cycle. As the cycle frequency increased, EMG was triggered significantly earlier (lower displacement and tension thresholds) in the flexion phase and terminated earlier (higher displacement and tension thresholds) in the extension phase. The peak EMG was significantly larger as cycle frequency increased.

CONCLUSIONS

Reflexive muscle forces are triggered at lower displacement or tension during flexion but diminish early during extension, leaving the spine unprotected for a substantial part of the extension movement. The muscle forces are recruited earlier and with larger intensity as the velocity of the movement increases, lending more protection to the spine. Faster extension movement, however, creates a larger window during which the spine is exposed to instability and injury because of lack of muscle forces.

Neuromuscular neutral zones sensitivity to lumbar displacement rate

OBJECTIVES

To determine the displacement and tension thresholds (developed during anterior lumbar flexion) which trigger reflexive muscular activity in the multifidus muscles; their variability with the velocity of flexion; and the pattern of threshold variability across the lumbar spine.Design. An in-vivo study of the feline during passive lumbar flexion applied via the L-4/5 supraspinous ligament.

METHOD

EMG from six pairs of intramuscular electrodes inserted in the L-1/2 to L-6/7 multifidus muscles was recorded while the lumbar spine was passively flexed to 75% of the physiological strain of the supraspinous ligament at rates of 17-100%/s. Three-dimensional models of tension threshold, flexion rate and lumbar levels were developed from the experimental data.

RESULTS

Displacement and tension thresholds were the lowest at the fastest flexion rate and gradually increased as flexion rates decreased. Electromyographic activity was detected at low thresholds at the center of the flexion and at gradually increasing thresholds at higher and lower lumbar segments.

CONCLUSION

Multifidus reflexive muscular activity, which stabilize the spine, is triggered at a displacement and tension thresholds of 5-15% of the physiological range. Earlier activation of muscular activity occurs as the velocity of flexion increases. Earlier activation also occurs near the center of flexion.

RELEVANCE

Sensory-motor neurological feedback maintains spine stability and is responsive to the velocity of lumbar motion. A neuromuscular silence exists in small lumbar movements in which spine stability is not protected by the musculature. Spine models constructed to predict risk factors could benefit from incorporating this new information.