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Summary We have demonstrated the feasibility of an endoscopic ultrasound-guided injectable hydrogel separation technique using a cadaveric model to increase the space between the head of the pancreas and duodenum. Using modeling studies, we identified the minimum distance of this separation for optimal sparing of the duodenum, setting the foundation for future clinical trials using this technique to enable dose escalation with either stereotactic or intensity-modulated radiation therapy for patients with unresectable pancreatic cancer. Purpose We assessed the feasibility and theoretical dosimetric advantages of an injectable hydrogel to increase the space between the head of the pancreas (HOP) and duodenum in a human cadaveric model. Methods and Materials Using 3 human cadaveric specimens, an absorbable radiopaque hydrogel was injected between the HOP and duodenum by way of open laparotomy in 1 case and endoscopic ultrasound (EUS) guidance in 2 cases. The cadavers were subsequently imaged using computed tomography and dissected for histologic confirmation of hydrogel placement. The duodenal dose reduction and planning target volume (PTV) coverage were characterized using pre- and postspacer injection stereotactic body radiation therapy (SBRT) plans for the 2 cadavers with EUS-guided placement, the delivery method that appeared the most clinically desirable. Modeling studies were performed using 60 SBRT plans consisting of 10 previously treated patients with unresectable pancreatic cancer, each with 6 different HOP–duodenum separation distances. The duodenal volume receiving 15 Gy (V15), 20 Gy (V20), and 33 Gy (V33) was assessed for each iteration. Results In the 3 cadaveric studies, an average of 0.9 cm, 1.1 cm, and 0.9 cm HOP–duodenum separation was achieved. In the 2 EUS cases, the V20 decreased from 3.86 cm3 to 0.36 cm3 and 3.75 cm3 to 1.08 cm3 (treatment constraint <3 cm3), and the V15 decreased from 7.07 cm3 to 2.02 cm3 and 9.12 cm3 to 3.91 cm3 (treatment constraint <9 cm3). The PTV coverage improved or was comparable between the pre- and postinjection studies. Modeling studies demonstrated that a separation of 8 mm was sufficient to consistently reduce the V15, V20, and V33 to acceptable clinical constraints. Conclusions Currently, dose escalation has been limited owing to radiosensitive structures adjacent to the pancreas. We demonstrated the feasibility of hydrogel separation of the HOP and duodenum. Future studies will evaluate the safety and efficacy of this technique with the potential for more effective dose escalation using SBRT or intensity-modulated radiation therapy to improve the outcomes in patients with unresectable pancreatic cancer.

Objectives: To evaluate the performance characteristics of seven predetermined imaging features on pretreatment computed tomography (CT) in identifying extranodal extension (ENE) in cervical lymph node metastases from human papillomavirus-positive oropharyngeal carcinoma (HPV-OPC).Study Design: Retrospective study. Methods: Seventy-three patients with HPV-OPC who underwent primary surgery and cervical lymph node dissection were included. Preoperative contrast-enhanced CT (cCT) imaging was evaluated by two radiologists blinded to pathological results. Each cCT was scored for seven imaging features of interest: 1) indistinct capsular contours, 2) irregular nodal margins, 3) perinodal fat stranding, 4) perinodal fat planes, 5) nodal necrosis, 6) intranodal cysts, and 7) nodal matting. Logistic regression was employed to determine radiologist-specific odds ratios (OR) of predicting ENE for each imaging feature and radiologistspecific receiver operating characteristics (sensitivity [Sn], specificity [Sp], area under the curve [AUC], positive predictive value [PPV], negative predictive value [NPV]) for each imaging feature.Results: Thirty-two (44%) patients had ENE-positive lymph nodes. The presence of irregular margins (OR A = 12.3, 95% confidence interval [CI] A = 2.3-65.9; OR B = 7.0, 95% CI B = 1.4-36.3) and absence of perinodal fat plane (OR A = 6.8, 95% CI A = 2.0-23.3; OR B = 14.2, 95% CI B = 1.7-120.5) were significantly associated with ENE for each radiologist. Irregular nodal margin status was most specific for ENE (Sn A = 45%, Sp A = 94%, AUC A = 69%, PPV A = 82%, NPV A = 73%; Sn B = 28%, Sp B = 95%, AUC B = 61%, PPV B = 80%, NPV B = 64%). Absence of perinodal fat plane was most sensitive for ENE (Sn A = 87%, Sp A = 50%, AUC A = 69%, PPV A = 59%, NPV A = 62%; Sn B = 96%, Sp B = 34%, AUC B = 65%, PPV B = 53%, NPV B = 63%).Conclusions: Of the seven imaging features hypothesized to be associated with ENE-status, the presence of irregular nodal margins and absence of perinodal fat plane were the most specific and sensitive features, respectively.

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Ultrasound is not currently used in the standard clinical evaluation of the oropharynx, but it is a promising imaging modality for evaluating the base of the tongue and the palatine tonsils. Ultrasound is comparable and complementary to CT and MRI, which have recognized limitations.