Evaluation of pseudocapsule of uterine myomas with contrast enhanced ultrasound (CEUS) Poster No.:

C-0376

Congress:

ECR 2014

Type:

Scientific Exhibit

Authors:

C. Martini , F. Lacelli , G. Grillo , N. Gandolfo , D. Orlandi , G.

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Serafini ; Genova/IT, Pietra Ligure/IT Keywords:

Genital / Reproductive system female, Ultrasound, Technical aspects

DOI:

10.1594/ecr2014/C-0376

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Aims and objectives Uterine leiomyomas are the most frequent benign tumors of the female genital tract (they affect 20-50% of all women), that arise from the smooth-muscle cells of the human uterus. Uterine myomas shows a heterogeneous vascularity. Wei et al. showed that hypoxia, as measured by HIF-1 expression, was higher throughout large fibroids (>10 cm diameter) than in normal myometrium or in small myomas. The authors concluded that small myomas and the periphery of large myomas are more 'biologically active' than myometrium and that large myomas grow from their periphery. This peripheral growth pattern explains the neurovascular pseudocapsule that surrounds myomas. The pseudocapsule vessels coming from the surrounding myometrium throw themselves in group to the centre of the vascular network to form a sort of pedicle: the veins surrounding myoma circulate under the pseudocapsule arranged in a plexus. The presence of an active angiogenesis is concordant with the histological studies that describe a parallel array of extremely dense capillaries in the pseudocapsule and in the adjacent myometrium that are absent in the myomas.

Images for this section:

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Fig. 1: Didactic scheme of PNB vascularity.

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Fig. 2: Myoma with PNB vascularity detectable at color Doppler evaluation.

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Fig. 3: Myoma with PNB vascularity detectable at CEUS. Asterisk: peripheral "ring of fire" detectable 2-4s before myoma enhancement.

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Methods and materials 134 uterine myomas in 115 patients (23-48y) were investigated with US, CEUS and FSE T2-weighted and contrast-enhanced WAVE T1 3D SPIR MRI previously and after UFE. Images were retrospectively evaluated by two experienced in gynecological system radiologists, in order to assess PNB features; in particular they noted: US b-mode evidenc, US b-mode features, vascularity at arterious and at venous time and MRI features and c.e. behavior. Images for this section:

Fig. 4: A) Myoma with no detectable vascularity at CD. B) Myoma with low PNB vascularity in CEUS arterial phase. C) CEUS venous phase.

Fig. 5: D) Axial FSE T2 and CE WAVE T1 (E) sequences

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Fig. 6: F-G) Pre-embolization CEUS and angiography myoma's vascularity assessment. H-I) Post- embolization CEUS and angiography myoma's vascularity assessment.

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Results PNB can be seen with ultrasound (US) in 84,3% of all myomas and in 100% of large myomas. It appears as an homogeneous ipoechoic thickening (3 mm ± 0,2), that is better detectable on the superficial side of the myoma. At color-Doppler evaluation the PNB appears as avascular in 75,7% of cases and only in 24,3% of cases the PC can be seen at color-Doppler as pulsating signal; this finding could be explained because of the predominant slow-flow venous vascularity. At contrast enhanced US (CEUS) PNB is well detectable as a ring of enhancement that surrounds the myoma ("ring of fire"). This enhancement is detectable in the arterial phase, 2-4 seconds before the enhance of the proper myoma's arteries. However this kind of pattern is not always detectable; in 75% of cases the PNB is detectable only in wash-out phase, with persistence up to 40 seconds; this feature suggests its maily venous nature. MRI is performed with FSE T2-weighted sequences the PNB appears as an hyperintense thin layer separated from the myometrium by a narrow avascular cleft. Contrastenhanced WAVE T1 3D SPIR sequences, showed an omogeneous c.e. of the PNB during uterus and myoma wash-in phase only in the 23,4% of cases, while in the 71,8% we detected the c.e. in the wash-out phase. Angiography is carachterized by an inferior spatial resolution than US, so with this technique PNB is clearly detectable only in the 37% of cases. It can be detectable during arterious phase as thin vessels peripheral to the myoma with earlier appearence (2-4 seconds) than myoma's vessels. Sometimes it appears in washout phase as a vascular halo that surrounds the myoma. PNB vessels have larger diameter tha myoma's ones and so, after uterine fibroid superselective embolization (UFE) primary with 500-700µm and, in presence of persitent patent vessels, with 700-900µm embospheres (Biospheres®) vascular features of PNB are presereved and appears the same than before the treatment. Images for this section:

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Fig. 7: A) B-Mode evaluation of myomas B)CEUS shows a early enhancement of PNB. Asterisk: peripheral "ring of fire" detectable 2-4s before myoma enhancement. C) CEUS venous phase. D) Sagittal CE WAVE T1 sequences before embolization. E) Preembolization angiography. F) Post-embolization CEUS vascularity evaluation showing embospheres (arrows) inside myoma's vessels and persistance of PNB vascularity. G) Post-embolization angiography. H) Post embolization sagittal CE WAVE T1 3D SPIR sequence showing no enhancement of myoma's vessels and persistance of PNB vascularity.

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Fig. 8: A) CEUS shows discontinuous early enhancement of PNB. B) CEUS venous phase showing a more evident late enhancement of PNB. C) Pre-embolization angiography. D) Pre-embolization sagittal FSE T2W sequence showing a poorly detectable pseudocapsule. E) Pre-embolization sagittal CE WAVE T1 3D SPIR sequence PNB enhancement (arrows) F) Post-embolization angiography.

Fig. 9: A) B-Mode evaluation of myoma B) Early arterial phase C) CEUS shows discontinuous enhancement of PNB in venous phase. D) Axial CE WAVE T1 3D SPIR sequence. Asterisk: hyaline degeneration E) Pre-embolization angiography. F,G) Post-embolization CEUS vascularity evaluation showing embospheres inside myoma's vessels (arrows) and persistance of PNB vascularity. H) Post-embolization angiography.

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Conclusion The pseudocapsule can be seen as the adaptive response of the uterus to mechanical overload, aimed to maintain uterus functionality, promoting muscular repair and regeneration. Furthermore PNB is not made up only by vessels, but it is also significantly innervated and it responds to Substance P (SP) and the Vasoactive Intestinal Polypeptide (VIP), both involved in the musculature regulation. On the basis of these observations, histological investigations on the fibroid vascular pseudocapsule were performed, to better understand their role in the modern minimally invasive surgical approach in women. The treatment of choice of myomas should save the PNB and avoid destructive proceedings such as diathermo coagulation, which alters these neuro-transmitters or damages the PNB vessels. Surgical intracapsular myomectomy, being able to preserve the PNB vessels, lead to an optimal reconstruction of the damaged tissue and a high quality muscle scar formation. CEUS allows an accurate assessment of uterine myomas vascularity and in our experience is also able to detect PNB preservation after superselective embolization with 500-700/ 700-900 µm embospheres. UFE rapresent a "gentle" therapy of myoma because the preservation of the pseducapsule is a key-point in the uterine healing and conservation of normal functionality. Images for this section:

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Fig. 10: Istological analisys of myometrium, pseudocapsule and myoma(A. Tinelli, JSLS 2012).

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Fig. 11: Intracapsular Myomectomy: after incision by Hook electrode at low wattage (30 watt) of the uterine serosa till to myome- trium, in the midline longitudinal plane, the myoma pseudocapsule arises (A.Tinelli, Human Reproduction 2012).

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Personal information References 1.

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