Quantitative magnetic resonance imaging and high-intensity focused ultrasound treatment of uterine fibroids

Magnetic resonance-guided high-intensity focused ultrasound (MRgHIFU) treatment is an emerging non-invasive treatment method in which the targeted tissue is heated by high-intensity ultrasound causing coagulative necrosis. Benign muscle tumors of the uterus alias uterine fibroids can be treated with MRgHIFU though treatment outcomes have been varying. Treatment outcomes are affected by different properties of uterine fibroid tissue such as blood flow and histological structure. The blood flow of uterine fibroids can be changed by oxytocin infusion even though oxytocin’s mechanism of action on the blood flow of uterine fibroids is unknown. The present magnetic resonance imaging (MRI) based evaluation methods of uterine fibroids’ suitability for MRgHIFU treatment are not completely satisfactory. Quantitative MRI techniques can be used for measuring the histological properties of tissues in an indirect manner, which could be better for uterine fibroids’ suitability evaluation. This study investigated the feasibility of applying quantitative MRI techniques; diffusion-weighted imaging (DWI) and T2 relaxation time mapping, to predict outcomes of the MRgHIFU treatment of uterine fibroids. Based on these results, new quantitative evaluation methods were developed and compared with currently used MRI-based evaluation methods. In addition, the effect of oxytocin on the blood flow of the uterine fibroid and the myometrium was studied quantitatively using dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI). The results of this study indicate that DWI and T2 relaxation time mapping are feasible for the evaluation of MRgHIFU treatment outcomes. Evaluation methods based on these techniques also appear to be more reliable than current approaches. When utilizing DCE-MRI, it was observed that oxytocin strongly reduced the blood flow of uterine fibroids without affecting the blood flow in the myometrium, indicating that oxytocin’s effect took place solely in the uterine fibroid. The results of this work are directly applicable to the clinical practice of treating uterine fibroids with MRgHIFU.Myoomien kvantitatiivinen magneettikuvantaminen ja korkea intensiteettinen fokusoitu ultraäänihoito Magneettikuvausohjattu korkeaintensiteettinen kohdennettu ultraäänihoito (magnetic resonance-guided high-intensity focused ultrasound, MRgHIFU) on uudenlainen kajoamaton hoitomenetelmä, jossa kohdekudosta lämmitetään korkeaintensiteettisen ultraäänen avulla, mikä aiheuttaa koagulaationekroosia. Kohdun hyvänlaatuisia lihaskasvaimia eli myoomia voidaan hoitaa MRgHIFUhoidolla, mutta hoitotulokset ovat kuitenkin vaihtelevia. Hoitotuloksiin vaikuttavat myoomakudoksen erilaiset ominaisuudet kuten verenvirtaus ja histologinen rakenne. Myoomien verenvirtausta voidaan muuttaa oksitosiini-infuusiolla, mutta oksitosiinin vaikutusmekanismi myoomien verenvirtaukseen ei ole tunnettu. Nykyiset magneettikuvaukseen perustuvat myoomien soveltuvuuden arviointimenetelmät MRgHIFU-hoitoon eivät ole täysin tyydyttäviä. Kvantitatiivisilla magneettikuvaustekniikoilla voidaan mitata epäsuorasti kudosten histologisia ominaisuuksia ja siten nämä tekniikat voisivat olla parempia myoomien soveltuvuuden arvioinnissa MRgHIFU-hoitoon. Tässä tutkimuksessa arvioitiin kvantitatiivisten magneettikuvaustekniikoiden (diffuusiopainotettu kuvantaminen ja T2-relaksaatioaikakartoitus) soveltuvuutta ennustaa myoomien MRgHIFU-hoitotuloksia. Näiden tulosten perusteella kehitettiin uudet kvantitatiiviset arviointimenetelmät ja verrattiin näitä menetelmiä nykyisiin magneettikuvaukseen perustuviin arviointimenetelmiin. Lisäksi oksitosiinin vaikutusta myooman ja kohdun seinämän verenvirtaukseen tutkittiin kvantitatiivisesti käyttäen dynaamista kontrastiainetehosteista magneettikuvantamista. Tutkimuksen tulokset osoittivat, että diffuusiopainotettu kuvantaminen ja T2-relaksaatioaikakartoitus soveltuvat myoomien MRgHIFU-hoitotulosten arviointiin. Näihin tekniikoihin perustuvat arviointimenetelmät vaikuttavat olevan myös luotettavampia kuin nykyiset arviointimenetelmät. Dynaamisen kontrastitehosteisen magneettikuvantamisen avulla havaittiin, että oksitosiini vähentää voimakkaasti myooman verenvirtausta vaikuttamatta kohdun seinämän verenvirtaukseen viitaten siihen, että oksitosiinin vaikutus tapahtuu vain myoomassa. Tämän työn tulokset ovat suoraan sovellettavissa myoomien MRgHIFU-hoitojen kliinisiin käytäntöihin

Kasvinjalostus luomutuotannon monimuotoisuuden turvaajana

Loppuraportti, COBRA201

High-intensity focused ultrasound therapy in the uterine fibroid: a clinical case study of poor heating efficacy

A clinical case study of high-intensity focused ultrasound (HIFU) treatment in the uterine fibroid was conducted. During the therapy, poor heating efficacy was observed which could be attributed to several factors such as the local perfusion rate, patient-specific anatomy or changes in acoustic parameters of the ultrasound field. In order to determine the cause of the diminished heating, perfusion analyses and ultrasound simulations were conducted using the magnetic resonance imaging (MRI) data from the treatment. The perfusion analysis showed high local perfusion rate in the myoma (301.0 +- 25.6 mL/100 g/min) compared to the surrounding myometrium (233.8 +- 16.2 mL/100 g/min). The ultrasound simulations did not show large differences in the focal point shape or the acoustic pressure (2.07 +- 0.06 MPa) when tilting the transducer. However, a small shift (-2.2 +- 1.3 mm) in the axial location of the focal point was observed. The main causes for the diminished heating were likely the high local perfusion and ultrasound attenuation due to the deep location of the myoma.Comment: Conference Proceedin

Työikäisten kognitiivisen toimintakyvyn hyvä arviointikäytäntö

TOIMIA-suositu

Chromosomal regions associated with nitrogen use efficiency and disease resistance in barley

201

Fiducial markers and their impact on ablation outcome for patients treated with MR-guided transurethral ablation (TULSA): a retrospective technical analysis

Objectives: Fiducial markers improve accuracy in external beam radiation therapy (EBRT) for treatment of prostate cancer (PCa). However, many patients recur after EBRT necessitating additional treatment, such as MR-guided transurethral ultrasound ablation (TULSA). Residual markers may compromise TULSA through ultrasound field distortions and generation of local susceptibility artifacts. The objective was to investigate how markers affect the ablation outcome during clinical TULSA treatments.Subjects and methods: A retrospective analysis was performed on nine patients with radiorecurrent PCa and residual markers who received TULSA. The MR susceptibility artifact was quantified as a function of marker type, size and orientation, in particular for thermometry. The spatial distribution of markers inside the prostate was recorded, and the resulting impact on the thermal dose was measured. The thermal dose measurements were directly compared to the residual enhancing prostatic tissue observed on the immediate and control post-TULSA contrast enhanced (CE) image.Results: Successful thermal dose accumulation to the target boundary occurred for 14/20 (70%) of markers, confirmed with CE imaging. Gold markers situated simultaneously close to the urethra (≤12 mm) and far from the target boundary (≥13 mm) reduced the ultrasound depth of heating. Nitinol markers produced large, hypointense artifacts that disrupted thermometry and compromised treatment. Artifacts from gold markers were less pronounced, but when located near the target boundary, also affected treatment.Conclusion: Marker composition, orientation and location inside the prostate can all potentially impact treatment outcome. Proper patient selection through detailed MRI screening is critical to ensure successful radiorecurrent PCa treatment outcomes with TULSA.</p

Feasibility of T2 relaxation time in predicting the technical outcome of MR-guided high-intensity focused ultrasound treatment of uterine fibroids

PurposeThe aim of this study was to assess the feasibility of T2 relaxation time in predicting the immediate technical outcome i.e., nonperfused volume ratio (NPVr) of magnetic resonance-guided high-intensity focused ultrasound (MRgHIFU) treatment of symptomatic uterine fibroids and to compare it with existing T2-weighted imaging methods (Funaki classification and scaled signal intensity, SSI).Materials and methods30 patients with 32 uterine fibroids underwent an MRI study including a quantitative T2 relaxation time measurement prior to MRgHIFU treatment. T2 relaxation times were measured with a multi-echo fast imaging-based technique with 16 echoes. The correlation between pretreatment values of the uterine fibroids and treatment outcomes, that is nonperfused volume ratios (NPVr), was assessed with nonparametric statistical measures. T2 relaxation time-based method was compared to existing T2-weighted imaging-based methods using receiver-operating-characteristics (ROC) curve analysis and Chi-square test.ResultsNonparametric measures of association revealed a statistically significant negative correlation between T2 relaxation time values and NPVr. The T2 relaxation time classification (T2 I, T2 II, and T2 III) resulted in the whole model p-value of 0.0019, whereas the Funaki classification resulted in a p-value of 0.56. The T2 relaxation time classification (T2 I and T2 II) achieved a whole model of a p-value of 0.0024, whereas the SSI classification had a p-value of 0.0749.ConclusionsA longer T2 relaxation time of the fibroid prior to treatment correlated with a lower NPVr. Based on our results, the T2 relaxation time classifications seem to outperform the Funaki classification and the SSI method.</p