Evaluation of short-term response of high intensity focused ultrasound ablation for primary hepatic carcinoma: Utility of contrast-enhanced MRI and diffusion-weighted imaging

Simultaneous proton resonance frequency T1 - MR shear wave elastography for MR-guided focused ultrasound multiparametric treatment monitoring

PURPOSE

To develop an efficient MRI pulse sequence to simultaneously measure multiple parameters that have been shown to correlate with tissue nonviability following thermal therapies.

METHODS

A 3D segmented EPI pulse sequence was used to simultaneously measure proton resonance frequency shift (PRFS) MR thermometry (MRT), T1 relaxation time, and shear wave velocity induced by focused ultrasound (FUS) push pulses. Experiments were performed in tissue mimicking gelatin phantoms and ex vivo bovine liver. Using a carefully designed FUS triggering scheme, a heating duty cycle of approximately 65% was achieved by interleaving FUS ablation pulses with FUS push pulses to induce shear waves in the tissue.

RESULTS

In phantom studies, temperature increases measured with PRFS MRT and increases in T1 correlated with decreased shear wave velocity, consistent with material softening with increasing temperature. During ablation in ex vivo liver, temperature increase measured with PRFS MRT initially correlated with increasing T1 and decreasing shear wave velocity, and after tissue coagulation with decreasing T1 and increasing shear wave velocity. This is consistent with a previously described hysteresis in T1 versus PRFS curves and increased tissue stiffness with tissue coagulation.

CONCLUSION

An efficient approach for simultaneous and dynamic measurements of PRSF, T1 , and shear wave velocity during treatment is presented. This approach holds promise for providing co-registered dynamic measures of multiple parameters, which correlates to tissue nonviability during and following thermal therapies, such as FUS.

Role of diffusion-weighted MRI for prediction of regional lymph node positivity in radiologically organ-confined renal tumour: a prospective study

Background

Lymph node metastasis is one of the major factors that decide the prognosis of renal cell carcinoma. Presently, lymphadenectomy is only accepted as the most precise and dependable staging method to detect lymph node invasion; still, its therapeutic value for renal cell carcinoma is controversial. Diffusion-weighted magnetic resonance imaging along with its apparent diffusion coefficient value has already shown great value as a non-invasive modality to detect early microstructural changes in various human tumours. The present study is done to know the role of DWMRI in determining regional lymph node positivity in radiologically organ-confined renal cell carcinoma.

Methods

In this prospective study, we measured the ADC value of renal mass and regional lymph node in patient of RCC. ADC value < 1.25 is taken as cut-off to determine lymph node involvement. A malignant lymph node was confirmed by histopathology postoperatively. After that, we analysed the data retrospectively and studied the association between cut-off ADC value and lymph node positivity.

Results

Total 44 patients of RCC were evaluated in the study. Out of 44 patients, lymph node was found to be malignant on histopathology in 25 (56.8%) patients, and of these, 23 patients had ADC value < 1.25. This association was statistically significant (p < 0.05). The findings of DW MRI were accurate in 72.7% of patients with sensitivity of 63.1%, specificity of 80% and positive predictive value of 70.5%.

Conclusions

Lymph node with ADC value < 1.25 × 10–3 mm2/s has higher probabilities of harbouring malignant cell, so ADC value of DWMRI can be used as a sensitive and specific parameter to differentiate malignant lymph node from benign lymph node. However, our futuristic observation needs to be validated by multi-institutional large sample cohort.

Systematic review of the role of high intensity focused ultrasound (HIFU) in treating malignant lesions of the hepatobiliary system

BACKGROUND

High Intensity Focused Ultrasound (HIFU) is an emerging non-invasive, targeted treatment of malignancy. The aim of this review was to assess the efficacy, safety and optimal technical parameters of HIFU to treat malignant lesions of the hepatobiliary system.

METHODS

A systematic search of the English literature was performed until March 2020, interrogating Pubmed, Embase and Cochrane Library databases. The following key-words were input in various combinations: 'HIFU', 'High intensity focussed ultrasound', 'Hepatobiliary', 'Liver', 'Cancer' and 'Carcinoma'. Extracted content included: Application type, Exposure parameters, Patient demographics, and Treatment outcomes.

RESULTS

Twenty-four articles reported on the clinical use of HIFU in 940 individuals to treat malignant liver lesions. Twenty-one studies detailed the use of HIFU to treat hepatocellular carcinoma only. Mean tumour size was 5.1 cm. Across all studies, HIFU resulted in complete tumour ablation in 55% of patients. Data on technical parameters and the procedural structure was very heterogeneous. Ten studies (n = 537 (57%) patients) described the use of HIFU alongside other modalities including TACE, RFA and PEI; 66% of which resulted in complete tumour ablation. Most common complications were skin burns (15%), local pain (5%) and fever (2%).

CONCLUSION

HIFU has demonstrated benefit as a treatment modality for malignant lesions of the hepatobiliary system. Combining HIFU with other ablative therapies, particularly TACE, increases the efficacy without increasing complications. Future human clinical studies are required to determine the optimal treatment parameters, better define outcomes and explore the risks and benefits of combination therapies.

High-Intensity Focused Ultrasound Ablation for Unresectable Primary and Metastatic Liver Cancer: Real-World Research in a Chinese Tertiary Center With 275 Cases

This retrospective analysis was conducted to evaluate the feasibility and safety of high-intensity focused ultrasound ablation for primary liver cancer and metastatic liver cancer. Patients with liver cancer who received high-intensity focused ultrasound were included in this analysis, including a primary liver cancer cohort (n=80) and a metastatic liver cancer cohort (n=195). The primary endpoint of our research was tumor response. The secondary endpoints included survival outcomes, visual analog scale pain scores, alpha-fetoprotein relief, and complications. Objective response rate and disease control rate were observed to be 71.8% and 81.2%, respectively, in patients with primary liver cancer and were 63.7% and 83.2% in cases with metastatic liver cancer. Alpha-fetoprotein levels and visual analogue scale levels significantly decreased after treatment compared with the baseline levels in patients with primary liver cancer (p<0.05). Median overall survival was estimated to be 13.0 and 12.0 months in the primary liver cancer and metastatic liver cancer cohorts. The 1-year survival rate was 70.69% and 48.00%, respectively. Multivariate regression analysis showed that visual analogue scale ≥ 5, longest diameter ≥ 5 cm, and portal vein invasion were the independent risk factors for poor survival in primary liver cancer. For patients with metastatic liver cancer, independent risk factors were identified as visual analogue scale ≥ 5, longest diameter ≥ 5 cm, existence of extrahepatic metastases, existence of portal vein invasion, and time to high-intensity focused ultrasound treatment from diagnosis < 3 months. Severe adverse events were rarely reported. In conclusion, high-intensity focused ultrasound might be an effective and safe option for patients with liver cancer regardless of primary and metastatic lesions.

Acute renal insufficiency and thrombocytopenia after high-intensity focused ultrasound (HIFU) ablation for uterine myomas

OBJECTIVE

Ultrasound-guided high-intensity focused ultrasound (USg-HIFU) has emerged in recent years as the new treatment modality for uterine myomas and adenomyosis with the advantages of being non-invasive, safe and effective. As its utility increases, adverse reactions emerge and deserve clinicians' attention for experience accrual. We herein report a case who suffered from acute renal insufficiency and thrombocytopenia immediately after receiving HIFU for uterine myomas.

CASE REPORT

A 38-year-old nulliparous healthy female received HIFU for huge uterine myoma that caused heavy vaginal bleeding and chronic anemia. The procedure went smoothly but the patient immediately suffered from oliguria and dark-colored urine. With conservative management and aggressive hydration, her condition had improved spontaneously after 1 week without leaving any long-term sequelae. Myoma size reduced by 70% 3 months post-treatment and her bleeding problems significantly improved.

CONCLUSION

This is the first report of post-HIFU acute renal failure and thrombocytopenia. Thermal injuries, drug toxicity and mechanical obstruction of ureters are some plausible explanations for speculations.

HIFU for the treatment of difficult colorectal liver metastases with unsuitable indications for resection and radiofrequency ablation: a phase I clinical trial

BACKGROUND

The goal of this study is to evaluate the safety and efficacy of high intensity focused ultrasound (HIFU) for patients with colorectal liver metastases (CRLM) but were contraindicated for resection and radiofrequency ablation.

METHODS

Patients between 20 and 80 years of age with 1-3 liver metastases from colorectal cancer were selected. Included patients have had their primary lesions removed with no evidence of extrahepatic metastasis prior to the study. Ultrasound-guided HIFU was employed and target regions' ablation was achieved with repeated sonications from the deep to shallow regions of the tumors section by section.

RESULTS

Thirteen patients were enrolled. The most common adverse events (AEs) were pain (n = 8), followed by fatigue (n = 7), increased aspartate aminotransferase (AST) (n = 7), increased alanine aminotransferase (ALT) (n = 5), and skin edema (n = 4). No grade ≥ 3 AEs occurred and while most patients (76.9%) achieved a complete response, three patients achieved a partial response. The objective response rate was 100% after the first HIFU treatment. Nine patients relapsed but the tumors were mostly isolated to the liver (8/9). The median follow-up period was 25 months. The 2-year progression-free survival (PFS) was 16.7%, and the median PFS was 9 months. Notably, the 2-year overall survival (OS) was 77.8%, and the median OS was 25 months.

CONCLUSION

This study indicates that the HIFU treatment is safe, is able to achieve a good tumor response rate and long-term prognosis even when the foci were in high-risk locations, and should be considered for patients who were considered unsuitable for other local treatments.

Prognostic Significance of Apparent Diffusion Coefficient in Hepatocellular Carcinoma Patients treated with Stereotactic Ablative Radiotherapy

The role of diffusion-weighted magnetic resonance imaging (DW MRI) in assessing durable tumor control for patients with hepatocellular carcinoma (HCC) treated with stereotactic ablative radiotherapy (SABR) was not defined. This retrospective study included 34 HCC patients with 45 lesions who had DW MRI data at baseline and within 6 months post-SABR. On the first post-SABR MRI, 13 lesions (28.9%) had a complete response (CR), 12 (26.7%) had a partial response (PR), 17 (37.8%) had stable disease, and 3 (6.7%) had progressive disease by modified Response Evaluation Criteria in Solid Tumors (mRECIST). On subsequent imaging, the response rate improved from 55.6% to 75.6%. The apparent diffusion coefficients (ADCs) (mean ± standard deviation) pre- and post-SABR were 1.43 ± 0.28 and 1.72 ± 0.34 (×10⁻³ mm²/s), respectively (p < 0.001). An ADC change ≥25% (DW[+]) was identified as a predictor of favorable in-field control (IFC) (1-year IFC, 93.3% vs. 50.0% for DW[−], p = 0.004), but an mRECIST-based positive response (CR and PR) at the first MRI was not (p = 0.130). In conclusion, ADC change on early MRI is closely related to IFC in HCCs treated with SABR. Standardization of the DW MRI protocol, as well as prospective validation studies, are warranted.

Role of diffusion-weighted imaging in monitoring treatment response following high-intensity focused ultrasound ablation of recurrent sacral chordoma

Chordoma is the most common malignant tumor of the sacrum and is associated with significant neurologic morbidity. Local recurrence is very common, and the long-term prognosis is poor. High-intensity focused ultrasound (HIFU) is a noninvasive and nonionising ablative therapy that has been successful in treating other tumor types and is being evaluated as a new therapy for sacral chordoma. Contrast-enhanced magnetic resonance imaging is typically used to evaluate tumor perfusion following HIFU; however, its utility is limited in poorly perfused tumors. Diffusion-weighted imaging (DWI) provides tissue contrast based on differences in the diffusion of extracellular water without using gadolinium-based contrast agents. We present novel DWI findings following a planned partial HIFU ablation of a large sacral chordoma which had recurred after radiotherapy. Following HIFU, the treated tumor volume demonstrated loss of restriction on DWI correlating with photopenia on positron emission tomography. This suggests successful ablation and tumor necrosis. This novel finding may provide guidance for sequence selection when evaluating HIFU therapy for sacral chordoma and other tumor types for which contrast-enhanced magnetic resonance imaging may have limited utility.

Value of texture analysis based on enhanced MRI for predicting an early therapeutic response to transcatheter arterial chemoembolisation combined with high-intensity focused ultrasound treatment in hepatocellular carcinoma

AIM

To evaluate the potential value of texture analysis (TA) based on contrast-enhanced magnetic resonance imaging (MRI) for predicting an early response of patients with hepatocellular carcinoma (HCC) who were treated with transcatheter arterial chemoembolisation (TACE) combined with high-intensity focused ultrasound (HIFU).

MATERIALS AND METHODS

Patients with HCC (n=89) who underwent contrast-enhanced MRI at 1.5 T 1 week before and 1 week, 1 month, and 3 months after TACE/HIFU were included in this retrospective study. Early responses were evaluated by two radiologists according to the Response Evaluation Criteria in Cancer of the Liver (RECICL). An independent Student's t-test and the Mann-Whitney U-test were used to compare the TA parameters between the complete response (CR) group and the non-complete response (NCR) group. Logistic regression and receiver operating characteristic (ROC) curve analyses were performed to assess the predictive value of the NCR lesions.

RESULTS

Among the 89 patients, 58 showed CR and 31 showed NCR. Before TACE/HIFU, the CR group showed higher uniformity and energy but lower entropy than the NCR group (p<0.05). After TACE/HIFU, the CR group showed higher uniformity and energy but lower entropy and skewness than the NCR group (p<0.05). The logistic regression and ROC curve analyses showed that the entropy before TACE/HIFU and the skewness and entropy 1 week after TACE/HIFU were predictors of an early response.

CONCLUSION

TA parameters based on contrast-enhanced MRI images 1 week before and after TACE/HIFU may act as imaging biomarkers to predict an early response of patients with HCC.

Fluorine MR Imaging Monitoring of Tumor Inflammation after High-Intensity Focused Ultrasound Ablation

Purpose To investigate whether high-intensity focused ultrasound (HIFU)-induced macrophage infiltration could be longitudinally monitored with fluorine 19 (¹⁹F) magnetic resonance (MR) imaging in a quantitative manner. Materials and Methods BALB/c mice were subcutaneously inoculated with 4T1 cells and were separated into three groups: untreated mice (control, n = 9), HIFU-treated mice (HIFU, n = 9), and HIFU- and clodronate-treated mice (HIFU+Clod, n = 9). Immediately after HIFU treatment, all mice were intravenously given perfluorocarbon (PFC) emulsion. MR imaging examinations were performed 2, 4, 7, 10, and 14 days after HIFU treatment. Two-way repeated measures analysis of variance was used to analyze the changes in ¹⁹F signal over time and differences between groups. Histologic examinations were performed to confirm in vivo data. Results Fluorine 19 signals were detected at the rims of tumors and the peripheries of ablated lesions. Mean ¹⁹F signal in tumors was significantly higher in HIFU-treated mice than in control mice up to day 4 (0.82 ± 0.26 vs 0.42 ± 0.17, P < .001). Fluorine 19 signals were higher in the HIFU+Clod group than in the control group from day 4 (0.82 ± 0.23, P < .001) to day 14 (0.55 ± 0.16 vs 0.28 ± 0.06, P < .05). Histologic examination revealed macrophage infiltration around ablated lesions. Immunofluorescence staining confirmed PFC labeling of macrophages. Conclusion Fluorine 19 MR imaging can longitudinally capture and quantify HIFU-induced macrophage infiltration in preclinical tumor models. ^© RSNA, 2018 Online supplemental material is available for this article.

Contrast-enhanced ultrasound evaluation of pancreatic cancer xenografts in nude mice after irradiation with sub-threshold focused ultrasound for tumor ablation

We evaluated the efficacy of contrast-enhanced ultrasound for assessing tumors after irradiation with sub-threshold focused ultrasound (FUS) ablation in pancreatic cancer xenografts in nude mice. Thirty tumor-bearing nude mice were divided into three groups: Group A received sham irradiation, Group B received a moderate-acoustic energy dose (sub-threshold), and Group C received a high-acoustic energy dose. In Group B, B-mode ultrasound (US), color Doppler US, and dynamic contrast-enhanced ultrasound (DCE-US) studies were conducted before and after irradiation. After irradiation, tumor growth was inhibited in Group B, and the tumors shrank in Group C. In Group A, the tumor sizes were unchanged. In Group B, contrast-enhanced ultrasound (CEUS) images showed a rapid rush of contrast agent into and out of tumors before irradiation. After irradiation, CEUS revealed contrast agent perfusion only at the tumor periphery and irregular, un-perfused volumes of contrast agent within the tumors. DCE-US perfusion parameters, including peak intensity (PI) and area under the curve (AUC), had decreased 24 hours after irradiation. PI and AUC were increased 48 hours and 2weeks after irradiation. Time to peak (TP) and sharpness were increased 24 hours after irradiation. TP decreased at 48 hours and 2 weeks after irradiation. CEUS is thus an effective method for early evaluation after irradiation with sub-threshold FUS.

Diffusion MRI in early cancer therapeutic response assessment

Imaging biomarkers for the predictive assessment of treatment response in patients with cancer earlier than standard tumor volumetric metrics would provide new opportunities to individualize therapy. Diffusion-weighted MRI (DW-MRI), highly sensitive to microenvironmental alterations at the cellular level, has been evaluated extensively as a technique for the generation of quantitative and early imaging biomarkers of therapeutic response and clinical outcome. First demonstrated in a rodent tumor model, subsequent studies have shown that DW-MRI can be applied to many different solid tumors for the detection of changes in cellularity as measured indirectly by an increase in the apparent diffusion coefficient (ADC) of water molecules within the lesion. The introduction of quantitative DW-MRI into the treatment management of patients with cancer may aid physicians to individualize therapy, thereby minimizing unnecessary systemic toxicity associated with ineffective therapies, saving valuable time, reducing patient care costs and ultimately improving clinical outcome. This review covers the theoretical basis behind the application of DW-MRI to monitor therapeutic response in cancer, the analytical techniques used and the results obtained from various clinical studies that have demonstrated the efficacy of DW-MRI for the prediction of cancer treatment response. Copyright © 2016 John Wiley & Sons, Ltd.

Radiological biomarkers for assessing response to locoregional therapies in hepatocellular carcinoma: From morphological to functional imaging (Review)

Many hepatocellular carcinoma (HCC) patients do not qualify for curative surgical intervention and are instead treated with locoregional therapies (LRTs) including ablative and endovascular therapies. Assessment of imaging response is essential in the management of HCC for determining efficacy of therapy and as a surrogate marker for improved survival. The established morphological image biomarkers for tumor burden measurement continue to be applied, as size measurement can easily be used in clinical practice. However, in the setting of liver-directed LRTs for HCC, simple tumor morphological changes can be less informative and usually appear later than biologic changes. Functional imaging (such as perfusion and diffusion imaging, PET-CT/MR and MR spectroscopy) has the potential to be a promising technique for assessment of HCC response to LRTs. Although promising, none of these functional imaging biomarkers have gone through all the required steps of standardization and validation and established accepted criteria for clinical practice.

Therapy Monitoring with Functional and Molecular MR Imaging

Cancer therapy is mainly based on different combinations of surgery, radiotherapy, and chemotherapy. Additionally, targeted therapies (designed to disrupt specific tumor hallmarks, such as angiogenesis, metabolism, proliferation, invasiveness, and immune evasion), hormonotherapy, immunotherapy, and interventional techniques have emerged as alternative oncologic treatments. Conventional imaging techniques and current response criteria do not always provide the necessary information regarding therapy success particularly to targeted therapies. In this setting, MR imaging offers an attractive combination of anatomic, physiologic, and molecular information, which may surpass these limitations, and is being increasingly used for therapy response assessment.

High intensity focused ultrasound (HIFU) applied to hepato-bilio-pancreatic and the digestive system-current state of the art and future perspectives

BACKGROUND

High intensity focused ultrasound (HIFU) is emerging as a valid minimally-invasive image-guided treatment of malignancies. We aimed to review to current state of the art of HIFU therapy applied to the digestive system and discuss some promising avenues of the technology.

METHODS

Pertinent studies were identified through PubMed and Embase search engines using the following keywords, combined in different ways: HIFU, esophagus, stomach, liver, pancreas, gallbladder, colon, rectum, and cancer. Experimental proof of the concept of endoluminal HIFU mucosa/submucosa ablation using a custom-made transducer has been obtained in vivo in the porcine model.

RESULTS

Forty-four studies reported on the clinical use of HIFU to treat liver lesions, while 19 series were found on HIFU treatment of pancreatic cancers and four studies included patients suffering from both liver and pancreatic cancers, reporting on a total of 1,682 and 823 cases for liver and pancreas, respectively. Only very limited comparative prospective studies have been reported.

CONCLUSIONS

Digestive system clinical applications of HIFU are limited to pancreatic and liver cancer. It is safe and well tolerated. The exact place in the hepatocellular carcinoma (HCC) management algorithm remains to be defined. HIFU seems to add clear survival advantages over trans arterial chemo embolization (TACE) alone and similar results when compared to radio frequency (RF). For pancreatic cancer, HIFU achieves consistent cancer-related pain relief. Further research is warranted to improve targeting accuracy and efficacy monitoring. Furthermore, additional work is required to transfer this technology on appealing treatments such as endoscopic HIFU-based therapies.

Application of Different Imaging Methods in the Early Diagnosis of Primary Hepatic Carcinoma

Primary hepatic carcinoma (PHC) is the one of the most common tumors and the common cause of cancer death in the world. Detecting PHC in its early stage by imaging methods may greatly increase survival rates of patients. Ultrasound, computed tomography, magnetic resonance imaging, and positron emission tomography/computed tomography are common imaging methods in the diagnosis of PHC. In this paper, the application of different imaging methods in diagnosing the primary hepatic carcinoma will be discussed.

Diffusion-Weighted MR Imaging of Hepatocellular Carcinoma: Current Value in Clinical Evaluation of Tumor Response to Locoregional Treatment

The established size-based image biomarkers for tumor burden measurement continue to be applied to solid tumors, as size measurement can easily be used in clinical practice. However, in the setting of novel targeted therapies and liver-directed locoregional treatments for hepatocellular carcinoma (HCC), simple tumor anatomic changes can be less informative and usually appear later than biologic changes. Functional magnetic resonance (MR) imaging has the potential to be a promising technique for assessment of HCC response to therapy. Diffusion-weighted MR imaging is now widely used as a standard imaging modality to evaluate the liver. This review discusses the current clinical value of diffusion-weighted MR imaging in the evaluation of tumor response after nonsurgical locoregional treatment of HCC.

MRI methods for the evaluation of high intensity focused ultrasound tumor treatment: Current status and future needs

Thermal ablation with high intensity focused ultrasound (HIFU) is an emerging noninvasive technique for the treatment of solid tumors. HIFU treatment of malignant tumors requires accurate treatment planning, monitoring and evaluation, which can be facilitated by performing the procedure in an MR-guided HIFU system. The MR-based evaluation of HIFU treatment is most often restricted to contrast-enhanced T1 -weighted imaging, while it has been shown that the non-perfused volume may not reflect the extent of nonviable tumor tissue after HIFU treatment. There are multiple studies in which more advanced MRI methods were assessed for their suitability for the evaluation of HIFU treatment. While several of these methods seem promising regarding their sensitivity to HIFU-induced tissue changes, there is still ample room for improvement of MRI protocols for HIFU treatment evaluation. In this review article, we describe the major acute and delayed effects of HIFU treatment. For each effect, the MRI methods that have been-or could be-used to detect the associated tissue changes are described. In addition, the potential value of multiparametric MRI for the evaluation of HIFU treatment is discussed. The review ends with a discussion on future directions for the MRI-based evaluation of HIFU treatment.

The Value of Proton Magnetic Resonance Spectroscopy in High-Intensity Focused Ultrasound Treatment of Experimental Liver Cancer

High-intensity focused ultrasound (HIFU) is a rapidly developing, non-invasive technique for local treatment of solid tumors that produce coagulative tumor necrosis. This study is aimed to investigate the feasibility of proton magnetic resonance spectroscopy (MRS) on early assessing treatment of HIFU ablation in rabbit with VX2 liver tumor. HIFU ablation was performed on normal liver and VX2 tumor in rabbit, and MRS was performed on normal liver and VX2 tumor before and 2 days after 100% HIFU ablation or 80% ablation in tumor volume. Choline (Cho) and choline/lipid (Cho/Lip) ratios between complete and partial HIFU ablation of tumor were compared. Tissues were harvested and sequentially sliced to confirm the necrosis. In normal liver, the Cho value liver was not obviously changed after HIFU (P > .05), but the Cho/Lip ratio was decreased (P < .05). Cho in liver VX2 tumor was much higher than that in normal liver (P < .001). Cho and Cho/Lip ratio were significantly decreased in tumor after complete HIFU ablation and partial HIFU ablation, and the Cho value in complete HIFU tumor ablation did not show any difference from that in normal liver after HIFU (P > .05); however, the Cho value in partial ablation was still higher than that in normal liver before or in tumor after complete HIFU treatment due to the residual part of tumors, and Cho/Lip ratio is lower than that in complete HIFU treatment (P < .001). The changes in MRS parameters were consistent with histopathologic changes of the tumor tissues after treatment. MRS could differentiate the complete tumor necrosis from residual tumor tissue, when combined with magnetic resonance imaging. We conclude that MRS may be applied as an important, non-invasive biomarker for monitoring the thoroughness of HIFU ablation.

Quality of MR thermometry during palliative MR-guided high-intensity focused ultrasound (MR-HIFU) treatment of bone metastases

BACKGROUND

Magnetic resonance (MR)-guided high-intensity focused ultrasound has emerged as a clinical option for palliative treatment of painful bone metastases, with MR thermometry (MRT) used for treatment monitoring. In this study, the general image quality of the MRT was assessed in terms of signal-to-noise ratio (SNR) and apparent temperature variation. Also, MRT artifacts were scored for their occurrence and hampering of the treatment monitoring.

METHODS

Analyses were performed on 224 MRT datasets retrieved from 13 treatments. The SNR was measured per voxel over time in magnitude images, in the target lesion and surrounding muscle, and was averaged per treatment. The standard deviation over time of the measured temperature per voxel in MRT images, in the muscle outside the heated region, was defined as the apparent temperature variation and was averaged per treatment. The scored MRT artifacts originated from the following sources: respiratory and non-respiratory time-varying field inhomogeneities, arterial ghosting, and patient motion by muscle contraction and by gross body movement. Distinction was made between lesion type, location, and procedural sedation and analgesic (PSA).

RESULTS

The average SNR was highest in and around osteolytic lesions (21 in lesions, 27 in surrounding muscle, n = 4) and lowest in the upper body (9 in lesions, 16 in surrounding muscle, n = 4). The average apparent temperature variation was lowest in osteolytic lesions (1.2°C, n = 4) and the highest in the upper body (1.7°C, n = 4). Respiratory time-varying field inhomogeneity MRT artifacts occurred in 85% of the datasets and hampered treatment monitoring in 81%. Non-respiratory time-varying field inhomogeneities and arterial ghosting MRT artifacts were most frequent (94% and 95%) but occurred only locally. Patient motion artifacts were highly variable and occurred less in treatments of osteolytic lesions and using propofol and esketamine as PSA.

CONCLUSIONS

In this study, the general image quality of MRT was observed to be higher in osteolytic lesions and lower in the upper body. Respiratory time-varying field inhomogeneity was the most prominent MRT artifact. Patient motion occurrence varied between treatments and seemed to be related to lesion type and type of PSA. Clinicians should be aware of these observed characteristics when interpreting MRT images.

Tumour eradication using synchronous thermal ablation and Hsp90 chemotherapy with protein engineered triblock biopolymer-geldanamycin conjugates

PURPOSE

Hepatocellular carcinoma (HCC) suffers high tumour recurrence rate after thermal ablation. Heat shock protein 90 (Hsp90) induced post-ablation is critical for tumour survival and progression. A combination therapy of thermal ablation and polymer conjugated Hsp90 chemotherapy was designed and evaluated for complete tumour eradication of HCC.

MATERIALS AND METHODS

A thermo-responsive, elastin-like polypeptide (ELP)-based tri-block biopolymer was developed and conjugated with a potent Hsp90 inhibitor, geldanamycin (GA). The anti-cancer efficacy of conjugates was evaluated in HCC cell cultures with and without hyperthermia (43 °C). The conjugates were also administered twice weekly in a murine HCC model as a single treatment or in combination with single electrocautery as the ablation method.

RESULTS

ELP-GA conjugates displayed enhanced cytotoxicity in vitro and effective heat shock inhibition under hyperthermia. The conjugates alone significantly slowed the tumour growth without systemic toxicity. Four doses of thermo-responsive ELP-GA conjugates with concomitant simple electrocautery accomplished significant Hsp90 inhibition and sustained tumour suppression.

CONCLUSION

Hsp90 inhibition plays a key role in preventing the recurrence of HCC, and the combination of ablation with targeted therapy holds great potential to improve prognosis and survival of HCC patients.

Multiparametric MRI analysis for the identification of high intensity focused ultrasound-treated tumor tissue

Purpose

In this study endogenous magnetic resonance imaging (MRI) biomarkers for accurate segmentation of High Intensity Focused Ultrasound (HIFU)-treated tumor tissue and residual or recurring non-treated tumor tissue were identified.

Methods

Multiparametric MRI, consisting of quantitative T₁, T₂, Apparent Diffusion Coefficient (ADC) and Magnetization Transfer Ratio (MTR) mapping, was performed in tumor-bearing mice before (n = 14), 1 h after (n = 14) and 72 h (n = 7) after HIFU treatment. A non-treated control group was included (n = 7). Cluster analysis using the Iterative Self Organizing Data Analysis (ISODATA) technique was performed on subsets of MRI parameters (feature vectors). The clusters resulting from the ISODATA segmentation were divided into a viable and non-viable class based on the fraction of pixels assigned to the clusters at the different experimental time points. ISODATA-derived non-viable tumor fractions were quantitatively compared to histology-derived non-viable tumor volume fractions.

Results

The highest agreement between the ISODATA-derived and histology-derived non-viable tumor fractions was observed for feature vector {T₁, T₂, ADC}. R₁ (1/T₁), R₂ (1/T₂), ADC and MTR each were significantly increased in the ISODATA-defined non-viable tumor tissue at 1 h after HIFU treatment compared to viable, non-treated tumor tissue. R₁, ADC and MTR were also significantly increased at 72 h after HIFU.

Conclusions

This study demonstrates that non-viable, HIFU-treated tumor tissue can be distinguished from viable, non-treated tumor tissue using multiparametric MRI analysis. Clinical application of the presented methodology may allow for automated, accurate and objective evaluation of HIFU treatment.

Magnetic resonance-guided high-intensity focused ultrasound (MR-HIFU) ablation of liver tumours

Recent decades have seen a paradigm shift in the treatment of liver tumours from invasive surgical procedures to minimally invasive image-guided ablation techniques. Magnetic resonance-guided high-intensity focused ultrasound (MR-HIFU) is a novel, completely non-invasive ablation technique that has the potential to change the field of liver tumour ablation. The image guidance, using MR imaging and MR temperature mapping, provides excellent planning images and real-time temperature information during the ablation procedure. However, before clinical implementation of MR-HIFU for liver tumour ablation is feasible, several organ-specific challenges have to be addressed. In this review we discuss the MR-HIFU ablation technique, the liver-specific challenges for MR-HIFU tumour ablation, and the proposed solutions for clinical translation.

Diffusion-weighted MR imaging in gynecologic cancers

Diffusion-weighted imaging (DWI) reflects changes in proton mobility caused by pathological alterations of tissue cellularity, cellular membrane integrity, extracellular space perfusion, and fluid viscosity. Functional imaging is becoming increasingly important in the evaluation of cancer patients because of the limitations of morphologic imaging. DWI is being applied to the detection and characterization of tumors and the evaluation of treatment response in patients with cancer. The advantages of DWI include its cost-effectiveness and brevity of execution, its complete noninvasiveness, its lack of ionizing radiation, and the fact that it does not require injection of contrast material, thus enabling its use in patients with renal dysfunction. In this article, we describe the clinical application of DWI to gynecological disorders and its diagnostic efficacy therein.