Towards mid-position based Stereotactic Body Radiation Therapy using online magnetic resonance imaging guidance for central lung tumours

Background and purpose: Central lung tumours can be treated by magnetic resonance (MR)-guided radiotherapy. Complications might be reduced by decreasing the Planning Target Volume (PTV) using mid-position (midP)-based planning instead of Internal Target Volume (ITV)-based planning. In this study, we aimed to verify a method to automatically derive patient-specific PTV margins for midP-based planning, and show dosimetric robustness of midP-based planning for a 1.5T MR-linac. Materials and methods: Central(n = 12) and peripheral(n = 4) central lung tumour cases who received 8x7.5 Gy were included. A midP-image was reconstructed from ten phases of the 4D-Computed Tomography using deformable image registration. The Gross Tumor Volume (GTV) was delineated on the midP-image and the PTV margin was automatically calculated based on van Herk's margin recipe, treating the standard deviation of all Deformation Vector Fields, within the GTV, as random error component. Dosimetric robustness of midP-based planning for MR-linac using automatically derived margins was verified by 4D dose-accumulation. MidP-based plans were compared to ITV-based plans. Automatically derived margins were verified with manually derived margins. Results: The mean D95% target coverage in GTV + 2 mm was 59.9 Gy and 62.0 Gy for midP- and ITV-based central lung plans, respectively. The mean lung dose was significantly lower for midP-based treatment plans (difference:-0.3 Gy; p<0.042). Automatically derived margins agreed within one millimeter with manually derived margins. Conclusions: This retrospective study indicates that mid-position-based treatment plans for central lung Stereotactic Body Radiation Therapy yield lower OAR doses compared to ITV-based treatment plans on the MR-linac. Patient-specific GTV-to-PTV margins can be derived automatically and result in clinically acceptable target coverage

MR-guided high-intensity focused ultrasound ablation of breast cancer with a dedicated breast platform

Optimizing the treatment of breast cancer remains a major topic of interest. In current clinical practice, breast-conserving therapy is the standard of care for patients with localized breast cancer. Technological developments have fueled interest in less invasive breast cancer treatment. Magnetic resonance-guided high-intensity focused ultrasound (MR-HIFU) is a completely noninvasive ablation technique. Focused beams of ultrasound are used for ablation of the target lesion without disrupting the skin and subcutaneous tissues in the beam path. MRI is an excellent imaging method for tumor targeting, treatment monitoring, and evaluation of treatment results. The combination of HIFU and MR imaging offers an opportunity for image-guided ablation of breast cancer. Previous studies of MR-HIFU in breast cancer patients reported a limited efficacy, which hampered the clinical translation of this technique. These prior studies were performed without an MR-HIFU system specifically developed for breast cancer treatment. In this article, a novel and dedicated MR-HIFU breast platform is presented. This system has been designed for safe and effective MR-HIFU ablation of breast cancer. Furthermore, both clinical and technical challenges are discussed, which have to be solved before MR-HIFU ablation of breast cancer can be implemented in routine clinical practice. © 2012 Springer Science+Business Media New York and the Cardiovascular and Interventional Radiological Society of Europe (CIRSE)

The added diagnostic value of dynamic contrast-enhanced MRI at 3.0 T in nonpalpable breast lesions.

To investigate the added diagnostic value of 3.0 Tesla breast MRI over conventional breast imaging in the diagnosis of in situ and invasive breast cancer and to explore the role of routine versus expert reading.We evaluated MRI scans of patients with nonpalpable BI-RADS 3-5 lesions who underwent dynamic contrast-enhanced 3.0 Tesla breast MRI. Initially, MRI scans were read by radiologists in a routine clinical setting. All histologically confirmed index lesions were re-evaluated by two dedicated breast radiologists. Sensitivity and specificity for the three MRI readings were determined, and the diagnostic value of breast MRI in addition to conventional imaging was assessed. Interobserver reliability between the three readings was evaluated.MRI examinations of 207 patients were analyzed. Seventy-eight of 207 (37.7%) patients had a malignant lesion, of which 33 (42.3%) patients had pure DCIS and 45 (57.7%) invasive breast cancer. Sensitivity of breast MRI was 66.7% during routine, and 89.3% and 94.7% during expert reading. Specificity was 77.5% in the routine setting, and 61.0% and 33.3% during expert reading. In the routine setting, MRI provided additional diagnostic information over clinical information and conventional imaging, as the Area Under the ROC Curve increased from 0.76 to 0.81. Expert MRI reading was associated with a stronger improvement of the AUC to 0.87. Interobserver reliability between the three MRI readings was fair and moderate.3.0 T breast MRI of nonpalpable breast lesions is of added diagnostic value for the diagnosis of in situ and invasive breast cancer

ROC analysis shows an AUC of 0.76 for the model with clinical characteristics and conventional imaging, which is displayed as the green, dashed line in the three graphs (a-c).

<p>The red, solid lines show the AUC's for the models after addition of MRI reading. The model for routine reading has an AUC of 0.81 (a), both models with expert MRI reading have an AUC of 0.87 (b-c).</p

Craniocaudal (a) and mediolateral oblique (b) mammogram of a 40 year old, asymptomatic woman underwent mammography during follow-up after right-sided breast cancer, for which she underwent mastectomy.

<p>Mammography showed BI-RADS 4 microcalcifications in the lateral upper quadrant of the left breast. Ultrasound imaging was unremarkable (BI-RADS 1). During routine MRI reading, a BI-RADS 1 classification was assigned. Expert reader 1 reported an area of non-mass-like enhancement with a diffuse distribution, heterogeneous internal enhancement and classified MR imaging as BI-RADS 4. In addition, expert reader 2 described an area of non-mass-like enhancement with a segmental distribution and clumped internal enhancement, and reported a BI-RADS 4. Kinetics showed a rapid initial rise and a plateau stage during the delayed phase. Figure 2 shows the dynamic contrast-enhanced MRI (c) and the MR image imported in the CAD software (d). The color-coded overlay indicates the type of enhancement after contrast injection in the late phase. Yellow and blue illustrate a plateau- and persistent- enhancement curve, respectively. Stereotactic biopsy showed normal breast tissue with minor fibrocystic changes and the extensive presence of microcalcifications.</p

ROC analysis shows an AUC of 0.76 for the model with clinical characteristics and conventional imaging, which is displayed as the green, dashed line in the three graphs (a-c).

<p>The red, solid lines show the AUC's for the models after addition of MRI reading. The model for routine reading has an AUC of 0.81 (a), both models with expert MRI reading have an AUC of 0.87 (b-c).</p

Baseline table presenting clinical patient characteristics and features on mammography and ultrasound for the 207 index lesions.

<p>*independent sample T-test, ∧chi-square test, ^&Fisher's exact test</p>a<p>occult or benign lesion on mammography (BI-RADS 1 or 2), classified as BI-RADS 3, 4 or 5 on ultrasound.</p>b<p>cystic lesions, hypoechoic areas not otherwise specified, and areas of architectural distortion.</p

Sensitivity and specificity for routine and expert reading of 3.0 T breast MRI.

<p>Sensitivity and specificity for routine and expert reading of 3.0 T breast MRI.</p

The interobserver reliability (κ statistics) and agreement (proportion of agreement) for BI-RADS MRI classifications.

<p>The interobserver reliability (κ statistics) and agreement (proportion of agreement) for BI-RADS MRI classifications.</p