Nienke Lynn Hansen

Assessment of BI-RADS Category 4 Lesions Detected with Screening Mammography and Screening US: Utility of MR Imaging

PURPOSE To investigate the utility of magnetic resonance (MR) imaging according to different types of Breast Imaging Reporting and Data System (BI-RADS) category 4 findings from screening mammography and/or screening ultrasonography (US). MATERIALS AND METHODS This institutional review board-approved prospective study included 340 patients in whom 353 lesions were detected at screening mammography or US and were rated BI-RADS category 4 after appropriate conventional work-up. Written informed consent was obtained from all patients. Women underwent standard dynamic contrast material-enhanced MR imaging for further assessment. Women with negative or benign MR findings who did not proceed to biopsy underwent intensified follow-up for at least 18 months. Pure clustered microcalcifications were followed up for at least 24 months. RESULTS Of the 353 study findings, 66 (18.7%) were finally shown to be true-positive (23 cases of ductal carcinoma in situ [DCIS], 43 invasive cancers) and 287 (81.3%) were false-positive. Assessment of MR imaging findings led to a correct diagnosis of no breast cancer in 264 of the 287 false-positive findings (92%) and helped confirm the presence of breast cancer in 63 of 66 malignancies. The false-negative rate for pure clustered microcalcifications was 12% (three of 25 cases) because of three nonenhancing low-grade DCIS cases; in turn, MR imaging depicted additional invasive cancers in three women with false-positive findings from mammography and US. For mammographic findings other than pure clustered microcalcifications, MR imaging increased the positive predictive value (PPV) from 17.5% (21 of 120 cases; 95% confidence interval [CI]: 10.7%, 24.3%) to 78% (21 of 27 cases; 95% CI: 62.1%, 93.5%), with a false-negative rate of 0%. For all US findings, MR imaging increased the PPV from 12.9% (20 of 155 cases; 95% CI: 7.6%, 18.2%) to 69% (20 of 29 cases; 95% CI: 52.2%, 85.8%), again with a false-negative rate of 0%. MR imaging resulted in false-positive findings that led to MR imaging-guided biopsy in five of the 340 patients (1.5%). CONCLUSION MR imaging is useful for the noninvasive work-up of lesions classified as BI-RADS category 4 at mammography or US and can help avoid 92% of unnecessary biopsies. The false-negative rate was 0% for all US findings and for all mammographic findings except pure clustered microcalcifications. Additional invasive cancers were identified in three women with false-positive findings from mammography and US.

Does MRI Breast “Density” (Degree of Background Enhancement) Correlate With Mammographic Breast Density?

To investigate whether mammographic breast densities and the respective degree of MRI background enhancement would correlate. Mammographic breast density is coded to communicate how likely a cancer is obscured by parenchyma. Similarly, background enhancement in breast MRI could obscure enhancing cancer tissue.

First in-human magnetic resonance visualization of surgical mesh implants for inguinal hernia treatment.

ObjectivesUntil today, there have been no conventional imaging methods available to visualize surgical mesh implants and related complications. In a new approach, we incorporated iron particles into polymer-based implants and visualized them by magnetic resonance imaging (MRI).After clinical approval of such implants, the purposes of this study were to evaluate the MRI conspicuity of such iron-loaded mesh implants in patients treated for inguinal hernias and to assess the immediate postsurgical mesh configuration. Materials and MethodsApproved by the ethics committee, in this prospective cohort study, 13 patients (3 patients with bilateral hernia treatment) were surgically treated for inguinal hernia receiving iron-loaded mesh implants between March and October 2012. The implants were applied via laparoscopic technique (transabdominal preperitoneal technique; n = 8, 3 patients with bilateral hernia treatment) or via open surgical procedure (Lichtenstein surgery; n = 5). Magnetic resonance imaging was performed 1 day after the surgery at a 1.5-T scanner (Achieva; Philips, Best, The Netherlands) with a 16-channel receiver coil using 3 different gradient echo sequences (first gradient echo sequence, second gradient echo sequence, and third gradient echo sequence [GRE1-3]) and 1 T2-weighted turbo spin-echo sequence (T2wTSE). Three radiologists independently evaluated mesh conspicuity and diagnostic value with respect to different structures using a semiquantitative scoring system (1, insufficient; 2, sufficient; 3, good; 4, optimal). Mesh deformation and coverage of the hernia were visually assessed and rated using a 5-point semiquantitative scoring system. Statistical analysis was performed using mixed models and linear contrast. ResultsAll 16 implants were successfully visualized by MRI. On gradient echo sequences, the mesh is clearly delineated as a thick hypointense line. On T2wTSE, the mesh was depicted as a faint hypointense line, which was difficult to identify. The first gradient echo sequence was rated best for visual conspicuity (mean [SD], 3.8 [0.4]). T2-weighted turbo spin-echo sequence was preferred for evaluation of the surrounding anatomy (mean [SD], 3.7 [0.3]). For the combined assessment of both mesh and anatomy, GRE3 was rated best (mean [SD], 2.9 [0.7]). Local air slightly reduced mesh delineation (lowest mean [SD] rating, 2.9 [0.7] for GRE3). Overall, in both implantation techniques, the meshes exhibited mild to moderate deformations (mean [SD], 3.3 [0.4], 3.1 [0.3], and 2.8 [0.3] on average with open technique, 2.7 [0.3], 2.7 [0.2], and 2.3 [0.3] with laparoscopic technique). Coverage of the hernia was achieved in 15 of the 16 implants. ConclusionsCombining iron-loaded implants and MRI, we achieved mesh visualization for the first time in patients. For MRI protocol, we propose a combination of different gradient echo sequences and T2-weighted turbo spin-echo sequences: first gradient echo sequence for mesh configuration, T2wTSE for anatomy assessment, and GRE3 for evaluation of hernia coverage and mesh localization. Using our approach, MRI could become a noninvasive alternative to open surgical exploration if mesh-related complications were suspected.

Diagnostic Accuracy of Diffusion-Weighted Magnetic Resonance Imaging Versus Positron Emission Tomography/Computed Tomography for Early Response Assessment of Liver Metastases to Y90-Radioembolization

Objectives Patients with hepatic metastases who are candidates for Y90-radioembolization (Y90-RE) usually have advanced tumor stages with involvement of both liver lobes. Per current guidelines, these patients have usually undergone several cycles of potentially hepatotoxic systemic chemotherapy before Y90-RE is at all considered, requiring split (lobar) treatment sessions to reduce hepatic toxicity. Assessing response to Y90-RE early, that is, already after the first lobar session, would be helpful to avoid an ineffective and potentially hepatotoxic second lobar treatment. We investigated the accuracy with which diffusion- weighted magnetic resonance imaging (DWI-MRI) and positron emission tomography/computed tomography (PET/CT) can provide this information. Methods An institutional review board–approved prospective intraindividual comparison trial on 35 patients who underwent fluorodeoxyglucose PET/CT and DWI-MRI within 6 weeks before and 6 weeks after Y90-RE to treat secondary-progressive liver metastases from solid cancers (20 colorectal, 13 breast, 2 other) was performed. An increase of minimal apparent diffusion coefficient (ADCmin) or decrease of maximum standard uptake value (SUVmax) by at least 30% was regarded as positive response. Long-term clinical and imaging follow-up was used to distinguish true- from false-response classifications. Results On the basis of long-term follow-up, 23 (66%) of 35 patients responded to the Y90 treatment. No significant changes of metastases size or contrast enhancement were observable on pretreatment versus posttreatment CT or magnetic resonance images.However, overall SUVmax decreased from 8.0 ± 3.9 to 5.5 ± 2.2 (P < 0.0001), and ADCmin increased from 0.53 ± 0.13 × 10−3 mm2/s to 0.77 ± 0.26 × 10−3 mm2/s (P < 0.0001). Pretherapeutic versus posttherapeutic changes of ADCmin and SUVmax correlated moderately (r = −0.53). In 4 of the 35 patients (11%), metastases were fluorodeoxyglucose-negative such that no response assessment was possible by PET. In 25 (71%) of the 35 patients, response classification by PET and DWI-MRI was concordant; in 6 (17%) of the 35, it was discordant. In 5 of the 6 patients with discordant classifications, follow-up confirmed diagnoses made by DWI. The positive predictive value to predict response was 22 (96%) of 23 for MRI and 15 (88%) of 17 for PET. The negative predictive value to predict absence was 11 (92%) of 12 for MRI and 10 (56%) of 18 for PET. Sensitivity for detecting response was significantly higher for MRI (96%; 22/23) than for PET (65%; 15/23) (P < 0.02). Conclusions Diffusion-weighted magnetic resonance imaging appears superior to PET/CT for early response assessment in patients with hepatic metastases of common solid tumors. It may be used in between lobar treatment sessions to guide further management of patients who undergo Y90-RE for hepatic metastases.

Time-dependent changes of magnetic resonance imaging-visible mesh implants in patients.

ObjectivesShrinkage and deformation of mesh implants used for hernia treatment can be the cause of long-term complications. The purpose of this study was to quantify noninvasively time-dependent mesh shrinkage, migration, and configuration changes in patients who were surgically treated for inguinal hernia using magnetic resonance imaging (MRI)–visible mesh implants. Materials and MethodsIn an agarose phantom, meshes in different shrinkage and folding conditions were used to validate the quantification process. Seven patients who were surgically (3 bilaterally) treated for inguinal hernia using iron-loaded mesh implants were prospectively examined using MRI. Gradient echo sequences in sagittal and transverse orientations were performed on day 1 after surgery and at day 90. The mesh-induced signal voids were semiautomatically segmented and a polygonal surface model was generated. A comparison of area and centroid position was performed between the 2 calculated surfaces (day 1 vs day 90). ResultsThe phantom study revealed a maximum deviation of 3.6% between the MRI-based quantification and the actual mesh size. All 10 implants were successfully reconstructed. The mean (SD) observed mesh shrinkage 90 days after surgery was 20.9% (7.1%). The mean (SD) centroid movement was 1.17 (0.47) cm. Topographic analysis revealed mean (SD) local configuration changes of 0.23 (0.03) cm. ConclusionsIn this study, significant mesh shrinkage (20.9%) but marginal changes in local mesh configuration occurred within 90 days after mesh implantation. Centroid shift of the mesh implant can be traced back to different patient positioning and abdominal distension. The developed algorithm facilitates noninvasive assessment of key figures regarding MRI-visible meshes. Consequently, it might help to improve mesh technology as well as surgical skills.

First in vivo visualization of MRI-visible IPOM in a rabbit model

BACKGROUND Application of a mesh in presence of pneumoperitoneum may cause deformation or wave formation when gas is released. Moreover, mesh shrinkage during subsequent wound healing cannot be detected in vivo without invasive diagnostics. Using MRI-visible polyvinylidene fluoride (PVDF) mesh, the extend of mesh deformation and shrinkage could be objectified by MRI for the first time. MATERIALS AND METHODS Laparoscopic intraperitoneal onlay mesh (IPOM) implantation was performed in 10 female rabbits using ferro-oxide loaded PVDF meshes. MRI measurements were performed postoperatively at days 1 and 90. After three-dimensional reconstruction of all MRI images the total surface and the effective surface of the implanted mesh were explored and calculated computer-assisted. RESULTS In all cases, the mesh could be identified in MRI. The subsequent three-dimensional reconstruction always allowed a calculation of the mesh area. In relation to the original size of the used textile implant, we found neither a significant reduction of the effective mesh surface after release of the pneumoperitoneum at day 1 after laparoscopic surgery nor a significant change of the total surface of this large pore mesh by the end of the observation period. CONCLUSIONS In vivo investigation of mesh surface via MRI could exclude a significant initial reduction of the effective mesh surface after release of pneumoperitoneum, in this IPOM rabbit model. A further subsequent shrinkage of these large pore PVDF meshes could be excluded, as well. Imaging of MRI-visible IPOM mesh turned out to be a sufficient tool to objectify mesh configuration and position in vivo.

Target lesion selection: an important factor causing variability of response classification in the Response Evaluation Criteria for Solid Tumors 1.1.

PurposeWe conducted a systematic analysis of factors (manual vs automated and unidimensional vs 3-dimensional size assessment, and impact of different target lesion selection) contributing to variability of response categorization in the Response Evaluation Criteria for Solid Tumors 1.1. Patients and MethodsA total of 41 female patients (58.1 ± 13.2 years old) with metastatic breast cancer underwent contrast-enhanced thoracoabdominal computed tomography for initial staging and first follow-up after systemic chemotherapy. Data were independently interpreted by 3 radiologists with 5 to 9 years of experience. In addition, response was evaluated by a computer-assisted diagnosis system that allowed automated unidimensional and 3-dimensional assessment of target lesions. ResultsOverall, between-reader agreement was moderate (&kgr; = 0.53), with diverging response classification observed in 19 of 41 patients (46%). In 25 patients, readers had chosen the same, and in 16, readers had chosen different target lesions. Selection of the same target lesions was associated with a 76% rate of agreement (19/25) with regard to response classification; selection of different target lesions was associated with an 81% rate of disagreement (13/16) (P < 0.001). After dichotomizing response classes according to their therapeutic implication in progressive versus nonprogressive, disagreement was observed in 11 of 41 patients (27%) (&kgr; = 0.57). In 9 of these 11 patients, readers had chosen different target lesions. Disagreement rates due to manual versus automated or unidimensional versus volumetric size measurements were less important (11/41 and 6/41; 27% and 15%, respectively). ConclusionsA major source of variability is not the manual or unidimensional measurement, but the variable choice of target lesions between readers. Computer-assisted diagnosis–based analysis or tumor volumetry can help avoid variability due to manual or unidimensional measurements only but will not solve the problem of target lesion selection.

Utility of Magnetic Resonance Imaging to Monitor Surgical Meshes: Correlating Imaging and Clinical Outcome of Patients Undergoing Inguinal Hernia Repair.

ObjectivesFrom a surgeon’s point of view, meshes implanted for inguinal hernia repair should overlap the defect by 3 cm or more during implantation to avoid hernia recurrence secondary to mesh shrinkage. The use of magnetic resonance imaging (MRI)–visible meshes now offers the opportunity to noninvasively monitor whether a hernia is still covered sufficiently in the living patient. The purpose of this study was therefore to evaluate the efficacy of hernia repair after mesh implantation based on MRI findings (mesh coverage, visibility of hernia structures) and based on the patient’s postoperative symptoms. Materials and MethodsIn this prospective study approved by the ethics committee, 13 MRI-visible meshes were implanted in 10 patients (3 bilaterally) for inguinal hernia repair between March 2012 and January 2013. Senior visceral surgeons (>7 years of experience) implanted the meshes via laparoscopic transabdominal preperitoneal procedure. Magnetic resonance imaging was performed within 1 week and at 3 months after surgery at a 1.5-T system. Mesh position, deformation, and coverage of the hernia were visually assessed in consensus and rated on a 4-point semiquantitative scoring system. Distances of hernia center point to the mesh borders (overlap) were measured. Mesh position and hernia coverage postoperatively and at 3 months after implantation were correlated with the respective patients’ clinical symptoms. Statistical analysis was performed using the Wilcoxon signed rank test. ResultsTwo of the 13 meshes presented with an atypical mesh configuration along the course of psoas muscle with a short medial overlap of less than 2 cm. Eleven of the 13 meshes exhibited a typical mesh configuration with lateral folding and initial overlap of more than 2 cm. Between baseline and 3 months’ follow-up, average overlap decreased in the medial direction by −10% (3.75 cm vs 3.36 cm, P = 0.22), in the lateral direction by −20% (3.55 cm vs 2.82 cm, P = 0.01), in the superior direction by −2% (5.82 cm vs 5.72 cm, P = 0.55), and in the posterior direction by −19% (4.11 cm vs 3.34 cm, P = 0.01). Between baseline and 3 months’ follow-up, mesh folding increased mildly in the medial direction, whereas no change was found in the other directions. Individual folds of the mesh were flexible over time, whereas the gross visual configuration and location of meshes did not change. Four of the 13 former hernia sites were mildly painful at follow-up, whereas 9 of the 13 were completely asymptomatic. No correlation between clinical symptoms and mesh position or hernia coverage was found. ConclusionsOur results suggest that the actual postoperative mesh position after release of laparoscopic pneumoperitoneum may deviate from its position during surgery. Gross mesh position and configuration differed between patients but did not change within a given patient over the observation period of 3 months after surgery. We did not find a correlation between clinical symptoms and mesh configuration or position. Shrinkage of meshes does occur, yet not as concentric process, but regionally variable, leading to a reduced hernia coverage of up to −20% in the lateral and posterior directions.

Positive Contrast MRI Techniques for Visualization of Iron-Loaded Hernia Mesh Implants in Patients.

Object In MRI, implants and devices can be delineated via susceptibility artefacts. To discriminate susceptibility voids from proton-free structures, different positive contrast techniques were implemented. The purpose of this study was to evaluate a pulse sequence-based positive contrast technique (PCSI) and a post-processing susceptibility gradient mapping algorithm (SGM) for visualization of iron loaded mesh implants in patients. Material and Methods Five patients with iron-loaded MR-visible inguinal hernia mesh implants were examined at 1.5 Tesla. A gradient echo sequence (GRE; parameters: TR: 8.3ms; TE: 4.3ms; NSA:2; FA:20°; FOV:350mm²) and a PCSI sequence (parameters: TR: 25ms; TE: 4.6ms; NSA:4; FA:20°; FOV:350mm²) with on-resonant proton suppression were performed. SGM maps were calculated using two algorithms. Image quality and mesh delineation were independently evaluated by three radiologists. Results On GRE, the iron-loaded meshes generated distinct susceptibility-induced signal voids. PCSI exhibited susceptibility differences including the meshes as hyperintense signals. SGM exhibited susceptibility differences with positive contrast. Visually, the different algorithms presented no significant differences. Overall, the diagnostic value was rated best in GRE whereas PCSI and SGM were barely “sufficient”. Conclusion Both “positive contrast” techniques depicted implanted meshes with hyperintense signal. SGM comes without additional acquisition time and can therefore be utilized in every patient.

MR-visualization of surgical textile implants

Abstract The use of surgical textile implants (so-called “mesh”) for hernia repair is an accepted standard. They may cause mesh-related problems such as chronic pain, migration or fistula formation. Nevertheless, these polymer-based textile meshes are often invisible by conventional imaging methods like computed tomography (CT) and magnetic resonance imaging (MRI). In this study we outlined the major steps in the development of a MR-visible textile implant, which can be used in patients. To achieve MR-visability, ferrooxide particles were incorporated into the base material polyvinylidene fluoride (PVDF), during the spinning process. We could proof the MR-visibility of this new textile implant in different phantoms. After clinical approval of these implants in vivo in different animal studies, we pursued to evaluate the MR-conspicuity of such ferrooxide-loaded mesh implants in patients treated for inguinal hernias and explored the postsurgical mesh configuration by MRI. In this study we described the development and first results of a ferrooxide-loaded MR-visible mesh. In animal model and in clinical use such implants turned out to be a valuable tool for diagnostic and development.