Facile synthesis of manganese-hafnium nanocomposites for multimodal MRI/CT imaging and in vitro photodynamic therapy of colon cancer.

Precise diagnosis of complex and soft tumors is challenging, which limits appropriate treatment options to achieve desired therapeutic outcomes. However, multifunctional nano-sized contrast enhancement agents based on nanoparticles improve the diagnosis accuracy of various diseases such as cancer. Herein, a facile manganese-hafnium nanocomposites (Mn3O4-HfO2 NCs) system was designed for bimodal magnetic resonance imaging (MRI)/computed tomography (CT) contrast enhancement with a complimentary function of photodynamic therapy. The solvothermal method was used to fabricate NCs, and the average size of Mn3O4 NPs and Mn3O4-HfO2 NCs was about 7 nm and 15 nm, respectively, as estimated by TEM. Dynamic light scattering results showed good dispersion and high negative (-33 eV) zeta potential, indicating excellent stability in an aqueous medium. Mn3O4-HfO2 NCs revealed negligible toxic effects on the NCTC clone 929 (L929) and mouse colon cancer cell line (CT26), demonstrating promising biocompatibility. The synthesized Mn3O4-HfO2 NCs exhibit significant enhancement in T1-weighted magnetic resonance imaging (MRI) and X-ray computed tomography (CT), indicating the appropriateness for dual-modal MRI/CT molecular imaging probes. Moreover, ultra-small Mn3O4-HfO2 NCs show good relaxivities for MRI/CT. These nanoprobes Mn3O4-HfO2 NCs further possessed outstanding reactive oxygen species (ROS) generation ability under minute ultraviolet light (6 mW·cm-2) to ablate the colon cancer cells in vitro. Therefore, the designed multifunctional Mn3O4-HfO2 NCs were ideal candidates for cancer diagnosis and photodynamic therapy.

Diet-Stimulated Marrow Adiposity Fails to Worsen Early, Age-Related Bone Loss.

INTRODUCTION: Longitudinal effect of diet-induced obesity on bone is uncertain. Prior work showed both no effect and a decrement in bone density or quality when obesity begins prior to skeletal maturity. We aimed to quantify long-term effects of obesity on bone and bone marrow adipose tissue (BMAT) in adulthood. METHODS: Skeletally mature, female C57BL/6 mice (n = 70) aged 12 weeks were randomly allocated to low-fat diet (LFD; 10% kcal fat; n = 30) or high-fat diet (HFD; 60% kcal fat; n = 30), with analyses at 12, 15, 18, and 24 weeks (n = 10/group). Tibial microarchitecture was analyzed by µCT, and volumetric BMAT was quantified via 9.4T MRI/advanced image analysis. Histomorphometry of adipocytes and osteoclasts, and qPCR were performed. RESULTS: Body weight and visceral white adipose tissue accumulated in response to HFD started in adulthood. Trabecular bone parameters declined with advancing experimental age. BV/TV declined 22% in LFD (p = 0.0001) and 17% in HFD (p = 0.0022) by 24 weeks. HFD failed to appreciably alter BV/TV and had negligible impact on other microarchitecture parameters. Both dietary intervention and age accounted for variance in BMAT, with regional differences: distal femoral BMAT was more responsive to diet, while proximal femoral BMAT was more attenuated by age. BMAT increased 60% in the distal metaphysis in HFD at 18 and 24 weeks (p = 0.0011). BMAT in the proximal femoral diaphysis, unchanged by diet, decreased 45% due to age (p = 0.0002). Marrow adipocyte size via histomorphometry supported MRI quantification. Osteoclast number did not differ between groups. Tibial qPCR showed attenuation of some adipose, metabolism, and bone genes. A regulator of fatty acid ß-oxidation, cytochrome C (CYCS), was 500% more abundant in HFD bone (p < 0.0001; diet effect). CYCS also increased due to age, but to a lesser extent. HFD mildly increased OCN, TRAP, and SOST. CONCLUSIONS: Long-term high fat feeding after skeletal maturity, despite upregulation of visceral adiposity, body weight, and BMAT, failed to attenuate bone microarchitecture. In adulthood, we found aging to be a more potent regulator of microarchitecture than diet-induced obesity.

Novel Approach to Percutaneous Lumbar Surgeries via Kambin's Triangle-Radiographic and Surgical Planning Analysis with Nerve Segmentation Technology.

OBJECTIVE: While Kambin's Triangle has become an ever more important anatomic window given its proximity to the exiting nerve root, there have been limited studies examining the effect of disease on the corridor. Our goal was to better understand how pathology can affect Kambin's Triangle, thereby altering the laterality of approach for percutaneous lumbar interbody fusion (percLIF). METHODS: The authors performed a single-center retrospective review of patients evaluated for percLIF. The areas of Kambin's Triangle were measured without and with nerve segmentation. For the latter, the lumbosacral nerve roots on 3-dimensional T2 magnetic resonance imaging were manually segmented. Next, the borders of Kambin's Triangle were delineated, ensuring no overlap between the area and nerve above. RESULTS: Fifteen patients (67.5 ± 9.7 years, 46.7% female) were retrospectively reviewed. We measured 150 Kambin's Triangles. The mean areas from L1-S1 were 50.0 ± 12.3 mm2, 73.8 ± 12.5 mm2, 83.8 ± 12.2 mm2, 88.5 ± 19.0 mm2, and 116 ± 29.3 mm2, respectively. When pathology was present, the areas significantly decreased at L4-L5 (P = 0.046) and L5-S1 (P = 0.049). Higher spondylolisthesis and smaller posterior disk heights were linked with decreased areas via linear regression analysis (P < 0.05). When nerve segmentation was used, the areas were significantly smaller from L1-L5 (P < 0.05). Among 11 patients who underwent surgery, none suffered from postoperative neuropathies. CONCLUSIONS: These results illustrate the feasibility of preoperatively segmenting lumbosacral nerves and measuring Kambin's Triangle to help guide surgical planning and determine the ideal laterality of approach for percLIF.

Evaluation of Surgical Indications for Full Endoscopic Discectomy at Lumbosacral Disc Levels Using Three-Dimensional Magnetic Resonance/Computed Tomography Fusion Images Created with Artificial Intelligence.

Background and Objectives: Although full endoscopic lumbar discectomy with the transforaminal approach (FED-TF) is a minimally invasive spinal surgery for lumbar disc herniation, the lumbosacral levels present anatomical challenges when performing FED-TF surgery due to the presence of the iliac bone. Materials and Methods: In this study, we simulated whether FED-TF surgery could be safely performed on a total of 52 consecutive cases with L5-S1 or L5-L6 disc herniation using fused three-dimensional (3D) images of the lumbar nerve root on magnetic resonance imaging (MRI) created with artificial intelligence and of the lumbosacral spine and iliac on computed tomography (CT) images. Results: Thirteen of the fifty-two cases were deemed operable according to simulated FED-TF surgery without foraminoplasty using the 3D MRI/CT fusion images. All 13 cases underwent FED-TF surgery without neurological complications, and their clinical symptoms significantly improved. Conclusions: Three-dimensional simulation may allow for the assessment from multiple angles of the endoscope entry and path, as well as the insertion angle. FED-TF surgery simulation using 3D MRI/CT fusion images could be useful in determining the indications for full endoscopic surgery for lumbosacral disc herniation.

Is it necessary for patients with potentially resectable esophageal squamous cell cancer to receive routine preoperative brain MRI/CT?

BACKGROUND: This study aimed to investigate the value and efficiency of routine brain MRI or CT in the preoperative workup for patients with potentially resectable (cT1-4a N0-3 ) thoracic esophageal squamous cell cancer (ESCC). METHODS: This was a prospective cross-sectional clinical trial (ChiCTR1800020304). A total of 385 patients with potentially resectable (cT1-4a N0-3 ) thoracic ESCC diagnosed from October 2018 to August 2020 were included. Plain brain MRI or CT was performed preoperatively to detect brain metastases (BrM). The primary endpoint was BrM detected by imaging. RESULTS: Of all 385 patients, the rate of positive brain MRI/CT findings was 1% (n = 4). BrM Patients received chemoradiotherapy, and the median OS was 6 months (95% CI: 4.303-7.697). All 381 remaining patients with initial negative brain MRI/CT diagnosis revealed no brain-associated symptoms within 6 months. The median follow-up for patients without BrM was 20 months (range, from 6 to 32). The sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) of plain MRI or CT to detect BrM were all 100%. CONCLUSIONS: Preoperative plain MRI or CT is an effective method to detect BrM for potentially resectable (cT1-4a N0-3 ) thoracic ESCC. However, due to the low incidence, the value of brain MRI/CT as a routinely preoperational examination in potentially resectable esophageal squamous cell cancer is rather limited. Therefore, preoperative brain MRI/CT should not be recommended as a routine preoperative examination for ESCC.

Imaging of Paget's Disease of Bone.

Paget's disease is a metabolic bone disorder affecting the elderly and characterized by bone resorption followed by compensatory bone formation. Radiography is the imaging modality of choice for the diagnosis whereas bone scintigraphy helps stage the extent of the disease and assess response to treatment. MRI and CT are important imaging methods in the assessment of complications and surgical planning. Osteolytic lesions of Paget's first phase present with well-defined margins on radiographs, most commonly in the femur, pelvis, and skull. Cortical thickening, trabecular coarsening, bone marrow sclerosis, and deformities of long bones are present in the mixed- and late-sclerotic phases.

Bilateral musculus sternalis - An anatomical and clinical review.

The musculus sternalis is an extremely rare anatomical variant of the anterior chest wall. A detailed review of the anatomy, historical background and prevalence of the sternalis muscle is presented, with both the significant radiological and surgical implications of this variant specifically discussed.

Arachnoiditis Ossificans.

This case shows the MRI and CT features of a rare entity, namely arachnoiditis ossificans, which should be recognized in patients with long-standing history of multiple spine surgery.

A feature invariant generative adversarial network for head and neck MRI/CT image synthesis.

With the emergence of online MRI radiotherapy treatments, MR-based workflows have increased in importance in the clinical workflow. However proper dose planning still requires CT images to calculate dose attenuation due to bony structures. In this paper, we present a novel deep image synthesis model that generates in an unsupervised manner CT images from diagnostic MRI for radiotherapy planning. The proposed model based on a generative adversarial network (GAN) consists of learning a new invariant representation to generate synthetic CT (sCT) images based on high frequency and appearance patterns. This new representation encodes each convolutional feature map of the convolutional GAN discriminator, leading the training of the proposed model to be particularly robust in terms of image synthesis quality. Our model includes an analysis of common histogram features in the training process, thus reinforcing the generator such that the output sCT image exhibits a histogram matching that of the ground-truth CT. This CT-matched histogram is embedded then in a multi-resolution framework by assessing the evaluation over all layers of the discriminator network, which then allows the model to robustly classify the output synthetic image. Experiments were conducted on head and neck images of 56 cancer patients with a wide range of shape sizes and spatial image resolutions. The obtained results confirm the efficiency of the proposed model compared to other generative models, where the mean absolute error yielded by our model was 26.44(0.62), with a Hounsfield unit error of 45.3(1.87), and an overall Dice coefficient of 0.74(0.05), demonstrating the potential of the synthesis model for radiotherapy planning applications.

Microendoscopic decompression for lumbosacral foraminal stenosis: a novel surgical strategy based on anatomical considerations using 3D image fusion with MRI/CT.

OBJECTIVE: Persistent lumbar foraminal stenosis (LFS) is one of the most common reasons for poor postoperative outcomes and is a major contributor to "failed back surgery syndrome." The authors describe a new surgical strategy for LFS based on anatomical considerations using 3D image fusion with MRI/CT analysis. METHODS: A retrospective review was conducted on 78 consecutive patients surgically treated for LFS at the lumbosacral junction (2013-2017). The location and extent of stenosis, including the narrowest site and associated pathology (bone or soft tissue), were measured using 3D image fusion with MRI/CT. Stenosis was defined as medial intervertebral foraminal (MF; inner edge to pedicle center), lateral intervertebral foraminal (LF; pedicle center to outer edge), or extraforaminal (EF; outside the pedicle). Lumbar (low-back pain, leg pain) and patient satisfaction visual analog scale (VAS) scores and Japanese Orthopaedic Association (JOA) scores were evaluated. Surgical outcome was evaluated 2 years postoperatively. RESULTS: Most instances of stenosis existed outside the pedicle's center (94%), including LF (58%), EF (36%), and MF (6%). In all MF cases, stenosis resulted from soft-tissue structures. The narrowest stenosis sites were localized around the pedicle's outer border. The areas for sufficient nerve decompression were extended in MF+LF (10%), MF+LF+EF (14%), LF+EF (39%), LF (11%), and EF (26%). No iatrogenic pars interarticularis damage occurred. The JOA score was 14.9 ± 2.6 points preoperatively and 22.4 ± 3.5 points at 2 years postoperatively. The JOA recovery rate was 56.0% ± 18.6%. The VAS score (low-back and leg pain) was significantly improved 2 years postoperatively (p < 0.01). According to patients' self-assessment of the minimally invasive surgery, 62 (79.5%) chose "surgery met my expectations" at follow-up. Nine patients (11.5%) selected "I did not improve as much as I had hoped but I would undergo the same surgery for the same outcome." CONCLUSIONS: Most LFS existed outside the pedicle's center and was rarely noted in the pars region. The main regions of stenosis were localized to the pedicle's outer edge. Considering this anatomical distribution of LFS, the authors recommend that lateral fenestration should be the first priority for foraminal decompression. Other surgical options including foraminotomy, total facetectomy, and hemilaminectomy likely require more bone resections than LFS treatment. The microendoscopic surgery results were very good, indicating that this minimally invasive surgery was suitable for treating this disease.

Magnetic resonance contrast agents in optical clearing: Prospects for multimodal tissue imaging.

Skin optical clearing effect ex vivo and in vivo was achieved by topical application of low molecular weight paramagnetic magnetic resonance contrast agents. This novel feature has not been explored before. By using collimated transmittance the diffusion coefficients of three clinically used magnetic resonance contrast agents, that is Gadovist, Magnevist and Dotarem as well as X-ray contrast agent Visipaque in mouse skin were determined ex vivo as (4.29 ± 0.39) × 10-7 cm2 /s, (5.00 ± 0.72) × 10-7 cm2 /s, (3.72 ± 0.67) × 10-7 cm2 /s and (1.64 ± 0.18) × 10-7 cm2 /s, respectively. The application of gadobutrol (Gadovist) resulted in efficient optical clearing that in general, was superior to other contrast agents tested and allowed to achieve: (a) more than 12-fold increase of transmittance over 10 minutes after application ex vivo; (b) markedly improved images of skin architecture obtained with optical coherence tomography; (c) an increase of the fluorescence intensity/background ratio in TagRFP-red fluorescent marker protein expressing tumor by five times after 15 minutes application into the skin in vivo. The obtained results have immediate implications for multimodality imaging because many contrast agents are capable of simultaneously enhancing the contrast of multiple imaging modalities.

Integration of Fe3O4 with Bi2S3 for Multi-Modality Tumor Theranostics.

The combination of reactive oxygen species (ROS)-induced chemodynamic therapy (CDT) and photothermal therapy (PTT) holds a promising application prospect for their superb anticancer efficiency. Herein, we created a novel Fe3O4@polydopamine (PDA)@bovine serum albumin (BSA)-Bi2S3 composite as a theranostic agent, by chemically linking the Fe3O4@PDA with BSA-Bi2S3 via the amidation between the carboxyl groups of BSA and the amino groups of PDA. In this formulation, the Fe3O4 NPs could not only work as a mimetic peroxidase to trigger Fenton reactions of the innate H2O2 in the tumor and generate highly cytotoxic hydroxyl radicals (•OH) to induce tumor apoptosis but also serve as the magnetic resonance imaging (MRI) contrast agent to afford the precise cancer diagnosis. Meanwhile, the PDA could prevent the oxidization of Fe3O4, thus supporting the long-term Fenton reactions and the tumor apoptosis in the tumor. The Bi2S3 component exhibits excellent photothermal transducing performance and computed tomography (CT) imaging capacity. In addition, the PDA and Bi2S3 endow the Fe3O4@PDA@BSA-Bi2S3 composite with an excellent photothermal transforming ability which could lead to tumor hyperthermia. All of these merits play the synergism with the tumor microenvironment and qualify the Fe3O4@PDA@BSA-Bi2S3 NPs for a competent agent in the MRI/CT-monitored enhanced PTT/CDT synergistic therapy. Findings in this research will evoke new interests in future cancer therapeutic strategies based on biocompatible nanomaterials.

Trigeminal Neuralgia Due to Compression of Primitive Trigeminal Artery Variant: Usefulness of Fusion Images of Constructive Interference in Steady-State Magnetic Resonance Imaging and Computed Tomography Angiography.

BACKGROUND: Trigeminal neuralgia (TN) is one of the neuropathic pain syndromes, most commonly caused by vascular compression in the root entry zone of the trigeminal nerve in the cerebellopontine angle. It was rare as offending artery that primitive trigeminal artery and primitive trigeminal artery variant (PTAv) as an anomaly that occurs carotid-basilar anastomosis. We report a case of TN caused by the PTAv, and usefulness of fusion images of magnetic resonance imaging (MRI) and computed tomography angiography (CTA). CASE DESCRIPTION: A 65-year-old man presented with a 2-year history of left paroxysmal facial pain in the second division of the trigeminal nerve. We diagnosed left TN due to PTAv using constructive interference in steady state magnetic resonance imaging (CISS MRI) and CTA. Microvascular decompression surgery disclosed trigeminal nerve compressed by PTAv consisted with findings from preoperative neuroimaging. We report a case of TN caused by PTAv, and usefulness of fusion images of CISS MRI and CTA to understand the neurovascular and bony structure during the perioperative period. CONCLUSIONS: The fusion image created by CISS MRI and 3-dimensional CTA was useful to identify the offending vessel and to clearly understand the neurovascular structure preoperatively.

Pelvic bone tumor resection: what a radiologist needs to know.

Pelvic bone tumors present a diagnostic and therapeutic challenge. Due to the deep anatomic location and resultant late clinical presentation, pelvic bone tumors tend to be large and located in close proximity to pelvic viscera as well as vital neurovascular structures. Operative management of pelvic bone tumors is indicated for a variety of orthopedic oncologic conditions. In general, limb-sparing pelvic resection rather than hemipelvectomy with amputation of the ipsilateral limb is considered when a functional limb can be preserved without compromising the surgical margins. There are various options for pelvic resection and reconstruction, and the selection depends on tumor histology, anatomic location, and extent. The decision regarding choice of surgical procedure and reconstruction method for a pelvic bone tumor requires a thorough knowledge of the pelvic anatomy, and careful inspection of the anatomic extent. The surgical plan must strike a balance between acceptable functional outcome and acceptable morbidity. In this review, we describe the different types of pelvic resection techniques, and the vital role preoperative imaging plays in defining the anatomic extent of a pelvic bone tumor and subsequent surgical planning.

Intraoperative Computed Tomography Navigation-Assisted Resection of Symptomatic Intramedullary Spinal Cord Cavernoma: A Technical Note and Case Report.

BACKGROUND: Intramedullary spinal cord cavernous malformations (ISCCMs) are a rare entity. Most commonly, ISCCMs present with neurologic decline from lesion hemorrhage, which can be catastrophic and irreversible irrespective of surgical intervention. Given the challenging anatomic location of these lesions in highly critical neurologic areas, precise surgical localization and visualization is necessary to limit collateral damage during resection particularly for deep ISCCMs that do not present to a pial surface. CASE DESCRIPTION: We present a case of a 54-year-old man who presented with incomplete paraplegia after hemorrhage of a deep ISCCM at T11. Surgical resection was undertaken using intraoperative computed tomography (CT) navigation assistance autofused with high-resolution preoperative magnetic resonance imaging for precise intramedullary lesion targeting and localization for myelotomy. Complete resection was demonstrated on postoperative imaging. At a 6-week follow-up appointment, the patient endorsed return of his bladder function and was noted to have some return of motor function to his left foot with 3 of 5 dorsiflexion. At 4 months, he had improved to 3 of 5 proximal, 4 of 5 distal on the left and 2 of 5 proximal, and 3 of 5 distal on the right. CONCLUSIONS: The approach represents a novel application of intraoperative CT navigation assistance in the resection of deep ISCCMs.

Interobserver variability of 3.0-tesla and 1.5-tesla magnetic resonance imaging/computed tomography fusion image-based post-implant dosimetry of prostate brachytherapy.

This study aimed to compare the interobserver variabilities in magnetic resonance imaging (MRI)/computed tomography (CT) fusion image-based post-implant dosimetry of permanent prostate brachytherapy (PPB) between 1.5-T and 3.0-T MRI. The study included 60 patients. Of these patients, 30 underwent 1.5-T MRI and CT 30 days after seed implantation (1.5-T group), and 30 underwent 3.0-T MRI and CT 30 days after seed implantation (3.0-T group). All patients received PPB alone. Two radiation oncologists performed MRI/CT fusion image-based post-implant dosimetry, and the interobserver variabilities of dose-volume histogram (DVH) parameters [dose (Gy) received by 90% of the prostate volume (prostate D90)], percentage of the prostate volume receiving at least the full prescribed dose (prostate V100), percentage of the prostate volume receiving at least 150% of the prescribed dose (prostate V150), dose (Gy) received by 5% of the urethral volume (urethral D5) and the urethral volume receiving at least 150% of the prescribed dose (urethral V150)] were retrospectively estimated using the paired Student's t test and Pearson's correlation coefficient. The Pearson's correlation coefficients of all DVH parameters were higher in the 3.0-T group than in the 1.5-T group (1.5-T vs 3.0-T: prostate D90, 0.65 vs 0.93; prostate V100, 0.62 vs 0.82; prostate V150, 0.97 vs 0.98; urethral D5, 0.92 vs 0.93; and urethral V150, 0.88 vs 0.93). In the paired Student's t test, no significant differences were observed in any of the DVH parameters between the two radiation oncologists in the 3.0-T group (0.068 ≤ P ≤ 0.842); however, significant differences were observed in prostate D90 (P = 0.004), prostate V100 (P = 0.011) and prostate V150 (P = 0.002) between the oncologists in the 1.5-T group. The interobserver variability of DVH parameters in the MRI/CT fusion image-based post-implant dosimetry analysis of brachytherapy was lower with 3.0-T MRI than with 1.5-T MRI.

Maximizing Sacral Chordoma Resection by Precise 3-Dimensional Tumor Modeling in the Operating Room Using Intraoperative Computed Tomography Registration with Preoperative Magnetic Resonance Imaging Fusion and Intraoperative Neuronavigation: A Case Series.

INTRODUCTION: The primary treatment for patients with sacral chordoma is en bloc surgical resection with negative margins, which has been shown to reduce local recurrence and tumor-related morbidity. Here we describe the use of intraoperative neuronavigation using preoperative spine magnetic resonance imaging fused to intraoperative computed tomography (CT) to create 3-dimensional tumor reconstructions in the operating room for intraoperative identification of bone and soft-tissue margins for maximal safe tumor resection. METHODS: A single-institution retrospective chart review was completed to encompass our experience of 6 consecutive patients who had sacral chordoma resections using our described navigation protocol. We collected data on patient demographics, previous surgeries, radiation therapy, preoperative examination, spinal levels involved, dural involvement, estimated blood loss, surgery time, tissue diagnosis, follow-up, postoperative examination, complications, and recurrence. Primary outcome was en bloc resection with negative margins as planned preoperatively. RESULTS: Negative surgical margins were achieved in 5 of 5 patients, who were preoperatively planned for en bloc resection with negative margins. The most common levels involved were S4-S5. All patients had a stable or improved neurologic examination after en bloc surgical resection. The average follow-up was 5.4 months ± 84.6 days. No patient had residual or recurrent tumor at last follow-up. CONCLUSIONS: Magnetic resonance imaging-CT fusion and 3-dimensional reconstruction techniques using an intraoperative CT scanner with image-guided navigation to aid preoperative planning and surgical resection of sacral chordomas are not well represented in the literature. This technique can be used for planning en bloc surgical resections and for more precisely identifying tumor margins intraoperatively.

Comparison of different registration landmarks for MRI-CT fusion in radiotherapy for lung cancer with post-obstructive lobar collapse.

The registration of the two sets of images based on the spine and pulmonary artery landmarks and the geometric center difference of the mean displacement in the X, Y, and Z directions (X, Y, and Z represent the directions of the body from left to right, superior to inferior, and anterior to posterior) between their MRI-CT fusions were compared, respectively. Fifty-five lung cancer patients with post-obstructive lobar collapse were enrolled in this study. Before radiation, two sets of simulating images according to the spine and the pulmonary artery registrations were obtained for each patient using MRI-CT fusion. The differences of mean displacement in the X, Y, and Z directions based on spine and pulmonary artery landmarks were of -0.29, 0.25, and 0.18 cm, respectively. The mean displacements of the pulmonary artery based images in the three directions were smaller than that in the spine registration images (P < 0.05). By the method of pulmonary artery landmark, MRI-CT has better registration accuracy and can better help confirm the target volume.

Neurovascular bundle-sparing radiotherapy for prostate cancer using MRI-CT registration: A dosimetric feasibility study.

PURPOSE: Sexual dysfunction after radiotherapy for prostate cancer remains an important late adverse toxicity. The neurovascular bundles (NVB) that lie posterolaterally to the prostate are typically spared during prostatectomy, but in traditional radiotherapy planning they are not contoured as an organ-at-risk with dose constraints. Our goal was to determine the dosimetric feasibility of "NVB-sparing" prostate radiotherapy while still delivering adequate dose to the prostate. METHODS: Twenty-five consecutive patients with prostate cancer (with no extraprostatic disease on pelvic magnetic resonance imaging [MRI]) who that were treated with external beam radiotherapy, with the same primary planning target volume margins, to a dose of 79.2 Gy were evaluated. Pelvic MRI and simulation computed tomography scans were registered using dedicated software to allow for bilateral NVB target delineation on T2-weighted MRI. A volumetric modulated arc therapy plan was generated using the NVB bilaterally with 2 mm margin as an organ to spare and compared to the patient's previously delivered plan. Dose-volume histogram endpoints for NVB, rectum, bladder, and planning target volume 79.2 were compared between the 2 plans using a 2-tailed paired t-test. RESULTS: The V70 for the NVB was significantly lower on the NVB-sparing plan (p <0.01), while rectum and bladder endpoints were similar. Target V100% was similar but V105% was higher for the NVB-sparing plans (p <0.01). CONCLUSIONS: "NVB-sparing" radiotherapy is dosimetrically feasible using CT-MRI registration, and for volumetric modulated arc therapy technology - target coverage is acceptable without increased dose to other normal structures, but with higher target dose inhomogeneity. The clinical impact of "NVB-sparing" radiotherapy is currently under study at our institution.

Edge-oriented dual-dictionary guided enrichment (EDGE) for MRI-CT image reconstruction.

In this paper, we formulate the joint/simultaneous X-ray CT and MRI image reconstruction. In particular, a novel algorithm is proposed for MRI image reconstruction from highly under-sampled MRI data and CT images. It consists of two steps. First, a training dataset is generated from a series of well-registered MRI and CT images on the same patients. Then, an initial MRI image of a patient can be reconstructed via edge-oriented dual-dictionary guided enrichment (EDGE) based on the training dataset and a CT image of the patient. Second, an MRI image is reconstructed using the dictionary learning (DL) algorithm from highly under-sampled k-space data and the initial MRI image. Our algorithm can establish a one-to-one correspondence between the two imaging modalities, and obtain a good initial MRI estimation. Both noise-free and noisy simulation studies were performed to evaluate and validate the proposed algorithm. The results with different under-sampling factors show that the proposed algorithm performed significantly better than those reconstructed using the DL algorithm from MRI data alone.