Pericardial lipoma: Ultrasound,computed tomography and magnetic resonance imaging findings

Primary tumours of the heart and pericardium are extremely rare. Cardiac lipomas account for only 10% of all primary cardiac tumours. A case of surgically proven pericardial lipoma demonstrated by ultrasound, CT and MRI is presented here.     

下咽癌颈部及咽后淋巴结转移的CT/MRI分析

背景与目的:下咽癌早期即可出现区域淋巴结转移,然而关于下咽癌区域淋巴结尤其是咽后淋巴结转移的报道少见。本研究旨在通过对下咽癌CT/MRI扫描结果的分析,探讨下咽癌区域淋巴结特别是咽后淋巴结转移的特性,为临床治疗提供参考。方法:回顾性分析2000年8月至2009年3月我院病理证实的88例下咽癌区域淋巴结转移的CT/MRI结果。对其局部分期、各区域淋巴结转移的相互关系采用χ2检验和Logistic多因素分析研究。结果:下咽癌的区域淋巴结转移率为73.9%,Ⅱa、Ⅱb、Ⅲ区淋巴结转移发生率最高,分别为61.4%、44.3%及37.5%。Ⅰ、Ⅳ、Ⅴ、Ⅵ区及咽后淋巴结转移都较少,并且均合并Ⅱ、Ⅲ区淋巴结转移。单因素分析显示Ⅰb、Ⅲ区淋巴结转移与Ⅳ区淋巴结转移,Ⅱb区、双侧颈部淋巴结转移与咽后淋巴结转移的关系有统计学意义。多因素分析结果显示Ⅳ区淋巴结转移与Ⅵ区淋巴结转移,双侧颈部淋巴结转移与咽后淋巴结转移的关系有统计学意义。结论:下咽癌区域淋巴结转移途径遵循一定的规律,跳跃性转移少见,以Ⅱ、Ⅲ区转移最常见。双侧颈部淋巴结可能是咽后淋巴结转移的危险因素。     

Automatic segmentation of kidneys in computed tomography images using U-Net

PurposeAccurate segmentation of target volumes and organs at risk from computed tomography (CT) images is essential for treatment planning in radiation therapy. The segmentation task is often done manually making it time-consuming. Besides, it is biased to the clinician experience and subject to inter-observer variability. Therefore, and due to the development of artificial intelligence tools and particularly deep learning (DL) algorithms, automatic segmentation has been proposed as an alternative. The purpose of this work is to use a DL-based method to segment the kidneys on CT images for radiotherapy treatment planning.Materials and methodsIn this contribution, we used the CT scans of 20 patients. Segmentation of the kidneys was performed using the U-Net model. The Dice similarity coefficient (DSC), the Matthews correlation coefficient (MCC), the Hausdorff distance (HD), the sensitivity and the specificity were used to quantitatively evaluate this delineation.ResultsThis model was able to segment the organs with a good accuracy. The obtained values of the used metrics for the kidneys segmentation, were presented. Our results were also compared to those obtained recently by other authors.ConclusionFully automated DL-based segmentation of CT images has the potential to improve both the speed and the accuracy of radiotherapy organs contouring.     

Prostate postbrachytherapy seed distribution: comparison of high-resolution, contrast-enhanced, T1- and T2-weighted endorectal magnetic resonance imaging versus computed tomography: initial experience

PURPOSE: To compare contrast-enhanced, T1-weighted, three-dimensional magnetic resonance imaging (CEMR) and T2-weighted magnetic resonance imaging (T2MR) with computed tomography (CT) for prostate brachytherapy seed location for dosimetric calculations. METHODS AND MATERIALS: Postbrachytherapy prostate MRI was performed on a 1.5 Tesla unit with combined surface and endorectal coils in 13 patients. Both CEMR and T2MR used a section thickness of 3 mm. Spiral CT used a section thickness of 5 mm with a pitch factor of 1.5. All images were obtained in the transverse plane. Two readers using CT and MR imaging assessed brachytherapy seed distribution independently. The dependency of data read by both readers for a specific subject was assessed with a linear mixed effects model. RESULTS: The mean percentage (+/- standard deviation) values of the readers for seed detection and location are presented. Of 1205 implanted seeds, CEMR, T2MR, and CT detected 91.5% +/- 4.8%, 78.5% +/- 8.5%, and 96.1% +/- 2.3%, respectively, with 11.8% +/- 4.5%, 8.5% +/- 3.5%, 1.9% +/- 1.0% extracapsular, respectively. Assignment to periprostatic structures was not possible with CT. Periprostatic seed assignments for CEMR and T2MR, respectively, were as follows: neurovascular bundle, 3.5% +/- 1.6% and 2.1% +/- 0.9%; seminal vesicles, 0.9% +/- 1.8% and 0.3% +/- 0.7%; periurethral, 7.1% +/- 3.3% and 5.8% +/- 2.9%; penile bulb, 0.6% +/- 0.8% and 0.3% +/- 0.6%; Denonvillier's Fascia/rectal wall, 0.5% +/- 0.6% and 0%; and urinary bladder, 0.1% +/- 0.3% and 0%. Data dependency analysis showed statistical significance for the type of imaging but not for reader identification. CONCLUSION: Both enumeration and localization of implanted seeds are readily accomplished with CEMR. Calculations with MRI dosimetry do not require CT data. Dose determinations to specific extracapsular sites can be obtained with MRI but not with CT.     

Automatic segmentation of pelvic structures from magnetic resonance images for prostate cancer radiotherapy

PURPOSE: Target-volume and organ-at-risk delineation is a time-consuming task in radiotherapy planning. The development of automated segmentation tools remains problematic, because of pelvic organ shape variability. We evaluate a three-dimensional (3D), deformable-model approach and a seeded region-growing algorithm for automatic delineation of the prostate and organs-at-risk on magnetic resonance images. METHODS AND MATERIALS: Manual and automatic delineation were compared in 24 patients using a sagittal T2-weighted (T2-w) turbo spin echo (TSE) sequence and an axial T1-weighted (T1-w) 3D fast-field echo (FFE) or TSE sequence. For automatic prostate delineation, an organ model-based method was used. Prostates without seminal vesicles were delineated as the clinical target volume (CTV). For automatic bladder and rectum delineation, a seeded region-growing method was used. Manual contouring was considered the reference method. The following parameters were measured: volume ratio (Vr) (automatic/manual), volume overlap (Vo) (ratio of the volume of intersection to the volume of union; optimal value = 1), and correctly delineated volume (Vc) (percent ratio of the volume of intersection to the manually defined volume; optimal value = 100). RESULTS: For the CTV, the Vr, Vo, and Vc were 1.13 (+/-0.1 SD), 0.78 (+/-0.05 SD), and 94.75 (+/-3.3 SD), respectively. For the rectum, the Vr, Vo, and Vc were 0.97 (+/-0.1 SD), 0.78 (+/-0.06 SD), and 86.52 (+/-5 SD), respectively. For the bladder, the Vr, Vo, and Vc were 0.95 (+/-0.03 SD), 0.88 (+/-0.03 SD), and 91.29 (+/-3.1 SD), respectively. CONCLUSIONS: Our results show that the organ-model method is robust, and results in reproducible prostate segmentation with minor interactive corrections. For automatic bladder and rectum delineation, magnetic resonance imaging soft-tissue contrast enables the use of region-growing methods.     

18F-fluoro-deoxy-glucose-positron emission tomography/computed tomography in diagnosis of head and neck squamous cell carcinoma: A systematic review and meta-analysis

18F-fluoro-deoxy-glucose-positron emission tomography/computed tomography-scan (PET/CT) is used increasingly for detection of cancer.Precise diagnostic assessment of tumour extension in head and neck squamous cell carcinoma (HNSCC) is of critical importance for ensuring that patients receive proper treatment. Preliminary studies have shown divergent results of PET/CT in diagnosis and staging of HNSCC. The aims of this study were (1) to systematically review and meta-analyse published data about the diagnostic accuracy of PET/CT for diagnosing patients with HNSCC and (2) to compare the diagnostic accuracy of PET/CT with that of standard conventional imaging (SCI).MethodsA systematic literature search in the PubMed, Embase and Cochrane databases on publications of PET/CT diagnostics of HNSCC from January 2005 to July 2013 was carried out. All retrieved studies were reviewed and qualitatively analysed. Along with the calculated pooled sensitivity and specificity of PET/CT and SCI, bubble- and summary receiver operating characteristics (SROC) plots were created.FindingsTwo meta-analyses of diagnostic accuracy were conducted. The first, on PET/CT, included 987 patients distributed across nine studies. The second, on SCI, included 517 patients participating in a total of six studies among those comparing PET/CT to SCI. The meta-analyses showed a pooled sensitivity of 89.3% (95% confidence interval [95% CI]: 83.4–93.2%) and specificity of 89.5% (95% CI: 82.9–93.7%) for PET/CT and correspondingly, a pooled sensitivity and specificity of 71.6% (95% CI: 44.3–88.9%) and 78.0% (95%CI: 30.2–96.7%) for SCI. A graphical comparison to SCI showed a clear difference in favour of PET/CT.InterpretationPET/CT is highly accurate in diagnosing patients suffering from HNSCC     

Nuclear magnetic resonance computed tomography (NMR-CT) of malignancies

The physical principles of nuclear magnetic resonance (NMR) imaging were initially outlined. In the present proton images, T1 and T2 relaxation times were more important than proton density in determining the varying intensity of the tissue. Early clinical experiences of NMR for malignancies of the head and neck region, chest, abdomen, pelvis and extremities were also presented. There was superb ability for soft tissue characterizations, accentuating intensity difference between tissues with different T1 and T2 relaxation time. Although the spatial resolution of NMR-CT appeared to be inferior to X-CT, the absence of streak artifacts or X-ray beam hardening were advantageous. Because of the absence of significant NMR signal from rapidly flowing blood, the differentiation of vessels and soft tissue masses was easily accomplished by NMR-CT without employing contrast material. Multisection scans were performed in most cases with not only transverse but sagittal or coronal imaging by simply varying the sequence of pulse gradient magnetic field. While more experience is required, NMR-CT has a promising future in the imaging modality for malignancies.     

Interest of positron-emission tomography and magnetic resonance imaging for radiotherapy planning and control

Computed tomography (CT) in the treatment position is currently indispensable for planning radiation therapy. Other imaging modalities, such as magnetic resonance imaging (MRI) and positron emission-tomography (PET), can be used to improve the definition of the tumour and/or healthy tissue but also to provide functional data of the target volume. Accurate image registration is essential for treatment planning, so MRI and PET scans should be registered at the planning CT scan. Hybrid PET/MRI scans with a hard plane can be used but pose the problem of the absence of CT scans. Finally, techniques for moving the patient on a rigid air-cushioned table allow PET/CT/MRI scans to be performed in the treatment position while limiting the patient's movements exist. At the same time, the advent of MRI–linear accelerator systems allows to redefine image-guided radiotherapy and to propose treatments with daily recalculation of the dose. The place of PET during treatment remains more confidential and currently only in research and prototype status. The same development of imaging during radiotherapy is underway in proton therapy.     

Narrow band deformable registration of prostate magnetic resonance imaging, magnetic resonance spectroscopic imaging, and computed tomography studies

PURPOSE: Endorectal (ER) coil-based magnetic resonance imaging (MRI) and magnetic resonance spectroscopic imaging (MRSI) is often used to obtain anatomic and metabolic images of the prostate and to accurately identify and assess the intraprostatic lesions. Recent advancements in high-field (3 Tesla or above) MR techniques affords significantly enhanced signal-to-noise ratio and makes it possible to obtain high-quality MRI data. In reality, the use of rigid or inflatable endorectal probes deforms the shape of the prostate gland, and the images so obtained are not directly usable in radiation therapy planning. The purpose of this work is to apply a narrow band deformable registration model to faithfully map the acquired information from the ER-based MRI/MRSI onto treatment planning computed tomography (CT) images. METHODS AND MATERIALS: A narrow band registration, which is a hybrid method combining the advantages of pixel-based and distance-based registration techniques, was used to directly register ER-based MRI/MRSI with CT. The normalized correlation between the two input images for registration was used as the metric, and the calculation was restricted to those points contained in the narrow bands around the user-delineated structures. The narrow band method is inherently efficient because of the use of a priori information of the meaningful contour data. The registration was performed in two steps. First, the two input images were grossly aligned using a rigid registration. The detailed mapping was then modeled by free form deformations based on B-spline. The limited memory Broyden-Fletcher-Goldfarb-Shanno algorithm (L-BFGS), which is known for its superior performance in dealing with high-dimensionality problems, was implemented to optimize the metric function. The convergence behavior of the algorithm was studied by self-registering an MR image with 100 randomly initiated relative positions. To evaluate the performance of the algorithm, an MR image was intentionally distorted, and an attempt was then made to register the distorted image with the original one. The ability of the algorithm to recover the original image was assessed using a checkerboard graph. The mapping of ER-based MRI onto treatment planning CT images was carried out for two clinical cases, and the performance of the registration was evaluated. RESULTS: A narrow band deformable image registration algorithm has been implemented for direct registration of ER-based prostate MRI/MRSI and CT studies. The convergence of the algorithm was confirmed by starting the registration experiment from more than 100 different initial conditions. It was shown that the technique can restore an MR image from intentionally introduced deformations with an accuracy of approximately 2 mm. Application of the technique to two clinical prostate MRI/CT registrations indicated that it is capable of producing clinically sensible mapping. The whole registration procedure for a complete three-dimensional study (containing 256 x 256 x 64 voxels) took less than 15 min on a standard personal computer, and the convergence was usually achieved in fewer than 100 iterations. CONCLUSIONS: A deformable image registration procedure suitable for mapping ER-based MRI data onto planning CT images was presented. Both hypothetical tests and patient studies have indicated that the registration is reliable and provides a valuable tool to integrate the ER-based MRI/MRSI information to guide prostate radiation therapy treatment.     

Prostate volumes defined by magnetic resonance imaging and computerized tomographic scans for three-dimensional conformal radiotherapy

To compare the prostate volumes defined on magnetic resonance imaging (MRI), and noncontrast computerized tomographic (CT) scans used for three-dimensional (3D) treatment planning.

: Ten patients simulated for treatment using immobilization and a retrograde urethrogram. 3D images were used to compare prostate volumes defined by MRI (4–6 mm thick slices) and CT images (5 mm thick slices). Prostate volumes were calculated in cm³ using the Scanditronix 3D planning system. MRI/CT images were merged using bony anatomy to define the regions of discrepancy om prostate volumes.

: The mean prostate volume was 32% larger (range −5–63%) when defined by noncontrast CT compared to MRI. The areas of nonagreement tended to occur in four distinct regions of discrepancy: (a) the posterior portion of the prostate, (b) the posterior-inferior-apical portion of the prostate, (c) the apex due to diasgreement between a urothrogram based definition and the location defined by MRL, (d) regions corresponding to the neurovascular bundle.

: There is a tendency to overestimate the prostate volume by noncontrast CT compared to MRI. Awareness of this tendency should allow us to be to more accurately define the prostate during 3-D treatment planning.     

多层螺旋CT诊断胰腺癌的进展

胰腺癌是恶性程度很高的癌症之一,目前诊断出胰腺癌的患者大多都错过了最佳手术时机。胰腺癌的早期且准确诊断对于患者的治疗和预后十分关键。多层螺旋CT（multidetector-row computed tomography,MDCT）已成为胰腺癌诊断、肿瘤分期、治疗计划制定和治疗后随访的重要检查方式。然而,大约11%的胰腺导管腺癌在多层螺旋CT图像中由于病变和邻近胰腺实质之间密度差异仍出现漏诊情况。本文总结当前的多层螺旋CT在胰腺癌诊断方面的进展、限制及其它影像学检查方式的临床应用。     

Effects of respiration-averaged computed tomography on positron emission tomography/computed tomography quantification and its potential impact on gross tumor volume delineation

PURPOSE: Patient respiratory motion can cause image artifacts in positron emission tomography (PET) from PET/computed tomography (CT) and change the quantification of PET for thoracic patients. In this study, respiration-averaged CT (ACT) was used to remove the artifacts, and the changes in standardized uptake value (SUV) and gross tumor volume (GTV) were quantified. METHODS AND MATERIALS: We incorporated the ACT acquisition in a PET/CT session for 216 lung patients, generating two PET/CT data sets for each patient. The first data set (PET(HCT)/HCT) contained the clinical PET/CT in which PET was attenuation corrected with a helical CT (HCT). The second data set (PET(ACT)/ACT) contained the PET/CT in which PET was corrected with ACT. We quantified the differences between the two datasets in image alignment, maximum SUV (SUV(max)), and GTV contours. RESULTS: Of the patients, 68% demonstrated respiratory artifacts in the PET(HCT), and for all patients the artifact was removed or reduced in the corresponding PET(ACT). The impact of respiration artifact was the worst for lesions less than 50 cm(3) and located below the dome of the diaphragm. For lesions in this group, the mean SUV(max) difference, GTV volume change, shift in GTV centroid location, and concordance index were 21%, 154%, 2.4 mm, and 0.61, respectively. CONCLUSION: This study benchmarked the differences between the PET data with and without artifacts. It is important to pay attention to the potential existence of these artifacts during GTV contouring, as such artifacts may increase the uncertainties in the lesion volume and the centroid location.     

Evaluation and management of kidney lesions: comparison of 16-MDCT and magnetic resonance imaging

We evaluated the diagnostic performance of 16-MDCT and MRI in the characterization of kidney lesions and noted, the differences between these two methods. We describe the most common lesions of kidney and urinary tract examined with MDCT performed in the unenhanced, arterial, and portal venous phases, and MRI performed at 1.5 T with T2-and T1-weighted and dynamic gadolinium-enhanced sequences. All lesions had histologic findings that confirmed the primary diagnosis. Both MDCT and MRI are excellent methods to characterize benign and malignant renal lesions.     

Prostate contouring uncertainty in megavoltage computed tomography images acquired with a helical tomotherapy unit during image-guided radiation therapy

PURPOSE: To evaluate the image-guidance capabilities of megavoltage computed tomography (MVCT), this article compares the interobserver and intraobserver contouring uncertainty in kilovoltage computed tomography (KVCT) used for radiotherapy planning with MVCT acquired with helical tomotherapy. METHODS AND MATERIALS: Five prostate-cancer patients were evaluated. Each patient underwent a KVCT and an MVCT study, a total of 10 CT studies. For interobserver variability analysis, four radiation oncologists, one physicist, and two radiation therapists (seven observers in total) contoured the prostate and seminal vesicles (SV) in the 10 studies. The intraobserver variability was assessed by asking all observers to repeat the contouring of 1 patient's KVCT and MVCT studies. Quantitative analysis of contour variations was performed by use of volumes and radial distances. RESULTS: The interobserver and intraobserver contouring uncertainty was larger in MVCT compared with KVCT. Observers consistently segmented larger volumes on MVCT where the ratio of average prostate and SV volumes was 1.1 and 1.2, respectively. On average (interobserver and intraobserver), the local delineation variability, in terms of standard deviations [Deltasigma = radical(sigma2MVCT-sigma2KVCT)], increased by 0.32 cm from KVCT to MVCT. CONCLUSIONS: Although MVCT was inferior to KVCT for prostate delineation, the application of MVCT in prostate radiotherapy remains useful.     

Comparison of 2D radiographic images and 3D cone beam computed tomography for positioning head-and-neck radiotherapy patients

PURPOSE: To assess the positioning accuracy using two-dimensional kilovoltage (2DkV) imaging and three-dimensional cone beam CT (CBCT) in patients with head and neck (H&N) cancer receiving radiation therapy. To assess the benefit of patient-specific headrest. MATERIALS AND METHODS: All 21 patients studied were immobilized using thermoplastic masks with either a patient-specific vacuum bag (11 of 21, IMA) or standard clear plastic (10 of 21, IMB) headrests. Each patient was imaged with a pair of orthogonal 2DkV images in treatment position using onboard imaging before the CBCT procedure. The 2DkV and CBCT images were acquired weekly during the same session. The 2DkV images were reviewed by oncologists and also analyzed by a software tool based on mutual information (MI). RESULTS: Ninety-eight pairs of assessable 2DkV-CBCT alignment sets were obtained. Systematic and random errors were <1.6 mm for both 2DkV and CBCT alignments. When we compared shifts determined by CBCT and 2DkV for the same patient setup, statistically significant correlations were observed in all three major directions. Among all CBCT couch shifts, 4.1% > or = 0.5 cm and 18.7% > or = 0.3 cm, whereas among all 2DkV (MI) shifts, 1.7% > or = 0.5 cm and 11.2% > or = 0.3 cm. Statistically significant difference was found on anteroposterior direction between IMA and IMB with the CBCT alignment only. CONCLUSIONS: The differences between 2D and 3D alignments were mainly caused by the relative flexibility of certain H&N structures and possibly by rotation. Better immobilization of the flexible neck is required to further reduce the setup errors for H&N patients receiving radiotherapy.     

Ultrasound,computed tomography and magnetic resonance in the investigation of iliopsoas compartment disease

The authors reviewed the results of imaging studies performed in 30 patients with diseases involving the iliopsoas compartment (IPC) to assess the role of Ultrasound (US), Computed Tomography (CT) and Magnetic Resonance (MR) in the investigation of these deep seated and offen cliaically undetectable lesions 16 (53%) patients had histologically proven benign or malignant IPC tumours with bacterial infection in 12 (40%) and haemorrhage into the IPC in 2 (7%). US correctly detected iliopsoas pathdogy in only 9 of 17 cases (53%) and was satisfactory only in limited situations, such as abscess formation in children and haemorrhage in haemophiliacs. CT was much more accurate (16/17, 94%) than US and correctly diagnosed 7 cases overlooked on US, while also offering greater information in 5 cases where both studies were abnormal. CT was particularly helpful for the detection of both abscess formation and calcification within mass lesion. MR was accurate in all 9 cases imaged, and was very helpful in the assessment of associated vertebral, disc or spinal canal involvement by tumour or infection. A review of the literature, and the results of this study, suggest that CT and MR often have complementary roles where IPC disease is known or suspected. The accuracy of US in IPC disease is limited, preferably being followed by CT or MR imaging.     

Simultaneous positron emission tomography and magnetic resonance imaging for the detection and characterisation of liver lesions in patients with colorectal cancer: A pictorial review

Patients with colorectal cancer undergo frequent diagnostic imaging to stage the extent of metastatic disease and assess response to treatment. Imaging is typically via diagnostic contrast‐enhanced CT or combined FDG‐PET/CT. However, recent research has demonstrated promising benefits of combined FDG‐PET/MRI in oncologic imaging due to the superior soft‐tissue contrast of MRI. The extent of both intrahepatic and extrahepatic disease is important in establishing treatment options for colorectal cancer patients, and FDG‐PET/CT and dedicated liver imaging are often both required. FDG‐PET/MRI offers the advantage of a single examination which can be completed within a similar duration as dedicated liver MRI imaging. This improves patient convenience and anatomical co‐registration between PET and MRI imaging and provides a potential cost benefit. The diagnostic benefits of FDG‐PET/MRI include the simultaneous characterisation of focal liver lesions, exclusion of extrahepatic disease, the detection of additional hepatic metastases and extrahepatic disease, and the multi‐parametric assessment of treatment response. This pictorial review highlights examples of these benefits.