Stereotactic body radiation therapy to the spine: contouring the cauda equina instead of the spinal cord is more practical as the organ at risk.

Background: Stereotactic body radiotherapy (SBRT) is recognized as a curative treatment for oligometastasis. The spinal cord becomes the cauda equina at the lumbar level, and the nerves are located dorsally. Recently, a consensus has been reached that the cauda equina should be contoured as an organ at risk (OAR). Here, we examined the separate contouring benefits for the spinal canal versus the cauda equina only as the OAR. Materials and methods: A medical physicist designed a simulation plan for 10 patients with isolated lumbar metastasis. The OAR was set with three contours: the whole spinal canal, cauda equina only, and cauda equina with bilateral nerve roots. The prescribed dose for the planning target volume (PTV) was 30 Gy/3 fx. Results: For the constrained QAR doses, D90 and D95 were statistically significant due to the different OAR contouring. The maximum dose (Dmax) was increased to the spinal canal when the cauda equina max was set to ≤ 20 Gy, but dose hotspots were observed in most cases in the medullary area. The Dmax and PTV coverage were negatively correlated for the cauda equina and the spinal canal if Dmax was set to ≤ 20 Gy for both. Conclusions: A portion of the spinal fluid is also included when the spinal canal is set as the OAR. Thus, the PTV coverage rate will be poor if the tumor is in contact with the spinal canal. However, the PTV coverage rate increases if only the cauda equina is set as the OAR.

Effect of stomach size on organs at risk in pancreatic stereotactic body radiotherapy.

BACKGROUND: In clinical practice, the organs at risk (OARs) should be carefully determined when performing pancreatic stereotactic body radiotherapy (SBRT). We conducted a simulation study to examine the effect of the stomach size on the radiation dose to the OARs when performing pancreatic SBRT. METHODS: Twenty-five cases were included in this study. Pancreatic head and body tumors were 2-cm-sized pseudotumors, which were included as gross target volume (GTV) contours. The stomach, pancreas, small intestine, liver, kidneys, and spinal cord were considered as the OARs. The prescription dose for planning target volume (PTV) was 40 Gy/5fx, and the dose limit for the OARs was determined. The dose to X% of the OAR volume at X values of 0.1, 5.0, and 10.0 cc (DX) and the percentage of the OAR volume that received more than X Gy were recorded. RESULTS: In terms of the radiation dose to the pancreatic body tumors, the stomach size was positively correlated with a dose of D10cc [correlation coefficient (r) = 0.5516) to the stomach. The r value between the radiation dose to the pancreatic head tumor and the stomach size was 0.3499. The stomach size and radiation dose to the head and body of the pancreas were positively correlated (pancreatic head D10cc: r = 0.3979, pancreatic body D10cc: r = 0.3209). The larger the stomach, the larger the radiation dose to the healthy portion of the pancreas outside the PTV. CONCLUSIONS: When performing pancreatic SBRT, the dose to the OARs depends on the stomach size. Reducing the dose to the stomach and pancreas can be achieved by shrinking the stomach.

Automated estimation of the upper surface of the diaphragm in 3-D CT images.

This communication describes a fully automated method by which the position of the diaphragm surface can be estimated by deforming a thin-plate model to match the bottom surface of the lung in CT images. This method was applied to 338 X-ray CT scans, and its validity was proved by the experimental results.

Automatic segmentation and recognition of anatomical lung structures from high-resolution chest CT images.

This paper describes a fully automated segmentation and recognition scheme, which is designed to recognize lung anatomical structures in the human chest by segmenting the different chest internal organ and tissue regions sequentially from high-resolution chest CT images. A sequential region-splitting process is used to segment lungs, airway of bronchus, lung lobes and fissures based on the anatomical structures and statistical intensity distributions in CT images. The performance of our scheme is evaluated by segmenting lung structures from high-resolution multi-slice chest CT images from 44 patients; the validity of our method was proved by preliminary experimental results.

Chest wall Castleman's disease: CT and MRI findings.

Castleman's disease is an usually benign lymphoid tumor of uncertain etiology that generally appears as a solitary mediastinal mass. We present a case of Castleman's disease in the right chest wall of a 60-year-old woman. Magnetic resonance imaging showed a well-defined, oval mass that was early enhanced on T1-weighted images. The mass was diagnosed by percutaneous core needle biopsy with computed tomography guidance. The patient has remained well for 5 years without an increase in tumor size. We also summarize the international literature.

Solitary mediastinal lymph node metastasis of hepatocellular carcinoma: MR imaging findings.

A 65-year-old man with multiple hepatocellular carcinomas in the liver with type C viral hepatitis had a solitary mediastinal lymph node metastasis in the right paratracheal to tracheobronchial region. Surgical resection for the mediastinal metastasis was undertaken based on magnetic resonance (MR) imaging findings, suggesting its radicality. We assess the MR imaging findings and presumable pathways of lymphatic metastasis from the liver to mediastinal lymph nodes in this report.

Neurogenic tumors of the mediastinum and chest wall: MR imaging appearance.

Various histologic types of neurogenic tumors may originate in the mediastinum and chest wall. It is possible to make accurate diagnosis of these tumors by using the multiplanar capability and high contrast resolution of MR imaging because of these characteristic imaging findings. MR and histologic features of these tumors are illustrated and described in this essay.

Nonfunctional mediastinal parathyroid cyst: imaging findings in two cases.

The authors describe the computed tomography (CT) and magnetic resonance (MR) imaging findings of a 69-year-old woman and a 69-year-old man with a nonfunctional mediastinal parathyroid cyst. In the described cases, unenhanced CT showed homogeneous areas of water density, and unenhanced MRI showed homogeneous areas that were isointense to cerebrospinal fluid, reflecting their serous fluid contents. Both cysts were located posterior to the left lower pole of the thyroid gland with an extension to the superior mediastinum, either anterior or posterior to the left brachiocephalic vein. CT and MR imaging findings of parathyroid cysts are nonspecific, and they are often difficult to differentiate from other cystic lesions located in the lower neck or in the superior mediastinum. However, a parathyroid cyst should be considered when radiologic images demonstrate its characteristic location, posterior to the thyroid gland, with an extension to the superior mediastinum.