Michel Feron

The contribution of magnetic resonance imaging to the three-dimensional treatment planning of localized prostate cancer.

PURPOSE To investigate whether the use of transaxial and coronal MR imaging improves the ability to localize the apex of the prostate and the anterior part of the rectum compared to the use of transaxial CT alone, and whether the incorporation of MR could improve the coverage of the prostate by the radiotherapy field and change the volume of rectum irradiated. METHODS AND MATERIALS Ten consecutive patients with localized prostate carcinoma underwent a CT and an axial and coronal MR scan in treatment position. The CT and MR images were mathematically aligned, and three observers were asked to contour independently the prostate and the rectum on CT and on MR. The interobserver variability of the prostatic apex location and of the delineation of the anterior rectal wall were assessed for each image modality. A dosimetry study was performed to evaluate the dose to the rectum when MR was used in addition to CT to localize the pelvic organs. RESULTS The interobserver variation of the prostatic apex location was largest on CT ranging from 0.54 to 1.07 cm, and smallest on coronal MR ranging from 0.17 to 0.25 cm. The interobserver variation of the delineation of the anterior rectum on MR was small and constant along the whole length of the prostate (0.09+/-0.02 cm), while for CT it was comparable to that for the MR delineation at the base of the prostate, but it increased gradually towards the apex, where the variation reached 0.39 cm. The volume of MR rectum receiving more than 80% of the prescribed dose was on average reduced by 23.8+/-11.2% from the CT to the MR treatment plan. CONCLUSION It can be concluded that the additional use of axial and coronal MR scans, in designing the treatment plan for localized prostate carcinoma, improves substantially the localization accuracy of the prostatic apex and the anterior aspect of the rectum, resulting in a better coverage of the prostate and a potential to reduce the volume of the rectum irradiated to a high dose.

Respiration-induced movement of the upper abdominal organs: a pitfall for the three-dimensional conformal radiation treatment of pancreatic cancer.

Respiration-induced movement of the upper abdominal organs (pancreas, liver and kidneys) was assessed in 12 subjects using dynamic magnetic resonance imaging. The movement of each organ in the cranio-caudal, the lateral and the anterior-posterior direction was deduced from the movement of the center of gravity on two-dimensional images. This center of gravity was computed from the volume delineated on sequential 8-mm slices of both sagittal and coronal dynamic series. The largest movements were noticed in the cranio-caudal direction for pancreas and liver (23.7+/-15.9 mm and 24.4+/-16.4 mm). The kidneys showed smaller movements in the cranio-caudal direction (left kidney 16.9+/-6.7 mm and right kidney 16.1+/-7.9 mm). The movements of the different organs in the anterior-posterior and lateral directions were less pronounced. It is of the greatest importance to be aware of these movements in the planning of a conformal radiation treatment for pancreatic cancer.

Interobserver variations in gross tumor volume delineation of brain tumors on computed tomography and impact of magnetic resonance imaging

PURPOSE (1) To assess the interobserver variability of brain tumor delineation on computed tomography (CT). (2) To assess the impact of the addition of magnetic resonance imaging (MRI) information. METHODS Nine physicians were asked to delineate the gross tumor volume (GTV) of five patients with supratentorial inoperable brain tumors on CT scans and 2 weeks (or more) later on MRIs. The delineations were performed on a computer screen. During delineation on MRI, the registered CT images (without delineation) were displayed on the screen (MRI+CT). RESULTS A high interobserver variability in GTV delineation on CT is found: the ratio of the largest to the smallest defined volumes varies for the five patients by factors of resp. 2.8, 1.8, 1.8, 1.9 and 1.7. The interobserver variability is as large on MRI+CT as on CT alone (ratio largest/smallest volume: 2.4, 1.7, 1.9, 2.7 and 1.5). Volumes delineated on MRI+CT (mean: 69.6 cm(3)) are larger than on CT alone (mean: 59.5 cm(3)). Residual volumes (volume delineated on one image modality but not on the other) are >0 for CT alone and for MRI+CT. CONCLUSIONS A large interobserver variability in GTV delineation of brain tumors is demonstrated. The addition of MRI to CT does not reduce interobserver variability. GTVs delineated on MRI+CT are larger than on CT alone, but some volumes are delineated on CT and not on MRI. Therefore, a combination of the two image modalities is recommended for brain tumor delineation for treatment planning.

Laryngeal tumor volume measurements determined with CT: A study on intra- and interobserver variability

PURPOSE To investigate the intra- and interobserver variability of computed tomography-based volume measurements of laryngeal tumors. METHODS AND MATERIALS The volume of 13 laryngeal tumors was repeatedly measured by five independent observers in four different sessions, using the summation-of-areas technique. Mean tumor volume and its standard deviation were calculated for each tumor. Statistical analysis was done with analysis of variance, Spearman rank correlation, and linear regression. RESULTS Both the effect of the observers (p < 0.0001) and the effect of the session (p < 0.01) on tumor volume was statistically significant. Interobserver variability was the most important component of total variability (89.3%). A significant rank correlation was found between mean volume and standard deviation (p < 0.01); the relationship between mean tumor volume and standard deviation can be described using linear regression [standard deviation = 0.28 volume + 0.35 (R = 0.79)]. CONCLUSION Total variability in the computed tomography-based measurement of laryngeal tumor volume can be reduced by having the measurements done by a single trained observer.

The relation of CT-determined tumor parameters and local and regional outcome of tonsillar cancer after definitive radiation treatment

PURPOSE To investigate the value of CT-derived tumor parameters as predictor of local and regional outcome of tonsillar squamous cell carcinoma treated by definitive radiation therapy. METHODS AND MATERIALS The pretreatment CT studies of 112 patients with tonsillar squamous cell carcinoma were reviewed. After redigitizing the films, primary and nodal tumor volume was calculated with the summation-of-areas technique. The nodal CT aspect was graded using a 3-point scale (homogenous, inhomogeneous, and necrotic). Mean follow-up time was 33 months. Actuarial statistical analysis of local and regional outcome was done for each of the covariates; multivariate analysis was performed using Coxs proportional hazards model. RESULTS In the actuarial analysis, CT-determined primary tumor volume was significantly correlated with local recurrence rate (p < 0.05) when all patients were considered, but primary tumor volume did not predict local control within the T2, T3, and T4 category. CT-determined nodal volume was significantly related to regional outcome (p < 0.01), but nodal density was not. Total tumor volume was not significantly related to locoregional outcome (p = 0.1). In the multivariate analysis, the T and N categories were the independent predictors of local and regional outcomes, respectively. CONCLUSION Compared to other head-and-neck sites, primary and nodal tumor volume have only marginal predictive value regarding local and regional outcome after radiation therapy in tonsillar cancer.

Evaluation of manual vs semi-automated delineation of liver lesions on CT images

Abstract. In this paper we compare a semi-automated delineation method with totally manual delineation for area quantification, with respect to efficiency, quality, and intra- and interobserver variability. Liver lesions on 28 CT images were delineated by three observers, twice using completely manual delineation and twice using a semi-automated method. Quantitative comparisons were performed with respect to delineated area and time required for the delineation tasks. Subjective comparisons were performed with respect to efficiency and perceived quality of the semi-automated method. The areas obtained using semi-automated delineation were significantly smaller (11 %) than those obtained using totally manual delineation. Intraobserver and interobserver variability with the semi-automated method were approximately three times lower than with manual delineation. Efficiency of the semi-automated method was subjectively rated favorable, although further improvements are possible. With respect to quality, the semi-automated method was ranked better than the manual method in 73 % of cases.

Tracheal Autotransplantation: A Reliable Reconstructive Technique for Extended Hemilaryngectomy Defects

Objectives: Current surgical treatment for a glottic cancer with significant subglottic extension is a total laryngectomy. The objective of this study was to expand laryngeal conservation procedures by using a reconstructive technique that allows for the repair of hemicricolaryngectomy defects.

PACS/HIS integration in handling and viewing ICU images generated by a phosphorplate scanner

We argue that efficient access to digital images for the Intensive Care Unit (ICU) requires the PACS to be strongly integrated within the overall working environment. This includes tailoring the imaging environment towards the specific working organization as well as integrating it with the HIS. The purpose of this project was to implement an integrated environment for chest images generated using a recently introduced phosphorplate scanner. PACS-HIS-Modality integration is reflected in our environment in different ways. The user interface of the viewing station is centered around often used patterns in ICU viewing. Information about bed occupancy is retrieved from the HIS and exploited in the viewing station. A digital connection between the phosphorplate scanner and the HIS ensures that images are correctly related to other patient information and to previous images of the patient. Using minor adaptations to the existing HIS, PACS and HIS have been made to cooperate in integrated presentation of images and reports. As work in progress, this integration has been expanded towards hypermedia, linking annotations in images to sections in a textual or spoken report. We discuss the relation between PACS and the global information environment, emphasizing organizational issues rather than technological aspects.

Integrating digital ICU viewing into the global working environment

We illustrate that to benefit from the advantages of Picture Archiving and Communication Systems (PACS) for the Intensive Care Unit (ICU), the PACS must be strongly integrated within the overall working environment. This includes adaptation of the PACS toward specific working patterns and integrating it with the Hospital Information System (HIS). This is reflected in our prototype system in different ways. The user interface of the viewing station is centered around often used patterns in ICU viewing. Information about bed occupancy is retrieved from the HIS and exploited in the viewing station. A digital connection between the phosphorplate scanner and the HIS ensures that images are correctly related to other patient information and to previous images. Using minor adaptations to the existing HIS, PACS and HIS have been made to cooperate in integrated presentation of images and radiological reports, as a step towards a multi-media medical information system. We discuss the relation between PACS and the global information environment, emphasizing organizational issues rather than technological aspects.

Design for user efficiency in a dedicated ICU viewing station

The intensive care unit (ICU) is one application where significant benefit is expected from the use of digital technology in the acquisition, management and presentation of images. However, the potential benefits should not be outweighed by disadvantages of current digital technology. One of the bottlenecks is the efficiency of image viewing using a workstation, especially if this viewing station is implemented using affordable commonly available hardware. In this paper we describe the design concepts of a relatively low-cost but efficient viewing station for chest images, and discuss clinical experience with this system at an ICU ward. The user interface has been optimized towards the specific patterns of ICU image viewing. By anticipating user requests and preparing images during idle times of the computer, the mean image access time could be reduced by a factor of 4, while most images could be presented instantaneously. Information from the hospital information system (HIS) is exploited in the user interface, and a simplified PAC-HIS coupling has been implemented for the simultaneous presentation of images and reports.