Linking dose delivery accuracy and planning target margin in radiosurgery based on dose-volume histograms derived from measurement-guided dose reconstruction.

In radiosurgery (SRS), the geometric uncertainties of machine-related delivery including image-guidance and hence the planning target volume (PTV) are often evaluated by the end-to-end gamma (γ) comparison that carries no information about the clinical relevance of deviations of individual SRS plans during delivery quality assurance (DQA). A proof-of-concept method was proposed to derive the PTV against both the plan- and the machine-specific delivery errors directly from the clinically relevant dose-volume histograms (DVHs) using measured-guided dose reconstruction (MGDR) during DQA. A liquid-filled detector array and a rotating phantom were used to measure sixteen arc-based radiosurgery treatments with 1 and 2 mm gross tumor volume (GTV)-to-PTV margins, producing MGDR-3D dose distribution on both the phantom and the patient CT for γ index and clinical DVH evaluations, respectively. The PTV was considered optimal when the MGDR showed the desired prescription dose coverage (V pres ) of the GTV (100% in this study). Associations of the binary V pres outcomes (

Sideways walk test: Reliability and association with lower limb motor function after stroke.

OBJECTIVES: To investigate (i) the intra-rater, inter-rater and test-retest reliability of sideways walk test times and counts in individuals with stroke; (ii) their correlations with stroke-specific measures of impairment; (iii) the cut-off sideways walk test times and counts between stroke survivors and healthy controls; and (iv) the minimum detectable changes in the sideways walk test times and counts. DESIGN: Cross-sectional study. SETTING: University-based rehabilitation centre. SUBJECTS: Twenty-nine older adults with stroke and 32 healthy controls. METHODS: The sideways walk test was conducted together with Fugl-Meyer motor assessments of the lower extremities, lower limb muscle strength tests, the Five-Times-Sit-To-Stand test, Berg Balance Scale, Timed Up-and-Go test, and Activity-based Confidence and Community Integration Measure questionnaires. RESULTS: The sideways walk test times and counts demonstrated good to excellent intra-rater, inter-rater, and test-retest reliabilities. The sideways walk test times and counts were significantly correlated with motor control and ankle dorsiflexor and plantarflexor strength of the affected leg, balance performance and functional mobility. The cut-off sideways walk test time and count that best discriminated between individuals with stroke and controls were 10.74 s and 8.83 steps, respectively. The minimal detectable change in the sideways walk test time in that situation was 1.85 s, and the count minimum detectable change was 1.12 steps. CONCLUSION: The sideways walk test is a reliable and easy-to-administer clinical test for assessing sideways walking ability of individuals with chronic stroke.

Lipiodol versus diaphragm in 4D-CBCT-guided stereotactic radiotherapy of hepatocellular carcinomas.

PURPOSE: The purpose of this work was to investigate the potential of lipiodol as a direct tumor surrogate alternative to the diaphragm surrogate on four-dimensional cone-beam computed tomography (4D-CBCT) image guidance for stereotactic radiotherapy of hepatocellular carcinomas. METHODS: A total of 29 hepatocellular carcinomas (HCC) patients treated by stereotactic radiotherapy following transarterial chemoembolization (TACE) with homogeneous or partial defective lipiodol retention were included. In all, 4-7 pretreatment 4D-CBCT scans were selected for each patient. For each scan, either lipiodol or the diaphragm was used for 4D registration. Resulting lipiodol/diaphragm motion ranges and position errors relative to the reconstructed midventilation images were analyzed to obtain the motion variations, and group mean (ΔM), systematic (Σ), and random (σ) errors of the treatment setup. RESULTS: Of the lipiodolized tumors, 55 % qualified for direct localization on the 4D-CBCT. Significant correlations of lipiodol and diaphragm positions were found in the left-right (LR), craniocaudal (CC), and anteroposterior (AP) directions. ΔM and σ obtained with lipiodol and diaphragm were similar, agreed to within 0.5 mm in the LR and AP, and 0.3 mm in the CC directions, and Σ differed by 1.4 (LR), 1.1 (CC), and 0.6 (AP) mm. Variations of diaphragm motion range > 5 mm were not observed with lipiodol and in one patient with diaphragm. The margin required for the tumor prediction error using the diaphragm surrogate was 6.7 (LR), 11.7 (CC), and 4.1 (AP) mm. CONCLUSION: Image-guidance combining lipiodol with 4D-CBCT enabled accurate localization of HCC and thus margin reduction. A major limitation was the degraded lipiodol contrast on 4D-CBCT.

Dosimetric evaluation of four-dimensional dose distributions of CyberKnife and volumetric-modulated arc radiotherapy in stereotactic body lung radiotherapy.

Advanced image-guided stereotatic body lung radiotherapy techniques using volumetric-modulated arc radiotherapy (VMAT) with four-dimensional cone-beam computed tomography (4D CBCT) and CyberKnife with real-time target tracking have been clinically implemented by different authors. However, dosimetric comparisons between these techniques are lacking. In this study, 4D CT scans of 14 patients were used to create VMAT and CyberKnife treatment plans using 4D dose calculations. The GTV and the organs at risk (OARs) were defined on the end-exhale images for CyberKnife planning and were then deformed to the midventilation images (MidV) for VMAT optimization. Direct 4D Monte Carlo dose optimizations were performed for CyberKnife (4D(CK)). Four-dimensional dose calculations were also applied to VMAT plans to generate the 4D dose distributions (4D(VMAT)) on the exhale images for direct comparisons with the 4D(CK) plans. 4D(CK) and 4D(VMAT) showed comparable target conformity (1.31 ± 0.13 vs. 1.39 ± 0.24, p = 0.05). GTV mean doses were significantly higher with 4D(CK). Statistical differences of dose volume metrics were not observed in the majority of OARs studied, except for esophagus, with 4D(VMAT) yielding marginally higher D1% than 4D(CK). The normal tissue volumes receiving 80%, 50%, and 30% of the prescription dose (V80%, V50%, and V30%) were higher with 4D(VMAT), whereas 4D(CK) yielded slightly higher V10% in posterior lesions than 4D(VMAT). VMAT resulted in much less monitor units and therefore greater delivery efficiency than CyberKnife. In general, it was possible to produce dosimetrically acceptable plans with both techniques. The selection of treatment modality should consider the dosimetric results as well as the patient's tolerance of the treatment process specific to the SBRT technique.