Evaluation of 4-Hz log files and secondary Monte Carlo dose calculation as patient-specific quality assurance for VMAT prostate plans

Purpose

In this study, 4‐Hz log files were evaluated with an independent secondary Monte Carlo dose calculation algorithm to reduce the workload for patient‐specific quality assurance (QA) in clinical routine.

Materials and Methods

A total of 30 randomly selected clinical prostate VMAT plans were included. The used treatment planning system (TPS) was Monaco (Elekta, Crawley), and the secondary dose calculation software was SciMoCa (Scientific‐RT, Munich). Monaco and SciMoCa work with a Monte Carlo algorithm. A plausibility check of Monaco and SciMoCa was performed using an ionization chamber in the BodyPhantom (BP). First, the original Monaco RT plans were verified with SciMoCa (pretreatment QA). Second, the corresponding 4‐Hz log files were converted into RT log file plans and sent to SciMoCa as on‐treatment QA. MLC shift errors were introduced for one prostate plan to determine the sensitivity of on‐treatment QA. For pretreatment and on‐treatment QA, a gamma analysis (2%/1mm/20%) was performed and dosimetric values of PTV and OARs were ascertained in SciMoCa.

Results

Plausibility check of TPS Monaco vs. BP measurement and SciMoCa vs. BP measurement showed valid accuracy for clinical VMAT QA. Using SciMoCa, there was no significant difference in PTV Dmean between RT plan and RT log file plan. Between pretreatment and on‐treatment QA, PTV metrics, femur right and left showed no significant dosimetric differences as opposed to OARs rectum and bladder. The overall gamma passing rate (GPR) ranged from 96.10% to 100% in pretreatment QA and from 93.50% to 99.80% in on‐treatment QA. MLC shift errors were identified for deviations larger than −0.50 mm and +0.75 mm using overall gamma criterion and PTV Dmean.

Conclusion

SciMoCa calculations of Monaco RT plans and RT log file plans are in excellent agreement to each other. Therefore, 4‐Hz log files and SciMoCa can replace labor‐intensive phantom‐based measurements as patient‐specific QA.

Error sensitivity of a log file analysis tool compared with a helical diode array dosimeter for VMAT delivery quality assurance

PURPOSE

Integrating log file analysis with LINACWatch® (LW) into clinical routine as part of the quality assurance (QA) process could be a time-saving strategy that does not compromise on quality. The purpose is to determine the error sensitivity of log file analysis using LINACWatch® compared with a measurement device (ArcCHECK®, AC) for VMAT delivery QA.

MATERIALS AND METHODS

Multi-leaf collimator (MLC) errors, collimator angle errors, MLC shift errors and dose errors were inserted to analyze error detection sensitivity. A total of 36 plans were manipulated with different magnitudes of errors. The gamma index protocols for AC were 3%/3 mm/Global and 2%/2 mm/Global, as well as 2%/2 mm/Global, and 1.5%/1.5 mm/Global for LW. Additionally, deviations of the collimator and monitor units between TPS and log file were calculated as RMS values. A 0.125 cm³ ionization chamber was used to independently examine the effect on dose.

RESULTS

The sensitivity for AC was 20.4% and 49.6% vs 63.0% and 86.5% for LW, depending on the analysis protocol. For MLC opening and closing errors, the detection rate was 19.0% and 47.7% for AC vs 50.5% and 75.5% for LW. For MLC shift errors, it was 29.6% and 66.7% for AC vs 66.7% and 83.3% for LW. AC could detect 25.0% and 44.4% of all collimator errors. Log file analysis detected all collimator errors using 1° detection level. 13.2% and 42.4% of all dose errors were detected by AC vs 59.0% and 92.4% for LW using gamma analysis. Using RMS value, all dose errors were detected by LW (1% detection level).

CONCLUSION

The results of this study clearly show that log file analysis is an excellent complement to phantom-based delivery QA of VMAT plans. We recommend a 1.5%/1.5 mm/Global criteria for log file-based gamma calculations. Log file analysis was implemented successfully in our clinical routine for VMAT delivery QA.

Intensified preoperative chemoradiation by adding oxaliplatin in locally advanced, primary operable (cT3NxM0) rectal cancer : Impact on long-term outcome. Results of the phase II TAKO 05/ABCSG R‑02 trial

Purpose

The major goals of preoperative treatment for locally advanced rectal cancers (LARCs) are improvement of local tumor control, tumor downsizing, and downstaging. Modifications with respect to standardized chemoradiation protocol, e. g., integrating oxaliplatin, are realized with the aim of improving primary tumor response and patient outcome.

Patients and methods

In this phase II multicenter study, patients with LARC of the mid- or lower rectum, cT3cNxcM0 as staged by MRI, were included and treated preoperatively with a combination of capecitabine and oxaliplatin following a standardized protocol during radiation. The focus of this long-term analysis was overall (OS) and disease-free survival (DFS).

Results

A total of 60 patients (19 women, 41 men, median age 60.5 years) were initially enrolled, 1 patient was excluded (violation of study protocol), and 1 was patient lost of follow-up, leading to a total of 58 patients for long-term analysis. The 3‑year OS was 85.5%; 3‑year DFS 71.2%. Over time, 15 patients (25.9%) developed tumor recurrence (1 locoregional, 6.7%; 11 distant, 73.3%; 3 locoregional+distant, 20%). Recurrence-specific therapy was planned in the majority of patients, in 9 of 15 patients (60%) with a radical surgical approach. Of these, 4 patients (44.4%) are again tumor-free at the end of investigation. While tumor downsizing (T level) or pathologically complete response did not influence patient survival, lymph node negativity (LNneg) after preoperative chemoradiation showed significant influence.

Conclusion

LNneg after preoperative treatment for LARC significantly influences patient survival. A radical surgical approach for recurrent LARC (locoregional, distant) should be contemplated when possible as we were able to clearly demonstrate its importance and efficacy.

Dynamic contrast-enhanced magnetic resonance imaging: a non-invasive method to evaluate significant differences between malignant and normal tissue

PURPOSE

An ever recurring challenge in diagnostic radiology is the differentiation between non-malignant and malignant tissue. Based on evidence that microcirculation of normal, non-malignant tissue differs from that of malignant tissue, the goal of this study was to assess the reliability of dynamic contrast-enhanced Magnetic Resonance Imaging (dcMRI) for differentiating these two entities.

MATERIALS AND METHODS

DcMRI data of rectum carcinoma and gluteus maximus muscles were acquired in 41 patients. Using an fast T1-mapping sequence on a 1.5-T whole body scanner, T1-maps were dynamically retrieved before, during and after constant rate i.v. infusion of a contrast medium (CM). On the basis of the acquired data sets, PI-values were calculated on a pixel-by-pixel basis. The relevance of spatial heterogeneities of microcirculation was investigated by relative frequency histograms of the PI-values.

RESULTS

A statistically significant difference between malignant and normal tissue was found for the mean PI-value (P < 0.001; 8.95 ml/min/100 g +/- 2.45 versus 3.56 ml/min/100 g +/- 1.20). Additionally relative frequency distributions of PI-values with equal class intervals of 2.5 ml/min/100 g revealed significant differences between the histograms of muscles and rectum carcinoma.

CONCLUSION

We could show that microcirculation differences between malignant and normal, non-malignant tissue can be reliably assessed by non-invasive dcMRI. Therefore, dcMRI holds great promise in the aid of cancer assessment, especially in patients where biopsy is contraindicated.

Irradiation Causes Biphasic Neutrophilic Granulocyte Phagocytic Function*

BACKGROUND AND PURPOSE

The anti-inflammatory effect of low-dose radiotherapy is clinically well described. Nevertheless, until now neither the optimal dose nor the background of tissue reactions have been defined. The current study examines the influence of low radiation doses on neutrophilic granulocyte function, which could be helpful in finding the optimal dose for either stimulation or suppression of anti-inflammatory activity.

MATERIAL AND METHODS

Lymphoprep density gradient-purified neutrophilic granulocytes of three voluntary, healthy donors were used for all experiments. Granulocytes were incubated 48 h in RPMI 1640 and irradiated with single doses of 0.5, 1.0, 1.5, 2.0, 2.5, 3.0, 3.5, 4.0, 6.0, and 12 Gy using a (137)Cs IBL 437L irradiator. Their function was assessed by measuring granulocytic release of reactive oxygen species (ROS) with luminol-enhanced chemiluminescence after stimulation with phorbol myristate acetate (PMA).

RESULTS

Relative changes of ROS release (ROS release before stimulation was set to 100%) increased after stimulation with PMA (mean +/- standard deviation [SD]): 0 Gy: 147.6% +/- 60%; 0.5 Gy: 153.6% +/- 70%; 1.0 Gy: 164.9% +/- 63%; 1.5 Gy: 177.8% +/- 66%; 2.0 Gy: 162.5% +/- 57%; 2.5 Gy: 156.2% +/- 60%; 3.0 Gy: 159.2% +/- 60%; 3.5 Gy: 126.9% +/- 55%; 4.0 Gy: 137.9% +/- 71%; 6.0 Gy: 148.3% +/- 65%; 12.0 Gy: 156.1% +/- 52%. The relative ROS release showed a significant increase at 1.5 Gy (p < 0.001) after PMA stimulation and a significant decrease of ROS release at 3.5 Gy (p < 0.005) and less markedly at 4.0 Gy (p < 0.05). 6.0 and 12.0 Gy showed a significant (p < 0.05) increase again.

CONCLUSION

This ex vivo in vitro study on native human neutrophilic granulocytes shows an increase at 1.5 Gy and a significant decrease of granulocyte function at 3.5 and 4.0 Gy, as it was described for different other phenomena in low-dose radiotherapy. These results may provide a further explanation for the local anti-inflammatory effect of low-dose ionizing irradiation.

Tumor microcirculation and diffusion predict therapy outcome for primary rectal carcinoma

PURPOSE

The aim of our study was to correlate perfusion indices and apparent diffusion coefficients with therapy outcome after chemoradiation.

METHODS AND MATERIALS

In 34 patients with primary rectal carcinoma (cT3) undergoing preoperative chemoradiation, pretherapeutic perfusion indices and apparent diffusion coefficients were obtained by dynamic or diffusion-weighted magnetic resonance imaging. Therapy response was defined if the pathologic observation revealed no invasion into the perirectal fat after chemoradiation.

RESULTS

In 18 patients, a response and in 16, no response was observed. Statistically significant differences were found for the mean perfusion index (p < 0.001; 7.5 +/- 1.5 mL/min/100 g vs. 10.7 +/- 2.7 mL/min/100 g) and for the intratumoral cumulative fraction of pixels with perfusion-indices > 12 mL/min/100 g (p < 0.001, 3.7 +/- 4.0% vs. 24.7 +/- 17.9%). A three-way ANOVA resulted in significant effects for therapy responder/nonresponder (p < 0.001) and for apparent diffusion coefficient and the individual patients.

CONCLUSION

Perfusion indices and apparent diffusion coefficients inside the tumor region seem to be of predictive value for therapy outcome of preoperative therapy in patients with primary rectal carcinoma. Higher parameter levels in the nonresponding group could be explained by increased shunt flow or increased angiogenic activity in aggressive tumor cell clusters resulting in reduced nutrients supply and higher fraction of intratumoral necrosis respectively.

Selenium in the treatment of radiation-associated secondary lymphedema

PURPOSE

The aim of this explorative study was to evaluate the impact of selenium in the treatment of lymphedema after radiotherapy.

MATERIALS AND METHODS

Between June 1996 and June 2001, 12 patients with edema of the arm and 36 patients with edema of the head-and-neck region were treated with selenium for therapy-related lymphedema. Of these 36 patients, 20 had interstitial endolaryngeal edema associated with stridor and dyspnea. All patients received sodium selenite over 4 to 6 weeks.

RESULTS

Self-assessment using a visual analog scale (n = 48) showed a reduction of 4.3 points when comparing pre- and posttreatment values (p < 0.05). Of 20 patients with endolaryngeal edema, 13 underwent no tracheostomy, 5 underwent a temporary tracheostomy, and only 2 underwent a permanent tracheostomy. Ten of 12 patients with arm edema showed a circumference reduction of the edematous limb and improvement in the Skin-Fold Index by 23.3 points. An improvement of one stage or more was shown by the Földi or the Miller score (n = 28) in 22 (Földi score) and in 24 (Miller score) patients.

CONCLUSIONS

Treatment with sodium selenite is well tolerated and easy to deliver. Additionally, our results suggest that sodium selenite has a positive effect on secondary-developing lymphedema caused by radiation therapy alone or by irradiation after surgery.

[Diffusion-weighted MRI--a new parameter for advanced rectal carcinoma?]

PURPOSE

To evaluate the predictive value of apparent diffusion coefficient (ADC) on therapy outcome of combined chemoradiation in patients with primary carcinoma of the rectum.

MATERIALS AND METHOD

Prior to standardized, combined, neoadjuvant chemoradiation, 16 patients with primary carcinoma of the rectum (cT3) were examined with magnetic resonance imaging (MRI). Diffusion-weighted spin echo echo-planar images (SE-EPI) and contrast-enhanced T 1 -weighted spin echo (SE) images at 1.5 Tesla were obtained. The mean ADC of the tumor region was calculated and correlated with the therapy outcome substantiated by postsurgical histopathologic staging.

RESULTS

Tumor down-staging (pT0-2) occurred in 9 patients (therapy responders) and no down-staging (pT3) in 7 patients (therapy non-responders). The mean ADC measured 0.476 +/- 0.114 x 10(-3) mm 2/s in the responder group and 0.703 +/- 0.085 x 10(-3) mm 2/s in the non-responder group. Comparison of the mean ADC between the groups reached statistical significance (p = 0.001).

CONCLUSION

The mean ADC might be a new quantitative parameter to predict therapy outcome of combined preoperative chemoradiation in patients with primary carcinoma of the rectum.

Diffusion-weighted magnetic resonance imaging for monitoring diffusion changes in rectal carcinoma during combined, preoperative chemoradiation: preliminary results of a prospective study

PURPOSE

To evaluate the clinical value of diffusion-weighted magnetic resonance imaging (DW-MRI) to monitor response of primary carcinoma of the rectum to preoperative chemoradiation by measuring tumor apparent diffusion coefficient (ADC).

MATERIALS AND METHODS

Diffusion data of nine patients undergoing preoperative combined chemoradiation for clinical staged T3, N(0-2), M(0) carcinoma of the rectum were analyzed. Diffusion-weighted echo-planar MR images were obtained prior to and at specified intervals during chemoradiation and ADCs calculated from acquired tumor images.

RESULTS

Comparison of mean ADC and cumulative radiation dose showed a significant decrease of mean ADC at the 2nd (P = 0.028), 3rd (P = 0.012), and 4th (P = 0.008) weeks of treatment. Cytotoxic edema and fibrosis were considered as reasons for ADC decrease.

CONCLUSION

This study demonstrated tumor ADC changes via detection of therapy-induced alterations in tumor water mobility. Our results indicate that diffusion-weighted imaging may be a valuable clinical tool to diagnose the early stage of radiation-induced fibrosis.