Preliminary evaluation of a novel secondary check tool for intensity modulated radiotherapy treatment planning

PURPOSE

To evaluate the dosimetric accuracy of the Delta4 Insight (DI) secondary-check dosimetry system.

METHODS

Absolute dosimetry in reference conditions, output factors, percent depth doses normalized and off-axis dose profiles for different field sizes calculated by DI were compared with measurements. Dose calculations for 20 clinical IMRT/VMAT plans generated in the TPS using both AAA or AcurosXB algorithms were compared with measurements. The average difference between calculated and measured point dose in high-dose region was calculated for all cases. 3D dose measurements were performed in Delta4 Phantom+ and a comparison between calculated and measured dose distributions was performed by means of the gamma analysis with 3 %/2 mm criteria. The dose distributions calculated by DI for 20 IMRT/VMAT plans were compared with those calculated by the TPS.

RESULTS

The absolute dosimetry computed by DI showed dose value in agreement with the measured one within 0.3 %. The average differences between measured and calculated output factors were less than 2.5 %. The average PDD differences were less than 0.6 %. An excellent agreement between calculations and off-axis measurements is found. The point doses calculated for the 20 recalculated plan showed good agreement with measurements with average differences less than 0.5 %. The average gamma pass rate values for the Delta4 Phantom + 3D dose analysis was greater than 97.%. The comparison of DI with theTPS showed good agreement for the used metrics.

CONCLUSIONS

Delta4 Insight may provide a useful independent secondary dose verification system for IMRT/VMAT plans, complementing the traditional global QA protocols.

Statement of the Italian Association of Medical Physics (AIFM) task group on radiation dose monitoring systems

The evaluation of radiation burden in vivo is crucial in modern radiology as stated also in the European Directive 2013/59/Euratom—Basic Safety Standard. Although radiation dose monitoring can impact the justification and optimization of radiological procedure, as well as effective patient communication, standardization of radiation monitoring software is far to be achieved. Toward this goal, the Italian Association of Medical Physics (AIFM) published a report describing the state of the art and standard guidelines in radiation dose monitoring system quality assurance. This article reports the AIFM statement about radiation dose monitoring systems (RDMSs) summarizing the different critical points of the systems related to Medical Physicist Expert (MPE) activities before, during, and after their clinical implementation. In particular, the article describes the general aspects of radiation dose data management, radiation dose monitoring systems, data integrity, and data responsibilities. Furthermore, the acceptance tests that need to be implemented and the most relevant dosimetric data for each radiological modalities are reported under the MPE responsibility.

Delta4 Discover transmission detector: A comprehensive characterization for in-vivo VMAT monitoring

OBJECTIVE

To investigate the dosimetric behaviour, influence on photon beam fluence and error detection capability of Delta⁴ Discover transmission detector.

METHODS

The transmission detector (TRD) was characterized on a TrueBeam linear accelerator with 6 MV beams. Linearity, reproducibility and dose rate dependence were investigated. The effect on photon beam fluence was evaluated in terms of beam profiles, percentage depth dose, transmission factor and surface dose for different open field sizes. The transmission factor of the 10x10 cm² field was entered in the TPS's configuration and its correct use in the dose calculation was verified recalculating 17 clinical IMRT/VMAT plans. Surface dose was measured for 20 IMRT fields. The capability to detect different delivery errors was investigated evaluating dose gamma index, MLC gamma index and leaf position of 15 manually modified VMAT plans.

RESULTS

TRD showed a linear dependence on MU. No dose rate dependence was observed. Short-term and long-term reproducibility were within 0.1% and 0.5%. The presence of the TRD did not significantly affect PDDs and profiles. The transmission factor of the 10x10 cm² field size was 0.985 and 0.983, for FF and FFF beams respectively. The 17 recalculated plans met our clinical gamma-index passing rate, confirming the correct use of the transmission factor by the TPS. The surface dose differences for the open fields increase for shorter SSDs and greater field size. Differences in surface dose for the IMRT beams were less than 2%. Output variation ≥2%, collimator angle variations within 0.3°, gantry angle errors of 1°, jaw tracking and leaf position errors were detected.

CONCLUSIONS

Delta⁴ Discover shows good linearity and reproducibility, is not dependent on dose rate and does not affect beam quality and dose profiles. It is also capable to detect dosimetric and geometric errors and therefore it is suitable for monitoring VMAT delivery.

Performance of Radiologists in the Evaluation of the Chest Radiography with the Use of a "new software score" in Coronavirus Disease 2019 Pneumonia Suspected Patients

OBJECTIVES

The purpose of this study is to assess the performance of radiologists using a new software called "COVID-19 score" when performing chest radiography on patients potentially infected by coronavirus disease 2019 (COVID-19) pneumonia. Chest radiography (or chest X-ray, CXR) and CT are important for the imaging diagnosis of the coronavirus pneumonia (COVID-19). CXR mobile devices are efficient during epidemies, because allow to reduce the risk of contagion and are easy to sanitize.

MATERIAL AND METHODS

From February-April 2020, 14 radiologists retrospectively evaluated a pool of 312 chest X-ray exams to test a new software function for lung imaging analysis based on radiological features and graded on a three-point scale. This tool automatically generates a cumulative score (0-18). The intra- rater agreement (evaluated with Fleiss's method) and the average time for the compilation of the banner were calculated.

RESULTS

Fourteen radiologists evaluated 312 chest radiographs of COVID-19 pneumonia suspected patients (80 males and 38 females) with an average age of 64, 47 years. The inter-rater agreement showed a Fleiss' kappa value of 0.53 and the intra-group agreement varied from Fleiss' Kappa value between 0.49 and 0.59, indicating a moderate agreement (considering as "moderate" ranges 0.4-0.6). The years of work experience were irrelevant. The average time for obtaining the result with the automatic software was between 7 s (e.g., zero COVID-19 score) and 21 s (e.g., with COVID-19 score from 6 to 12).

CONCLUSION

The use of automatic software for the generation of a CXR "COVID-19 score" has proven to be simple, fast, and replicable. Implementing this tool with scores weighed on the number of lung pathological areas, a useful parameter for clinical monitoring could be available.

Combined chemoradiation for head and neck region myxofibrosarcoma of the maxillary sinus

Aims and background

Adult sarcomas of the head and neck region (HNSs) are considered a rare clinicopathological entity. They account for only 2–15% of all adult sarcomas and for less than 1% of all head and neck malignancies. The preferred initial treatment option is wide surgical excision. Whenever surgery is considered infeasible, a frontline combined-modality approach including radiotherapy and chemotherapy might be proposed. We here report on a case of localized sarcoma of the maxillary sinus treated with induction chemotherapy and subsequent intensity-modulated radiation therapy (IMRT), achieving a persistent complete remission status.

Methods

A 66-year-old man was referred to our institution hospital for left-sided facial pain with swollen left cheek and ipsilateral facial palsy. Magnetic resonance imaging showed a mass within the left maxillary sinus extending to the orbital floor and adjacent alveolar bones. Histological examination of the biopsy specimen demonstrated a myxofibrosarcoma. The patient underwent induction chemotherapy with gemcitabine 900 mg/m2 (days 1–8) and taxotere 80 mg/m2 every 3 weeks for 3 cycles and sequential simultaneous integrated boost (SIB) IMRT up to a total dose of 70 Gy/35 fractions to the macroscopic disease with 59.5 Gy/35 fractions to the level IB-II lymph nodes in the left neck.

Results

Treatment was well tolerated with mild acute toxicity. Complete remission was achieved at restaging MRI 6 months after the end of the combined modality approach. The patient remains in complete, unmaintained clinical and instrumental complete remission 18 months after treatment, with no late side effects.

Conclusion

Combination therapy with induction chemotherapy and sequential SIB-IMRT could therefore be a promising modality for head and neck sarcomas, allowing for simultaneous tumor control and normal tissue sparing.

Leptomeningeal Metastasis from Prostate Cancer

Aims and background

Metastatic prostate carcinoma commonly involves bones and extrapelvic lymph nodes, with occasional visceral deposits. Central nervous system involvement is unusual and particularly the occurrence of leptomeningeal metastasis (LM) is extremely rare, with few cases described in the medical literature. The clinical presentation is characterized by multifocal neurological deficit and the prognosis is generally dismal, with survival ranging between 3 and 6 months. We report on a patient affected by LM due to prostate cancer who was treated with a combined-modality approach consisting of sequential chemotherapy and radiotherapy.

Methods

A 70-year-old man was referred to our group for cognitive mental disorder, left-sided frontal headache and nausea; the patient had a previous history of metastatic prostate cancer. LM was diagnosed neuroradiologically with brain MRI and evidence of a detectable level of PSA in the cerebrospinal fluid. He was treated with docetaxel and prednisone for 3 cycles followed by external beam radiotherapy (EBRT) to the whole brain to a total dose of 30 Gy in 10 fractions with a simultaneous integrated boost to the macroscopic disease (total dose of 35 Gy in 10 fractions). No acute toxicity was observed.

Results

A substantial clinical response was obtained after EBRT with neurological improvement and radiologically stable disease at post-treatment imaging until 10 weeks after radiation. The patient died of sudden general condition deterioration 3 months after EBRT.

Conclusion

Since LM derived from prostate cancer is likely to become a more common clinical event, such patients would need to be included in clinical trials evaluating new therapeutic approaches, considering that the current treatment strategies have been shown to be rather ineffective.

TomoDirect: An efficient means to deliver radiation at static angles with tomotherapy

Aims and background

The TomoTherapy Hi-Art II system is able to deliver dynamic intensity-modulated radiation therapy within a helical geometry providing robust conformality and modulation, abrupt dose falloff, and reliable accuracy. A new upgrade named TomoDirect was introduced recently, allowing delivery of radiation at discrete angles with a fixed gantry. We present our preliminary clinical experience with TomoDirect.

Methods

Three specific clinical contexts were chosen for the implementation of TomoDirect, namely palliation of bone metastasis pain (BP), whole brain radiation therapy for intracranial secondary lesions (WBRT), and adjuvant whole breast radiation therapy after conservative surgery for early stage breast cancer (AWBRT). After appropriate positioning, planning CT, contouring, and plan generation, all patients were treated with the TomoDirect upgrade of the TomoTherapy Hi-Art II system with different doses and fractionation according to clinical decision-making.

Results

Between May and December 2010, 41 patients were treated with TomoDirect. Eighteen patients were treated for BP (mainly vertebral metastases) with a predominant posterior field arrangement. Seven patients were treated for WBRT (multiple brain lesions) with a parallel-opposed latero-lateral approach and 16 patients were treated for conventionally fractionated AWBRT mainly with a 2-field tangential approach. Radiation treatments were generally well tolerated and the acute toxicity was mild.

Conclusions

While helical tomotherapy allows the delivery of very sophisticated treatment plans, in certain anatomical sites and clinical contexts where the number of beam directions is constrained and supposed not to affect plan quality, TomoDirect might be an efficient means to deliver radiation at static angles with consistent dosimetric and clinical results.

Dosimetric characterization and behaviour in small X-ray fields of a microchamber and a plastic scintillator detector

OBJECTIVE

The aim of this work was to investigate the main dosimetric characteristics and the performance of an A26 Exradin ionization microchamber (A26 IC) and a W1 Exradin plastic scintillation detector (W1 PSD) in small photon beam dosimetry for treatment planning system commissioning and quality assurance programme.

METHODS

Detector characterization measurements (short-term stability, dose linearity, angular dependence and energy dependence) were performed in water for field sizes up to 10 × 10 cm². Polarity effect (P_pol) was examined for the A26 IC. The behaviour of the detectors in small field relative dosimetry [percentage depth dose, dose profiles often called the off-axis ratio and output factors (OFs)] was investigated for field sizes ranging from 1 × 1 to 3 × 3 cm².

RESULTS

Results were compared with those obtained with other detectors we already use for small photon beam dosimetry. A26 IC and W1 PSD showed a linear dose response. While the A26 IC showed no energy dependence, the W1 PSD showed energy dependence within 2%; no angular dependence was registered. P_pol values for A26 IC were below 0.9% (0.5% for field size >2 × 2 cm²). A26 IC and W1 PSD depth-dose curves and lateral profiles agreed with those obtained with an EDGE diode. No differences were observed among the detectors in OF measurement for field sizes larger than 1 × 1 cm², with average differences <1%. For field sizes <1 × 1 cm², the effective volume of ionization chamber and non-water equivalence of EDGE diode become significant. A26 IC OF values were significantly lower than EDGE diode and W1 PSD values, with percentage differences of about -23 and -13% for the smallest field, respectively. W1 PSD OF values lay between ion chambers and diode values, with a maximum percentage difference of about -10% with respect to the EDGE diode, for a 6 × 6-mm² field size.

CONCLUSION

The results of our investigation confirm that A26 IC and W1 PSD could play an important role in small field relative dosimetry. Advances in knowledge: Dosimetric characteristics of Exradin A26 ionization microchamber and W1 plastic scintillation detector for small field dosimetry.

Does accelerated hypofractionated adjuvant whole-breast radiotherapy increase mammographic density or change mammographic features?

OBJECTIVE

To compare mammographic features before and after accelerated hypofractionated adjuvant whole-breast radiotherapy (AWB-RT) and to evaluate possible appearance of modifications.

METHODS

A retrospective review of 177 females before and after an AWB-RT treatment (follow-up ranging from 5 to 9 years) was performed by four radiologists focused in breast imaging who independently evaluated diffuse mammographic density patterns and reported on possible onset of focal alterations; modifications in density and fibrosis with parenchymal distortion were deemed as indicators of AWB-RT treatment impact in breast imaging.

RESULTS

Prevalent mammographic density (D) patterns in the 177 females evaluated were according to the American College of Radiology-Breast Imaging Reporting and Data System (ACR-BIRADS): D1, fibroadipose density (score percentage from 55.9% to 43.5%); and D2, scattered fibroglandular density (from 42.9% to 32.7%). No change in diffuse mammographic density and no significant difference in mammographic breast parenchymal structure were observed. "No change" was reported with score percentage from 87% to 79.6%. Appearance of fibrosis with parenchymal distortion was reported by all radiologists in only two cases (1.1%, p = 0.3); dystrophic calcification was identified with percentage score from 2.2% to 3.3% (small type) and from 9.6% to 12.9% (coarse type).

CONCLUSION

No statistically significant changes in follow-up mammographies 5-9 years after AWB-RT were detected, justifying large-scale selection of AWB-RT treatment with no risk of altering radiological breast parameters of common use in tumour recurrence detection.

ADVANCES IN KNOWLEDGE

The hypofractionated radiotherapy (AWB-RT treatment) is a new proven, safe and effective modality in post-operative patients with early breast cancer with excellent local control and survival. In our study, the absence of changes in mammographic density patterns and in breast imaging before and after AWB-RT treatment (up to 5-9 years after radiotherapy) justifies large-scale use of AWB-RT treatment without hindrance in tumour recurrence diagnosis.

Image-guided Intensity-modulated Radiotherapy for Prostate Cancer Employing Hypofractionation and Simultaneous Integrated Boost: Results of a Consecutive Case Series with Focus on Erectile Function

AIM

To report on clinical outcomes of prostate cancer patients treated with hypofractionated radiotherapy employing a simultaneous integrated boost strategy.

PATIENTS AND METHODS

A consecutive series of 104 patients affected with prostate cancer was treated with intensity-modulated radiotherapy using a hypofractionated schedule and a simultaneous integrated boost consisting of 70 Gy (2.5 Gy daily) to the prostate gland, 63 Gy to the seminal vesicles (2.25 Gy daily) and 53.2 Gy to the pelvic nodes (1.9 Gy daily) when needed, delivered in 28 fractions. All patients underwent image-guided radiotherapy procedure consisting of daily cone-beam computed tomography.

RESULTS

After a median observation time of 26 (range=15-48) months, the 3-year biochemical failure-free survival was 96.5% [95% confidence interval (CI)=89%-98%], 3-year cancer-specific survival was 98.5% (95% CI=91%-99%) and 3-year overall survival was 96.5% (95% CI=89%-98%). The gastrointestinal and genitourinary toxicity profiles were mild with fewer than 2% of grade 3 events. Erectile function was partially affected by radiation in men potent at baseline.

CONCLUSION

Hypofractionation delivered with intensity-modulated radiotherapy and a simultaneous integrated boost approach proved to be a safe and effective treatment option for patients with prostate cancer. Patients with a preserved baseline erectile function experience a decrease in functionality correlated with the mean dose received by penile bulb.

Hypofractionation and concomitant boost to deliver adjuvant whole-breast radiation in ductal carcinoma in situ (DCIS): a subgroup analysis of a prospective case series

To report the four-year outcomes of accelerated hypofractionated whole-breast radiotherapy (WBRT) with a concomitant boost (CB) to the tumor bed in ductal carcinoma in situ (DCIS), we performed a subgroup analysis of 103 patients affected with DCIS within a cohort of 960 early breast cancer patients treated with breast conservation and hypofractionated WBRT. Prescription dose to the whole breast was 45 Gy (2.25 Gy/20 fractions) with an additional daily CB of 0.25 Gy to the surgical cavity (2.5 Gy/20 fractions up to 50 Gy). With a median follow-up of 48 months (range 12-91), no local recurrence was observed. Maximum detected acute skin toxicity was as follows: G0 in 35 % of patients, G1 in 54 %, G2 in 9 % and G3 in 2 %. Late skin and subcutaneous toxicity were generally mild with only 1 % of patients experiencing ≥G3 events (telangiectasia). No major lung and heart toxicity were detected. Cosmetic results were excellent in 50 % of patients, good in 37 %, fair in 9 % and poor in 4 %. Quality of life had a generally favorable profile both within the functioning and symptoms domains. The present result supports the hypothesis that DCIS patients could be safely treated with a hypofractionated schedule employing a CB to the lumpectomy cavity.

Exposures from nuclear medicine diagnostic procedures: the dose impact on the Aosta Valley population

The present work evaluates the per-procedure, annual collective and per-capita effective doses to the Aosta Valley region population from nuclear medicine (NM) examinations performed from 2005 to 2011 at the regional NM department. Based on its demographical and socioeconomics characteristics, this area can be considered as representative of the level I countries, as defined by the United Nations Scientific Committee on the Effects of Atomic Radiation. The NM per-procedures effective doses were within the range of 0.018-35 mSv. A steady frequency per 10 000 inhabitants has been observed, together with a decrease for thyroid and whole-body bone scintigraphy. Myocardial and bone scintigraphy studies were the major contributors to the total collective effective dose. The mean annual collective and per-capita effective doses to the population were 15 man Sv y(-1) and 120 µSv y(-1), respectively. The NM contribution to the total per-capita effective dose accounts for 5.9 % of that due to the medical ionising radiation examinations overall.

Combined chemoradiation for head and neck region myxofibrosarcoma of the maxillary sinus

AIMS AND BACKGROUND

Adult sarcomas of the head and neck region (HNSs) are considered a rare clinicopathological entity. They account for only 2-15% of all adult sarcomas and for less than 1% of all head and neck malignancies. The preferred initial treatment option is wide surgical excision. Whenever surgery is considered infeasible, a frontline combined-modality approach including radiotherapy and chemotherapy might be proposed. We here report on a case of localized sarcoma of the maxillary sinus treated with induction chemotherapy and subsequent intensity-modulated radiation therapy (IMRT), achieving a persistent complete remission status.

METHODS

A 66-year-old man was referred to our institution hospital for left-sided facial pain with swollen left cheek and ipsilateral facial palsy. Magnetic resonance imaging showed a mass within the left maxillary sinus extending to the orbital floor and adjacent alveolar bones. Histological examination of the biopsy specimen demonstrated a myxofibrosarcoma. The patient underwent induction chemotherapy with gemcitabine 900 mg/m2 (days 1-8) and taxotere 80 mg/m2 every 3 weeks for 3 cycles and sequential simultaneous integrated boost (SIB) IMRT up to a total dose of 70 Gy/35 fractions to the macroscopic disease with 59.5 Gy/35 fractions to the level IB-II lymph nodes in the left neck.

RESULTS

Treatment was well tolerated with mild acute toxicity. Complete remission was achieved at restaging MRI 6 months after the end of the combined modality approach. The patient remains in complete, unmaintained clinical and instrumental complete remission 18 months after treatment, with no late side effects.

CONCLUSION

Combination therapy with induction chemotherapy and sequential SIB-IMRT could therefore be a promising modality for head and neck sarcomas, allowing for simultaneous tumor control and normal tissue sparing.

Leptomeningeal metastasis from prostate cancer

AIMS AND BACKGROUND

Metastatic prostate carcinoma commonly involves bones and extrapelvic lymph nodes, with occasional visceral deposits. Central nervous system involvement is unusual and particularly the occurrence of leptomeningeal metastasis (LM) is extremely rare, with few cases described in the medical literature. The clinical presentation is characterized by multifocal neurological deficit and the prognosis is generally dismal, with survival ranging between 3 and 6 months. We report on a patient affected by LM due to prostate cancer who was treated with a combined-modality approach consisting of sequential chemotherapy and radiotherapy.

METHODS

A 70-year-old man was referred to our group for cognitive mental disorder, left-sided frontal headache and nausea; the patient had a previous history of metastatic prostate cancer. LM was diagnosed neuroradiologically with brain MRI and evidence of a detectable level of PSA in the cerebrospinal fluid. He was treated with docetaxel and prednisone for 3 cycles followed by external beam radiotherapy (EBRT) to the whole brain to a total dose of 30 Gy in 10 fractions with a simultaneous integrated boost to the macroscopic disease (total dose of 35 Gy in 10 fractions). No acute toxicity was observed.

RESULTS

A substantial clinical response was obtained after EBRT with neurological improvement and radiologically stable disease at post-treatment imaging until 10 weeks after radiation. The patient died of sudden general condition deterioration 3 months after EBRT.

CONCLUSION

Since LM derived from prostate cancer is likely to become a more common clinical event, such patients would need to be included in clinical trials evaluating new therapeutic approaches, considering that the current treatment strategies have been shown to be rather ineffective.

Five-year results of a prospective case series of accelerated hypofractionated whole breast radiation with concomitant boost to the surgical bed after conserving surgery for early breast cancer

Accelerated hypofractionation (HF) using larger dose per fraction, delivered in fewer fractions over a shorter overall treatment time, is presently a consistent possibility for adjuvant whole breast radiation (WBRT) after breast-conserving surgery for early breast cancer (EBC). Between 2005 and 2008, we submitted 375 consecutive patients to accelerated hypofractionated WBRT after breast-conserving surgery for EBC. The basic course of radiation consisted of 45 Gy in 20 fractions over 4 weeks to the whole breast (2.25 Gy daily) with an additional daily concomitant boost of 0.25 Gy up to 50 Gy to the surgical bed. Overall survival (OS), cancer-specific survival (CSS), disease-free survival (DFS) and local control (LC) were assessed. Late toxicity was scored according to the CTCAE v3.0; acute toxicity using the RTOG/EORTC toxicity scale. Cosmesis was assessed comparing treated and untreated breast. Quality of life (QoL) was determined using EORTC QLQ-C30/QLQ-BR23 questionnaires. With a median follow-up of 60 months (range 42-88), 5 years OS, CSS, DFS and LC were 97.6, 99.4, 96.6 and 100 %, respectively. Late skin and subcutaneous toxicity was generally mild, with few events > grade 2 observed. Cosmetic results were excellent in 75.7 % of patients, good in 20 % and fair in 4.3 %. QoL, assessed both through QLQ-C30/QLQ-BR23, was generally favorable, within the functioning and symptoms domains. Our study is another proof of principle that HF WBRT with a concurrent boost dose to the surgical cavity represents a safe and effective postoperative treatment modality with excellent local control and survival, consistent cosmetic results and mild toxicity.

Dosimetric characterization and use of GAFCHROMIC EBT3 film for IMRT dose verification

Radiochromic film has become an important tool to verify dose distributions in highly conformal radiation therapy such as IMRT. Recently, a new generation of these films, EBT3, has become available. EBT3 has the same composition and thickness of the sensitive layer of the previous EBT2 films, but its symmetric layer configuration allows the user to eliminate side orientation dependence, which is reported for EBT2 films. The most important EBT3 characteristics have been investigated, such as response at high-dose levels, sensitivity to scanner orientation and postirradiation coloration, energy and dose rate dependence, and orientation dependence with respect to film side. Additionally, different IMRT fields were measured with both EBT3 and EBT2 films and evaluated using gamma index analysis. The results obtained show that most of the characteristics of EBT3 film are similar to the EBT2 film, but the orientation dependence with respect to film side is completely eliminated in EBT3 films. The study confirms that EBT3 film can be used for clinical practice in the same way as the previous EBT2 film.

Does TomoDirect 3DCRT represent a suitable option for post-operative whole breast irradiation? A hypothesis-generating pilot study

BACKGROUND

This study investigates the use of TomoDirect™ 3DCRT for whole breast adjuvant radiotherapy (AWBRT) that represents a very attractive treatment opportunity, mainly for radiotherapy departments without conventional Linacs and only equipped with helical tomotherapy units.

METHODS

Plans were created for 17 breast cancer patients using TomoDirect in 3DCRT and IMRT modality and field-in-field 3DCRT planning (FIF) and compared in terms of PTV coverage, overdosage, homogeneity, conformality and dose to OARs. The possibility to define patient-class solutions for TD-3DCRT employment was investigated, correlating OARs dose constraints to patient specific anatomic parameters.

RESULTS

TD-3DCRT showed PTV coverage and homogeneity significantly higher than TD-IMRT and FIF. PTV conformality was significantly better for FIF, while no differences were found between TD-3DCRT and TD-IMRT. TD-3DCRT showed mean values of the OARs dosimetric endpoints significantly higher than TD-IMRT; with respect to FIF, TD-3DCRT showed values significantly higher for lung V(20Gy), mean heart dose and V(25Gy), while contralateral lung maximum dose and contralateral breast mean dose resulted significantly lower. The Central Lung Distance (CLD) and the maximal Heart Distance (HD) resulted as useful clinical tools to predict the opportunity to employ TD-3DCRT: positive correlations were found between CLD and both V(20Gy) and mean lung dose and between HD and both V25Gy and the mean heart dose. TD-3DCRT showed a significantly shorter mean beam-on time than TD-IMRT.

CONCLUSIONS

The present study showed that TD-3DCRT and TD-IMRT are two feasible and dosimetrically acceptable treatment approach for AWBRT, with an optimal PTV coverage and adequate OARs sparing. Some concerns might be raised in terms of dose to organs at risks if TD-3DCRT is applied to a general population. A correct patients clusterization according to simple quantitative anatomic measures, would help to correctly allocate patients to the appropriate treatment planning strategy in terms of target coverage, but also of normal tissue sparing.

Effective dose delivered by conventional radiology to Aosta Valley population between 2002 and 2009

OBJECTIVE

Medical diagnostic procedures can be considered the main man-made source of ionising radiation exposure for the population. Conventional radiography still represents the largest contribution to examination frequency. The present work evaluates procedure frequency and effective dose from the majority of conventional radiology examinations performed at the Radiological Department of Aosta Hospital from 2002 to 2009.

METHOD

Effective dose to the patient was evaluated by means of the software PCXMC. Data provided by the radiological information system allowed us to obtain collective effective and per caput dose.

RESULTS

The biggest contributors to per caput effective dose from conventional radiology are vertebral column, abdomen, chest, pelvis and (limited to females) breast. Vertebral column, pelvis and breast procedures show a significant dose increment in the period of the study. The mean effective dose per inhabitant from conventional radiology increased from 0.131 mSv in 2002 to 0.156 mSv in 2009. Combining these figures with those from our study of effective dose from CT (0.55 mSv in 2002 to 1.03 mSv in 2009), the total mean effective dose per inhabitant increased from 0.68 mSv to 1.19 mSv. The contribution of CT increased from 81% to 87% of the total. In contrast, conventional radiology accounts for 85% of the total number of procedures, but only 13% of the effective dose.

CONCLUSION

The study has demonstrated that conventional radiography still represents the biggest contributor to examination frequency in Aosta Valley in 2009. However, the frequency of the main procedures did not change significantly between 2002 and 2009.

TomoDirect: an efficient means to deliver radiation at static angles with tomotherapy

AIMS AND BACKGROUND

The TomoTherapy Hi-Art II system is able to deliver dynamic intensity-modulated radiation therapy within a helical geometry providing robust conformality and modulation, abrupt dose falloff, and reliable accuracy. A new upgrade named TomoDirect was introduced recently, allowing delivery of radiation at discrete angles with a fixed gantry. We present our preliminary clinical experience with TomoDirect.

METHODS

Three specific clinical contexts were chosen for the implementation of TomoDirect, namely palliation of bone metastasis pain (BP), whole brain radiation therapy for intracranial secondary lesions (WBRT), and adjuvant whole breast radiation therapy after conservative surgery for early stage breast cancer (AWBRT). After appropriate positioning, planning CT, contouring, and plan generation, all patients were treated with the TomoDirect upgrade of the TomoTherapy Hi-Art II system with different doses and fractionation according to clinical decision-making.

RESULTS

Between May and December 2010, 41 patients were treated with TomoDirect. Eighteen patients were treated for BP (mainly vertebral metastases) with a predominant posterior field arrangement. Seven patients were treated for WBRT (multiple brain lesions) with a parallel-opposed latero-lateral approach and 16 patients were treated for conventionally fractionated AWBRT mainly with a 2-field tangential approach. Radiation treatments were generally well tolerated and the acute toxicity was mild.

CONCLUSIONS

While helical tomotherapy allows the delivery of very sophisticated treatment plans, in certain anatomical sites and clinical contexts where the number of beam directions is constrained and supposed not to affect plan quality, TomoDirect might be an efficient means to deliver radiation at static angles with consistent dosimetric and clinical results.

Late rectal bleeding after 3D-CRT for prostate cancer: development of a neural-network-based predictive model

The aim of this study was to develop a model exploiting artificial neural networks (ANNs) to correlate dosimetric and clinical variables with late rectal bleeding in prostate cancer patients undergoing radical radiotherapy and to compare the ANN results with those of a standard logistic regression (LR) analysis. 718 men included in the AIROPROS 0102 trial were analyzed. This multicenter protocol was characterized by the prospective evaluation of rectal toxicity, with a minimum follow-up of 36 months. Radiotherapy doses were between 70 and 80 Gy. Information was recorded for comorbidity, previous abdominal surgery, use of drugs and hormonal therapy. For each patient, a rectal dose-volume histogram (DVH) of the whole treatment was recorded and the equivalent uniform dose (EUD) evaluated as an effective descriptor of the whole DVH. Late rectal bleeding of grade ≥ 2 was considered to define positive events in this study (52 of 718 patients). The overall population was split into training and verification sets, both of which were involved in model instruction, and a test set, used to evaluate the predictive power of the model with independent data. Fourfold cross-validation was also used to provide realistic results for the full dataset. The LR was performed on the same data. Five variables were selected to predict late rectal bleeding: EUD, abdominal surgery, presence of hemorrhoids, use of anticoagulants and androgen deprivation. Following a receiver operating characteristic analysis of the independent test set, the areas under the curves (AUCs) were 0.704 and 0.655 for ANN and LR, respectively. When evaluated with cross-validation, the AUC was 0.714 for ANN and 0.636 for LR, which differed at a significance level of p = 0.03. When a practical discrimination threshold was selected, ANN could classify data with sensitivity and specificity both equal to 68.0%, whereas these values were 61.5% for LR. These data provide reasonable evidence that results obtained with ANNs are superior to those achieved with LR when predicting late radiotherapy-related rectal bleeding. The future introduction of patient-related personal characteristics, such as gene expression profiles, might improve the predictive power of statistical classifiers. More refined morphological aspects of the dose distribution, such as dose surface mapping, might also enhance the overall performance of ANN-based predictive models.

Head and neck region consolidation radiotherapy and prophylactic cranial irradiation with hippocampal avoidance delivered with helical tomotherapy after induction chemotherapy for non-sinonasal neuroendocrine carcinoma of the upper airways

Background

Non-sinonasal neuroendocrine carcinomas (NSNECs) of the head and neck are considered an unfrequent clinico-pathological entity. Combined modality treatment represents an established therapeutic option for undifferentiated forms where distant metastasis is a common pattern of failure.

Methods

We report on a case of NSNEC treated with sequential chemo-radiation consisting of 6 cycles of cisplatin and etoposide followed by loco-regional radiation to the head and neck and simultaneous prophylactic cranial irradiation to prevent from intracranial spread, delivered with helical tomotherapy with the 'hippocampal avoidance' technique in order to reduce neuro-cognitive late effects.

Results

One year after the end of the whole combined modality approach, the patient achieved complete remission, with no treatment-related sub-acute and late effects.

Conclusions

The present report highlights the importance of multidisciplinary management for NSNECs of the head and neck, as the possibility to achieve substantial cure rates with mild side effects with modern radiotherapy techniques.

Population exposure to ionising radiation from CT examinations in Aosta Valley between 2001 and 2008

Recent and continuous advances in CT, such as the development of multislice CT, have promoted a rapid increase in its clinical application. Today, CT accounts for approximately 10% of the total number of medical radiographic procedures worldwide. However, the growing performance of the new CT generations have increased not only the diagnostic opportunities, but also the radiation dose to the patient. The relative contribution to the collective radiation dose is now estimated to be approximately 50%. Several papers have been published concerning the intensive use of CT and its contribution to the collective dose. However, most of the literature concerns the years 1997-2003 and the dosimetric evaluations are generally limited to the main standard protocols (chest, head and abdomen), deriving the effective dose by the simple application of the diagnostic reference levels. Only specific dosimetric analyses of single and innovative procedures have been published recently. Moreover, few data comes from Italian radiology departments. This paper aims to bridge these gaps. Firstly, it characterises in terms of measured CT dose index (CTDI) two last-generation scanners of the Radiological Department of Aosta Hospital. Secondly, it evaluates the effective dose from most of the CT examinations performed from 2001 to 2008 to compare protocols and technologies in line with the suggestions of the 2007 Recommendations of the International Commission on Radiological Protection, Publication 103. Finally, it estimates the collective dose to the population.

The use of a diode matrix in commissioning activities for electron energies > or = 9 MeV: a feasibility study

The contribution of a commercially available diode matrix (MapCHECK, provided by Sun Nuclear, Melbourne, FL) for the commissioning procedures of the voxel based Monte Carlo (VMC++) algorithm for electron beams of MasterPlan treatment planning system was investigated. The attention is mainly focused on the calculation in homogeneous and heterogeneous phantoms. With this aim, following a data set similar to that proposed by Electron Collaborative Working Group (ECWG), the dose profiles and two-dimensional (2D) dose distributions measured by the diode matrix were compared with the calculated ones using the gamma analysis method with acceptance criteria for the dose difference and the distance to agreement equal to 4% and 4 mm, respectively. The average and standard deviation of the percentage of points satisfying the constraint gamma < or = 1 are 98.3 +/- 4.1% and 99.3 +/- 1.7% for the 9 and 12 MeV electron beam, respectively, showing that the accuracy of MasterPlan electron beam algorithm is good for simple two-dimensional geometries as well as for more complicated three-dimensional ones. The results are in agreement with those reported in literature by Cygler et al. ["Evaluation of the first commercial Monte Carlo dose calculation engine for electron beam treatment planning," Med. Phys. 31, 142-153 (2004)]. In addition, the authors have also analyzed the response of the 2D array in terms of dose profiles at different depths, comparing the results with those obtained in water phantom using an electron diode. The results show that in the low gradient regions there were no deviations larger than the criteria of acceptability set by Van Dyk et al. ["Commissioning and quality assurance of treatment planning computers," Int. J. Radiat. Oncol. Biol. Phys. 26, 261-273 (1993)]; in the high gradient region, the maximum deviations are less than 2 mm with most of the values less than 1 mm. The present article shows that MapCHECK can play a useful role in the commissioning of electron algorithms of treatment planning systems in the evaluation of the 2D dose distributions in homogeneous and heterogeneous phantoms. In fact, it provides accurate results with the merit of expediting the commissioning process by using measuring device that requires minimal setup time and data processing time.

Verification of Varian Enhanced Dynamic Wedge implementation in masterplan treatment planning system

This paper investigates the accuracy of the two available calculation algorithms of the Oncentra MasterPlan three‐dimensional treatment planning system (TPS) – the pencil beam method and collapsed‐cone convolution – in modeling the Varian enhanced dynamic wedge (EDW). Measurements were carried out for a dual high energy (6–15 MV) Varian DHX‐S linear accelerator using ionization chambers for beam axis measurements (wedge factors and depth doses), film dosimetry for off‐axis dose profiles measurements, and a diode matrix detector for two dimensional absolute dose distributions. Using both calculation algorithms, different configuration of symmetric and asymmetric fields varying the wedge's angle were tested. Accuracy of the treatment planning system was evaluated in terms of percentage differences between measured and calculated values for wedge factors, depth doses, and profiles. As far as the absolute dose distribution was concerned, the gamma index method (Low et al.⁽¹³⁾) was used with 3% and 3 mm as acceptance criteria for dose difference and distance‐to‐agreement, respectively. Wedge factors and percentage depth doses were within 1% deviation between calculated and measured values. The comparison of measured and calculated dose profiles shows that the Van Dyk's acceptance criteria (Van Dyk et al.⁽¹⁴⁾) are generally met; a disagreement can be noted for large wedge angles and field size limited to the low dose‐low gradient region only. The 2D absolute dose distribution analysis confirms the good accuracy of the two calculation algorithms in modeling the enhanced dynamic wedge.

PACS number: 87.53.Bn, 87.55.kn, 87.56.ng

Transmission, Penumbra and Leaf Positional Accuracy in Commissioning and Quality Assurance Program of a Multileaf Collimator for Step-and-Shoot IMRT Treatments

Aims and background

The performance characteristics of a commercial multileaf collimator (MLC) for intensity modulated radiation therapy (IMRT) and a comprehensive quality assurance program (QA) to be performed during the commissioning of the MLC were investigated.

Materials and methods

The midleaf transmission and interleaf leakage, the in-plane penumbra and its in-plane/cross-plane variation, the cross-plane penumbra and its in-plane/cross-plane variation, and the leaf positional accuracy of a high-energy photon (6 MV) Sli Precise Elekta linear accelerator were measured. Kodak EDR2 Ready Pack film was used for MLC transmission measurement; for the other characterization measurements we used Kodak X-Omat XV2 Ready Pack film placed at 5 cm depth in a solid RW3 phantom. Each film was digitized with a laser scanning photodensitometer VXR-12 Plus using the Omni Pro-Accept 6.0A film dosimetry system and converted to dose by means of H&D curves. The dose calibration measurements were performed with a Farmer ionization chamber according to the guidelines of the IAEA Technical Report No. 277.

Results

The average midleaf transmission and interleaf leakage were 1.8% ± 0.1% and 2.1% ± 0.2%, respectively. The average value of the cross-plane penumbra was 5.4 mm ± 0.3 mm with maximum variation less than 0.4 mm and 1.0 mm in the in-plane and cross-plane direction, respectively. The average value of the in-plane penumbra was 3.2 mm ± 0.2 mm and 3.5 mm ± 0.2 mm for the step side and groove side of the leaves, respectively. A dose profile perpendicular to the direction of the leaf travel passing through the central axis shows a tongue-and-groove effect of about 33%. The positional accuracy of the leaves was investigated according to AAPM Report No. 72 TG50; the deviation of the net optical density along all the match lines was less than ± 20%. Moreover, the results obtained with a step field technique showed a positional accuracy of less than 1 mm.

Conclusions

The results suggest the necessity of extensive knowledge of the MLC dosimetric characteristics for IMRT applications in order to allow physicists to study their influence on treatment delivery and to perform a comprehensive routine QA program of the investigated parameters.

Emptying the rectum before treatment delivery limits the variations of rectal dose - volume parameters during 3DCRT of prostate cancer

PURPOSE

To investigate the impact of rectum motion on dose - volume histograms of the rectum including filling and of the wall (DVH and DWH, respectively), during 3D-conformal radiotherapy (3DCRT) for localized prostate cancer.

MATERIALS AND METHODS

Ten patients received a planning CT scan (CT(0)) and 11-14 CT during 3DCRT for prostate cancer (total CT scans=126). CT images were 3D matched using bony anatomy. A single observer drew the external contours of rectum and rectum wall and the CTV (prostate + seminal vesicles) on CT(0). Patients were asked to empty their rectum before every CT, as generally performed at the Institute for Cancer Research and Treatment (IRCC) before treatment delivery. Bladder was kept full by drinking 500 cm(3) of water 60 min before the scan, according to our protocol. A 4-field box 3DCRT technique was planned and dose statistics/dose - volume histograms of the rectum were calculated for each contour referred to CT(0),CT(1),...,CT(n) for each patient. Average DVHs during treatment were calculated along with their standard deviation (SD(rand)) and compared to the planned DVH. The analyses on the patient population included the assessment of systematic deviation (average difference and SD, named SD(sys)) as well as the average SD(rand) value expressing the random component of organ motion. Rectum shifts were also assessed by anterior and lateral BEV projections.

RESULTS

As to the rectum, 8/10 patients showed a "better" average DVH than DVH on CT(0). Wilcoxon test showed a statistically significant reduction when correlating the difference Delta between the average DVH during therapy and planning DVH at CT(0): for instance V(70)Delta = -3.6% and p = 0.022, V(50)Delta = -5.5% and p = 0.022, D(med)Delta = -3.2 Gy and p = 0.007. Average values of DVH systematic difference (average difference between planning scan and treatment), standard deviations (SD(sys)) and average standard deviations of the random fluctuation (SD(random)) were -4.0%, 4.7% and 6.6%, respectively. Whilst the fluctuation results were slightly smaller for DWH. Volume analysis showed a slight systematic variation of the rectal volume between planning and treatment BEV. The average rectal volume during therapy was larger than at the planning CT in 8/10 patients. The systematic shifts of the rectal wall between the planning phase and the treatment were rather small, both below and above the flexure. The larger random fluctuation of the rectum shape was found to be in the cranial half (1 SD=4.4 mm).

CONCLUSIONS

The practice of carefully emptying the rectum during simulation and therapy for prostate cancer, which is a safe and simple procedure, reduces the impact of organ motion on dose - volume parameters of the rectum.

Dosimetric evaluation of a commercial 3D treatment planning system using the AAPM Task Group 23 test package

The accuracy of the dose calculation algorithm is one of the most critical steps in assessing the radiotherapy treatment to achieve the 5% accuracy in dose delivery, which represents the suggested limit to increase the complication-free local control of tumor. We have used the AAPM Task Group 23 (TG-23) test package for clinical photon external beam therapy to evaluate the accuracy of the new version of the PLATO TPS algorithm. The comparison between tabulated values and calculated ones has been performed for 266 and 297 dose values for the 4 and 18 MV photon beams, respectively. Dose deviations less than 2% were found in the 98.5%- and 90.6% analyzed dose points for the two considered energies, respectively. Larger deviations were obtained for both energies, in large dose gradients, such as the build-up region or near the field edges and blocks. As far as the radiological field width is concerned, 64 points were analyzed for both the energies: 53 points (83%) and 64 points (100%) were within +/-2 millimeters for the 4 and 18 MV photon beams, respectively. The results show the good accuracy of the algorithm either in simple geometry beam conditions or in complex ones, in homogeneous medium, and in the presence of inhomogeneities, for low and high energy beams. Our results fit well the data reported by several authors related to the calculation accuracy of different treatment planning systems (TPSs) (within a mean value of 0.7% and 1.2% for 4 and 18 MV respectively). The TG-23 test package can be considered a powerful instrument to evaluate dose calculation accuracy, and as such may play an important role in a quality assurance program related to the commissioning of a new TPS.

[A quality control test of the image obtained with electronic portal imaging devices]

INTRODUCTION

A quality control of the digital image obtained from two electronic portal imaging devices is discussed. The devices are used to verify the radiotherapic treatment setup by comparing online images of the irradiated volume with those of the simulation devices.

MATERIAL AND METHODS

Both iView and Target View devices, respectively installed on a dual energy SLi Precise Elekta and Saturne 42 Ge linear accelerators, consist of highly efficient phosphor screen and high quality videocamera, controlled by a workstation, able to generate digital portal images from few cGy doses. A phantom and software package are used to assess the spatial resolution and signal to noise ratio, and to compare tha data obtained. Spatial resolution and signal to noise ratio of both systems were studied as a function of energy, gantry angle and image acquisition parameters.

RESULTS

The mean spatial resolutions obtained from the first 30 measurements were 0,265+/-0,012 and 0,220+/-0,010 lp/mm respectively for 6 and 18 MV of Saturne 42 (Target View) and 0,241+/-0,006 and 0,239+/-0,005 lp/mm for 4 and 6 MV of SLi (iView). Spatial resolution decreases as a function of energy, meanwhile there are no significant statistical differences as regards of the acquisition parameters; signal to noise ratio, instead, increases with integration time. Different values of the spatial resolution as a function of gantry angle are due to changes in the screen-camera distance and flexing of the detector housing. The quality control test is performed every 15 days by the technicians of our Radiotherapy Department. We set the reject level of spatial resolution and signal to noise ratio to be three standard deviations below the mean value obtained during the initial EPID characterization: if the measures fall below these values preventative maintenance is scheduled.

CONCLUSIONS

The efficacy of the use electronic portal imaging devices for visualizing and quantifying the relative positions of anatomical structures within the radiation field depends on the image quality. It is therefore essential to devise quality control tests for the devices themselves, to guarantee an optimal level of system performance in a fast and efficient manner.

[Physical-dosimetric characterization of a multi-leaf collimator system for clinical implementation in conformational radiotherapy]

INTRODUCTION

In the present paper we discuss the main dosimetric characteristics of the multileaf collimator (MLC) installed on the Elekta SLi Precise accelerators. To evaluate the effectiveness of the MLC in conformal radiotherapy, beam transmission through leaves and/or diaphragms, leakage between the leaves, central axis depth dose, surface dose, effective penumbra, scalopping effect and field size factors were measured.

MATERIALS AND METHODS

The MLC installed on the dual energy (4 and 6 MV) linear accelerator Elekta SLi Precise consists of 40 opposed pairs of 75 mm thick tungsten leaves, set in two raws mounted in place of the upper collimator. Each leaf has a nominal projected width of 10 mm. The maximum field size attainable is 40 x 40 cm2 at 100 cm SAD. Beam transmission through leaves and/or diaphragms and field size factors were measured in RW3 phantom with a ionization chamber, leakage between the leaves and effective penumbra were instead evaluated with radiographic films (X-Omat-V) and a laser scanning photodensitometer. Percentage depth doses were measured in an automatic water phantom.

RESULTS

For both energies, approximately 1% of the incident radiation on the multileaf collimator is transmitted through the backup collimator, while the transmission through the different combinations of leaves and collimators is between 0.03 and 0.14%. These values show a good agreement with literature data and are in general lower than the peak values specified by the manufacturer. The peak value of the leakage between the leaves was about 2% for both energies, without significative variation with gantry or collimator angle or distance from the axis. MLC shaped fields show a skin dose less (about 3%) than the one of cerrobend block shaped fields, because of the electronic contamination due to the plexiglass tray of the cerrobend blocks; in both cases, the depth doses are similar, as are flatness and symmetry of irradiation fields. The effective penumbra increases with field dimension, depth and leaves positioning, with a mean value of about 9 mm for both energies. The different beam configurations do not significantly affect the values of the field size factors.

CONCLUSIONS

The dosimetric characteristics and the case of use of the Elekta multileaf collimator make its application to conformal radiotherapy convenient and reliable, able to improve the accuracy and the effectiveness of radiation therapy and to develop new kinds of treatments. However, because of the complexity of the MLC, its implementation in radiotherapic practice requires careful dosimetric characterization to evaluate those parameters (transmission, penumbra and output factors) that play a fundamental role in the accuracy of the treatment.