Spinal cord biological safety of image-guided radiation therapy versus conventional radiation therapy

Tumor models were simulated in purebred Beagles at the T9-10 levels of the spinal cord and treated with spinal image-guided radiation therapy or conventional radiation therapy with 50 or 70 Gy total radiation. Three months after radiation, neuronal injury at the T9-10 levels was observed, including reversible injury induced by spinal image-guided radiation therapy and apoptosis induced by conventional radiation therapy. The number of apoptotic cells and expression of the proapoptotic protein Fas were significantly reduced, but expression of the anti-apoptotic protein heat shock protein 70 was significantly increased after image-guided radiation therapy compared with the conventional method of the same radiation dose. Moreover, the spinal cord cell apoptotic index positively correlated with the ratio of Fas/heat shock protein 70. These findings indicate that 3 months of radiation therapy can induce a late response in the spinal cord to radiation therapy; image-guided radiation therapy is safer and results in less neuronal injury compared with conventional radiation therapy.

Portal hypertension: Imaging of portosystemic collateral pathways and associated image-guided therapy

Portal hypertension is a common clinical syndrome, defined by a pathologic increase in the portal venous pressure. Increased resistance to portal blood flow, the primary factor in the pathophysiology of portal hypertension, is in part due to morphological changes occurring in chronic liver diseases. This results in rerouting of blood flow away from the liver through collateral pathways to low-pressure systemic veins. Through a variety of computed tomographic, sonographic, magnetic resonance imaging and angiographic examples, this article discusses the appearances and prevalence of both common and less common portosystemic collateral channels in the thorax and abdomen. A brief overview of established interventional radiologic techniques for treatment of portal hypertension will also be provided. Awareness of the various imaging manifestations of portal hypertension can be helpful for assessing overall prognosis and planning proper management.

Progress in image-guided radiotherapy for the treatment of non-small cell lung cancer

Lung cancer is one of the most common malignant tumors. It has the highest incidence and mortality rate of all cancers worldwide. Late diagnosis of nonsmall cell lung cancer(NSCLC) is very common in clinical practice, and most patients miss the chance for radical surgery. Thus, radiotherapy plays an indispensable role in the treatment of NSCLC. Radiotherapy technology has evolved from the classic two-dimensional approach to three-dimensional conformal and intensity-modulated radiotherapy. However, how to ensure delivery of an accurate dose to the tumor while minimizing the irradiation of normal tissues remains a huge challenge for radiation oncologists, especially due to the positioning error between fractions and the autonomous movement of organs. In recent years, image-guided radiotherapy(IGRT) has greatly increased the accuracy of tumor irradiation while reducing the irradiation dose delivered to healthy tissues and organs. This paper presents a brief review of the definition of IGRT and the various technologies and applications of IGRT. IGRT can help ensure accurate dosing of the target area and reduce radiation damage to the surrounding normal tissue. IGRT may increase the local control rate of tumors and reduce the incidence of radio-therapeutic complications.

Image-guided lens extraction surgery: a systematic review

A systematic review of the recent literature regarding the current image-guided systems used for cataract surgery or refractive lens exchange was performed based on the PubMed and Google Scholar databases in March 2018. Literature review returned 21 eligible studies. These studies compared image-guided systems with other keratometric devices regarding their accuracy, repeatability and reproducibility in measurement of keratometric values, astigmatism magnitude and axis, as well as in IOL power calculation. Additionally, the image-guided systems were compared with conventional manual ink-marking techniques for the alignment of toric IOLs. In conclusion, image-guided systems seem to be an accurate and reliable technology with measurements of high repeatability and reproducibility regarding the keratometry and IOL power calculation, but not yet interchangeable with the current established and validated keratometric devices. However, they are superior over the conventional manual inkmarking techniques for toric IOL alignment.

Real-time fluorescence image-guided gastrointestinal oncologic surgery:Towards a new era

Technological improvements are crucial in the evolution of surgery.Real-time fluorescence-guided surgery(FGS)has spread worldwide,mainly because of its usefulness during the intraoperative decision-making processes.The success of any gastrointestinal oncologic resection is based on the anatomical identification of the primary tumor and its regional lymph nodes.FGS allows also to evaluate the blood perfusion at the gastrointestinal stumps after colorectal or esophageal resections.Therefore,a reduction on the anastomotic leak rates has been postulated as one of the foreseeable benefits provided by the use of FGS in these procedures.Although the use of fluorescence in lymph node detection was initially described in breast cancer surgery,the technique is currently applied in gastric or splenic flexure cancers,as they both present complex and variable lymphatic drainages.FGS allows also to perform intraoperative lymphograms or sentinel lymph node biopsies.New applications of FGS are being developed to assist in the detection of peritoneal metastases or in the evaluation of the tumor resection margins.The present review aims to provide a general overview of the current status of real-time FGS in gastrointestinal oncologic surgery.We put a special focus on the different applications of FGS,discussing the main findings and limitations found in the contemporary literature and also the promising near future applications.

Biological effects of human lung cells MRC-5 in CBCT positioning for image-guided radiotherapy

Image-guided radiotherapy(IGRT) provides precise positioning for the tumor target, but it may bring extra irradiation dose in the target positioning with a cone beam CT(CBCT) which has been increasingly used in IGRT. In this work, we focused on biological effects of the low-dose irradiation in IGRT, which have not been considered so far. Primary human fibroblasts cells from the lung and MRC-5 were irradiated by a CBCT. DNA doublestrand breaks(c-H2 AX foci) and micronucleus frequency of the irradiated samples were analyzed. Compared to the control, the c-H2 AX foci yields of the samples irradiated to 16 m Gy increased significantly, and the micronuclei rate of the samples irradiated for 3 days increased notably. The dose by imaging guidance device can be genotoxic to normal tissue cells, suggesting a potential risk of a secondary cancer. The effects, if confirmed by clinical studies,should be considered prudentially in designing IGRT treatment plans for the radiosensitive population, especially for children.

A novel technique for sacropelvic fixation using image-guided sacroiliac screws:a case series and biomechanical study

In this study, we sought to assess the safety and accuracy of sacropelvic fixation performed with image-guided sacroiliac screw placement using postoperative computed tomography and X-rays. The sacroiliac screws were placed with navigation in five patients. Intact specimens were mounted onto a six-degrees-of-freedom spine motion simulator. Long lumbosacral constructs using bilateral sacroiliac screws and bilateral S1 pedicle and iliac screws were tested in seven cadaveric spines. Nine sacroiliac screws were well-placed under an image guidance system(IGS);one was placed poorly without IGS with no symptoms. Both fixation techniques significantly reduced range of motion(P<0.05) at L5-S1. The research concluded that rigid lumbosacral fixation can be achieved with sacroiliac screws,and image guidance improves its safety and accuracy. This new technique of image-guided sacroiliac screw insertion should prove useful in many types of fusion to the sacrum, particularly for patients with poor bone quality,complicated anatomy, infection, previous failed fusion and iliac harvesting.

Long-term clinical outcomes of lipiodol marking using standard gastroscopy for image-guided radiotherapy of upper gastrointestinal cancers

BACKGROUND Image-guided radiotherapy(IGRT)has significantly improved the precision in which radiotherapy is delivered in cancer treatment.Typically,IGRT uses bony landmarks and key anatomical structures to locate the tumor.Recent studies have demonstrated the feasibility of peri-tumor fiducials in enabling even more accurate delineation of target and normal tissue.The use of gold coils as fiducials in gastrointestinal tumors has been extensively studied.However,placement requires expertise and specialized endoscopic ultrasound equipment.This article reports the long-term outcomes of using a standard gastroscopy to inject liquid fiducials for the treatment of oesophageal and gastric tumors with IGRT.AIM To assess the long-term outcomes of liquid fiducial-guided IGRT in a cohort of oesophageal and gastric cancer patients.METHODS A retrospective cohort study of consecutive adults with Oesophagogastric cancers referred for liquid fiducial placement before definitive/neo-adjuvant or palliative IGRT between 2013 and 2021 at a tertiary hospital in Melbourne,Australia was conducted.Up to four liquid fiducials were inserted per patient,each injection consisting of 0.2-0.5mL of a 1:1 mixture of iodized oil(Lipiodol;Aspen Pharmacare)and n-butyl 2-cyanoacrylate(Histoacryl®;B.Braun).A 23-gauge injector(Cook Medical)was used for the injection.All procedures were performed by or under the supervision of a gastroenterologist.Liquid fiducial-based IGRT(LF-IGRT)consisted of computer-assisted direct matching of the fiducial region on cone-beam computerised tomography at the time of radiotherapy.Patients received standard-IGRT(S-IGRT)if fiducial visibility was insufficient,consisting of bone match as a surrogate for tumor position.Radiotherapy was delivered to 54Gy in 30 fractions for curative patients and up to 45Gy in 15 fractions for palliative treatments.RESULTS 52 patients were referred for liquid fiducial placement within the study period.A total of 51 patients underwent liquid fiducial implantation.Of these a total of 31 patients received radiotherapy.Among these,the median age was 77.4 years with a range between 57.5 and 88.8,and 64.5%were male.Twenty-seven out of the 31 patients were able to have LF-IGRT while four had S-IGRT.There were no complications after endoscopic implantation of liquid fiducials in our cohort.The cohort overall survival(OS)post-radiotherapy was 19 mo(range 0 to 87 mo).Whilst the progression-free survival(PFS)post-radiotherapy was 13 mo(range 0 to 74 mo).For those treated with curative intent,the median OS was 22.0 mo(range 0 to 87 mo)with a PFS median of 14.0 mo(range 0 to 74 mo).Grade 3 complication rate post-radiotherapy was 29%.CONCLUSION LF-IGRT is feasible in 87.1%of patients undergoing liquid fiducial placement through standard gastroscopy injection technique.Our cohort has an overall survival of 19 mo and PFS of 13 mo.Further studies are warranted to determine the long-term outcomes of liquid-fiducial based IGRT.

Diffusion-weighted imaging and variable flip angle T1 mapping: a supplement for image-guided biopsy in follow-up analysis of liver fibrosis

Purpose To evaluate the performance of diffusion-weighted imaging(DWI) and variable flip angle(VFA) T1 mapping as a supplement to image-guided biopsy in follow-up analysis of liver fibrosis. Materials and Methods This prospective study was approved by the institution's committee on human research, and written informed consent was provided from the enrolled patients. We investigated five MRI parameters of DWI and VFA T1 mapping, collected from 11 patients who underwent serial ultrasound image-guided biopsy with follow-up MRI within 1.5 years after treatment for liver fibrosis/cirrhosis. For each patient, four consecutive MRI examinations were conducted, including baseline MRI before treatment and three follow-up MRI examinations after treatment at each 0.5-year interval. ADC values at four b values and T1 relaxation times were correlated to pathology-confirmed liver fibrosis stages, which were subsequently divided into two groups, stages F2–3 and F4. The receiver operating characteristic(ROC) analysis and repeated measurement analysis of variance were used for statistical analysis. Results Among these ADC parameters, ADC value(b = 500 s/mm^2) was the most consistent in differentiating between stage F2–3 and F4 liver fibrosis. Repeated measurement analysis showed that the intra-group and inter-group differences were 0.447 and 0.024, respectively. T1 relaxation time could not consistently differentiate between the F2–3 and F4 groups; however, it was repeatable, and the intra-group and inter-group differences were 0.410 and 0.042, respectively. Conclusion MRI-ADC value at a b value of 500 s/mm^2 can be a promising biomarker for differentiating stages F2–3 and F4 liver fibrosis. A combination of this biomarker with repeatable T1 relaxation time may function as a non-invasive tool for follow-up liver fibrosis in patients who reject repeated image-guided biopsy.

The Associations for Vaginal Point Doses of Vaginal Stenosis in Image-Guided Brachytherapy

Purpose: To evaluate the associations for vaginal dose points of vaginal stricture in image-guided brachytherapy. Materials and Methods: Twenty-six patients of locally advanced cervical cancer were treated with Image-Guided Brachytherapy (IGBT) with the dose at least 7 Gy per fraction to the D90 of High-Risk Clinical Target Volume (HR-CTV). The vaginal dose points of recommendations of the American Brachytherapy Society (ABS) were added into the plan and cumulative dose to these points was evaluated in Equivalent Dose of 2 Gy (EQD2) concepts. Results: The mean doses to right vaginal dose point (VR), left vaginal dose point (VL) and average dose of VR/VL ((VR + VL)/2) were 101.5 Gy, 98.2 Gy and 99.8 Gy in EQD2 concepts, respectively. Volume-based planning significantly reduced the cumulative dose in EQD2 concepts at vaginal points. At the median follow-up time of 22 months, grade-2 vaginal stricture was observed in two patients. The incidences of vaginal stricture were not differed between the cumulative dose to vaginal dose points in EQD2 concepts of ≤90 Gy versus >90 Gy (P = 1.000) and ≤100 Gy versus >100 Gy (P = 0.815). Conclusion: No association for cumulative vaginal doses and events of vaginal stricture was found.

Computer planned, image-guided combined resection and ablation for bilobar colorectal liver metastases

For patients with extensive bilobar colorectal liver metastases (CRLM), initial surgery may not be feasible and a multimodal approach including microwave ablation (MWA) provides the only chance for prolonged survival. Intraoperative navigation systems may improve the accuracy of ablation and surgical resection of so-called &#x0201c;vanishing lesions&#x0201d;, ultimately improving patient outcome. Clinical application of intraoperative navigated liver surgery is illustrated in a patient undergoing combined resection/MWA for multiple, synchronous, bilobar CRLM. Regular follow-up with computed tomography (CT) allowed for temporal development of the ablation zones. Of the ten lesions detected in a preoperative CT scan, the largest lesion was resected and the others were ablated using an intraoperative navigation system. Twelve months post-surgery a new lesion (Seg IVa) was detected and treated by trans-arterial embolization. Nineteen months post-surgery new liver and lung metastases were detected and a palliative chemotherapy started. The patient passed away four years after initial diagnosis. For patients with extensive CRLM not treatable by standard surgery, navigated MWA/resection may provide excellent tumor control, improving longer-term survival. Intraoperative navigation systems provide precise, real-time information to the surgeon, aiding the decision-making process and substantially improving the accuracy of both ablation and resection. Regular follow-ups including 3D modeling allow for early discrimination between ablation zones and recurrent tumor lesions.

Image-guided resection of cerebral cavernous malformations

Objective To evaluate retrospectively the effectiveness of image-guided navigation techniques in the management of cerebral CMs.Methods Between July 1997 and January 2001,44 patients underwent image-guided resection of cerebral CMs. To counteract brain shift,a small silicon catheter was implanted as a guide in the case of deep-seated lesions (except in the case of brain stem CMs) and before excision of multiple lesions. Results A total of 27 men and 17 women with a mean age of 35 years underwent surgical procedures (5 patients had multiple lesions). The lesions were located in the frontal (n=14),lobe temporal lobe (n=12),parietal lobe (n=6),cerebellum (n=6),thalamus (n=5),pons (n=5),and orbital region (n=1). Under the guidance of a StealthStation navigator,total removal of the lesions was achieved in all patients. Follow-up revealed marked improvement of preoperative symptoms in 26 patients and no additional deficits in 13 patients. Five patients suffered from additional neurological deficits,but two of them gradually improved during the follow-up period. Conclusions With the assistance of an image-guided surgical system,functional areas can be effectively avoided and surgical injury can be decreased. This system is well suited for accurate localization and safe resection of small,deep-seated CMs.

A Dosimetric Comparison between Conventional Fractionated and Hypofractionated Image-guided Radiation Therapies for Localized Prostate Cancer

Background： Image-guided radiation therapy （IGRT） is the preferred method for curative treatment of localized prostate cancer, which could improve disease outcome and reduce normal tissue toxicity reaction. 1GRT using cone-beam computed tomography （CBCT） in combination with volumetric-modulated arc therapy （VMAT） potentially allows smaller treatment margins and dose escalation to the prostate. The aim of this study was to compare the difference of dos^metric diffusion in conventional IGRT using 7-field, step-and-shoot intensity-modulated radiation therapy （IMRT） and hypofractionated IGRT using VMAT for patients with localized prostate cancer. Methods： We studied 24 patients who received 78 Gy in 39 daily fractions or 70 Gy in 28 daily fractions to their prostate with/without the seminal vesicles using IMRT （n = 12） or VMAT （n = 12） for prostate cancer between November 2013 and October 2015. Image guidance was performed using kilovoltage CBCT scans equipped on the linear accelerator. Offline planning was performed using the daily treatment images registered with simulation computed tomography （CT） images. A total of 212 IMRT plans in conventional cohort and 292 VMAT plans in hypofractionated cohort were enrolled in the study. Dose distributions were recalculated on CBCT images registered with the planning CT scanner. Results： Compared with 7-field, step-and-shoot IMRT, VMAT plans resulted in improved planning target volume （PTV） D95% （7663.17 ± 69.57 cGy vs. 7789.17± 131.76 cGy, P 〈 0.001）. VMAT reduced the rectal D25 （P 〈 0.001）, D35 （P 〈 0.001）, and D50 （P 〈 0.001）, bladder V50 （P 〈 0.001）, D25 （P = 0.002）, D35 （P = 0.028）, and D50 （P = 0.029）. However, VMAT did not statistically significantly reduce the rectal V50, compared with 7-field, step-and-shoot IMRT （25.02 ± 5.54% vs. 27.43 ±8.79%, P - 0.087）. Conclusions： To deliver the hypofractionated radiotherapy in prostate cancer, VMAT significantly increased PTV D95% dose and decreased the dose of radiation delivered to adjacent normal tissues comparing to 7-field, step-and-shoot IMRT. Daily online image-guidance and better management of bladder and rectum could make a more precise treatment delivery.

Image-guided color mapping for categorical data visualization

Appropriate color mapping for categorical data visualization can significantly facilitate the discovery of underlying data patterns and effectively bring out visual aesthetics.Some systems suggest pre-defined palettes for this task.However,a predefined color mapping is not always optimal,failing to consider users’needs for customization.Given an input cate-gorical data visualization and a reference image,we present an effective method to automatically generate a coloring that resembles the reference while allowing classes to be easily distinguished.We extract a color palette with high perceptual distance between the colors by sampling dominant and discriminable colors from the image’s color space.These colors are assigned to given classes by solving an integer quadratic program to optimize point distinctness of the given chart while preserving the color spatial relations in the source image.We show results on various coloring tasks,with a diverse set of new coloring appearances for the input data.We also compare our approach to state-of-the-art palettes in a controlled user study,which shows that our method achieves comparable performance in class discrimination,while being more similar to the source image.User feedback after using our system verifies its efficiency in automatically generating desirable colorings that meet the user’s expectations when choosing a reference.

Surface-adaptive nanoparticles with near-infrared aggregation-induced emission for image-guided tumor resection

Aggregation-induced emission(AIE)nanoparticles(NPs)are widely used for image-guided tumor resection because of their high signal-to-noise ratios and long systemic circulation time.These NPs are derived by encapsulating small-molecule fluorescent dyes with AIE property inside the cores of NPs assembled by amphiphilic polymers.Although the systemic circulation of AIE NPs is prolonged,hydrophilic polymer coatings simultaneously decrease the binding and uptake of AIE NPs by tumor cells.To overcome this problem,surface-adaptive AIE dye-encapsulated mixed-shell micelles(MSMs)with polyethylene glycol/poly(β-amino ester)(PEG/PAE)surfaces were prepared.Due to the charge conversion ability of PAE,MSMs demonstrated enhanced cellular uptake by tumor cells in acidic conditions.In addition,compared with single-PEG-shelled micelles(PEGSMs),MSMs exhibited prolonged systemic circulation due to the presence of micro-phase separated surfaces.Moreover,due to the coordination effect of enhanced cancer cell uptake and prolonged systemic circulation time,MSMs were more enriched than PEGSMs in the tumor cells and exhibited excellent performance during image-guided tumor resection.

A facile phototheranostic nanoplatform integrating NIR-Ⅱ fluorescence/PA bimodal imaging and image-guided surgery/PTT combinational therapy for improved antitumor efcacy

Phototheranostic with highly integrated functions is an attractive platform for cancer management. It remains challenging to develop a facile phototheranostic platform with complementary bimodal imaging and combinational therapy capacity. Herein, the small-molecule cyanine IR780 loaded liposomes have been harnessed as a nanoplatform to simultaneously realize photoacoustic(PA)/the second near-infrared window(NIR-Ⅱ) fluorescence imaging and image-guided surgery/adjuvant photothermal therapy(PTT).This nanoplatform exhibits attractive properties like uniform controllable size, stable dispersibility, NIR-Ⅱ fluorescence emission, photothermal conversion, and biocompatibility. Benefiting from the complementary PA/NIR-Ⅱ fluorescence bimodal imaging, this nanoplatform was successfully applied in precise vasculature delineation and tumor diagnosis. Interestingly, the tumor was clearly detected by NIR-Ⅱ fluorescence imaging with the highest tumor-to-normal-tissue ratio up to 12.69, while signal interference from the liver was significantly reduced, due to the difference in the elimination rate of the nanoplatform in the liver and tumor. Under the precise guidance of the image, the tumor was accurately resected, and the simulated residual lesion after surgery was completely ablated by adjuvant PTT. This combined therapy showed improved antitumor efcacy over the individual surgery or PTT. This work develops a facile phototheranostic nanoplatform with great significance in accurately diagnosing and effectively treating tumors using simple NIR light irradiation.

Enabling AIEgens close assembly in tumor-overexpressed protein cluster for boosted image-guided cancer surgery

Development of efficient fluorescent probes that can realize precise fluorescence image-guided cancer surgery(FIGCS)with extremely high tumor-to-normal tissue(T/NT)ratio is urgently desirable.Herein,we report the design and synthesis of an aggregation-induced emission(AIE)-active,peptide-based fluorescence turn-on probe MPA-Ph-R-FFGYSAYPDSVPMMS(MPA-Ph-R-FFGYSA for short),which consists of a new near-infrared emissive AIE luminogen(AIEgen)MPA-Ph-R,a self-assembling peptide sequence“FFG”,and an“active”targeting peptide YSAYPDSVPMMS that can selectively bind to EphA2 protein cluster overexpressed in many cancers.As compared to the control probe MPA-Ph-R-YSA without“FFG”,MPA-Ph-R-FFGYSA exhibits much higher fluorescent brightness and sensitivity in both cellular and in vivo studies on EphA2 cluster detection/imaging,as“FFG”is beneficial to closer assembly of AIEgens in EphA2 cluster,leading to more effective restriction of the intramolecular motion of AIEgen.In vivo studies demonstrate that MPA-Ph-R-FFGYSA is a safe bioprobe and gives excellent performance in FIGCS with a rather high T/NT ratio of^13.4 upon intravenous administration into peritoneal carcinomatosis-bearing mice.This study provides a new strategy of utilizing the close assembly of tumor microenvironment-responsive AIE probes for boost FIGCS.

A NIR-Ⅱ theranostics nanoprobe for tumor diagnosis and image-guided therapy

With the support by the National Natural Science Foundation of China and the National Key R&.D Program,the research team led by Prof.Sun Yao,Prof.Li HaiBing and Prof.Yang GuangFu(杨光富)at the Laboratory of Pesticide 8.Chemical Biology.Ministry of Education,Central China Normal University,cooperated with the research team led by Prof.Peter J.Stang from the University of Utah,and developed a novel NIR-II nanoprobe for tumor diagnosis and evaluation of anti-tumor efficiency.

Adaptive Dose-Compensation Technique for Image-Guided Radiotherapy of Prostate Cancer

Background: For image-guided radiotherapy(IGRT) of prostate cancer, the current standard is online image guidance which can effectively correct setup errors and inter-fraction rigid organ motion. However, planning margins are still necessary for deformation and intra-fraction motion. Objective: This paper aims to investigate an adaptive planning technique incorporating offline dose feedback to manage interfraction motion and residuals from online corrections. Methods:Repeated CT scans from 28 patients were studied. Online IG was simulated by matching center-of-mass of prostate. A seven-beam IMRT plan with zero margins was designed for each patient. Dose distribution at each fraction was evaluated based on actual target and OARs from that fraction. Cumulative dose was calculated using deformable registration and compared to initial plan. If deviation exceeded pre-defined 2% threshold in prostate D99 an adaptive planning technique called dose compensation was invoked, in which cumulative dose was fed back to the planning system and dose deficit was made up through boost radiation in future fractions through IMRT. Results: If 2% under-dose was allowed at the end of course, then 11 patients failed. If the same criteria was assessed at the end of each week(every 5 fractions), then 14 patients failed. The average dose deficit for these 14 patients was4.4%. They improved to 2% after weekly compensation. 10(out of 14) patients passed criterion after weekly dose compensation; 3 failed marginally; 1 failed significantly(10% deficit). A more aggressive compensation frequency(every 3 fractions) could reduce the dose deficit to the acceptable level for this patient. The doses to OARs were not significantly different from online IG only without dose compensation.Conclusion: We demonstrated an offline dose compensation technique in prostate IGRT which can effectively account for residual uncertainties uncorrectable in online IG. Dose compensation allows further margin reduction and critical organs sparing.

Hi'CT:a pixel sensor-based device for ion tomography

Carbon ions,commonly referred to as particle therapy,have become increasingly popular in the last decade.Accurately predicting the range of ions in tissues is important for the precise delivery of doses in heavy-ion radiotherapy.Range uncertainty is currently the largest contributor to dose uncertainty in normal tissues,leading to the use of safety margins in treatment planning.One potential method is the direct relative stopping measurement(RSP)with ions.Heavy-ion CT(Hi′CT),a compact segmented full digital tomography detector using monolithic active pixel sensors,was designed and evaluated using a 430 MeV/u high-energy carbon ion pencil beam in Geant4.The precise position of the individual carbon ion track can be recorded and reconstructed using a 30μm×30μm small pixel pitch size.Two types of customized image reconstruction algorithms were developed,and their performances were evaluated using three different modules of CAT-PHAN 600-series phantoms.The RSP measurement accuracy of the tracking algorithm for different types of materials in the CTP404 module was less than 1%.In terms of spatial resolution,the tracking algorithm could achieve a 20%modulation transfer function normalization value of CTP528 imaging results at 5 lp/cm,which is significantly better than that of the fast imaging algorithm(3 lp/cm).The density resolution obtained using the tracking algorithm of the customized CTP515 was approximately 10.5%.In conclusion,a compact digital Hi'CT system was designed,and its nominal performance was evaluated in a simulation.The RSP resolution and image quality provide potential feasibility for scanning most parts of an adult body or pediatric patient,particularly for head and neck tumor treatment.