Does ultra-low-dose CT with a radiation dose equivalent to that of KUB suffice to detect renal and ureteral calculi?

The objective of this study was to evaluate the diagnostic yield of multislice CT using a radiation dose equivalent to that of conventional abdominal x-ray (KUB). One hundred forty-two patients were prospectively examined with ultrasound and a radically dose-reduced CT protocol (120 kV, 6.9 eff. mAs). Number and size of calculi, presence of urinary obstruction, and alternative diagnoses were recorded and confirmed by stone removal/discharge or by clinical and imaging follow-up. The mean effective whole-body dose was 0.5 mSv in men and 0.7 mSv in women. The sensitivity and specificity in detecting patients with calculi was 97% and 95% for CT and 67% and 90% for ultrasound. Urinary obstruction was similarly assessed, whereas CT identified significantly more alternative diagnoses than ultrasound (P<0.001). With regard to published data for standard-dose CT, the present CT protocol seems to be comparable in its diagnostic yield in assessing patients with calculi, and its radiation dose is equivalent to that of KUB.     

Dosimetric advantages of generalised equivalent uniform dose-based optimisation on dose–volume objectives in intensity-modulated radiotherapy planning for bilateral breast cancer

Objective

We compared and evaluated the differences between two models for treating bilateral breast cancer (BBC): (i) dose–volume-based intensity-modulated radiation treatment (DV plan), and (ii) dose–volume-based intensity-modulated radiotherapy with generalised equivalent uniform dose-based optimisation (DV-gEUD plan).

Methods

The quality and performance of the DV plan and DV-gEUD plan using the Pinnacle³® system (Philips, Fitchburg, WI) were evaluated and compared in 10 patients with stage T2–T4 BBC. The plans were delivered on a Varian 21EX linear accelerator (Varian Medical Systems, Milpitas, CA) equipped with a Millennium 120 leaf multileaf collimator (Varian Medical Systems). The parameters analysed included the conformity index, homogeneity index, tumour control probability of the planning target volume (PTV), the volumes V_{20 Gy} and V_{30 Gy} of the organs at risk (OAR, including the heart and lungs), mean dose and the normal tissue complication probability.

Results

Both plans met the requirements for the coverage of PTV with similar conformity and homogeneity indices. However, the DV-gEUD plan had the advantage of dose sparing for OAR: the mean doses of the heart and lungs, lung V_{20 Gy}, and heart V_{30 Gy} in the DV-gEUD plan were lower than those in the DV plan (p<0.05).

Conclusions

A better result can be obtained by starting with a DV-generated plan and then improving it by adding gEUD-based improvements to reduce the number of iterations and to improve the optimum dose distribution.

Advances to knowledge

The DV-gEUD plan provided superior dosimetric results for treating BBC in terms of PTV coverage and OAR sparing than the DV plan, without sacrificing the homogeneity of dose distribution in the PTV.Breast cancer is the most common cancer and the leading cause of cancer deaths in females worldwide, with about 500 000 fatalities each year. In the USA and Europe, breast cancer constitutes, on average, one in four cancer cases among females [1,2]. Breast cancer among females in Asian countries mostly occurs between the ages of 40 and 50 years; however, in females in Western countries, it mostly occurs between the ages of 50 and 60 years [2,3].Bilateral breast cancer (BBC) is very rare, accounting for only 1–3% of all breast cancer cases [4-6]. Generally, no treatment guidelines exist for BBC. The treatment of BBC relies on surgery, chemotherapy and radiation therapy; additionally, BBC has previously demonstrated a poor prognosis. Current evidence indicates that the survival rate of patients with BBC is similar to that of patients with unilateral breast cancer [7,8]. The difficulty in treatment planning for BBC varies greatly, case by case, and is thus a great challenge for radiotherapy. Important issues have been raised concerning how to reduce the dose of radiation to normal tissues, how to maintain a certain tumour control probability (TCP) and how to improve the quality of life for patients with BBC.Most intensity-modulated radiotherapy (IMRT) planning systems apply dose–volume (DV)-based objective functions for dose optimisation, and an acceptable plan can be generated in most cases. For more complex plans, more iterations are required because many parameters need to be finely tuned. A successful improvement tool—the generalised equivalent uniform dose (gEUD)—was developed with fewer parameter settings [9-13] to improve the quality of plans. However, gEUD-based optimisation cannot demonstrate such advantages on the first run; more iterations are required to sculpt the dose distribution [14].To overcome the disadvantages mentioned above, we started with a DV-generated plan, and then improved it by adding gEUD-based improvements. The goal was to reduce the number of iterations and to improve the optimum dose distribution. This method first determined the approximate solutions for most of the treatment targets by DV-based optimisation, and then adjusted the DV histogram (DVH) by gEUD-based optimisation to obtain a superior solution. This study also compared and evaluated the differences between two different methods for the treatment of BBC—(i) a DV plan with DV-based optimisation (DV plan), and (ii) a DV-gEUD plan with mainly DV-based optimisation assisted by gEUD-based optimisation (DV-gEUD plan)—thus providing a quantitative indicator model for reference.     

Radiolabeling of the biologically active peptide 163–171 of human interleukin-1β

N-succinimidyl[2,3-³H]propionate was used for the radiolabeling of the biologically active peptide fragment 163–171 of human interleukin-1β (VQGEESNDK). Suitable reaction conditions were studied to obtain useful labeling of the molecule. A mixture of mono- (70%) and bi- (30%) propionyl derivatives was obtained with a total ³H specific activity of 87 Ci/mmol of peptide. The conditions for an efficient chromatographic separation of labeled peptide from unreacted reagents and by-products were established. The labeled peptide maintained the same biological activity as that of the corresponding unlabeled molecule, indicating that the labeling procedure did not alter the biological characteristics of the peptide. This thus allows the use of the radiolabeled peptide for receptor binding studies.     

Analysis of high–dose rate brachytherapy dose distribution resemblance in CyberKnife hypofractionated treatment plans of localized prostate cancer

The present study is to analyze the CyberKnife hypofractionated dose distribution of localized prostate cancer in terms of high–dose rate (HDR) brachytherapy equivalent doses to assess the degree of HDR brachytherapy resemblance of CyberKnife dose distribution. Thirteen randomly selected localized prostate cancer cases treated using CyberKnife with a dose regimen of 36.25 Gy in 5 fractions were considered. HDR equivalent doses were calculated for 30 Gy in 3 fractions of HDR brachytherapy regimen. The D_5% of the target in the CyberKnife hypofractionation was 41.57 ± 2.41 Gy. The corresponding HDR fractionation (3 fractions) equivalent dose was 32.81 ± 1.86 Gy. The mean HDR fractionation equivalent dose, D_98%, was 27.93 ± 0.84 Gy. The V_100% of the prostate target was 95.57% ± 3.47%. The V_100% of the bladder and the rectum were 717.16 and 79.6 mm³, respectively. Analysis of the HDR equivalent dose of CyberKnife dose distribution indicates a comparable resemblance to HDR dose distribution in the peripheral target doses (D_98% to D_80%) reported in the literature. However, there is a substantial difference observed in the core high-dose regions especially in D_10% and D_5%. The dose fall-off within the OAR is also superior in reported HDR dose distribution than the HDR equivalent doses of CyberKnife.     

Carcinogenicity of radon/radon decay product inhalation in rats – effect of dose,dose rate and unattached fraction

Purpose: The effects of inhalation of radon/radon decay products at different total doses, dose rates and ‘unattached’ fractions were investigated in a life span study in rats.

Materials and methods: 1574 rats inhaled radon/radon decay products in a purpose-built recirculating exposure system that provided stable/reproducible exposure conditions. 501 were maintained as controls.

Results: Lung tumour incidences were significantly elevated in most exposed groups. The study power was insufficient to resolve the shape of the dose and dose rate response curves, but combination of this data with that from other studies demonstrated that for high cumulative exposures, the lifetime excess absolute risk increases with increasing exposure durations and for low cumulative exposures the opposite trend occurs. Exposure did not increase leukaemia incidences. A small number of non-lung tumour types including mammary fibroadenoma showed elevated incidences in some exposed groups, however not consistently across all exposure groups and showed no dose or dose rate relationship.

Conclusions: Radon/radon decay product exposure caused excess lung tumours in rats along with limited non-lung effects. The results are consistent with the findings that at low cumulative exposures decreasing exposure concentrations or protracting the time over which the dose is delivered, reduces lung tumour risk. At higher levels, decreasing exposure concentrations or protracting exposure time increases lung tumour risk.     

Absorbed dose and biologically effective dose in patients with high-risk non-Hodgkin’s lymphoma treated with high-activity myeloablative <Superscript>90</Superscript>Y-ibritumomab tiuxetan (Zevalin®)

Purpose

The aim of this study was to carry out two different dose estimation approaches in patients with non-Hodgkin’s lymphoma (NHL) treated with a myeloablative amount of ⁹⁰Y-labelled ibritumomab tiuxetan (Zevalin®) in an open-label dose escalation study.

Methods

Twenty-seven patients with relapsed/refractory or de novo high-risk NHL receiving one myeloablative dose of ⁹⁰Y-ibritumomab tiuxetan followed by tandem stem cell reinfusion were evaluated for dose estimate. The injected activity was 30 MBq/kg in 12 patients and 45 MBq/kg in 15 patients. Dose estimation was performed 1 week prior to ⁹⁰Y-ibritumomab tiuxetan by injection of ¹¹¹In-ibritumomab tiuxetan (median activity: 200 MBq). The absorbed dose (D) and the biologically effective dose (BED) were calculated.

Results

The absorbed doses per unit activity (Gy/GBq) were [median (range)]: heart wall 4.6 (2.5–9.7), kidneys 5.1 (2.8–10.5), liver 6.1 (3.9–10.4), lungs 2.9 (1.5–6.8), red marrow 1.0 (0.5–1.7), spleen 7.0 (1.5–14.4) and testes 4.9 (2.9–16.7). The absorbed dose (Gy) for the 15 patients treated with 45 MBq/kg were: heart wall 17.0 (8.7–25.4), kidneys 17.1 (7.9–22.4), liver 20.8 (15.4–28.3), lungs 8.1 (5.4–11.4), red marrow 3.1 (2.0–4.0), spleen 26.2 (17.0–35.6) and testes 17.3 (9.0–28.4). At the highest activities the acute haematological toxicity was mild or moderate and of very short duration, and it was independent of the red marrow absorbed dose. No secondary malignancy or treatment-related myelodysplastic syndrome was observed. No non-haematological toxicity (liver, kidney, lung) was observed during a follow-up period of 24–48 months.

Conclusion

The use of 45 MBq/kg of ⁹⁰Y-ibritumomab tiuxetan in association with stem cell autografting resulted in patients being free of toxicity in non-haematological organs. These clinical findings were in complete agreement with our dose estimations, considering both organ doses and BED values.

     

Influence of magnesium chloride on the dose–response of polyacrylamide-type gel dosimeters

We investigated the effect of magnesium chloride (MgCl₂) on the nuclear magnetic resonance dose–response of polyacrylamide-type (PAGAT, NIPAM, and VIPET) gel dosimeters containing acrylamide, N-isopropylacrylamide, and N-vinylpyrrolidone as a monomer, respectively. The dose-transverse relaxation rates (1/T₂?=?R₂) obtained from magnetic resonance imaging data revealed that a substantial increase in the dose–R₂ response occurred as the concentration of MgCl₂ in the gel dosimeters increased. The sensitivity of the PAGAT gel with 1.0 M MgCl₂ was found to be approximately one order higher than that of the same gel without MgCl₂. In addition, the water equivalences of the gels with MgCl₂ were evaluated over a wide range of photon energies. The results indicated that MgCl₂ acts as a powerful sensitizer to radiation-induced free-radical polymerization in polyacrylamide-type gel dosimeters, but does not interfere with the desirable properties of basic polyacrylamide-type gel dosimeters (i.e., the dose rate and dose integration).     

High or low dose radioiodine ablation of thyroid remnants?

The need for high dose radioiodine for ablation of remnants in patients with thyroid cancer is still in question. We compared the effectiveness of high and low dose 131I for ablation in patients in a prospective randomized study after surgical thyroidectomy. Twenty patients with differentiated pT2-3NoMo thyroid cancer were studied. The uptake was 5%-10% at 24 h. Ten patients received 100 mCi, the others 30 mCi 131I. Three months later all patients received a therapeutic dose of 150 mCi 131I. Another twenty patients with known distant metastases (pulmonary and/or bone) of differentiated thyroid cancer were studied. The remnant uptake was between 4%-10%. Ten patients received 300 mCi and ten 30 mCi 131I as ablation dose. Three months later all received 300 mCi 131I. The uptake at day seven was calculated for the same metastases from a whole body scan after both treatments. If effective ablation was defined as 24 h uptake in the remnant of less than 1%, then the ablation was effective in eight out of ten of the high dose and in seven out of ten of the low dose group. In pT2-3, N X M1 patients the ablation was effective in seven out of ten cases in both groups. If "effective" ablation was defined as an uptake of less than 0.5%, then the ablation was effective both in NoMo and in N X M1 patients in five out of ten with low dose and in six out of ten with high dose ablation treatment.(ABSTRACT TRUNCATED AT 250 WORDS)     

High or low dose radioiodine ablation of thyroid remnants?

The need for high dose radioiodine for ablation of remnants in patients with thyroid cancer is still in question. We compared the effectiveness of high and low dose¹³¹I for ablation in patients in a prospective randomized study after surgical thyroidectomy. Twenty patients with differentiatedpT2-3NoMo thyroid cancer were studied. The uptake was 5%–10% at 24 h. Ten patients received 100 mCi, the others 30 mCi¹³¹I. Three months later all patients received a therapeutic dose of 150 mCi¹³¹I. Another twenty patients with known distant metastases (pulmonary and/or bone) of differentiated thyroid cancer were studied. The remnant uptake was between 4%–10%. Ten patients received 300 mCi and ten 30 mCi¹³¹I as ablation dose. Three months later all received 300 mCi¹³¹I. The uptake at day seven was calculated for the same metastases from a whole body scan after both treatments. If effective ablation was defined as 24h uptake in the remnant of less than 1%, then the ablation was effective in eight out of ten of the high dose and in seven out of ten of the low dose group. In pT2-3, NxM1 patients the ablation was effective in seven out of ten cases in both groups. If effective ablation was defined as an uptake of less than 0.5%, then the ablation was effective both in NoMo and in NxM1 patients in five out of ten with low dose and in six out of ten with high dose ablation treatment. Seventh day uptake in 20 metastases after the second dose was at mean 3.6 times (range 2.8–4.3) higher than after the first, while there was no significant difference in TSH levels. In two patients,¹³¹I kinetics over a bone metastasis were recorded continuously during 300 mCi ablation treatment and 300 mCi therapeutic treatment without any significant difference. We therefore recommend a 30 mCi ablation dose for all patients with differentiated thyroid cancer after surgical thyroidectomy, followed by a 300 mCi treatment dose in pT2-3N1M x or pT2-3N x M1 patients, while in pT2-3NoMo low dose ablation will be a sufficient treatment.Supported in part by Deutsche Forschungsgemeinschaft (grant Cr 52/4-1)     

Single dose planning for radioiodine-131 therapy of Graves’ disease

Objective  Patients with Graves’ disease were studied one year after radioiodine-131 therapy to assess the relationship between the effectiveness of the therapy and the radioiodine doses used.Methods: Patients were classified into three groups according to thyroid function as hyperthyroidism, euthyroidism and hypothyroidism at one year after I-131 therapy. In these groups we compared the mean values of dose, dose per thyroid weight calculated with I-123 uptake before the therapy (pre D/W), dose per thyroid weight calculated with therapeutic I-131 uptake (post D/W), and absorbed dose. Results  No significant differences were found between the three groups in terms of dose or pre D/W. The mean values of post D/W and absorbed dose in the non-hyperthyroid (euthyroid and hypothyroid) group were significantly greater than those in the hyperthyroid group. Post D/W of 6.3 MBq/g was a threshold separating the non-hyperthyroid group from the hyperthyroid group. There was no correlation between pre D/W and post D/W; however, the mean post D/W was significantly greater than the mean pre D/W. All patients with pre D/W above 6.3 MBq/g showed non-hyperthyroidism at one year after the radioiodine treatment. Conclusions  No indicators before the radioiodine therapy had significant relationships with the effectiveness of the therapy at one year after the treatment. However, the single therapy planned for setting the pre D/W above 6.3 MBq/g will certainly make the patients non-hyperthyroid. As this proposal of dose planning is based on a small number of patients, further study is needed.     

Is MRI equivalent to CT in the guidance of TAVR? A pilot study

Objectives

To compare a comprehensive cardiovascular magnetic resonance imaging (MRI) protocol with contrast-enhanced computed tomography angiography (CTA) for guidance in transcatheter aortic valve replacement (TAVR) evaluation.

Methods and results

Non-contrast three-dimensional (3D) ‘whole heart’ MRI imaging for aortic annulus sizing and measurements of coronary ostia heights, contrast-enhanced MRI angiography (MRA) for evaluation of transfemoral routes as well as aortoiliofemoral-CTA were performed in 16 patients referred for evaluation of TAVR. Aortic annulus measurements by MRI and CTA showed a very strong correlation (r=0.956, p<0.0001; effective annulus area for MRI 430±74 vs. 428±78 mm² for CTA, p=0.629). Regarding decision for valve size there was complete consistency between MRI and CTA. Moreover, vessel luminal diameters and angulations of aortoiliofemoral access as measured by MRA and CTA showed overall very strong correlations (r= 0.819 to 0.996, all p<0.001), the agreement of minimal vessel diameter between the two modalities revealed a bias of 0.02 mm (upper and lower limit of agreement: 1.02 mm and -0.98 mm).

Conclusions

In patients referred for TAVR, MRI measurements of aortic annulus and minimal aortoiliofemoral diameters showed good to excellent agreement. Decisions based on MRI measurements regrading prosthesis sizing and transfemoral access would not have modified TAVR-strategy as compared to a CTA-based choice.

Key Points

? ‘Whole heart’ MRI and CTA measurements of aortic annulus correlate very strongly. ? MRI- and CTA-based prostheses sizing are in excellent agreement. ? MRA and CTA equally guide TAVR access strategy.

     

The dynamic range of digital radiographic systems: dose reduction or risk of overexposure?

OBJECTIVES: To investigate the range of diagnostically acceptable digital radiographs and film as a function of exposure time, as well as the relationship to dose reduction and consequences for dental practice. METHODS: Five systems for intraoral radiography were used to take a series of radiographs, with increasing exposure times, of five different dry bone specimens. Seven observers evaluated the 25 series of radiographs. The observers had to determine which radiographs of each series were acceptable for dental diagnostics and which radiograph of each series they preferred. RESULTS: For Ektaspeed Plus film, the exposure time for the preferred radiograph was 0.52 s, with a range of diagnostically acceptable radiographs from 0.23-1.02 s. The preferred radiograph of the solid-state systems required less radiation than film (Sirona, 0.13 s; MPDx 0.35 s). The exposure range of these systems is narrow. In contrast, the exposure range of the phosphor plate systems is very wide. The preferred radiograph of the phosphor plate systems required high exposure (Digora, 1.21 s; Gendex DenOptix, 1.16 s). CONCLUSIONS: All digital systems require less exposure than film for diagnostically acceptable radiographs, but this is less obvious for preferred radiographs. Solid-state systems alert the dentist when a too long exposure time is used by a lack of image quality; phosphor plate systems, however, produce good quality radiographs even at high exposure times, which may result in an unnecessarily high dose.     

Survey of computed tomography techniques and absorbed dose in Italian hospitals: a comparison between two methods to estimate the dose–length product and the effective dose and to verify fulfilment of the diagnostic reference levels

The aim of this study was the production of the first Italian survey of radiation dose in computed tomography (CT) prior to the widespread adoption of multislice CT, in order to have a reference point to facilitate later investigation of dose exposure changes brought by this new CT modality. The collected dose data were compared with diagnostic reference levels (DRLs). The agreement between experimental dose evaluation and Monte Carlo (MC) simulations was investigated. The survey was carried out in 29 Italian hospitals, covered 48 CT scanners and 232 examinations. The dose–length product (DLP) and effective dose (E) values were estimated based on MC simulations for seven clinical protocols using the CT-Dose program. Statistical analysis showed a significant difference (p<0.01) in the DLP between the two methods, with MC values being greater than the experimental ones. For E, the MC values were greater in routine head (8.2%), cervical spine (2.7%) and lumbar spine (2.9%) studies. The weighted CT dose index, the DLP and E were always below the DRLs set by the European Community. This dose survey gives a good but incomplete picture of the Italian CT dose situation and may be useful as a reference baseline for defining clinical multislice protocols in the near future.     

Predicting adherence of dose–volume constraints for personalized partial-breast irradiation technique

PurposeMulticatheter interstitial brachytherapy (MIB) and external-beam (EB) radiotherapy are established partial-breast irradiation (PBI) techniques. Although EB-PBI is widely available, it requires extra irradiated margins for target uncertainties. We examined the impact of EB-PBI on dose–volume constraints as compared to MIB-PBI.Methods and MaterialsAmong 653 patients receiving MIB-PBI between October 2008 and April 2020, consequent 159 patients after September 2018 were examined. Clinical target volume (CTV) included the lumpectomy cavity plus 1.0 cm. Planning target volume (PTV) for EB-PBI was defined as CTV with 1.0-cm expansion. Because the ratio of PTV to breast volume (RPB) was related to cosmesis, <25% of RPB was defined as suitable for the ipsilateral breast constraints. Preoperative breast size was classified as very small (<350 cm³), small (350–699 cm³), and medium or large (≥700 cm³). According to each category, the dose–volume constraints of the organs at risk were compared between the two PBI techniques.ResultsPatients including 84 very small, 59 small, and 16 moderate to large breasts were examined. Although RPB was suitable in all patients receiving MIB-PBI, it was achieved in 74 patients (46.5%) receiving EB-PBI (p < 0.0001). The suitable RPB in patients with very small, small, and moderate to large breast was 32.1%, 55.9%, and 100%, respectively (p < 0.0001). Normal-tissue constraints for the other organs could be satisfied in patients with moderate to large breasts.ConclusionAlthough EB-PBI may be an appropriate option for patients with moderate to large breasts, MIB-PBI could still be a crucial technique, especially for patients with small breasts.     

Does selective pleural irradiation of malignant pleural mesothelioma allow radiation dose escalation?

Background

After lung-sparing radiotherapy for malignant pleural mesothelioma (MPM), local failure at sites of previous gross disease represents the dominant form of failure. Our aim is to investigate if selective irradiation of the gross pleural disease only can allow dose escalation.

Materials and methods

In all, 12 consecutive stage I–IV MPM patients (6 left-sided and 6 right-sided) were retrospectively identified and included. A magnetic resonance imaging-based pleural gross tumor volume (GTV) was contoured. Two sets of planning target volumes (PTV) were generated for each patient: (1) a “selective” PTV (S-PTV), originating from a 5-mm isotropic expansion from the GTV and (2) an “elective” PTV (E-PTV), originating from a 5-mm isotropic expansion from the whole ipsilateral pleural space. Two sets of volumetric modulated arc therapy (VMAT) treatment plans were generated: a “selective” pleural irradiation plan (SPI plan) and an “elective” pleural irradiation plan (EPI plan, planned with a simultaneous integrated boost technique [SIB]).

Results

In the SPI plans, the average median dose to the S?PTV was 53.6?Gy (range 41–63.6?Gy). In 4 of 12 patients, it was possible to escalate the dose to the S?PTV to >58?Gy. In the EPI plans, the average median doses to the E?PTV and to the S?PTV were 48.6?Gy (range 38.5–58.7) and 49?Gy (range 38.6–59.5?Gy), respectively. No significant dose escalation was achievable.

Conclusion

The omission of the elective irradiation of the whole ipsilateral pleural space allowed dose escalation from 49?Gy to more than 58?Gy in 4 of 12 chemonaive MPM patients. This strategy may form the basis for nonsurgical radical combined modality treatment of MPM.