bluuebunny/crossref_metadata_2025 huggingface dataset:
Evaluation of pulmonary nodules and lung cancer with one‐inch crystal gamma coincidence positron emission tomography/CT versus dedicated positron emission tomography/CT
Authors: Moodie K , Cherk MH , Lau E , Turlakow A , Skinner S , Hicks RJ , Kelly MJ , Kalff V
Published: April 2009

Dedicated positron emission tomography (PET)/CT scanners using BGO and related detectors (d‐PET) have become standard imaging instruments in many malignancies. Hybrid gamma camera systems using NaI detectors in coincidence mode (g‐PET) have been compared to d‐PET but reported usefulness has been variable when gamma cameras with half‐inch to three‐fourth‐inch thick crystals have been used without CT. Our aim was to compare g‐PET with a 1‐in.‐thick crystal and inbuilt CT for lesion localization and attenuation correction (g‐PET/CT) and d‐PET/CT in patients presenting with potential and confirmed lung malignancies. One hour after 18F‐fluorodeoxyglucose (FDG), patients underwent BGO d‐PET/CT from jaw to proximal thigh. This was followed by one to two bed position g‐PET/CT 194 ± 27 min after FDG. Each study pair was independently analysed with concurrent CT. d‐PET/CT was interpreted by a radiologist experienced in both PET and CT, and g‐PET/CT by consensus reading of an experienced PET physician and an experienced CT radiologist. A TNM score was assigned and studies were then unblinded and compared. Fifty‐seven patients underwent 58 scan pairs over 2 years. Eighty‐nine per cent concordance was shown between g‐PET/CT and d‐PET/CT for the assessment of intrapulmonary lesions, with 100% concordance for intrapulmonary lesions >10 mm (36 of 36). Eighty‐eight per cent (51 of 58) concordance was shown between g‐PET/CT and d‐PET/CT for TNM staging. Coincidence imaging using an optimized dual‐head 1‐in.‐thick crystal gamma camera with inbuilt CT compares reasonably well with dedicated PET/CT for evaluation of indeterminate pulmonary lesions and staging of pulmonary malignancies and may be of some value when d‐PET/CT is not readily available.
Comparison of intra‐arterial digital subtraction angiography using carbon dioxide by ‘home made’ delivery system and conventional iodinated contrast media in the evaluation of peripheral arterial occlusive disease of the lower limbs
Authors: Madhusudhan KS , Sharma S , Srivastava DN , Thulkar S , Mehta SN , Prasad G , Seenu V , Agarwal S
Published: April 2009

To prospectively compare the feasibility, safety and diagnostic role of carbon dioxide (CO2) digital subtraction angiography (DSA) using a ‘home made’ delivery system with iodinated contrast medium (ICM) DSA in the evaluation of peripheral arterial occlusive diseases (PAOD) of lower limbs. Twenty‐one patients (27 limbs; all men; mean age, 47.6 years) who presented with PAOD of lower limbs underwent DSA using both intra‐arterial CO2 and ICM. Conventional ICM DSA was performed first and used as gold standard. Carbon dioxide was then injected by hand using a locally improvised home made plastic bag delivery system. Patient tolerance was assessed subjectively. Arteries from aortic bifurcation to the ankle were independently evaluated by two radiologists and graded for stenosis using a five‐point scale. For each patient, the quality of CO2 DSA images were compared with the corresponding images of ICM DSA and an overall grade of ‘good’, ‘acceptable’ or ‘poor’ was assigned. Cohen’s kappa coefficient was used to determine inter‐observer agreement. Carbon dioxide opacified 86.2% (188/195) of major arteries and depicted stenosis adequately in 84.5% (191/226) of arterial segments. A good or acceptable image quality of CO2 DSA was obtained in over 95% of patients. Infrapopliteal arteries were inadequately visualized. Mild pain was seen in six (28.6%) patients with both contrast agents; one patient developed severe pain during CO2 DSA. Inter‐observer agreement was good (k > 0.75) at 70% of the segments. Administration of CO2 into lower limb arteries is well tolerated. Carbon dioxide DSA using the locally improvised home made delivery system is a feasible and safe alternative to ICM DSA in the evaluation of PAOD. It provides adequate imaging of arteries of lower extremities except infrapopliteal segments.
Investigation of acute lower gastrointestinal bleeding with 16‐ and 64‐slice multidetector CT†
Authors: Lee S , Welman CJ , Ramsay D
Published: April 2009

We evaluated the usefulness of 16‐ and 64‐slice multidetector CT (MDCT) in the detection of a bleeding site in acute lower gastrointestinal tract (GIT) haemorrhage by conducting a retrospective study of cases of presumed acute lower GIT haemorrhage imaged with CT in two teaching hospitals in an 11‐month period. The patients underwent contrast enhanced CT using either a 16 or 64 MDCT. No oral contrast was used. One hundred milliliters of non‐ionic intravenous contrast agent was injected at 4.5 mL/s, followed by a 60 mL saline flush at 4 mL/s through a dual head injector. Images were acquired in arterial phase with or without non‐contrast and portal phase imaging with 16 × 1.5 mm or 64 × 0.625 mm collimation. Active bleeding was diagnosed by the presence of iodinated contrast extravasation into the bowel lumen on arterial phase images with attenuation greater than and distinct from the normal mucosal enhancement or focal pooling of increased attenuation contrast material within a bowel segment on portal‐venous images. Further management and final diagnosis was recorded. Fourteen patients and 15 studies were reviewed. CT detected and localized a presumed bleeding site or potential causative pathology in 12 (80%) of the patients. Seven of these were supported by other investigations or surgery, while five were not demonstrated by other modalities. Eight patients had mesenteric angiography, of which only four corroborated the site of bleeding. CT did not detect the bleeding site in three patients, of which two required further investigation and definitive treatment. We propose that MDCT serves a useful role as the initial rapid investigation to triage patients presenting with lower GIT bleeding for further investigation and management.
Screening for breast cancer with MRI: recent experience from the Australian Capital Territory
Authors: Price J , Chen SW
Published: April 2009

The American Cancer Society now recommends annual MRI screening for women at 20–25% or greater lifetime risk of breast cancer. The role of MRI screening in other risk subgroups is unproved because of insufficient data. Our study comprised 209 breast MRI scans carried out in 171 asymptomatic patients (age range 22–67 years, mean 46 years), referred between January 2005 and June 2008. Targeted ultrasound was carried out in 32 episodes (15%) and biopsies were taken in 23 patients (13%). In four patients, MR‐guided procedures were required to establish a diagnosis, two using hook‐wire localization and two by means of vacuum‐assisted biopsy. Seven cancers were detected by MRI in the 171 patients, with a yield of 4.1%. Only one of the seven cancers was also shown by x‐ray mammography. Four patients had invasive ductal cancer (all axillary node negative) and three had high‐grade ductal carcinoma in situ or pleomorphic lobular carcinoma in situ. The three women with in situ disease were all potentially high risk, based on the National Breast and Ovarian Cancer Centre (NBOCC) criteria. Three women with invasive breast cancer were at only average risk based on NBOCC criteria, but two of these had extremely dense breasts. A fourth patient, found to have multifocal invasive cancer, had a personal history of contralateral breast cancer, but no relevant family history. Our findings suggest that breast MRI could be used to screen a larger Australian population at increased risk of developing breast cancer.
Use of radiotherapy to treat life‐threatening Kasabach–Merritt syndrome
Authors: Leong E , Bydder S
Published: April 2009

Kasabach–Merritt syndrome involves thrombocytopenia, which is usually severe, in association with haemangiomata. We describe two newborn infants who developed life‐threatening Kasabach–Merritt syndrome but who were successfully treated. Both had failed to respond adequately to corticosteroids and α‐interferon. They subsequently received emergency radiotherapy. Both patients had an improvement in their platelet counts. The first infant’s haemangioma gradually faded during the first 3 years of life, whereas the second infant’s haemangioma had resolved 2 months after radiotherapy. No significant late effects of the radiotherapy have been noted at the 8 and 5 years follow up respectively. Radiotherapy remains an important treatment method in Kasabach–Merritt syndrome when patients fail to respond to other treatments.
Dosimetric comparison of intensity modulated radiotherapy techniques and standard wedged tangents for whole breast radiotherapy*
Authors: Fong Andrew , Bromley Regina , Beat Mardi , Vien Din , Dineley Jude , Morgan Graeme
Published: April 2009

Prior to introducing intensity modulated radiotherapy (IMRT) for whole breast radiotherapy (WBRT) into our department we undertook a comparison of the dose parameters of several IMRT techniques and standard wedged tangents (SWT). Our aim was to improve the dose distribution to the breast and to decrease the dose to organs at risk (OAR): heart, lung and contralateral breast (Contra Br). Treatment plans for 20 women (10 right‐sided and 10 left‐sided) previously treated with SWT for WBRT were used to compare (a) SWT; (b) electronic compensators IMRT (E‐IMRT); (c) tangential beam IMRT (T‐IMRT); (d) coplanar multi‐field IMRT (CP‐IMRT); and (e) non‐coplanar multi‐field IMRT (NCP‐IMRT). Plans for the breast were compared for (i) dose homogeneity (DH); (ii) conformity index (CI); (iii) mean dose; (iv) maximum dose; (v) minimum dose; and dose to OAR were calculated (vi) heart; (vii) lung and (viii) Contra Br. Compared with SWT, all plans except CP‐IMRT gave improvement in at least two of the seven parameters evaluated. T‐IMRT and NCP‐IMRT resulted in significant improvement in all parameters except DH and both gave significant reduction in doses to OAR. As on initial evaluation NCP‐IMRT is likely to be too time consuming to introduce on a large scale, T‐IMRT is the preferred technique for WBRT for use in our department.
Inter‐observer variability of clinical target volume delineation for bladder cancer using CT and cone beam CT
Authors: Foroudi F , Haworth A , Pangehel A , Wong J , Roxby P , Duchesne G , Williams S , Tai KH
Published: April 2009

To compare the image quality of cone beam CT (CBCT) with that of planning CT (pCT) scan, and quantify inter‐observer differences in therapeutic indices based on these scans prior to the introduction of an adaptive radiation therapy protocol for bladder cancer. Four consecutive patients were selected with muscle invasive bladder cancer receiving radical dose radiation therapy. Four radiation oncologists specializing in genitourinary malignancies contoured the clinical target volume (CTV) and rectum on both a pCT and a randomly chosen CBCT of the same patient. A conformity index (CI) for CTV and the rectum was determined for both pCT and CBCT. The maximal lateral, anterior, posterior, cranial and caudal extensions of the CTV for both CT and CBCT were determined for each observer. Variation in volumes of both the CTV and rectum for both pCT and were also compared using Varian Eclipse planning software (Varian Medical Systems, Palo Alto, CA, USA). Using pCT the mean CI for the CTV was 0.79; using CBCT the mean CI for the CTV was 0.75. For the rectum, the mean CI for using CT was 0.80 and for CBCT was 0.74. Greatest variation on CBCT CTV contours was seen in the supero‐inferior direction with variation up to 2.1 cm between different radiation oncologists. With the variation in CI for pCT and CBCT of the CTV and rectum (0.04 and 0.06 respectively), CBCT is not significantly inferior to the pCT in terms of inter‐observer contouring variability.
Implementation of daily image‐guided radiation therapy using an in‐room CT scanner for prostate cancer isocentre localization
Authors: Knight K , Touma N , Zhu L , Duchesne GM , Cox J
Published: April 2009

The Tattersall’s Cancer Centre has been performing image‐guided radiation therapy (IGRT) using an in‐room CT on rails since 2003 to verify accurate patient setup position (relative to bony anatomy) immediately prior to treatment delivery for prostate cancer patients. While the concept of online correction for bony anatomy is well established, the use of an in‐room CT scanner also enables the collection and offline analysis of soft tissue volumetric data. Although initially IGRT was implemented under a research protocol, in‐room CT verification has continued to be used to measure and correct for patient setup variations for all patients undergoing intensity modulated radiation therapy (IMRT) treatments. The present paper outlines the protocol that was used to implement IGRT using an in‐room CT scanner at the Tattersall’s Cancer Centre. Online corrections that minimize patient setup uncertainties allow confidence in delivering dose escalation as well as decreasing the margins required around the target volume. With improvements in auto‐contouring tools, IGRT will also have the ability to measure and correct for variations in target and critical structure positioning online, rather than the current offline methods utilized.
Recurrent malignant pilomatrixoma invading the cranial cavity: Improved local control with adjuvant radiation
Authors: Aherne NJ , Fitzpatrick DA , Gibbons D , Collins CD , Armstrong JG
Published: April 2009

We report the case of a 41‐year‐old mentally retarded male with recurrent pilomatrix carcinoma of the occipital region which invaded the occipital bone, left cerebellum and left temporal lobe. At his initial presentation the patient had a craniotomy and subtotal excision of the lesion with positive margins. He received no adjuvant therapy. After an early intracranial recurrence he had subtotal debulking and was referred for external beam radiotherapy. At 27 months follow‐up after adjuvant external beam radiotherapy the intracranial component has not progressed and the patient remains clinically well.
Isolation, characterization and chromosome locations of polymorphic black‐billed magpie Pica pica (Corvidae, AVES) microsatellite loci
Authors: MARTÍN‐GÁLVEZ DAVID , DAWSON DEBORAH A. , HORSBURGH GAVIN J. , BURKE TERRY
Published: April 2009

One‐hundred and two unique loci were isolated from a microsatellite‐enriched black‐billed magpie Pica pica genomic library. Sixteen of these new loci, along with 148 existing microsatellite passerine loci, were tested for polymorphism in four unrelated black‐billed magpies. We identified a total of 43 unique polymorphic loci (10 and 33 respectively) that we characterized in 24 unrelated individuals from a population in Guadix, Spain. The putative chromosomal locations of loci polymorphic in black‐billed magpie were assigned based on the location of their orthologues in the assembled zebra finch and chicken genomes.
Highly polymorphic microsatellite loci from the giant mottled eel (Anguilla marmorata)
Authors: XIAO‐LING GONG , SHENG‐JIE REN , SHU‐QIANG CHEN , ZHI‐YING JIA
Published: April 2009

Eighteen polymorphic microsatellite loci from the giant mottled eel (Anguilla marmorata) were identified and their characteristics were described. These markers were tested in two wild populations from China (n = 20) and Australia (n = 20) respectively. The number of alleles ranged from 9 to 14 with an average of 11.28 per locus. The mean expected heterozygosity (HE) was 0.8696 in the population from China, 0.8823 in the population from Australia. No locus deviates significantly from Hardy–Weinberg proportions (P < 0.05).
Electrophysiological evaluation and visual outcome in patients with central retinal vein occlusion, primary open‐angle glaucoma and neovascular glaucoma
Authors: Wittström Elisabeth , Ponjavic Vesna , Lövestam‐Adrian Monica , Larsson Jörgen , Andréasson Sten
Published: April 2009

Purpose:  To evaluate patients with central retinal vein occlusion (CRVO) and neovascular glaucoma (NVG) using electrophysiology in order to gain better understanding of visual outcome and risk factors, such as previously diagnosed primary open‐angle glaucoma (POAG).

Methods:  Eighty‐three patients (83 eyes) initially presenting with CRVO and examined with full‐field electroretinography (ERG) within 3 months of the thrombotic event were analysed retrospectively regarding treatment, risk factors and visual outcome. In addition, 30 patients initially presenting with NVG caused by CRVO were also investigated regarding risk factors using electrophysiology in order to determine the cause of their visual impairment.

Results:  Nineteen (23%) of the 83 patients initially presenting with CRVO had been diagnosed previously with POAG. Ninety‐five per cent (18/19) of all the patients with previously diagnosed glaucoma developed ischaemic CRVO. Thirty‐four per cent of the patients initially presenting with CRVO (28/83) developed NVG. Sixty‐eight per cent (13/19) of the patients with previous glaucoma developed NVG, compared to 23% (15/64) of the patients without previous POAG. In the patients who initially presented with NVG, full‐field ERG demonstrated a remaining retinal function of both cones and rods, indicating that the main cause of visual impairment is ischaemia of the ganglion cell layer.

Conclusion:  Glaucoma is a significant risk factor for developing ischaemic CRVO and subsequent NVG. The presence of POAG in CRVO worsens visual outcome. NVG is associated with preserved photoreceptor function, thus indicating ischaemia of the ganglion cell layer as the primary cause of visual impairment. This emphasizes the importance of prompt treatment of ischaemia and elevated intraocular pressure in these patients.
Quantifying the effect of intraocular pressure reduction on the occurrence of glaucoma
Authors: Peeters Andrea , Webers Carroll A. B. , Prins Martin H. , Zeegers Maurice P. , Hendrikse Fred , Schouten Jan S. A. G.
Published: April 2009

Purpose:  To estimate the effect of reducing intraocular pressure (IOP) on: (i) the incidence of primary open‐angle glaucoma (POAG) in patients with ocular hypertension (OH), and (ii) the progression of glaucoma.

Methods:  A meta‐analysis of relevant randomized controlled trials was conducted. A literature search was performed to identify trials with: a randomized comparison of IOP‐lowering intervention versus placebo or no treatment; visual field loss or optic disc changes as outcome; and follow‐up >6 months. A pooled relative risk (RR) was calculated by a random effects model. Risk reduction of glaucoma conversion per mmHg of IOP reduction was quantified in a meta‐regression model.

Results:  We identified nine OH and one POAG trials. A meta‐analysis of OH trials gives a pooled RR of 0.61 [95% confidence interval (CI) 0.45–0.83]. A meta‐regression shows a decrease of the RR of glaucoma conversion by 14% with each mmHg extra IOP reduction (P = 0.045). No meta‐analysis of POAG trials was performed because only one study has been identified.

Conclusion:  There is sufficient evidence that OH therapy reduces the risk of conversion to glaucoma. This risk reduction increases with greater IOP reduction.
Comparative anatomical and micromorphological studies on Teucrium creticum and Teucrium orientale var. orientale (T. sect. Teucrium, Lamiaceae)
Authors: Dinç Muhittin , Doğu Süleyman , Bilgili Bilgehan , Duran Ahmet
Published: April 2009

Teucrium creticum L. and T. orientale L. var. orientale are two related taxa in Teucrium sect. Teucrium. In this study, the value of anatomical and micromorphological characters for distinguishing between these two taxa is analysed. Transverse sections of the stem, as well as both transverse and surface sections of the leaves were examined anatomically. According to the data obtained, collenchyma and sclerenchyma do grow more in T. creticum than in T. orientale var. orientale. The leaves of T. creticum are hypostomatic and have a characteristic hypodermis, which is under the upper epidermis, as well as abundant spherocrystals in the upper epidermis. The leaves of T. orientale var. orientale are amphistomatic, yet no spherocristals exists in epidermal cells and the hypodermis is absent. The results obtained from studies carried out under scanning electron microscope (SEM) shows that the nutlet micromorphology varies between the two taxa. In both taxa, the nutlet surfaces are reticulate and glandular. Eglandular hairs do occur. However, in T. orientale var. orientale, 20–60 μm long eglandular hairs with scabrid surface occur only along the margins of the nutlets, whereas the ¾ dorsal sides of the nutlets in T. creticum are all covered with 90–500 μm long, smooth‐surfaced hairs. Additionally, while the glandular hairs on the nutlets of T. creticum are subsessile, those on the nutlets of T. orientale var. orientale are capitate and distinctly stalked.
Astragalus sect. Trachycercis (Fabaceae) in Iran
Authors: Ranjbar Massoud
Published: April 2009

A diagnostic key, and new data are provided for seven species of Astragalus sect. Trachycercis, which occur within the area covered by the Flora of Iran. Astragalus brevipedunculatus Ranjbar is described as new, and A. armeniacus Boiss. is reported as new for the flora of Iran. The micromorphology of the seed coat surface of ten Astragalus taxa has been studied by SEM. Considerably different types of sculpturing at species level and similarities between related taxa were observed. In addition, differences between A. sect. Trachycercis and the closely related sections A. sect. Erioceras and A. sect. Wettsteiniana are discussed. Astragalus durandianus, A. pseudoshebarensis and A. shebarensis, which all have strongly inflated pods, are transferred from A. sect. Erioceras to A. sect. Wettsteiniana. Astragalus brevipedunculatus sp. nov., described from a small region near Aras River in Iran, is the only geographically isolated species of the section. Members of the section prefer habitats from coastal dune climates of the Azarbaijan Sharqi Province to the Armenian and Azarbaijan frontiers, although possibly also growing in the adjacent southern parts of Armenia and Azarbaijan. Astragalus brevipedunculatus sp. nov. is the only species of the section in Iran and neighboring countries that has few pairs of leaflets and is completely glabrous. The new species should be considered as a ‘Critically Endangered’ (CR) following the IUCN criteria. A distribution map for A. brevipedunculatus and A. armeniacus is presented.
Chromosome numbers of some species of Salvia (Lamiaceae) from the Sichuan Province, China
Authors: Yang Zaijun , Zhang Li , Zhao Hongxia , Yang Ruiwu , Ding Chunbang , Zhou Yonghong , Wan Deguang
Published: April 2009

The present study reports the chromosome number of 12 accessions belonging to 10 species of Salvia from the Sichuan Province in China. Most accessions have the chromosome number 2n=2x=16. However, three species (S. evansiana, S. przewalskii and S. brevilabra) are tetraploid with a chromosome number of 2n=4x=32. A B‐chromosome was observed in S. tricuspis. The basic chromosome number x=8 was inferred for all accessions studied. The chromosome number of all the species was determined for the first time, except for S. evansiana, S. przewalskii, S. flava and S. miltiorrhiza. The chromosomes in this genus are mostly small (0.46–2.94 μm). The small size of the chromosomes, together with their unclear centromeres, has hampered a detailed karyotype analysis.
New empirical formula for neutron dose level at the maze entrance of 15 MV medical accelerator facilities
Authors: Kim Hong‐Suk , Jang Ki‐Won , Park Youn‐Hwan , Kwon Jeong‐Wan , Choi Ho‐Sin , Lee Jai‐Ki , Kim Jong‐Kyung
Published: April 2009

An easily applicable empirical formula was derived for use in the assessment of the photoneutron dose at the maze entrance of a 15 MV medical accelerator treatment room. The neutron dose equivalent rates around the Varian medical accelerator head calculated with the Monte Carlo code MCNPX were used as the source term in producing the base data. The dose equivalents were validated by measurements with bubble detectors. Irradiation geometry conditions expected to yield higher neutron dose rates in the maze were selected: a irradiation field, gantry rotation plane parallel to the maze walls, and the photon beams directed to the opposite wall to the maze entrance. The neutron dose equivalents at the maze entrance were computed for 697 arbitrary single‐bend maze configurations by extending the Monte Carlo calculations down to the maze entrance. Then, the empirical formula was derived by a multiple regression fit to the neutron dose equivalents at the maze entrance for all the different maze configurations. The goodness of the empirical formula was evaluated by applying it to seven operating medical accelerators of different makes. When the source terms were fixed, the neutron doses estimated from the authors’ formula agreed better with the corresponding MCNPX simulations than the results of the Kersey method. In addition, compared with the Wu‐McGinley formula, the authors’ formula provided better estimates for the mazes with length longer than 8.5 m. There are, however, discrepancies between the measured dose rates and the estimated values from the authors’ formula, particularly for the machines other than a Varian model. Further efforts are needed to characterize the neutron field at the maze entrance to reduce the discrepancies. Furthermore, neutron source terms for the machines other than a Varian model should be simulated or measured and incorporated into the formula for accurate extended application to a variety of models.
The energy dependence and dose response of a commercial optically stimulated luminescent detector for kilovoltage photon, megavoltage photon, and electron, proton, and carbon beams
Authors: Reft Chester S.
Published: April 2009

Optically stimulated luminescent detectors, which are widely used in radiation protection, offer a number of potential advantages for application in radiation therapy dosimetry. Their introduction into this field has been somewhat hampered by the lack of information on their radiation response in megavoltage beams. Here the response of a commercially available optically stimulated luminescent detector (OSLD) is determined as a function of energy, absorbed dose to water, and linear energy transfer (LET). The detector response was measured as a function of energy for absorbed doses from 0.5 to 4.0 Gy over the following ranges: 125 kVp to18 MV for photons, 6–20 MeV for electrons, 50–250 MeV for protons, and 290 MeV/u for the carbon ions. For the low LET beams, the response of the detector was linear up to 2 Gy with supralinearity occurring at higher absorbed doses. For the kilovoltage photons, the detector response relative to 6 MV increased with decreasing energy due to the higher atomic number of aluminum oxide (11.2) relative to water (7.4). For the megavoltage photons and electrons, the response was independent of energy. The response for protons was also independent of energy, but it was about 6% higher than its response to 6 MV photons. For the carbon ions, the dose response was linear for a given LET from 0.5 to 4.0 Gy, and no supralinearity was observed. However, it did exhibit LET dependence on the response relative to 6 MV photons decreasing from 1.02 at to 0.41 at . These results provide additional information on the dosimetric properties for this particular OSL detector and also demonstrate the potential for their use in photon, electron, and proton radiotherapy dosimetry with a more limited use in high LET radiotherapy dosimetry.
Quantitative imaging of element composition and mass fraction using dual‐energy CT: Three‐material decomposition
Authors: Liu Xin , Yu Lifeng , Primak Andrew N. , McCollough Cynthia H.
Published: April 2009

In principle, dual‐energy CT can only accurately decompose a mixture into two materials. To decompose a mixture into three constitute materials using dual‐energy CT measurements, a third criteria must be provided to solve for three unknowns with only two spectral measurements. One solution is to assume that the sum of the volumes of three constituent materials is equivalent to the volume of the mixture (i.e., volume conservation), but this is not always true. A more generalized solution is to use the principle of mass conservation, which assumes that the sum of the masses of the three constituent materials is equivalent to the mass of the mixture. In this article, a mass‐conservation based, three‐material decomposition dual‐energy CT algorithm is described and experimental validation of the accuracy of the technique presented. The results demonstrate that the proposed method can accurately measure elemental concentrations under low noise imaging conditions. Clinically, this may be applied to measure the mass fraction of any chemical element in a three‐material mixture of solutions without the requirement of volume conservation.
Evaluation of a novel 4D in vivo dosimetry system
Authors: Cherpak A. , Ding W. , Hallil A. , Cygler J. E.
Published: April 2009

A prototype of a new 4D in vivo dosimetry system capable of simultaneous real‐time position monitoring and dose measurement has been developed. The radiation positioning system (RADPOS) is controlled by a computer and combines two technologies: MOSFET radiation detector coupled with an electromagnetic positioning device. Special software has been developed that allows sampling position and dose either manually or automatically in user‐defined time intervals. Preliminary tests of the new device include a dosimetric evaluation of the detector in , 6 MV, and 18 MV beams and measurements of spatial position stability and accuracy. In addition, the effect of metals and other materials on the performance of the positioning system has been investigated. Results show that the RADPOS system can measure in‐air dose profiles that agree, on average, within 3%–5% of diode measurements for the energies tested. The response of the detector is isotropic within 1.6% (1 SD) with a maximum deviation of ±4.0% over 360°. The maximum variation in the calibration coefficient over field sizes from to was 2.3% for RADPOS probe with the high sensitivity MOSFET and 4.6% for the probe with the standard sensitivity MOSFET. Of the materials tested, only aluminum, lead, and brass caused shifts in the RADPOS read position. The magnitude of the shift varied between materials and size of the material sample. Nonmagnetic stainless steel (Grade 304) caused a distortion of less than 2 mm when placed within 10 mm of the detector; therefore, it can provide a reasonable alternative to other metals if required. The results of the preliminary tests indicate that the device can be used for in vivo dosimetry in and high‐energy beams from linear accelerators.
Comparison of organ residence time estimation methods for radioimmunotherapy dosimetry and treatment planning—patient studies
Authors: He Bin , Wahl Richard L. , Sgouros George , Du Yong , Jacene Heather , Kasecamp Wayne R. , Flinn Ian , Hammes Richard J. , Bianco Jay , Kahl Brad , Frey Eric C.
Published: April 2009

The estimation of organ residence time is essential for high‐dose myeloablative regimens in radioimmunotherapy (RIT). Frequently, this estimation is based on a series of simple planar scans and planar processing. The authors previously performed a simulation study which demonstrated that the accuracy of this methodology is limited compared to a hybrid planar/SPECT residence time estimation method. In this work the authors applied this hybrid method to data from a clinical trial of high‐dose myeloablative yttrium‐90 ibritumomab tiuxetan therapy. Image data acquired from 18 patients were comprised of planar scans at five time points ranging from 1 to 144 h postinjection and abdominal and thoracic SPECT/CT scans obtained at 24 h postinjection. The simple planar processing method used in this work was based on the geometric mean method with energy window based scatter compensation. No explicit background subtraction nor object or source thickness corrections were performed. The SPECT projections were reconstructed using iterative reconstruction with compensations for attenuation, scatter, and full collimator‐detector response. Large differences were observed when residence times were estimated using the simple planar method compared to the hybrid method. The differences were not constant but varied in magnitude and sign. For the dose‐limiting organ (liver), the average difference was −18% and variation in the difference was 19%, similar to the differences observed in a previously reported simulation study. The authors also looked at the relationship between the weight of the patient and the liver residence time and found that there was no meaningful correlation for either method. This indicates that weight would not be an adequate proxy for an experimental estimate of residence time when choosing the activity to administer for therapy. The authors conclude that methods such as the simple planar method used here are inadequate for RIT treatment planning. More sophisticated methods, such as the hybrid SPECT/planar method investigated here, are likely to be better predictors of organ dose and, as a result, organ toxicities.
Operation logic and functionality of automatic dose rate and image quality control of conventional fluoroscopy
Authors: Lin Pei‐Jan Paul
Published: April 2009

New generation of fluoroscopic imaging systems is equipped with spectral shaping filters complemented with sophisticated automatic dose rate and image quality control logic called “fluoroscopy curve” or “trajectory.” Such fluoroscopy curves were implemented first on cardiovascular angiographic imaging systems and are now available on conventional fluoroscopy equipment. This study aims to investigate the control logic operations under the fluoroscopy mode and acquisition mode (equivalent to the legacy spot filming) of a conventional fluoroscopy system typically installed for upper‐lower gastrointestinal examinations, interventional endoscopy laboratories, gastrointestinal laboratory, and pain clinics.
Pediatric organ dose measurements in axial and helical multislice CT
Authors: McDermott Alanna , White R. Allen , Mc‐Nitt‐Gray Mike , Angel Erin , Cody Dianna
Published: April 2009

An anthropomorphic pediatric phantom (5‐yr‐old equivalent) was used to determine organ doses at specific surface and internal locations resulting from computed tomography (CT) scans. This phantom contains four different tissue‐equivalent materials: Soft tissue, bone, brain, and lung. It was imaged on a 64‐channel CT scanner with three head protocols (one contiguous axial scan and two helical scans [ and 0.984]) and four chest protocols (one contiguous axial scan and three helical scans [, 0.984, and 1.375]). Effective was kept nearly constant at 200 effective for head and 290 effective for chest protocols. Dose measurements were acquired using thermoluminescent dosimeter powder in capsules placed at locations internal to the phantom and on the phantom surface. The organs of interest were the brain, both eyes, thyroid, sternum, both breasts, and both lungs. The organ dose measurements from helical scans were lower than for contiguous axial scans by 0% to 25% even after adjusting for equivalent effective . There was no significant difference in organ dose values between the 0.516 and 0.984 pitch values for both head and chest scans. The chest organ dose measurements obtained at a pitch of 1.375 were significantly higher than the dose values obtained at the other helical pitches used for chest scans . This difference was attributed to the automatic selection of the large focal spot due to a higher tube current value. These findings suggest that there may be a previously unsuspected radiation dose benefit associated with the use of helical scan mode during computed tomography scanning.
Patient‐specific finite element modeling of respiratory lung motion using 4D CT image data
Authors: Werner René , Ehrhardt Jan , Schmidt Rainer , Handels Heinz
Published: April 2009

Development and optimization of methods for adequately accounting for respiratory motion in radiation therapy of thoracic tumors require detailed knowledge of respiratory dynamics and its impact on corresponding dose distributions. Thus, computer aided modeling and simulation of respiratory motion have become increasingly important. In this article a biophysical approach for modeling respiratory lung motion is described: Major aspects of the process of lung ventilation are formulated as a contact problem of elasticity theory which is solved by finite element methods; lung tissue is assumed to be isotropic, homogeneous, and linearly elastic. A main focus of the article is to assess the impact of biomechanical parameters (values of elastic constants) on the modeling process and to evaluate modeling accuracy. Patient‐specific models are generated based on 4D CT data of 12 lung tumor patients. Simulated motion patterns of inner lung landmarks are compared with corresponding motion patterns observed in the 4D CT data. Mean absolute differences between model‐based predicted landmark motion and corresponding breathing‐induced landmark displacements as observed in the CT data sets are in the order of (end expiration to end inspiration) and (end expiration to midrespiration). Modeling accuracy decreases with increasing tumor size both locally (landmarks close to tumor) and globally (landmarks in other parts of the lung). The impact of the values of the elastic constants appears to be small. Outcomes show that the modeling approach is an adequate strategy in predicting lung dynamics due to lung ventilation. Nevertheless, the decreased prediction quality in cases of large tumors demands further study of the influence of lung tumors on global and local lung elasticity properties.
Stochastic noise characteristics in matrix inversion tomosynthesis (MITS)
Authors: Godfrey Devon J. , McAdams H. P. , Dobbins James T.
Published: April 2009

Matrix inversion tomosynthesis (MITS) uses known imaging geometry and linear systems theory to deterministically separate in‐plane detail from residual tomographic blur in a set of conventional tomosynthesis (“shift‐and‐add”) planes. A previous investigation explored the effect of scan angle (ANG), number of projections , and number of reconstructed planes (NP) on the MITS impulse response and modulation transfer function characteristics, and concluded that , , and is the optimal MITS imaging technique for chest imaging on our prototype tomosynthesis system. This article examines the effect of ANG, , and NP on the MITS exposure‐normalized noise power spectra (ENNPS) and seeks to confirm that the imaging parameters selected previously by an analysis of the MITS impulse response also yield reasonable stochastic properties in MITS reconstructed planes. ENNPS curves were generated for experimentally acquired mean‐subtracted projection images, conventional tomosynthesis planes, and MITS planes with varying combinations of the parameters ANG, , and NP. Image data were collected using a prototype tomosynthesis system, with 11.4 cm acrylic placed near the image receptor to produce lung‐equivalent beam hardening and scattered radiation. Ten identically acquired tomosynthesis data sets (realizations) were collected for each selected technique and used to generate ensemble mean images that were subtracted from individual image realizations prior to noise power spectra (NPS) estimation. NPS curves were normalized to account for differences in entrance exposure (as measured with an ion chamber), yielding estimates of the ENNPS for each technique. Results suggest that mid‐ and high‐frequency noise in MITS planes is fairly equivalent in magnitude to noise in conventional tomosynthesis planes, but low‐frequency noise is amplified in the most anterior and posterior reconstruction planes. Selecting the largest available number of projections does not incur any appreciable additive electronic noise penalty compared to using fewer projections for roughly equivalent cumulative exposure. Stochastic noise is minimized by maximizing and NP but increases with increasing ANG. The noise trend results for NP and ANG are contrary to what would be predicted by simply considering the MITS matrix conditioning and likely result from the interplay between noise correlation and the polarity of the MITS filters. From this study, the authors conclude that the previously determined optimal MITS imaging strategy based on impulse response considerations produces somewhat suboptimal stochastic noise characteristics, but is probably still the best technique for MITS imaging of the chest.
Algorithm and simulation for real‐time positron emission based tumor tracking using a linear fiducial marker
Authors: Churchill Nathan W. , Chamberland Marc , Xu Tong
Published: April 2009

The effectiveness of radiotherapy in cancer treatment remains significantly limited by the accuracy of tumor dose delivery. The ideal solution lies in real‐time localization of patient tumors during therapy; one such method is by tracking implanted low‐activity positron emitters using two pairs of orthogonally placed gamma‐ray detectors. Prior studies have examined multiple point sources, which have potential patient complications during implantation. A linear source geometry is proposed as a less invasive alternative, with potential higher‐precision tracking. A source localization algorithm has been devised using cost‐function minimization of the source position estimate relative to annihilation gamma coincidence lines. The algorithm was tested via Monte Carlo simulation methods using a Geant4 application for emission tomography (GATE) package for a source of length of and width of . The midpoint of the linear marker was located within submillimeter accuracy at 200 coincidence events and the orientation of the source determined with less than 5° angular deviation at 300 events. At an optimal event count of 700, tracking had mean midpoint error of and mean angular deviation of . The source and tracking algorithm may prove effective for future clinical implementation in radiotherapy treatment.
Differences among Monte Carlo codes in the calculations of voxel values for radionuclide targeted therapy and analysis of their impact on absorbed dose evaluations
Authors: Pacilio M. , Lanconelli N. , Lo Meo S. , Betti M. , Montani L. , Torres Aroche L. A. , Coca Pérez M. A.
Published: April 2009

Several updated Monte Carlo (MC) codes are available to perform calculations of voxel values for radionuclide targeted therapy. The aim of this work is to analyze the differences in the calculations obtained by different MC codes and their impact on absorbed dose evaluations performed by voxel dosimetry. Voxel values for monoenergetic sources (electrons and photons) and different radionuclides (, , and ) were calculated. Simulations were performed in soft tissue. Three general‐purpose MC codes were employed for simulating radiation transport: MCNP4C, EGSnrc, and GEANT4. The data published by the MIRD Committee in Pamphlet No. 17, obtained with the EGS4 MC code, were also included in the comparisons. The impact of the differences (in terms of voxel values) among the MC codes was also studied by convolution calculations of the absorbed dose in a volume of interest. For uniform activity distribution of a given radionuclide, dose calculations were performed on spherical and elliptical volumes, varying the mass from 1 to 500 g. For simulations with monochromatic sources, differences for self‐irradiation voxel values were mostly confined within 10% for both photons and electrons, but with electron energy less than 500 keV, the voxel values referred to the first neighbor voxels showed large differences (up to 130%, with respect to EGSnrc) among the updated MC codes. For radionuclide simulations, noticeable differences arose in voxel values, especially in the bremsstrahlung tails, or when a high contribution from electrons with energy of less than 500 keV is involved. In particular, for the updated codes showed a remarkable divergence in the bremsstrahlung region (up to about 90% in terms of voxel values) with respect to the EGS4 code. Further, variations were observed up to about 30%, for small source‐target voxel distances, when low‐energy electrons cover an important part of the emission spectrum of the radionuclide (in our case, for ). For and , the differences among the various codes have a negligible impact (within few percents) on convolution calculations of the absorbed dose; thus either one of the MC programs is suitable to produce voxel values for radionuclide targeted therapy dosimetry. However, if a low‐energy beta‐emitting radionuclide is considered, these differences can affect also dose depositions at small source‐target voxel distances, leading to more conspicuous variations (about 9% for ) when calculating the absorbed dose in the volume of interest.
A novel three‐dimensional image reconstruction method for near‐field coded aperture single photon emission computerized tomography
Authors: Mu Zhiping , Hong Baoming , Li Shimin , Liu Yi‐Hwa
Published: April 2009

Coded aperture imaging for two‐dimensional (2D) planar objects has been investigated extensively in the past, whereas little success has been achieved in imaging 3D objects using this technique. In this article, the authors present a novel method of 3D single photon emission computerized tomography (SPECT) reconstruction for near‐field coded aperture imaging. Multiangular coded aperture projections are acquired and a stack of 2D images is reconstructed separately from each of the projections. Secondary projections are subsequently generated from the reconstructed image stacks based on the geometry of parallel‐hole collimation and the variable magnification of near‐field coded aperture imaging. Sinograms of cross‐sectional slices of 3D objects are assembled from the secondary projections, and the ordered subset expectation and maximization algorithm is employed to reconstruct the cross‐sectional image slices from the sinograms. Experiments were conducted using a customized capillary tube phantom and a micro hot rod phantom. Imaged at approximately from the detector, hot rods in the phantom with diameters as small as could be discerned in the reconstructed SPECT images. These results have demonstrated the feasibility of the authors’ 3D coded aperture image reconstruction algorithm for SPECT, representing an important step in their effort to develop a high sensitivity and high resolution SPECT imaging system.