ABSTRACT
PURPOSE: This study was performed to suggest reference line-pair values of panoramic images with clinically desirable qualities using an arch-form phantom stand. MATERIALS AND METHODS: The line-pair test phantom was chosen. A real skull model was selected for setting the arch-form model of the phantom stand. The phantom stand had slits in four regions (incisor, premolar, molar, TMJ). Four raw images of the test phantom in each region and one raw image of the real skull were converted into 50 test phantom images and 50 skull phantom images with various line-pair values. 50 post-processed real skull phantom images were divided into 4 groups and were randomly submitted to 14 evaluators. Image quality was graded on a 4 point scale (1. good, 2. normal, 3. poor but interpretable, and 4. not interpretable). The reference line pair was determined as the first line-pair value scored less than 2 points. RESULT: The mean scores tended to decrease as the line-pair values increased. The reference line-pair values were 3.19 LP/mm in the incisor, 2.32 LP/mm in the premolar and TMJ, and 1.88 LP/mm in the molar region. CONCLUSION: Image quality evaluation methods and criteria should be able to assess various regions considering the characteristics of panoramic systems. This study suggested overall and regional reference line-pair values and established a set of standard values for them.
Subject(s)
Bicuspid , Incisor , Molar , Phantoms, Imaging , Radiography, Panoramic , Skull , Temporomandibular JointABSTRACT
ObjectiveTo compare detection rate of pulmonary nodules and the radiation doses of digital tomosynthesis (DTS) and MSCT chest scanning by using the anthropomorphic chest phantom which containsthermoluminescent dosimeters( TLD ) and simulated pulmonary nodules.Methods The radiation doses of DTS and MSCT scanning were measured by using the anthropomorphic chest phantom which contains 45 TLD and simulated pulmonary nodules.The radiation doses of najor organs were converted into effective dose ( ED ). Three radiologists of different clinical experiences independently reviewed and recorded the density,diameter and position of pulmonary nodules.The sensitivity of nodule detection by DTS and MSCT were compared by Fisher exact test and Chi-square test. The paired t test was conducted to analyze the dose levels of DTS and MSCT.ResultsThe sensitivity of detection nodule by DTS and MSCT were 66.7％ (30/45) and 91.1％ (41/45) respectively.Statistically significant difference between the two examinations existed ( x2 =8.073,P ＜ 0.05).The sensitivity of detection - 650 HU ground glass opacity pulmonary nodule by MSCT and DTS were 93.3％ (14/15) and 73.3％ (11/15) respectively.There was no significant difference between DTS and MSCT ( P ＞ 0.05 ).The sensitivity of detection - 800 HU ground glass opacity nodule and ground glass opacity nodule (d ＜ 8 mm) by DTS were 33.3％ (5/15) and 16.7％ (2/12) respectively,which were lower than those by CT[80.0％ (12/15) and 66.7％ (8/12)].The radiation doses of DTS for various organs in the chest were lower than those of CT. Statistical significant difference between DTS and MSCT existed ( lung t =19.69,thoracic vertebral t =30.01,heart t =16.33,liver t =5.06,breast t =9.43,thyroid gland t =8.05 ;P ＜ 0.05).The effective doses of the DTS and MSCT were 0.65 and 7.71 mSv respectively.ConclusionsThere is no difference between the DTS and MSCT in the detection rate of -650 HU ground glass opacity nodule.For detecting the ground glass opacity nodule ( - 800 HU) and ground glass opacity nodule (d ＜ 8 mm),MSCT is superior to DTS. However,the radiation dosage of DTS is 8.41％ of the MSCT scanning.
ABSTRACT
Objectlve To demonstrate the feasibility of three-dimensional(3D)spin-lattice relaxation time in the rotating frame(T1ρ)-weighted imaging of porcine patellar cartilage in vitro at 7.0 T and the measurement of T1ρ of agarose phantom and patellar cartilage.Methods All the MR Imaging experiments were performed on a 7.0 T Varian scanner using a 6.0-cm-diameter quadrature birdcage RF coil tuned to 300 MHz.A 3D spin-echo sequence with a self.compensating spin-lock pulse cluster was used to acquire 3D-T1ρ-weighted images.The time of spin-locking(TSL)was from 0 to 50 ms with an interval of 10 ms.Spin-lock power wag 440 Hz.3D-T1ρweighted imaging was done three times for 6 phantoms (concentration 1%t0 6%),as well as once for 8 porcine patellar cartilages in order to assess the reproducibility of this technique.Signal-to-noise ratio(SNR)was measured on the acquired images of both phantoms and patellar cartilages,which were tested for significance using Two-way ANOVA.The images were processed on Vnmr J workstation using home-built processing software to construct 3 D T1ρ maps.T1ρ values were calculated within manually drawn regions-of-interest(ROI),and differences between groups were tested for significance using analysis of variance(One-way ANOVA).Results T1ρ -weighted images with a shorter TSL had a higher SNR value,which measured between 48±8 and 95±8 in the global cartilage.Cartilage images had a higher SNR(TSL＜30 ms)compared to agarose phantoms and a lower SNR(TSL ＞30 ms)only compared to l%agarose phantorm T1ρ relaxation times in agarose phantoms increased as agarose concentrations decreased in global regions.The CV of T1ρ in agarose phantoms was less than 10%.Global and regional analyses of patellar cartilage T1ρ were 68.9±6.3 ms,80.7±12.8 ms,65.7±7.0 ms,82.4±7.7 ms,and 69.7±6.4 ms in the global cartilage,the superficial layer,the transitional layer,the deep layer,and the calcified layer,respectively.T1ρ in the superficial and deep layer was significantly higher than in the transitional,calcified layer and global cartilage(F=6.436,P＜0.05).Conclusions The present study demonstrates the feasibihty of 3D-T1ρ-weighted imaging of porcine patellar cartilage at 7.0 T with hish image quality.T1ρ maps can be used to quantify the laminar structures in 3D-T1ρ-weighted images of articular cartilage,which pave the way to evaluate early osteoarthritis and cartilage regeneration.