Proton Density-weighted MRI Research Articles

Utility of three-dimensional proton density-weighted sequence MRI in knee for the assessment of Anterolateral complex in Anterior cruciate ligament injury.

To assess the proportion and pattern of injury of the anterolateral ligament (ALL) and the Kaplan fibre (KF) complex in knees with anterior cruciate ligament (ACL) injuries on MRI using three-dimensional (3D) proton density (PD) sequences. A total of 88 patients having ACL injury were included in this cross-sectional study. 3D PD sequences were used to assess injury of ALL and the KF complex and were graded on a scale of 0 to 3. MR images were evaluated by two radiologists. Interobserver agreement was determined using Cohen Kappa. Femoral, meniscal, and tibial portions of ALL were visualized in 90.9%, 92%, and 94.3% of the study subjects, respectively. Proximal and distal KF were visualized in 92% and 93.2% of patients, respectively. Injury to ALL and KF was seen in 63.6% and 17% of the patients, respectively. Excellent interobserver agreement was noted for the identification and grading of ALL and KF complex injuries. Oblique reformatted 3DPD MRI reliably detect ALC; however, ALL injury is better characterized than KF injury using this sequence. Given the potential role of anterolateral complex (ALC) in maintaining the rotational stability of the knee, ALC assessment using the 3D PD sequences and their oblique reformatted images should be incorporated as routine review area of the knee MRI, particularly in the setting of ACL tear.

Medial meniscus extrusion is invariably observed and consistent with tibial osteophyte width in elderly populations: The Bunkyo Health Study

We reported that the full-length width of medial tibial osteophytes comprising cartilage and bone parts correlates with medial meniscus extrusion (MME) in early-stage knee osteoarthritis (OA). However, no data exist on the prevalence of MME and its relationship with osteophytes in the elderly population. 1191 elderly individuals (females 57%; 72.9 years old on average) in the Bunkyo Health Study underwent standing plain radiograph and proton density-weighted MRI on knee joints. MRI-detected OA changes were evaluated according to the Whole-Organ Magnetic Resonance Imaging Score. A new method of assessing the cartilage and bone parts of osteophytes was developed using pseudo-coloring images of proton density-weighted fat-suppressed MRI. Most subjects showed Kellgren-Lawrence grade 1 or 2 radiographic medial knee OA (88.1%), MME (98.7%, 3.90 ± 2.01 mm), and medial tibial osteophytes (99.3%, 3.27 ± 1.50 mm). Regarding OA changes, MME was closely associated with the full-length width of medial tibial osteophytes (β = 1.114; 95% CI 1.069–1.159; p < 0.001) in line with osteophyte width (intraclass correlation coefficient, 0.804; 95% CI 0.783–0.823). Our data revealed that MME and medial tibial osteophytes are observed in the elderly and demonstrate that the degree of MME is consistent with the full-length width of medial tibial osteophytes, suggesting that osteophytes might be implicated in MME.

Anterior meniscus extrusion is associated with anterior tibial osteophyte width in knee osteoarthritis – The Bunkyo Health Study

BackgroundIn knee osteoarthritis (OA), medial meniscus extrudes both medially and anteriorly. We reported that full-length width of medial tibial osteophyte, which comprises cartilage and bone parts, is directly associated with medial meniscus extrusion in early-stage knee OA and hypothesized that anterior tibial osteophyte (ATO) is also associated with anterior meniscus extrusion (AME). Thus, we aimed to examine their prevalence and relationship. MethodsElderly subjects (638 females and 507 males; average 72.9 years old) in the Bunkyo Health Study cohort were enrolled. MRI-detected OA changes were evaluated according to the Whole Organ Magnetic Resonance Imaging Score. ATO was evaluated using the method which can assess both cartilage and bone parts of osteophyte by pseudo-coloring images of proton density-weighted fat-suppressed MRI. ResultsMost subjects showed the Kellgren-Lawrence grade 1/2 of the medial knee OA (88.1%), AME (94.3%, 3.7 ​± ​2.2 ​mm), and ATO (99.6%, 4.2 ​± ​1.5 ​mm). Among the OA changes, AME was most closely associated with full-length width of ATO (multivariable β ​= ​0.877, p ​< ​0.001). The area under the receiver operating characteristic curve for determining the presence of AME as evaluated by ATO width was 0.75 (95% confidence interval 0.60–0.84, p ​< ​0.001). The odds ratio for the presence of AME as evaluated by ATO width at 2.9 ​mm was 7.16 (4.23–12.15, p ​< ​0.001, age, gender, BMI, and K-L adjusted). ConclusionsAME and ATO were inevitably observed in the elderly subjects and AME was closely associated with full-length width of ATO. Our study provides the first evidence on the close relationship between AME and ATO in knee OA.

Direct targeting of the ventral intermediate nucleus of the thalamus in deep brain stimulation for essential tremor: a prospective study with comparison to a historical cohort.

The ventral intermediate nucleus of the thalamus (VIM) is an effective target for deep brain stimulation (DBS) to control symptoms related to essential tremor. The VIM is typically targeted using indirect methods, although studies have reported visualization of the VIM on proton density-weighted MRI. This study compares the outcomes between patients who underwent VIM DBS with direct and indirect targeting. Between August 2013 and December 2019, 230 patients underwent VIM DBS at the senior author's institution. Of these patients, 92 had direct targeting (direct visualization on proton density 3-T MRI). The remaining 138 patients had indirect targeting (relative to the third ventricle and anterior commissure-posterior commissure line). Coordinates of electrodes placed with direct targeting were significantly more lateral (p < 0.001) and anterior (p < 0.001) than those placed with indirect targeting. The optimal stimulation amplitude for devices measured in voltage was lower for those who underwent direct targeting than for those who underwent indirect targeting (p < 0.001). Patients undergoing direct targeting had a greater improvement only in their Quality of Life in Essential Tremor Questionnaire hobby score versus those undergoing indirect targeting (p = 0.04). The direct targeting group had substantially more symptomatic hemorrhages than the indirect targeting group (p = 0.04). All patients who experienced a postoperative hemorrhage after DBS recovered without intervention. Patients who underwent direct VIM targeting for DBS treatment of essential tremor had similar clinical outcomes to those who underwent indirect targeting. Direct VIM targeting is safe and effective.

T2-weighted spoiled gradient echo sequence (MERGE): A different perspective on the forensic age estimation

Introduction Age estimation methods using MRI are dependent on staging systems used in T1, T2 and fast spin-echo proton density-weighted sequences. The staging system created by Dedouit [1] from images obtained by fast spin-echo proton density-weighted MRI sequences depends on the assessment of horizontal cartilage hyperintensity. Images obtained by this method, detecting 1.5 mm hyperintensity thickness, and in some cases, detecting continuity of hyperintensity could be challenging. The purpose of this preliminary study was to investigate the utility of T2-weighted spoiled gradient echo sequence in determining the degree of ossification of epiphyses. Material and methods In this study, fast spin-echo proton density-weighted and MERGE T2-weighted spoiled gradient echo sequences of the knee of 25 patients (10–30 years, 10 female and 15 male) were evaluated using Dedouit et al.’s [1] five-stage method. Results The horizontal cartilages assessed with MERGE exhibited hyperintensity and clearly visible borders ( Fig. 1 ). Stage 2 and 3 were easily distinguishable and the epiphyseal scar line observed in stage 5 (complete fusion) was easily observed in contrast to the fast spin-echo proton density-weighted sequence. The hyperintense line that was assessed in fast spin-echo proton density-weighted sequence in stage 3 cases was seen as continuous and intermittent hypointense line in MERGE sequence. It was suggested that substages may be necessary for the distinction of stage 3 and 4. Discussion At present, due to the ethical concerns, non-ionized methods (ultrasound and MRI) are more frequently used in living individuals’ age estimations. MRI assessments in spoiled T2-weighted spoiled gradient echo sequence for age determination may be advantageous in the examination of epiphyseal lines and may produce different options in staging.

The relation of patellofemoral joint alignment and trochlear morphology to superolateral Hoffa’s fat pad edema: the most study

Purpose: The infrapatellar or Hoffa’s fat pad (HFP) is an intracapsular but extrasynovial fat tissue in the knee joint located inferior to the patella and posterior to the patellar tendon. It is highly innervated and may be a source of knee pain. Impingement of HFP between the lateral femoral condyle and the patellar tendon is hypothesized to cause inflammation/edema in the superolateral region of HFP. This impingement may be a result of patellofemoral joint (PFJ) alignment and abnormal trochlear morphology. Previous studies in young individuals have demonstrated conflicting results as to which measures of PFJ alignment and trochlear morphology are related to superolateral HFP edema. More generalized inflammation/edema in HFP is present in older individuals with knee osteoarthritis (OA). The aim of the current study was to assess whether measures of PFJ alignment and trochlear morphology are related to superolateral HFP edema and if superolateral HFP edema is related to knee pain in older individuals with or at risk for knee OA. Methods: The Multicenter Osteoarthritis (MOST) study is a NIH-funded longitudinal cohort study of older individuals with or at risk for knee OA. For the current cross-sectional study we used data from the 60-month study visit where all eligible subjects had their knee MRI assessed for other structural features of knee OA. Signal changes in three areas (superolateral, infrapatellar and intercondylar) of HFP were assessed on sagittal proton density-weighted fat-suppressed MRI images from 0 to 3 (0 = normal, 1 = mild, 2 = moderate, 3 = severe) by two musculoskeletal radiologists and dichotomized into presence (>1) and absence (=0). PFJ alignment (bisect offset and patellar tilt angle) and trochlear morphology (lateral trochlear inclination, sulcus angle and trochlear angle) were assessed on axial MRI images and divided into quintiles. Subjects were also queried about the presence of frequent knee pain (FKP) defined as pain on most days of the last month. We determined the relation of measures of PFJ alignment and trochlear morphology to the presence of superolateral HFP edema using logistic regression, adjusting for age, sex and body mass index. We additionally determined the relation of superolateral HFD edema to FKP using logistic regression, adjusting for age, sex, body mass index, depressive symptoms, catastrophizing and presence of signal changes in the infrapatellar/intercondylar HFP. Results: To date, 433 knees have been assessed for PFJ alignment, trochlear morphology and superolateral HFP edema. Superolateral HFP edema was present in 63 (17.7%) of knees. Compared with knees in the lowest quartile of bisect offset, those in the highest had 6.4 (2.6, 15.7) times the odds of having superolateral HFP edema. Compared with knees in the lowest quartile of trochlear angle, those in the highest had 2.7 (1.2, 6.3) times the odds of having superolateral HFP edema. There was no relation of other PFJ alignment/trochlear morphology measures to superolateral HFP edema. There was also no relation of superolateral HFP edema to FKP. Conclusions: Knees with the greatest lateral displacement of the patella had the greatest odds of superolateral HFP edema. Treatments that attempt to normalize PFJ alignment may help to reduce the prevalence of superolateral HFP edema.Tabled 1Table. Relation of PFJ alignment and trochlear morphology to superolateral HFP edema% Patella lateral to midline (Bisect Offset)Quartile 1Quartile 2Quartile 3Quartile 4Range33.91–52.5952.6–58.1658.17–64.664.61–92.79# of knees108109109108Superolateral HFP edema%≥16.511.113.828.7Adjusted OR* (95% CI)1.0 (reference)1.9 (0.70, 5.0)2.5 (0.95, 6.4)6.4 (2.6, 15.7)Trochlear Morpholgy (Trochlear Angle)Quartile 1Quartile 2Quartile 3Quartile 4 (flat trochlea)Range−5.32–0.940.95–3.553.56–5.835.84–26.57# of knees108109109108Superolateral HFP edema%≥18.313.814.724.3Adjusted OR* (95% CI)1.0 (reference)1.6 (0.65, 3.8)1.6 (0.67, 3.9)2.7 (1.2, 6.3)∗Adjusted for age, sex and BMI Open table in a new tab ∗Adjusted for age, sex and BMI

High-resolution MRI of the vessel wall in patients with symptomatic atherosclerotic stenosis of the middle cerebral artery

Intracranial atherosclerosis is associated with recurrent ischemic stroke. High-resolution MRI (HR MRI) can provide information about atheroma in vivo. We aimed to analyze and compare vascular wall imaging characteristics between patients with symptomatic and asymptomatic atherosclerotic stenosis of the middle cerebral artery (MCA) using 3.0 Tesla HR MRI. The HR MRI protocol included four different scans: black blood T1-weighted, T2-weighted and proton density-weighted MRI, as well as three-dimensional turbo spin echo imaging techniques with multiplanar reconstruction. Plaque characteristics, including location, morphology, and signal intensity, were analyzed in 51 patients (29 symptomatic, 22 asymptomatic) with atherosclerotic stenosis of the middle cerebral artery. The vessel wall area, lumen area, and plaque area (PA) were also calculated and compared between the symptomatic and asymptomatic groups. We found that PA, remodeling index (RI), and positive remodeling (PR) prevalence were significantly greater in the symptomatic group than in the asymptomatic group (PA: p=0.033; RI: p=0.020; PR: p=0.032). Plaque location in the superior aspect of the vessel wall and irregular plaque surface were more frequently observed in the symptomatic group than in the asymptomatic group (superior location: p=0.031; irregular surface: p=0.036). Moreover, multivariate logistic regression identified plaque location on the superior wall as an independent predictor of symptomatic MCA stenosis (odds ratio: 4.471; p=0.039). Therefore, we can conclude that patients with symptomatic atherosclerotic stenosis of the MCA are more likely to have larger plaques, PR, superiorly located plaques, and irregular plaque surface. These characteristics are promising factors for stratifying stroke risk.

Interhemispheric interactions of the human thalamic reticular nucleus.

The thalamic reticular nucleus is an important structure governing the recurrent interactions between the thalamus and cortex that may provide a substrate for unified perception. Despite the importance of the TRN, its activity has been scarcely investigated in vivo in animal models, and never in humans. Here we anatomically identify the human TRN using multiple registered and averaged proton density-weighted structural MRI scans and drive its functional activity with a dual phase-encoded stimulus. We characterize the retinotopic and temporal response properties in the visual sector of the TRN and measured an inhibitory relationship with the contralateral LGN. These observations provide a basis for further gross characterizations of the role of the TRN in human behavior.

Clinical significance of T2*-weighted gradient-echo MRI to monitor graft maturation over one year after anatomic double-bundle anterior cruciate ligament reconstruction: a comparative study with proton density-weighted MRI.

This study examined the feasibility of T2*-weighted imaging (T2*WI) gradient-echo MRI to reflect actual function of the graft after anatomic double-bundle ACL reconstruction. T2*WI and proton density-weighted imaging (PDWI) were compared in the assessment of ACL grafts. Sixty-one patients underwent T2*WI and PDWI at 3, 6, and 12 months postoperatively. Signal intensity of the anteromedial bundle (AMB) or posterolateral bundle (PLB) graft standardized to the intensity of the PCL was defined as signal intensity ratio (SIR). Correlations between degree of knee instability and SIR were assessed for each bundle, each time point, and each sequence. The diagnostic efficacy of T2*WI sequence to detect poorly functioning knee with anteroposterior translation ≥ 4 mm was assessed. Significant correlations were observed between SIR and KT values for both AMB and PLB at 12 months on T2*WI (r=0.39 and 0.53, respectively), but not on PDWI. Notably, 9 of 10 patients with poorly functioning graft showing anteroposterior translation ≥ 4 mm at 12 months formed an isolated group with high T2*WI-SIR. Six of the 10 patients displayed an increase in SIR from 6 to 12 months. Defining anteroposterior translation ≥ 4 mm at 12 months as the diagnostic standard for poorly functioning graft, increasing T2*WI-SIR offered 60% sensitivity and > 90% specificity. ACL graft intensity on T2*WI is more strongly associated with actual function of the graft than that on PDWI. An increasing trend in T2*WI-SIR from 6 to 12 months postoperatively represents a possible surrogate indicator for poorly functioning grafts.

Preoperative deltoid size and fatty infiltration of the deltoid and rotator cuff correlate to outcomes after reverse total shoulder arthroplasty.

Reverse total shoulder arthroplasty (RTSA) allows the deltoid to substitute for the nonfunctioning rotator cuff. To date, it is unknown whether preoperative deltoid and rotator cuff parameters correlate with clinical outcomes. We asked whether associations exist between 2-year postoperative results (ROM, strength, and outcomes scores) and preoperative (1) deltoid size; (2) fatty infiltration of the deltoid; and/or (3) fatty infiltration of the rotator cuff. A prospective RTSA registry was reviewed for patients with cuff tear arthropathy or massive rotator cuff tears, minimum 2-year followup, and preoperative shoulder MRI. Final analysis included 30 patients (average age, 71±10 years; eight males, 22 females). Only a small proportion of patients who received an RTSA at our center met inclusion and minimum followup requirements (30 of 222; 14%); however, these patients were found to be similar at baseline to the overall group of patients who underwent surgery in terms of age, gender, and preoperative outcomes scores. The cross-sectional area of the anterior, middle, and posterior deltoid was measured on axial proton density-weighted MRI. Fatty infiltration of the deltoid, supraspinatus, infraspinatus, teres minor, and subscapularis were quantitatively assessed on sagittal T1-weighted MR images. Patients were followed for Constant-Murley score, American Shoulder and Elbow Surgeons (ASES) scores, subjective shoulder value, pain, ROM, and strength. Correlations of muscle parameters with all outcomes measures were calculated. Preoperative deltoid size correlated positively with postoperative Constant-Murley score (67.27±13.07) (ρ=0.432, p=0.017), ASES (82.64±14.25) (ρ=0.377; p=0.40), subjective shoulder value (82.67±17.89) (ρ=0.427; p=0.019), and strength (3.72 pounds±2.99 pounds) (ρ=0.454; p=0.015). Quantitative deltoid fatty infiltration (7.91%±4.32%) correlated with decreased postoperative ASES scores (ρ=-0.401; p=0.047). Quantitative fatty infiltration of the infraspinatus (30.47%±15.01%) correlated with decreased postoperative external rotation (34.13°±16.80°) (ρ=-0.494; p=0.037). Larger preoperative deltoid size correlates with improved validated outcomes scores, whereas fatty infiltration of the deltoid and infraspinatus may have deleterious effects on validated outcomes scores and ROM after RTSA. The current study is a preliminary exploration of this topic; future studies should include prospective enrollment and standardized MRI with a multivariate statistical approach. Quantitative information attained from preoperative imaging not only holds diagnostic value, but, should future studies confirm our findings, also might provide prognostic value. This information may prove beneficial in preoperative patient counseling and might aid preoperative and postoperative decision-making by identifying subpopulations of patients who may benefit by therapy aimed at improving muscle properties. Level III, prognostic study.

Improve definition of titanium tandems in MR-guided high dose rate brachytherapy for cervical cancer using proton density weighted MRI

BackgroundFor cervical cancer patients treated with MR-guided high dose rate brachytherapy, the accuracy of radiation delivery depends on accurate localization of both tumors and the applicator, e.g. tandem and ovoid. Standard T2-weighted (T2W) MRI has good tumor-tissue contrast. However, it suffers from poor uterus-tandem contrast, which makes the tandem delineation very challenging. In this study, we evaluated the possibility of using proton density weighted (PDW) MRI to improve the definition of titanium tandems.MethodsBoth T2W and PDW MRI images were obtained from each cervical cancer patient. Imaging parameters were kept the same between the T2W and PDW sequences for each patient except the echo time (90 ms for T2W and 5.5 ms for PDW) and the slice thickness (0.5 cm for T2W and 0.25 cm for PDW). Uterus-tandem contrast was calculated by the equation C = (Su-St)/Su, where Su and St represented the average signal in the uterus and the tandem, respectively. The diameter of the tandem was measured 1.5 cm away from the tip of the tandem. The tandem was segmented by the histogram thresholding technique.ResultsPDW MRI could significantly improve the uterus-tandem contrast compared to T2W MRI (0.42±0.24 for T2W MRI, 0.77±0.14 for PDW MRI, p=0.0002). The average difference between the measured and physical diameters of the tandem was reduced from 0.20±0.15 cm by using T2W MRI to 0.10±0.11 cm by using PDW MRI (p=0.0003). The tandem segmented from the PDW image looked more uniform and complete compared to that from the T2W image.ConclusionsCompared to the standard T2W MRI, PDW MRI has better uterus-tandem contrast. The information provided by PDW MRI is complementary to those provided by T2W MRI. Therefore, we recommend adding PDW MRI to the simulation protocol to assist tandem delineation process for cervical cancer patients.

Contribution of thin-slice (1 mm) axial proton density MR images for identification and classification of meniscal tears: correlative study with arthroscopy

To evaluate the diagnostic efficacy of thin-slice (1 mm) axial proton density-weighted (PDW) MRI of the knee for meniscal tear detection and classification. We prospectively assessed pre-operative MR images of 58 patients (41 males, 17 females; age range 18-62 years) with arthroscopically confirmed meniscal tear. First, we evaluated the performance of the sagittal and thin-slice axial MR images for the diagnosis of meniscal tears. Second, we compared the correlation of tear types presumed from sagittal and axial MRI with arthroscopy and tear classification from axial MRI. Tears were classified on the sagittal plane and the axial plane separately. The diagnostic performance and tear classification were compared statistically with arthroscopy results, which is accepted as the standard of reference. 8 of 58 patients were removed from the study group because they had complex or degenerative tears. A total of 62 tears were detected with arthroscopy in 50 patients. On the sagittal images, sensitivity and specificity values were 90.62% and 70.37%, respectively, for medial meniscus tears and 72.73% and 77.14%, respectively, for lateral meniscus tears. The corresponding values for axial images were 97.30% and 84.00%, respectively, for medial meniscus tears and 95.65% and 80.50%, respectively, for lateral meniscus tears. There was no significant difference in tear classification between the arthroscopy results and the thin-slice axial PDW MRI results (p>0.05). thin-slice axial PDW MRI increases the sensitivity and specificity of meniscal tear detection and especially classification, which is important for surgical procedure decisions.

SU‐E‐J‐79: Proton Density Weighted MRI for MR‐Guided Radiotherapy for Cervical Cancer

Purpose: For cervical cancer patients treated by MR‐guided HDR brachytherapy, the accuracy of radiation delivery depends on accurate localization of both tumors and the “tandem and ovoid” applicator. Although T2‐weighted (T2W) MRI has a good tumor contrast, it is not a good choice for defining the applicator because of signal dropout and geometric distortion around the titanium applicator. In this study, we evaluated the possibility of using proton density weighted (PDW) MRI to improve the definition of the applicator. Methods: Both T2W and PDW images in the para‐sagittal plane were obtained from a 1.5T MRI scanner. For both images sets, in‐plane resolution was 1mm*1mm, spacing between slices was 0mm, TR was set to be between 3000ms and 6000ms, and FOV and the number of slices was adjusted based on the anatomy of individual patients. TE was 90ms and 5.5ms; slice thickness was 5mm and 2.5mm for T2W and PDW MRI respectively. PDW MRI had a smaller coverage in R/L direction. Images were sent to a workstation for treatment planning and another workstation after de‐identification for further image analysis. Results: Images from 10 patients were retrospectively reviewed. PDW MRI had a better definition of the applicator for all cases. A smaller ROI was placed around the tip of the tandem, which only included two structures: the tandem and the uterus. Histograms of signal intensity within the ROI showed that two peaks corresponding to the two structures were clearly separated in PDW MRI but not in T2W MRI. Conclusions: We showed that PDW MRI could provide a good visualization of the applicator. Therefore, we recommend adding PDW MRI to the imaging protocol for MR‐guided radiotherapy for cervical cancer. This will enable us to precisely localize both tumors and the applicator, which is essential for ensuring dose delivery accuracy.

109 3T MRI of acute atherosclerotic plaque rupture and downstream embolic injury

<h3>Introduction</h3> Luminal stenosis is a poor predictor of the risk posed by any given atherosclerotic plaque, therefore current angiographic imaging techniques cannot reliably determine which patients are most likely to suffer future ischaemic events. However, MRI may be able to detect features of atherosclerotic plaque rupture that have been associated with an increased risk of recurrent atherothrombosis. <h3>Hypothesis</h3> 3T MRI of the carotid artery can identify atherosclerotic plaque rupture in patients presenting with TIA or minor stroke. <h3>Methods</h3> 81 patients with carotid artery disease were recruited; 41 presented acutely with TIA or minor stroke and 40 asymptomatic patients acted as the control group. Median time from symptom onset to MRI in the symptomatic group was 2.1 days (range 0.17–7.0). All patients underwent T1, T2 and proton density-weighted turbo spin echo MRI to 10 mm either side of the carotid. As part of a combined scan protocol, study participants then underwent diffusion-weighted imaging (DWI) and Fluid-Attenuated Inversion Recovery (FLAIR) imaging of the brain to assess acute and chronic injury, respectively. If physically able, patients underwent follow-up scanning a minimum of six weeks later. Plaques were graded according to the MRI modified American Heart Association (AHA) system by two independent reviewers blinded to the clinical status of the patient. Statistical analysis was performed using the Wilcoxon sign rank test and Fisher′s exact test to compare plaques, in addition to the Mann Whitney U test to compare cerebral injury. <h3>Results</h3> AHA type VI (ruptured) plaque was seen in 22/41(54%) in the symptomatic group vs 8/41(20%) in the asymptomatic group (p&lt;0.05), either due to intra-plaque haemorrhage (34% vs 18%, p=0.08; Abstract 109 figure 1A), surface rupture (24% vs 5%, p=0.03; Abstract 109 figure 1B), or luminal thrombus (7% vs 0%, p=0.24; Abstract 109 figure 1C). Of particular note, 17/30 (57%) cases of AHA VI (ruptured) plaque were seen to cause &lt;70% stenosis―the current cut-off for surgical treatment. At follow-up scanning a minimum of 6 weeks later, only two cases of AHA VI plaque showed evidence of full healing. Of the 41 patients in the acute group, evidence of cerebral injury on DWI imaging was seen in 32/41 patients; the median number of lesions per patient was 7 and the median total lesion volume was 10.62 ml (range 0–522 ml). No significant associations were noted between AHA plaque type and downstream cerebral injury, however the presence of plaque surface rupture independently predicted a higher number of DWI lesions, a higher total DWI burden at presentation, and higher total cerebral FLAIR signal at follow-up when compared to all other plaque types (p&lt;0.05). <h3>Conclusion</h3> Acute atherosclerotic plaque rupture can be visualised using 3T MRI. In particular, MRI can provide detailed information on plaque morphology that can predict downstream embolic injury, independent of the degree of luminal stenosis caused.

On the Use of Hyperpolarized Helium MRI for Conformal Avoidance Lung Radiotherapy

We wanted to illustrate the feasibility of using hyperpolarized helium magnetic resonance imaging (HPH-MRI) to obtain functional information that may assist in improving conformal avoidance of ventilating lung tissue during thoracic radiotherapy. HPH-MRI images were obtained from a volunteer patient and were first fused with a proton density-weighted (PD w) MRI to provide corresponding anatomic detail; they were then fused with the treatment planning computed tomography scan of a patient from our treatment planning database who possessed equivalent thoracic dimensions. An optimized treatment plan was then generated using the TomoTherapy treatment planning system, designating the HPH-enhancing regions as ventilation volume (VV). A dose-volume histogram compares the dosimetry of the lungs as a paired organ, the VV, and the lungs minus the VV. The clinical consequences of these changes was estimated using a bio-effect model, the parallel architecture model, or the local damage ( f dam ) model. Model parameters were chosen from published studies linking the incidence of grade 3+ pneumonitis, with the dose and volume irradiated. For two hypothetical treatment plans of 60 Gy in 30 fractions delivered to a right upper-lobe lung mass, one using and one ignoring the VV as an avoidance structure, the mean normalized total dose (NTD mean) values for the lung subvolumes were: lungs = 12.5 Gy 3 vs. 13.52 Gy 3, VV = 9.94 Gy 3 vs. 13.95 Gy 3, and lungs minus VV = 16.69 Gy 3 vs. 19.16 Gy 3. Using the f dam values generated from these plans, one would predict a reduction of the incidence of grade 3+ radiation pneumonitis from 12%–4% when compared with a conventionally optimized plan. The use of HPH-MRI to identify ventilated lung subvolumes is feasible and has the potential to be incorporated into conformal avoidance treatment planning paradigms. A prospective clinical study evaluating this imaging technique is being developed.

MRI assessment of the alar ligaments in the late stage of whiplash injury--a study of structural abnormalities and observer agreement.

Our aim was to characterise and classify structural changes in the alar ligaments in the late stage of whiplash injuries by use of a new MRI protocol, and to evaluate the reliability and the validity of this classification. We studied 92 whiplash-injured and 30 uninjured individuals who underwent proton density-weighted MRI of the craniovertebral junction in three orthogonal planes. Changes in the alar ligaments (grades 0-3) based on the ratio between the high signal area and the total cross-sectional area were rated twice at a 4-month interval, independently by three radiologists. Inter- and intraobserver statistics were calculated by ordinary and weighted kappa. Cases classified differently were reviewed to identify potential causes for disagreement. The alar ligaments were satisfactorily demonstrated in all cases (244 ligaments in 122 individuals). The lesions, 2-9 years after the injury, varied from small high-signal spots to high signal throughout the cross-sectional area. Signal was highest near the condylar insertion in 82 of 94 ligaments, indicating a lesion near that insertion, and near the dental insertion in eight, indicating a medial lesion. No grade 2 or 3 lesion was found in the control group. At least two observers assigned the same grade to 214 ligaments (87.7%) on the second occasion. In 30 ligaments (12.3%) this agreement was not obtained. Pair-wise interobserver agreement (weighted kappa) was fair to moderate (0.31-0.54) in the first grading, improving to moderate (0.49-0.57) in the second. Intraobserver agreement (weighted kappa) was moderate to good (0.43-0.70). Whiplash trauma can cause permanent damage to the alar ligaments, which can be shown by high-resolution proton density-weighted MRI. Reliability of classification of alar ligament lesions needs to be improved.