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Knee injuries are common, and MRI is a highly accurate way to visualize the problem. But, there are five knee injuries that are frequently overlooked, particularly by inexperienced readers.

While catching these injuries might not change clinical management or lead to surgery, it can reduce patient symptoms, such as pain, tenderness, clicking, locking, and instability. Identifying them can also potentially help patient avoid further injury.

a team from The Chinese University of Hong Kong outlined what these commonly missed injuries are and what providers should look for to detect them.

This injury is most common with young male patients who play contact sports. There are five types of lesions, and they typically involve:

vertical longitudinal tears located at the peripheral meniscocapsular junction of the posterior horn medial meniscus

the peripheral part of the posterior horn or attachments to the posterior horn, particularly the meniscocapsular and meniscotibial ligaments.

These lesions are best seen on sagittal proton density-weighted and T2-weighted fat-saturated MR sequences. To catch them, radiologists should become familiar with the normal appearance of the meniscocapsular junction of the posterior horn or the medial meniscus. When viewing these images look for:

non-compact tissue applied to the posterior horn of the medial meniscus that comprises the meniscocapsular ligament and the meniscotibial ligament with intervening fatty issue 

thin vertical peripheral tears of the meniscus or small corner tears of the meniscocapsular and meniscotibial ligaments with fluid interposition

These tears can occur at the posterior horn medial meniscus, the medial meniscal body or posterior horn and lateral meniscus body, and they can lead to hypermobility in the knee that can cause clicking and locking, as well as further injury.

The superior and inferior popliteomeniscal fasciles (PMF) seen with these injuries are best seen on T2-weighted or proton density-weighted sagittal sequences, particularly a 45-degree oblique coronal proton density-weighted sequence.

be familiar with the normal appearance of meniscocapsular attachments

routinely inspect the peripheral attachments of menisci in all knee MRI exams

look for PMF tears and posterior root ligament tears

evaluate the posterior horn of the lateral meniscus

exclude the abnormal far lateral extension of the meniscofemoral attachment

These injuries mostly affect the posterior roots of the medial or lateral menisci, but they can also impact anterior roots. Posterior roots are more susceptible because they are relatively immobile and experience significant force during knee flexion.

There are five types of tears, and they are best seen on proton density-weighted and T2-weighted fat suppressed coronal and sagittal imaging. When reviewing images, do not mistake a fissured appearance of the posterior root of the medial meniscus as a tear.

always inspect the root ligaments, following the meniscal tissue into its bony attachment

do not mistake loose fibrotic or reparative-type T2-weighted or proton density-weighted hyperintense tissue at the attachment site as normal root ligament

inspect posterior root of the lateral meniscus using oblique coronal imaging

In unclear circumstances, report findings as “possible root ligament tear.”

These injuries are difficult to diagnose because the ligament cannot be identified directly and capsular-ligamentous discontinuity is uncommon. They are best visualized on axial images at the level of the knee joint.

Although edema can occur with these ligaments in both non-trauma and trauma situations, the amount and location of swelling is used for diagnosis. It can indicate mild, moderate, and severe injury.

Accounting for approximately 30 percent of all ACL tears, these injuries are often overlooked because they are difficult to evaluate clinically and on routine arthroscopy.

Double oblique axial proton density-weighted sequences are helpful for evaluation. However, flexion sagittal views are more helpful to distinguish between partial and complete ACL tears.

When looking at an MRI image, suspect a partial tear when:

ACL seems indistinct, attenuated, bowed, and more separate than usual

complete tear of one bundle, roughly affecting the anteromedial and posterolateral bundles equally

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These injuries are easy misses for radiologists unfamiliar with the problems – here’s what you should look for.

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Having a lower heart rate can improve the image quality of a patient’s coronary CT angiography (CCTA), as well as lower the radiation dose used.

In a research letter published June 15 in 

a multi-institutional, multi-national group of researchers demonstrated that, across a wide variety of CT scanners, patient with heart rates lower than 60 beats per minute enjoyed these benefits. The results, they said, support using beta blockers to help control heart rate for some individuals unless there are contraindications.

“The results from this international multi-vendor, real-world analysis confirm the notion that heart rate has significant influence on image quality in coronary CTA,” said the team led by Thomas J. Stocker, M.D., from Medizinische Klinik and Poliklinik I, Ludwig-Maximilians-Universität in Germany. “The results suggest that cardiologists and radiologists should aim for a lower patient heart rate to obtain the best image quality and simultaneously allow for lower radiation dose in coronary CTA imaging.”

Heart rate is a known independent indicator for CCTA image quality of radiation exposure, but given improvements to scanner equipment and protocols, it is unclear if there is an optimal heart rate for these studies. To figure out if one exists, Stocker’s team conducted a sub-analysis of the Prospective Multi-Center Registry on Radiation Dose Estimates of Cardiac CT Angiography in Daily Practice (PROTECTION).

For their study, between March 2017 and December 2017, they analyzed the first 50 percent of CCTAs from 57 sites worldwide, including 1,911 patients (43 percent women) with an average age of 59 and average heart rate of 60 beats-per-minute (BPM). Scans were conducted on equipment from Siemens Healthineers, GE Healthcare, Canon Medical, and Philips Healthcare.

The team grouped study participants into heart-rate cohorts based on 5-BPM intervals, such as 45-to-50. Two radiologists analyzed the scans, examining signal-to-noise ratio, contrast-to-noise ratio, and dose-length product. They categorized the image quality of the left main artery, left anterior descending artery, left circumflex artery, and right coronary artery in a four-point scale that ranged from non-diagnostic (1) to excellent (4). In addition, they assessed the effect heart rate reduction had on image quality and radiation exposure.

CT angiographs show representative grading of the image quality for the right coronary artery. A, Grade 1 (nondiagnostic); B, grade 2 (adequate); C, grade 3 (good); D, grade 4 (excellent).

Overall, they identified a median signal-to-noise ratio of 14, median contrast-to-noise of 11, and median dose-length product of 170 mGy cm, as well as an average image quality score of 3.5. Patients with stable sinus rhythm had better image quality scores.

However, the team said, image quality scores were higher than 3.5 for patients with heart rates lower than 60 BPM. In fact, the image quality scores increased by 0.18 for every 10-BPM reduction. Median dose-length product dropped by 48 mGy cm for every 10-BPM decrease, as well.

Based on these findings, the team recommended beta blocker use with patients who have a heart rate higher than 75 BPM, and they cautiously recommended use for patients with heart rates between 60-and-75 BPM.

The results of this study add substantially to the existing body of knowledge around the role heart rate plays in image quality and dose exposure, said U. Joseph Schoepf, M.D., a radiology, medicine, and pediatrics professor, and Josua Decker, M.D., a post-doctoral cardiovascular imaging fellow, both from the Medical University of South Carolina. Not only is their work relevant to clinical practice, they said in an 

, but it is based on outcomes from multiple scanner types in sites around the world that have their own CT protocols.

Knowing how to improve image quality and control radiation dose will become increasingly important, they said, because the number of CCTAs will increase as the population ages.

“The study by Stocker and colleagues has real-world results that show that even with our modern high-resolution CT scanners, heart rate significantly influences diagnostic quality and radiation dose of coronary CTA,” they said. “Given these results, the heart rate of every patient should be carefully evaluated prior to the examination.”

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Identification of optimal heart rate supports use of beta blockers when possible.

Lower Heart Rate Improves CCTA Image Quality, Dose Exposure

F-DCFPyL, used with PET imaging, can detect and localize recurrent prostate cancer, according to new research results.

In a phase III clinical trial, this radiotracer was able to bind selectively to prostate-specific membrane antigen (PMSA) with high affinity and identify metastatic lesions no matter the anatomic region with high positive predictive value (PPV), further indicating that PMSA-targeted radiotracers are useful in prostate cancer imaging. 

F-DCFPyL was approved by the U.S. Food & Drug Administration in May, and the trial outcomes were presented during the Society of Nuclear Medicine and Molecular Imaging 2021 Annual Meeting.

In a 14-site prospective study across the United States and Canada, researchers from Johns Hopkins University examined both the PPV and detection rate of PET/CT with the radiotracer by anatomic region –specifically prostate/prostate bed, pelvic lymph nodes, and regions outside the pelvis. For the study, they included men with rising prostate-specific antigen (PSA) levels post-local therapy and negative or equivocal conventional imaging results.

Case example: A 54-year-old man with a history of RP+LND and a subsequent PSA of 1.25 ng/mL had no evidence of disease by baseline imaging. Piflufolastat F 18 (18F-DCFPyL)- PET/CT accurately detected biochemically recurrent prostate cancer with the PSMA PET/CT scan identifying positive left (left panel) and right peri-rectal lymph nodes (right panel).

Credit: Steven Rowe, M.D., Ph.D., Johns Hopkins University

For the study, the team, led by Steven Rowe, M.D., Ph.D., associate professor of radiology and radiological science, imaged patients with 

F-DCFPyL at the start of the study and, again, after 60 days to verify suspected lesions using a composite “standard of truth” that included histopathology, correlative imaging findings, and PSA response. They, then, compared the radiotracer imaging to the “standard” to determine the PPV and detection rate.

Based on their analysis, the team determined 

F-DCFPyL-PET/CT effectively detected and pinpointed metastatic lesions with high PPV no matter the location for men who had biochemically recurrent prostate cancer and standard imaging that was uninformative.

Specifically, the median detection rates for prostate and prostate bed, lymph nodes, and extra-pelvic region were 20.2 percent, 35.1 percent, and 26.4 percent, respectively. In addition, the median PPV for the anatomic regions was 79.5 percent, 70.9 percent, and 67.4 percent, respectively. The extra-pelvic lymph node and bone PPVs compared to soft tissue regions, the team said.

With these results – and with these agents becoming more widely available -- Rowe said, patients who have newly diagnosed, recurrent, metastatic prostate cancer could soon have additional therapy options.

Recently approved PMSA-targeted radiotracer can pinpoint biochemical recurrent prostate cancer in men with unhelpful standard imaging. 

Radiotracer Identifies Metastatic Prostate Cancer Regardless of Anatomic Region

65-year-old male presents with left sensorineural hearing loss.


MRI images demonstrate an avidly enhancing, T1-isointense, T2-hypointense lesion in the basal turn of the cochlea, characteristic of schwannoma. The T2 hypointesity appears as a filling defect within the surrounding hyperintense perilymph fluid.

Acute labyrinthitis is characterized by T1 hyperintense signal secondary to permeability of the blood-labyrinth barrier and accumulation in the intralabyrinthine compartment. Post-gadolinium T1-weighted images demonstrate diffuse, but faint, enhancement of the labyrinth. Intravestibular lipomas are nonenhancing and demonstrate T1 hyperintense, T2-iso, or hypointense signal with complete saturation on fat-saturation images. Intralabyrinthine hemorrhage is  characterized by both T1- and T2-hyperintense signal on precontrast sequences.


Vestibular schwannoma is a benign nerve sheath neoplasm derived from perineural Schwann cells. They are similar in pathology to peripheral schwannomas and comprise approximately 8% of adult intracranial tumors. Median age at diagnosis is 50, and they are rare in children unless associated with neurofibromatosis type 2 (NF2). The majority of these tumors (90%) are unilateral, with bilateral involvement characteristic of NF2.  In sporadic cases, there is often biallelic inactivation of the NF2 gene, which produces schwannomin and serves as a tumor suppressor. Childhood exposure to radiation increases the risk for developing vestibular schwannoma in later life.

Presenting symptoms include hearing loss and tinnitus (cochlear nerve) or unsteady gait and vertigo (vestibular nerve) depending on the affected nerve. 

Patients who are young, have large tumors and/or significant hearing loss should be treated early to prevent progressive hearing loss. In older patients with small tumors and minimal hearing loss, rate of growth may be used to guide treatment, with rapid growth defined as  > 2.5 mm per year.

1. Park JK, Vernick DM, Ramakrishma N. Vestibular schwannoma (acoustic neuroma). http://www.uptodate.com/contents/vestibular-schwannoma-acoustic-neuroma

2. Salzman KL, et al. Intralabyrinthine schwannomas: imaging diagnosis and classification. 

Poll

Image IQ: 65-year old Male, Left Sensorineural Hearing Loss

The patient’s brain and bones hold on to much higher levels of linear gadolinium-based contrast agents (GBCAs) than macrocyclic contrasts.

Even though GBCAs are used widely with patients, there is little known about how it is retained in and eliminated from the body. In a study published June 15 in 

a team of investigators from the University of Washington in Seattle shared their data that compared retention and elimination rates between GBCAs and macrocyclic contrasts.

Specifically, they said, linear GBCAs (gadobenate dimeglumine) has retention rates of 2.9-to-6.5 times higher in the brain, bone, and skin than macrocyclic (gadoteridol).

“This study provides direct evidence that the linear agent gadobenate dimeglumine is retained at several-fold higher levels of gadolinium in the brain and bone compared with the macrocycle agent gadoteridol,” said Masahiro Kobayashi, M.D., from the University of Washington’s radiology department.

To reach this conclusion, they conducted a retrospective study from August 2014 to July 2019 and examined 28 cadavers that had received one or more gadoteridol dose and nine cadavers that had been exposed to gadobenate dimeglumine.

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Using inductively coupled plasma mass spectrometry, the team assessed gadolinium levels in the brain, skin, and bone, and they compared gadolinium retention between agents. They also estimated elimination rates of retained gadolinium based on time between last injection and death.

According to their evaluation, they determined that, compared to gadoteridol, gadobenate dimeglumine had higher median retention rates in the brain (3-to-6.5 times higher), bone (4.4-times higher), and skin (2.9-times higher). In addition, they identified “non-zero” gadolinium elimination from the skin and white matter.

Despite these higher levels, though, Michael F. Tweedle, Ph.D., Stefanie Spielman professor of cancer imaging in The Ohio State University and James Comprehensive Cancer Center, said the clinical impact of retention is low. Intact GBCAs are unlikely to cause long-term toxic impacts, and gadolinium ion deposits are equally as unlikely to cause negative effects, particularly in patient who have normal kidney function.

, more research is needed so radiologists continue to get a better understanding of how gadolinium functions on the body and the effects it has.

“Radiologists and patients need reassurance on the ultimate safety of the use of contrast agents to properly manage the risks and benefits, as is done every day for the use of ionizing radiation,” he said.

Retention rates are higher, but clinical impact could be low.

Gadolinium-Based Contrast Retention Rates Higher Than Thought

PET imaging shows lipophilic statin use by patients who are experiencing mild cognitive decline results is significant impacts on the posterior cingulate cortex, the area of the brain that is first affected by Alzheimer’s.

In research presented during the Society of Nuclear Medicine and Molecular Imaging 2021 Annual Meeting, investigators from the University of California at Los Angeles (UCLA) shared evidence that metabolism in this area of the brain is significantly reduced in this patient group. In fact, they face more than double the risk of developing dementia than do similar patients not taking the medication.

While statins are the most widely used drugs in the developed world for lowering cholesterol and reducing heart attack and stroke risk, many studies have pointed to a higher risk associated with lipophilic statins because they are better able to cross the blood-brain barrier. To date, though, investigators have not been able to identify a direct link between the medication and cognitive decline.

Significant metabolic decline in the posterior cingulate cortex in lipophilic statin users after five to six years (top) compared to hydrophilic statin users and non-statin users (bottom).

Credit: Image created by Prasanna Padmanabham and Daniel Silverman, UCLA

“While some claim that statins protect users against dementia, others assert that they accelerate the development of dementia,” said Prasanna Padmanabham, lead study author and project head of statins and cognition in UCLA’s molecular and medical pharmacology student research program. “Our study aimed to clarify the relationship between statin use and subject’s long-term cognitive trajectory.”

Padmanabham’s team sought to clarify this relationship between a patient’s medication use and their long-term cognitive path. To do so, they compared 

F-FDG-PET scans that showed blood-brain barrier penetration in patients who used statins with moderate (atorvastatin) or high (simvastatin) lipophilicity to patients who either didn’t use statins or who used different ones. They also examined eight years of clinical data.

The team divided 392 patients with mild cognitive impairment into groups based on three parameters: baseline cognitive status, baseline cholesterol levels, and type of statin used.

During the eight-year timeframe, the team said, more patients in the lipophilic group progressed to dementia than did patients who were not taking statins – 24 percent and 10 percent, respectively. They saw no significant difference between patients taking other statins and those who didn’t.

Most significantly, they said, they were only able to identify a decline in posterior cingulate metabolism in patients using the lipophilic statins. Specifically, Padmanabham said, these results point to a more than double risk among lipophilic statin users for developing dementia.

Overall, the team said, their findings could point to a new use of PET imaging that could augment the knowledge base around the link between these medications and the aging brain.

“Findings from these scans could be used to inform patients’ decisions regarding which statin would be most optimal to use with respect to preservation of their cognition and ability to foundation independently,” Padmanabham said.

Patients with mild cognitive impairment who take lipophilic statins have a more than doubled risk of progressing to dementia.

PET Imaging Shows Increased Dementia Risk with Lipophilic Statins

PET/CT images can non-invasively measure levels of a non-small cell lung cancer (NSCLC) biomarker, eliminating the need for biopsy and predicting the patient’s response to therapy.

Checkpoint inhibitors that target the PD1/PD-L1 signaling pathway are an effective treatment for NSCLC, but it only works in roughly half of patients. Investigators from Moffitt Cancer Center demonstrated, in a study published this week in the 

that PET/CT can effectively assess the patient’s PD-L1 level, helping patients and providers to side-step the risks that come with invasive biopsy.

“This study is important, as it is the single largest multi-institutional radiomic study population of NSCLC patients to date treated with immunotherapy to predict PD-L1 status and subsequent treatment response using PET/CT scans,” said Robert Gillies, Ph.D., chair of Moffitt’s cancer physiology department. “Because images are routinely obtained and are not subject to sampling bias per se, we propose that the individualized risk assessment information provided by these analyses may be useful as a future clinical decision support tool pending larger prospective trials.”

For their study, the team examined PET/CT scans for nearly 700 patients who had NSCLC who were treated in three institutions. They assessed shape, size, pixel intensity, and textures to train a deep learning tool to accurately measure PD-L1 expression. Using the data, they developed a deep learning score that could predict PD-L1 expression which, after validation, could predict checkpoint inhibitor outcomes in these patients.

Their results point to the usefulness of using images as a replacement for biopsy, said Matthew Schabath, Ph.D., associate member of the cancer epidemiology department.

“These data demonstrate the feasibility of using an alternative non-invasive approach to predict expression of PD-L1,” he said. “This approach could help physicians determine optimum treatment strategies for their patients, especially when tissue samples are not available or when common testing approaches for PD-L1 fail.”

Using PET/CT images to assess the level of a non-small cell lung cancer biomarker can help patients avoid invasive biopsy.

PET/CT Effective Measures NSCLC Biomarker, Predicts Therapy Response

A lower dose of gadobutrol performs equally as well with contrast-enhanced brain MRI when compared to a full standard dose of gadoterate, according to new research.

 investigators from Germany’s University Medical School of Saarland shared results that showed reduced gadobutrol dose by one-fourth could change treatment decisions for some patients.

“A 25-percent reduced gadobutrol dose demonstrated non-inferior efficacy versus standard dose gadoterate for contrast-enhanced brain MRI,” said corresponding author Jan Endrikat, professor of medicine, “warranting particular consideration in patients undergoing multiple contrast-enhanced examinations.”

61-year-old man with left hemispheric brain metastasis from lung cancer. Axial T1-weighted MR images obtained using (A) standard-dose gadoterate and (B) reduced-dose gadobutrol 4 days later.

Credit: American Journal of Roentgenology

To determine the impact of a lower dose, Endrikat’s team conducted an international, prospective, multi-center, open-label, crossover trial called LEADER-75. They enrolled 141 patients – 78 men and 63 women who averaged age 58.5. All patients either had or were suspected of central nervous system pathology, and they underwent contrast-enhanced brain MRI with the standard gadoterate dose – 0.1 mmol/kg.

Patients who had an enhancing lesion emerge on the first MRI had a second scan with reduced-dose gadobutrol – 0.075 mmol/kg – after 15 days.

The team looked at three efficacy measures – subjective lesion enhancement, lesion border delineation, and lesion internal morphology – when comparing the lower-dose gadobutrol and standard-dose gadoterate to unenhanced imaging. Based on their analysis, they determined non-inferiority using a 20-percent margin for those measures.

In addition, in a post-hoc analysis, the team calculated that the mean readings for subjective lesion enhancement, lesion border delineation, and lesion internal morphology differed by less than 1 percent, supporting equivalence using a narrow +/- 5-percent margin.

Specifically, 301 total lesions were detected by mean reading for reduced-dose gadobutrol, and 291 were detected for standard-dose gadoterate. In addition, mean confidence was 3.3 +/- 0.6 for both reduced dose and standard dose. Sensitivity, specificity, and accuracy were also identical for both from majority reading – 58.7 percent, 91.8 percent, and 70.2 percent, respectively.

Alongside these measures, the team said, other secondary variables also supported the non-inferiority of reduced-dose gadobutrol.

Findings could lead to changes in treatment decisions.

 Lower Gadobutrol Dose Effective for Contrast-Enhanced Brain MRI

In the next step toward increasing MRI use with lung imaging, new research shows 0.55T MRI has the potential to effectively reveal common lung abnormalities.

While CT is largely employed for lung imaging, MRI is an attractive alternative because it is free of ionizing radiation. Ongoing efforts have explored the use of 1.5T and 3.0T MRI, but this is the first investigation to assess whether 0.55T can be useful clinically.

a team of researchers from National Institutes of Health shared data that shows capturing lung images with a 0.55T MRI with a closed-bore super-conducting magnet design performs comparably to conventional CT.

0.55T MRI Performs Comparably to CT with COVID-19 Imaging

“Our findings in this small sample of patients indicate excellent image quality that shows promise for clinical diagnosis and evaluation of common lung diseases,” said the team led by Adrienne E. Campbell-Washburn, Ph.D., the staff scientist who leads the National Heart, Lung, and Blood Institute’s Laboratory of MRI Technology.

For their study, they captured respiratory-triggered T2-weighted turbo-spin echo MRI image sets on 18 participants with common lung abnormalities between November 2018 and December 2019. The average participant age was 59 years, and the average acquisition time was 10.5 minutes.

Axial multi-section imaging yielded full lung coverage using (A) CT (reformatted to 0.8 × 0.8 × 6 mm) and (B) T2-weighted MRI (1.1 × 1.1 × 6 mm) in a 69-year-old woman with bronchiectasis, cavitary lesions, and scattered pulmonary nodules.

The MRI images were captured with a clinical 1.5T MRI that had been modified to operate at 0.55T. Lung imaging was performed with an 18-channel spine phased-array coil and a six-channel body phased-array coil for 0.55T.

Axial multi-section imaging yielded full lung coverage using (A) CT (reformatted to 0.8 × 0.8 × 6 mm) and (B) T2-weighted MRI (1.1 × 1.1 × 6 mm) in a 41-year-old woman with lymphangioleiomyomatosis resulting in innumerable thin-walled pulmonary cysts.

Three radiologists assessed the exams, compared them to the same images captured with conventional CT, and graded them on a five-point scale with “1” indicating the images were non-diagnostic in quality and “5” indicating excellent image quality.

0.55T MRI and CT Clinical Findings Comparison

According to their evaluation, most of the images were deemed “good,” with 37 out of 54 images receiving a score of 4 or 5. Overall, the team said, there was almost perfect consensus between MRI and CT for consolidations, cavitation, mucus plug, scattered nodules, bronchiectasis or bronchial wall thickening, and pleural effusion (k range, 0.61 to 1). However, there was less agreement between the modalities for ground-glass opacities, tree-in-bud pattern nodularity, and scarring (k range, 0.48 to 0.57).

The next step, the team said, is an effort to focus on eliminating motion artifacts that cause image-quality disruptions.

Low-field strength MRI can successfully visualize common lung problems.



PET/CT Effective Measures NSCLC Biomarker, Predicts Therapy Response

Lower Gadobutrol Dose Effective for Contrast-Enhanced Brain MRI

0.55T MRI Effective in Lung Imaging