Comparison of Radiologists and Other Specialists in the Performance of Lumbar Puncture Procedures Over Time

BACKGROUND AND PURPOSE

Lumbar punctures may be performed by many different types of health care providers. We evaluated the percentages of lumbar punctures performed by radiologists-versus-nonradiologist providers, including changes with time and discrepancies between specialties.

MATERIALS AND METHODS

Lumbar puncture procedure claims were identified in a 5% sample of Medicare beneficiaries from 2004 to 2017 and classified by provider specialty, site of service, day of week, and patient complexity. Compound annual growth rates for 2004 versus 2017 were calculated; t test and χ² statistical analyses were performed.

RESULTS

Lumbar puncture use increased from 163.3 to 203.4 procedures per 100,000 Medicare beneficiaries from 2004 to 2017 (overall rate, 190.3). Concurrently, the percentage of lumbar punctures performed by radiologists increased from 37.1% to 54.0%, while proportions performed by other major physician specialty groups either declined (eg, neurologists from 23.5% to 10.0%) or were largely unchanged. While radiologists saw the largest absolute increase in the percentage of procedures, the largest relative increase occurred for nonphysician providers (4.2% in 2004 to 7.5% in 2017; +78.6%). In 2017, radiologists performed most procedures on weekdays (56.2%) and a plurality on weekends (38.2%). Comorbidity was slightly higher in patients undergoing lumbar puncture by radiologists (P < .001).

CONCLUSIONS

Radiologists now perform most lumbar puncture procedures for Medicare beneficiaries in both the inpatient and outpatient settings. The continuing shift in lumbar puncture responsibility from other specialists to radiologists has implications for clinical workflows, cost, radiation exposure, and postgraduate training.

Board Certification Characteristics of Practicing Neuroradiologists

BACKGROUND AND PURPOSE

Insight into the status of neuroradiology subspecialty certification across the United States could help to understand neuroradiologists' perceived value of subspecialty certification as well as guide efforts to optimize pathways for broader voluntary certification participation. Our aim was to assess board certification characteristics of practicing US neuroradiologists.

MATERIALS AND METHODS

The American Board of Radiology public search engine was used to link Medicare-participating radiologists with American Board of Radiology diplomates. Among linked diplomates, 4670 neuroradiologists were identified on the basis of 3 criteria: current or prior neuroradiology subspecialty certification or currently >50% clinical work effort in neuroradiology based on work relative value unit-weighted national Medicare claims ("majority-practice neuroradiologists"). Subspecialty certification status was studied in each group, using Centers for Medicare & Medicaid Services data to identify additional physician characteristics.

RESULTS

Of 3769 included radiologists ever subspecialty certified, 84.1% are currently subspecialty certified. Of 1777/3769 radiologists ever subspecialty-certified and with lifetime primary certificates (ie, nonmandated Maintenance of Certification), only 66.6% are currently subspecialty certified. Of 3341 included majority-practice neuroradiologists, 73.0% were ever subspecialty certified; of these, 89.1% are currently subspecialty certified. Of 3341 majority-practice neuroradiologists, the fraction currently subspecialty certified was higher for those in academic (81.3%) versus nonacademic (58.2%) practices, larger versus smaller practices (72.1% for those in ≥100 versus 36.1% for <10-member practices), US regions other than the West (64.1%-70.6% versus 56.5%), fewer years in practice (77.5% for 11-20 years versus 31.3% for >50 years), and time-limited (73.5%) versus lifetime (54.9%) primary certificates.

CONCLUSIONS

More than one-quarter of majority-practice neuroradiologists never obtained neuroradiology subspecialty certification. Even when initially obtained, that certification is commonly not maintained, particularly by lifetime primary certificate diplomates and those in nonacademic and smaller practices. Further investigation is warranted to better understand neuroradiologists' decisions regarding attaining and maintaining subspecialty certification.

PI-RADS version 2.1: one small step for prostate MRI

Multiparametric (mp) prostate magnetic resonance imaging (MRI) is playing an increasingly prominent role in the diagnostic work-up of patients with suspected prostate cancer. Performing mpMRI before biopsy offers several advantages including biopsy avoidance under certain clinical circumstances and targeting biopsy of suspicious lesions to enable the correct diagnosis. The success of the technique is heavily dependent on high-quality image acquisition, interpretation, and report communication, all areas addressed by previous versions of the Prostate Imaging-Reporting and Data System (PI-RADS) recommendations. Numerous studies have validated the approach, but the widespread adoption of PI-RADS version 2 has also highlighted inconsistencies and limitations, particularly relating to interobserver variability for evaluation of the transition zone. These limitations are addressed in the recently released version 2.1. In this article, we highlight the key changes proposed in PI-RADS v2.1 and explore the background reasoning and evidence for the recommendations.

Does normalisation improve the diagnostic performance of apparent diffusion coefficient values for prostate cancer assessment? A blinded independent-observer evaluation

AIM

To evaluate the performance of normalised apparent diffusion coefficient (ADC) values for prostate cancer assessment when performed by independent observers blinded to histopathology findings.

MATERIALS AND METHODS

Fifty-eight patients undergoing 3 T phased-array coil magnetic resonance imaging (MRI) including diffusion-weighted imaging (DWI; maximal b-value 1000 s/mm(2)) before prostatectomy were included. Two radiologists independently evaluated the images, unaware of the histopathology findings. Regions of interest (ROIs) were drawn within areas showing visually low ADC within the peripheral zone (PZ) and transition zone (TZ) bilaterally. ROIs were also placed within regions in both lobes not suspicious for tumour, allowing computation of normalised ADC (nADC) ratios between suspicious and non-suspicious regions. The diagnostic performance of ADC and nADC were compared.

RESULTS

For PZ tumour detection, ADC achieved significantly higher area under the receiver operating characteristic curve (AUC; p=0.026) and specificity (p=0.021) than nADC for reader 1, and significantly higher AUC (p=0.025) than nADC for reader 2. For TZ tumour detection, nADC achieved significantly higher specificity (p=0.003) and accuracy (p=0.004) than ADC for reader 2. For PZ Gleason score >3+3 tumour detection, ADC achieved significantly higher AUC (p=0.003) and specificity (p=0.005) than nADC for reader 1, and significantly higher AUC (p=0.023) than nADC for reader 2. For TZ Gleason score >3+3 tumour detection, ADC achieved significantly higher specificity (p=0.019) than nADC for reader 1.

CONCLUSION

In contrast to prior studies performing unblinded evaluations, ADC was observed to outperform nADC overall for two independent observers blinded to the histopathology findings. Therefore, although strategies to improve the utility of ADC measurements in prostate cancer assessment merit continued investigation, caution is warranted when applying normalisation to improve diagnostic performance in clinical practice.

Assessment of change in prostate volume and shape following surgical resection through co-registration of in-vivo MRI and fresh specimen ex-vivo MRI

AIM

To compare the size and shape of the prostate between in-vivo and fresh ex-vivo magnetic resonance imaging (MRI), in order to quantify alterations in the prostate resulting from surgical resection.

MATERIAL AND METHOD

Ten patients who had undergone 3 T prostate MRI using a phased-array coil and who were scheduled for prostatectomy were included in this prospective study. The ex-vivo specimen underwent MRI prior to formalin fixation or any other histopathological processing. Prostate volume in vivo and ex vivo was assessed using planimetry. Prostate shape was assessed by calculating ratios between the diameters of the prostate in all three dimensions.

RESULTS

Mean prostate volume was significantly smaller ex vivo than in vivo (39.7 ± 18.6 versus 50.8 ± 26.8 cm(3); p = 0.008), with an average change in volume of -19.5%. The right-to-left (RL)/anteroposterior (AP) ratio of the prostate, representing the shape of the prostate within its axial plane, was significantly larger ex vivo than in vivo (1.33 ± 0.14 versus 1.21 ± 0.12; p = 0.015), with an average percent change in RL/AP ratio of the prostate of +12.2%. There was no significant difference between in-vivo and ex-vivo acquisitions in terms of craniocaudal (CC)/AP (p = 0.963, median change = -2.1%) or RL/CC (p = 0.265, median change = +1.3%) ratios.

CONCLUSION

The observed volume and shape change following resection has not previously been assessed by comparison of in-vivo and fresh ex-vivo MRI and likely represents loss of vascularity and of connective tissue attachments in the ex-vivo state. These findings have implications for co-registration platforms under development to facilitate improved understanding of the accuracy of MRI in spatial localization of prostate tumours.

Preliminary experience with a novel method of three-dimensional co-registration of prostate cancer digital histology and in vivo multiparametric MRI

AIM

To assess a novel method of three-dimensional (3D) co-registration of prostate cancer digital histology and in-vivo multiparametric magnetic resonance imaging (mpMRI) image sets for clinical usefulness.

MATERIAL AND METHODS

A software platform was developed to achieve 3D co-registration. This software was prospectively applied to three patients who underwent radical prostatectomy. Data comprised in-vivo mpMRI [T2-weighted, dynamic contrast-enhanced weighted images (DCE); apparent diffusion coefficient (ADC)], ex-vivo T2-weighted imaging, 3D-rebuilt pathological specimen, and digital histology. Internal landmarks from zonal anatomy served as reference points for assessing co-registration accuracy and precision.

RESULTS

Applying a method of deformable transformation based on 22 internal landmarks, a 1.6 mm accuracy was reached to align T2-weighted images and the 3D-rebuilt pathological specimen, an improvement over rigid transformation of 32% (p = 0.003). The 22 zonal anatomy landmarks were more accurately mapped using deformable transformation than rigid transformation (p = 0.0008). An automatic method based on mutual information, enabled automation of the process and to include perfusion and diffusion MRI images. Evaluation of co-registration accuracy using the volume overlap index (Dice index) met clinically relevant requirements, ranging from 0.81-0.96 for sequences tested. Ex-vivo images of the specimen did not significantly improve co-registration accuracy.

CONCLUSION

This preliminary analysis suggests that deformable transformation based on zonal anatomy landmarks is accurate in the co-registration of mpMRI and histology. Including diffusion and perfusion sequences in the same 3D space as histology is essential further clinical information. The ability to localize cancer in 3D space may improve targeting for image-guided biopsy, focal therapy, and disease quantification in surveillance protocols.

Pancreatic cancer: lack of association between apparent diffusion coefficient values and adverse pathological features

AIM

To identify retrospectively potential associations between apparent diffusion coefficient (ADC) values of pancreatic adenocarcinoma and tumour grade as well as other pathological features, using histopathological assessment from the Whipple procedure as the reference standard.

MATERIALS AND METHODS

Thirty patients with pancreatic adenocarcinoma underwent magnetic resonance imaging (MRI) including diffusion-weighted imaging with b-values of 0 and 500 s/mm(2) before the Whipple procedure. Two radiologists independently recorded the ADC values of the tumour and benign pancreas for all cases. ADC values were compared with histopathological findings following the Whipple procedure.

RESULTS

The intra-class correlation coefficient was 0.689 for benign pancreas and 0.695 for tumours, indicating good inter-reader agreement for ADC values. The mean ADC value was significantly lower in tumours than in benign pancreas for both readers (reader 1: 1.74 ± 0.34 × 10(-3) mm(2)/s versus 2.08 ± 0.48 × 10(-3) mm(2)/s, respectively, p = 0.006; reader 2: 1.69 ± 0.41 × 10(-3) mm(2)/s versus 2.11 ± 0.54 × 10(-3) mm(2)/s, respectively, p < 0.001). However, there was no significant difference in mean ADC between poorly and well/moderately differentiated tumours for either reader (reader 1: 1.69 ± 0.36 × 10(-3) mm(2)/s versus 1.78 ± 0.33 × 10(-3) mm(2)/s, respectively, p = 0.491; reader 2: 1.62 ± 0.33 × 10(-3) mm(2)/s versus 1.75 ± 0.49 × 10(-3) mm(2)/s, respectively, p = 0.405). The area under the curve (AUC) for differentiation of poorly and well/moderately differentiated tumours was 0.611 and 0.596 for readers 1 and 2, respectively, and was not significantly better than an AUC of 0.500 for either reader (p ≥ 0.306). In addition, ADC was not significantly different for either reader between tumours with stage T3 versus stage T1/T2, between tumours with and without metastatic peri-pancreatic lymph nodes, or between tumours located in the pancreatic head versus other pancreatic regions (p ≥ 0.413).

CONCLUSION

No associations between ADC values of pancreatic adenocarcinoma and tumour grade or other adverse pathological features were observed.

Infiltrative hepatocellular carcinoma: comparison of MRI sequences for lesion conspicuity

AIM

To characterize the magnetic resonance imaging (MRI) features of infiltrative hepatocellular carcinoma (I-HCC), with emphasis on its relative conspicuity on different sequences.

MATERIALS AND METHODS

Nineteen patients exhibiting HCC with non-mass-like appearance and ill-defined margins, and who died within 1 year following diagnosis of I-HCC, were included. For each sequence, two observers independently assessed the lesion's signal intensity relative to benign liver as well as subjective visual conspicuity. The observers also selected the sequence exhibiting the greatest visual conspicuity. A separate radiologist placed regions of interest to measure tumour-to-liver contrast for each lesion. Tumour size and clinical features were also assessed.

RESULTS

Eighteen of the 19 patients exhibited central portal vein tumour thrombus; eight of the 19 patients had metastatic disease. All I-HCC measured over 5 cm. The two observers identified hyperintensity on T2-weighted imaging (WI) in 19 and 19 cases, hyperintensity on high b-value diffusion-weighted imaging (DWI) in 18 and 19 cases, arterial-phase hyperintensity in six and 10 cases, and venous-phase hypo-intensity in 17 and 16 cases. T2WI, DWI, and venous-phase images exhibited significantly greater subjective visual conspicuity than arterial-phase images for both observers (all p ≤ 0.040). Also, T2WI and DWI tended to exhibit greater tumour-to-liver contrast than arterial- and venous-phase images (all p ≤ 0.055). The arterial-phase was not selected as having greatest conspicuity for any case by either reader.

CONCLUSION

I-HCC is an aggressive form of HCC that is often less conspicuous on arterial-phase images than typical mass-forming HCC; T2WI and DWI may be more useful sequences for its diagnosis. Awareness of the distinct imaging features of I-HCC may be important for proper diagnosis.

Imaging appearance of bulk fat within an oncocytic adrenocortical neoplasm, a rare and potentially malignant tumour

Oncocytic adrenocortical neoplasm is a rare adrenal tumour that usually follows a benign clinical course. In some cases, however, these tumours have exhibited malignant behaviour. Here, we present the first published case showing bulk fat within an oncocytic adrenocortical neoplasm on CT and MRI, a finding that mimics fat within an adrenal myelolipoma. The distinction between these entities is important, as the current suggested management of an oncocytic adrenocortical neoplasm is resection with subsequent imaging surveillance.

MRI appearance of massive renal replacement lipomatosis in the absence of renal calculus disease

Renal replacement lipomatosis is a rare benign entity in which extensive fibrofatty proliferation of the renal sinus is associated with marked renal atrophy. In this report, we present a case of massive renal replacement lipomatosis demonstrated on MRI. The presentation was atypical given an absence of associated renal calculus disease, and an initial CT scan was interpreted as suspicious for a liposarcoma. The differential diagnosis and key MRI findings that served to establish this specific diagnosis are reviewed. Histopathological correlation is also presented, as the patient underwent nephroureterectomy.

CT and MRI appearance of solitary parapelvic neurofibroma of the kidney

We report an extremely rare case of a renal parapelvic neurofibroma. The mass was an incidental finding on an abdominal CT scan of an asymptomatic 59-year-old male with hepatitis C. Subsequent MRI demonstrated a complex mass occupying the left renal sinus that had mass effect on the pelvicalyceal system. The patient underwent left radical nephrectomy, and histological and immunohistochemical findings confirmed the lesion to be a neurofibroma. Given that similar imaging features have been reported previously in four additional cases, we suggest that it may be possible to include this entity in the pre-operative differential diagnosis.