C-arm flat-panel CT arthrography of the wrist and elbow: first experiences in human cadavers

Objective

To determine the optimal intra-articular iodine concentration for C-arm flat-panel computed tomography (FPCT) arthrography using advanced joint phantoms and to evaluate its application in human cadaveric wrists and elbows. Multi-detector (MD) CT served as the standard of reference.

Materials and methods

Joint phantoms and 10 human cadaveric wrist and elbow joints were scanned with C-arm FPCT (5-s, 8-s, and 20-s runs) and standard MDCT using different and optimal concentrations of iodinated contrast material. CT numbers of contrast material, tissue, and noise were measured and contrast-to-noise ratios (CNR) calculated for quantitative analysis. Image and depiction of cartilage, bone, and soft tissues were rated. Radiation doses were compared.

Results

In FPCT, iodine concentrations positively correlated with CT numbers and noise of contrast material and with radiation dose (r?=?0.713–0.996, p?<?0.05 each). At an iodine concentration of 45 mg/ml, CNR of cartilage and soft tissues were highest for all FPCT acquisitions and higher than in MDCT. The 20-s FPCT run performed best for image quality and depiction of anatomical structures and was rated overall equal to MDCT (p?=?0.857).

Conclusion

The optimal iodine concentration for C-arm FPCT arthrography in this study is 45 mg/ml, leading to superior CNR and image quality for an optimal FPCT protocol compared with standard MDCT arthrography in human cadaveric joints.     

Effective dose estimates for cone beam computed tomography in interventional radiology

Objectives

To compare radiation doses in cone beam computed tomography (CBCT) with those of multi-detector computed tomography (MDCT) using manufacturers’ standard protocols.

Methods

Dose-levels in head and abdominal imaging were evaluated using a dosimetric phantom. Effective dose estimates were performed by placing thermoluminescent dosimeters in the phantom. Selected protocols for two CBCT systems and comparable protocols for one MDCT system were evaluated. Organ doses were measured and effective doses derived by applying the International Commission on Radiological Protection 2007 tissue weighting factors.

Results

Effective doses estimated for the head protocol were 4.4 and 5.4 mSv for the two CBCT systems respectively and 4.3 mSv for MDCT. Eye doses for one CBCT system and MDCT were comparable (173.6 and 148.4 mGy respectively) but significantly higher compared with the second CBCT (44.6 mGy). Two abdominal protocols were evaluated for each system; the effective doses estimated were 15.0 and 18.6 mSv, 25.4 and 37.0 mSv, and 9.8 and 13.5 mSv, respectively, for each of the CBCT and MDCT systems.

Conclusions

The study demonstrated comparable dose-levels for CBCT and MDCT systems in head studies, but higher dose levels for CBCT in abdominal studies. There was a significant difference in eye doses observed between the CBCT systems.

Key Points

? Cone beam computed tomography (CBCT) is increasingly utilised in interventional radiology. ? Effective doses for selected CBCT and MDCT protocols were estimated and compared. ? Dose levels in CBCT and MDCT were comparable for head studies. ? Dose levels were higher in CBCT for abdominal studies.     

The role of MDCT arthrography in the follow-up of scapholunate stabilisation

Purpose

The aim of this study was to assess outcomes in a group of patients with scapholunate dissociation treated with stabilisation surgery (Brunelli-Stanley) and to compare arthrography with multidetector computed tomography (MDCT) with conventional radiography, the gold standard in the follow-up of wrist surgery.

Materials and methods

Twelve patients (13 wrists) underwent surgery for scapholunate dissociation and were followed up with clinical (visual analogue scale, Mayo Wrist Score, Patient-Rated Wrist Evaluation, and Disabilities of the Arm, Shoulder, and Hand) and radiological assessment (conventional radiography and CT arthrography). Conventional radiography was assessed for: the scapholunate gap, scapholunate angle, radiolunate angle, capitate-lunate angle, and carpal height index; the CT arthrography images were also evaluated for: the distance between the dorsal exit hole of the bone tunnel and the proximal scaphoid pole, the thickness and tension of the flexor carpi radialis (FCR) strip, and any signs of joint degeneration.

Results

Analysis of the data from conventional radiography and MDCT arthrography demonstrated a significant statistical correlation among the measurements obtained on the radiograms and multiplanar CT reconstructions and the patients’ clinical outcome.

Conclusions

Our results show that MDCT arthrography has the same value as conventional radiography in the evaluation of standard parameters (scapholunate gap, scapholunate angle, radiolunate angle, capitolunate angle, carpal height index), but in addition provides an accurate delineation of the FCR tendon graft, allowing differentiation of its thickness, direction and degree of tension.     

C-arm flat-panel CT arthrography of the shoulder: Radiation dose considerations and preliminary data on diagnostic performance

Objectives

To investigate radiation dose and diagnostic performance of C-arm flat-panel CT (FPCT) versus standard multi-detector CT (MDCT) shoulder arthrography using MRI-arthrography as reference standard.

Methods

Radiation dose of two different FPCT acquisitions (5 and 20 s) and standard MDCT of the shoulder were assessed using phantoms and thermoluminescence dosimetry. FPCT arthrographies were performed in 34 patients (mean age 44?±?15 years). Different joint structures were quantitatively and qualitatively assessed by two independent radiologists. Inter-reader agreement and diagnostic performance were calculated.

Results

Effective radiation dose was markedly lower in FPCT 5 s (0.6 mSv) compared to MDCT (1.7 mSv) and FPCT 20 s (3.4 mSv). Contrast-to-noise ratios (CNRs) were significantly (p?<?0.05) higher in FPCT 20-s versus 5-s protocols. Inter-reader agreements of qualitative ratings ranged between к?=?0.47–1.0. Sensitivities for cartilage and rotator cuff pathologies were low for FPCT 5-s (40 % and 20 %) and moderate for FPCT 20-s protocols (75 % and 73 %). FPCT showed high sensitivity (81–86 % and 89–99 %) for bone and acromioclavicular-joint pathologies.

Conclusion

Using a 5-s protocol FPCT shoulder arthrography provides lower radiation dose compared to MDCT but poor sensitivity for cartilage and rotator cuff pathologies. FPCT 20-s protocol is moderately sensitive for cartilage and rotator cuff tendon pathology with markedly higher radiation dose compared to MDCT.

Key Points

? FPCT shoulder arthrography is feasible with fluoroscopy and CT in one workflow. ? A 5-s FPCT protocol applies a lower radiation dose than MDCT. ? A 20-s FPCT protocol is moderately sensitive for cartilage and tendon pathology.

     

Feasibility and preliminary results of SPECT/CT arthrography of the wrist in comparison with MR arthrography in patients with suspected ulnocarpal impaction

Purpose

To evaluate the feasibility and performance of SPECT/CT arthrography of the wrist in comparison with MR arthrography in patients with suspected ulnocarpal impaction.

Methods

This prospective study included 28 wrists of 27 patients evaluated with SPECT/CT arthrography and MR arthrography. Iodine contrast medium and gadolinium were injected into the distal radioulnar and midcarpal joints. Late-phase SPECT/CT was performed 3.5 h after intravenous injection of approximately 650 MBq ^99mTc-DPD. MR and SPECT/CT images were separately reviewed in relation to bone marrow oedema, radionuclide uptake, and tears in the scapholunate (SL) and lunotriquetral (LT) ligaments and triangular fibrocartilage complex (TFCC), and an overall diagnosis of ulnar impaction. MR, CT and SPECT/CT imaging findings were compared with each other, with the surgical findings in 12 patients and with clinical follow-up.

Results

The quality of MR arthrography and SPECT/CT arthrography images was fully diagnostic in 23 of 28 wrists (82 %) and 25 of 28 wrists (89 %), respectively. SPECT/CT arthrography was not diagnostic for ligament lesions due to insufficient intraarticular contrast in one wrist. MR and SPECT/CT images showed concordant findings regarding TFCC lesions in 22 of 27 wrists (81 %), SL ligament in 22 of 27 wrists (81 %) and LT ligament in 23 of 27 wrists (85 %). Bone marrow oedema on MR images and scintigraphic uptake were concordant in 21 of 28 wrists (75 %). MR images showed partial TFCC defects in four patients with normal SPECT/CT images. MR images showed bone marrow oedema in 4 of 28 wrists (14 %) without scintigraphic uptake, and scintigraphic uptake was present without MR bone marrow oedema in three wrists (11 %). Regarding diagnosis of ulnar impaction the concordance rate between CT and SPECT/CT was 100 % and reached 96 % (27 of 28) between MR and SPECT/CT arthrography. The sensitivity and specificity of MR, CT and SPECT/CT arthrography were 93 %, 100 % and 100 %, and 93 %, 93 % and 93 %, respectively.

Conclusion

SPECT/CT arthrography of the wrist is feasible. Regarding diagnosis of ulnar impaction we found a high concordance with MR arthrography. SPECT/CT arthrography of the wrist is an alternative to MR arthrography in patients with contraindications to MR imaging.     

Intraprocedural 3D perfusion measurement during chemoembolisation with doxorubicin-eluting beads in liver metastases of malignant melanoma

Objectives

To study feasibility and validity of a new software application for intraprocedural assessment of perfusion during chemoembolisation of melanoma metastases.

Methodology

In a prospective phase-II trial, ten melanoma patients with liver-only metastases underwent chemoembolisation with doxorubicin-eluting beads (DEBDOX-TACE). Tumour perfusion was evaluated immediately before and after treatment at cone beam computer tomography (CBCT) using a new software application. For control and comparison, patients underwent perfusion measurement via contrast-enhanced multidetector CT (MDCT) before and after treatment.

Results

CBCT showed 94.7 % reduction in perfusion in metastases after DEBDOX-TACE, whereas MDCT showed 96.8 %. Reduction in perfusion after treatment was statistically significant (p < 0.01) for both methods. The additional time needed for data acquisition during treatment was 5 min per case or less; the post-processing data analysis was 10 min or less. Perfusion imaging was associated with additional contrast agent and patient exposure to radiation (dose-length product [DLP]): 18 ml and 394 mGy*cm in CBCT and 100 ml and 446 mGy*cm in MDCT, respectively.

Conclusions

Reduction in perfusion of melanoma metastases after DEBDOX-TACE can be reliably assessed during the intervention via perfusion software at CBCT. Data acquisition and analysis require additional time but can be easily performed during the treatment.

Key Points

? Tumour perfusion of melanoma metastases can be assessed at cone beam CT. ? The software shows a significant decrease of tumour perfusion after DEBDOX-TACE. ? Data acquisition and analysis require an acceptable additional time during the procedure. ? CBCT requires less radiation exposure and contrast for perfusion study than MSCT. ? This software can monitor the course of DEBDOX-TACE in melanoma metastases.

     

The diagnostic value of direct CT arthrography using MDCT in the evaluation of acetabular labral tear: with arthroscopic correlation

Objective

The purpose of this study was first, to determine the sensitivity, specificity, and accuracy of MDCT arthrography (CTA) for the diagnosis of acetabular labral tear and sulcus; second, to correlate tear types using the Lage classification system on CTA compared with the arthroscopic classification; and third, to correlate CTA localization with arthroscopic localization.

Materials and methods

Direct CTA was performed using 16- or 64-slice MDCT in 126 hips (124 patients) who had chronic groin pain and positive impingement test. Images were reviewed and evaluated by two experienced musculoskeletal radiologists preoperatively. CTA findings were compared with arthroscopic findings in 58 hips (56 patients) under consensus by two orthopedic surgeons.

Results

Forty-one of the 58 hips were diagnosed as labral tears on CT arthrography. Forty-three of the 58 hips were shown to have a labral tear on arthroscopy. Sensitivity, specificity, and accuracy for detecting labral tear and sulcus by CTA were 90.7%, 86.7%, and 89.7%, and 93.8%, 97.6% and 96.6% respectively for observer 1, and 90.7% and 80.0%, 87.9% and 87.5%, 95.2%, and 93.1 % respectively for observer 2. Thirty-five out of 41 hips (85%) that were diagnosed with labral tear on CTA correlated substantially with arthroscopic Lage classification (kappa coefficient = 0.65). CTA and arthroscopic findings showed similar distribution patterns of the tears with most lesions located in antero- and postero-superior areas (p?=?0.013).

Conclusion

Direct CT arthrography using MDCT may be a useful diagnostic technique in the detection of acetabular labral tear.     

Darstellung subtiler Schläfenbeinstrukturen

Purpose

The purpose of this study was to compare the visualization of subtle, non-pathological temporal bone structures on cone beam computed tomography (CBCT) and multi-detector computed tomography (MDCT) in vivo.

Materials and methods

Temporal bone studies of images from 38 patients archived in the picture archiving and communication system (PACS) were analyzed (slice thickness MDCT 0.6 mm and CBCT 0.125 mm) of which 23 were imaged by MDCT and 15 by CBCT using optimized standard protocols. Inclusion criteria were normal radiological findings, absence of previous surgery and anatomical variants. Images were evaluated blind by three trained observers. Using a five-point scale the visualization of ten subtle structures of the temporal bone was analyzed.

Results

Subtle middle ear structures showed a tendency to be more easily distinguishable by CBCT with significantly better visualization of the tendon of the stapedius muscle and the crura of the stapes on CBCT (p?=?0.003 and p?=?0.033, respectively). In contrast, inner ear components, such as the osseus spiral lamina and the modiolus tended to be better detectable on MDCT, showing significant differences for the osseous spiral lamina (p?=?0.001). The interrater reliability was 0.73 (Cohen’s kappa coefficient) and intraobserver reliability was 0.89.

Conclusion

The use of CBCT and MDCT allows equivalent and excellent imaging results if optimized protocols are chosen. With both imaging techniques subtle temporal bone structures could be visualized with a similar degree of definition. In vivo differences do not seem to be as large as suggested in several previous studies.     

Dose reduction in spiral CT coronary angiography with dual-source equipment. Part I. A phantom study applying different prospective tube current modulation algorithms

Purpose

The authors sought to compare different algorithms for dose reduction in retrospectively echocardiographically (ECG)-gated dual-source computed tomography (CT) coronary angiography (DSCT-CA) in a phantom model.

Materials and methods

Weighted CT dose index (CTDI) was measured by using an anthropomorphic phantom in spiral cardiac mode (retrospective ECG gating) at five pitch values adapted with two heart-rate-adaptive ECG pulsing windows using four algorithms: narrow pulsing window, with tube current reduction to 20% (A) and 4% (B) of peak current outside the pulsing window; wide pulsing window, with tube current reduction to 20% (C) and 4% (D). Each algorithm was applied at different heart rates (45, 60, 75, 90, 120 bpm).

Results

Mean CTDI volume (CTDIvol) was 36.9±9.7 mGy, 23.9±5.6 mGy, 49.7±16.2 mGy and 38.5±12.3 mGy for A, B, C and D, respectively. Consistent dose reduction was observed with protocols applying the 4% tube current reduction (B and D). Using the conversion coefficient for the chest, the mean effective dose was the highest for C (9.6 mSv) and the lowest for B (4.6 mSv). Heart-ratedependent pitch values (pitch=0.2, 0.26, 0.34, 0.43, 0.5) and the use of heart-rate-adaptive ECG pulsing windows provided a significant decrease in the CTDIvol with progressively higher heart rates (45, 60, 75, 90, 120 bpm), despite using wider pulsing windows.

Conclusions

Radiation exposure with DSCT-CA using a narrow pulsing window significantly decreases when compared with a wider pulsing window. When using a protocol with reduced tube current to 4%, the radiation dose is significantly lower.     

CT arthrography of the wrist using a novel, mobile, dedicated extremity cone-beam CT (CBCT)

Purpose

To evaluate the feasibility and intra- and interobserver agreement of CBCT arthrography of wrist ligaments, triangular fibrocartilaginous complex (TFCC), and to assess the sensitivity (SE), specificity (SP), accuracy (ACC), and positive and negative predictive value (PPV, NPV) of CBCT arthrography in the diagnosis of scapholunate (SLL) and lunotriquetral (LTL) ligament tears, TFCC, and cartilage abnormalities of the scaphoid and lunate with their corresponding radial surfaces (scaphoid and lunate fossa) using a novel, mobile, dedicated extremity CBCT scanner.

Materials and methods

Fifty-two consecutively enrolled subjects (26 M, 26 F, mean age 38 years, range 18–66 years) with suspected wrist ligament tears underwent CBCT-arthrography before normally scheduled MR arthrography.An extremity CBCT was used for imaging with isotropic voxel size of 0.4 × 0.4 × 0.4 mm³. Subsequent routine 1.5 T MRI was performed using a dedicated wrist coil.Two observers reviewed the anonymized CBCT images twice for contrast enhancement (CE) and technical details (TD), for tears of the SLL, LTL, and TFCC. Also, cartilage abnormalities of the scaphoid and lunate with their corresponding radial surfaces (scaphoid and lunate fossa) were evaluated. Inter- and intraobserver agreement was determined using weighted kappa statistics. Since no surgery was performed, MRI served as a reference standard, and SE and SP, ACC, PPV, and NPV were calculated.

Results

Intra- and interobserver kappa values for both readers (reader 1/reader 2; first reading/second reading) with 95 % confidence limits were: CE 0.54 (0.08–1.00)/ 0.75 (0.46–1.00); 0.73 (0.29–1.00)/ 0.45 (0.07–0.83), TD 0.53 (0.30–0.88)/ 0.86 (0.60–1.00); 0.56 (0.22–0.91)/ 0.67 (0.37–0.98), SLL 0.59 (0.25–0.93)/ 0.66 (0.42–0.91); 0.31 (0.06–0.56)/ 0.49 (0.26–0.73), LTL 0.83 (0.66–1.00)/ 0.68 (0.46–0.91); 0.90 (0.79–1.00)/ 0.48 (0.22–0.74); TFCC (0.72–1.00)/ (0.79–1.00); 0.65 (0.43–0.87)/ 0.59 (0.35–0.83), radius (scaphoid fossa) 0.45 (0.12–0.77)/ 0.64 (0.31–0.96); 0.58 (0.19–0.96)/ 0.38 (0.09–0.66), scaphoid 0.43 (0.12–0.74)/ 0.76 (0.55–0.96); 0.37 (0.00–0.75)/ 0.32 (0.04–0.59), radius (lunate fossa) 0.68 (0.36–1.00)/ 0.42 (0.00–0.86); 0.62 (0.29–0.96)/ 0.51 (0.12–0.91), and lunate 0.53 (0.16–0.90)/ 0.68 (0.44–0.91); 0.59 (0.29–0.88)/ 0.42 (0.00–0.84), respectively. The overall mean accuracy was 82–92 % and specificity was 81–94 %. Sensitivity for LTL and TFCC tears was 76–83, but for SLL tears it was 58 %. For cartilage abnormalities, the accuracy and negative predictive value were high, 90–98 %.

Conclusions

A dedicated CBCT extremity scanner is a new method for evaluating the wrist ligaments and radiocarpal cartilage. The method has an overall accuracy of 82–86 % and specificity 81–91 %. For cartilage abnormalities, the accuracy and negative predictive value were high.     

Injuries of the scapholunate and lunotriquetral ligaments as well as the TFCC in intra-articular distal radius fractures. Prevalence assessed with MDCT arthrography

Objectives

To evaluate the prevalence of injuries of the scapholunate and lunotriquetral interosseous ligaments (SLIL, LTIL) as well as the triangular fibrocartilage complex (TFCC) in intra-articular distal radius fractures (iaDRF).

Methods

Two hundred and thirty-three patients with acute iaDRF underwent MDCT arthrography. The SLIL and LTIL were described as normal, partially or completely ruptured. Major injuries of the SLIL were defined as completely ruptured dorsal segments, those of the LTIL as completely ruptured palmar segments. The TFCC was judged as normal or injured. Interobserver variability was calculated. Injury findings were correlated with the types of iaDRF (AO classification).

Results

In 159 patients (68.2 %), no SLIL injuries were seen. Minor SLIL injuries were detected in 54 patients (23.2 %), major injuries in 20 patients (8.6 %). No correlation was found between the presence of SLIL lesions and the types of iaDRF. Minor LTIL injuries were seen in 23 patients (9.9 %), major injuries in only 5 patients (2.2 %). The TFCC was altered in 141 patients (60.5 %). Interobserver variability was high for MDCT arthrography in assessing SLIL and TFC lesions, and fair for LTIL lesions.

Conclusion

In iaDRF, prevalence of major injuries of the most relevant SLIL is about 9 % as evaluated with CT arthrography.

Key Points

? The C-shaped SLIL is built of dorsal, middle and palmar segments. ? In iaDRF, major SLIL injuries are associated in 8.6 % of the cases. ? In iaDRF, the SLIL remains intact in 68.3 % of the cases. ? IaDRF and SLIL ruptures can comprehensively be depicted with MDCT arthrography. ? A three-compartment approach is recommended to assess intrinsic ligaments and the TFCC.

     

MR versus MR arthrography in detection of supraspinatus tendon tears in patients without previous shoulder surgery

Purpose

We report the prevalence of supraspinatus tendon tears seen on MR arthrography that are not seen on conventional MR exam in the same patient population.

Materials and methods

A total of 150 consecutive conventional shoulder MR and MR arthrography exams performed on the same patients who went on to arthroscopy were reviewed retrospectively by consensus reading of two musculoskeletal radiologists. Full-thickness supraspinatus tendon tears were assessed. None of the patients had previous shoulder surgery.

Results

There were 113 full-thickness supraspinatus tendon tears seen on conventional MR exam while there were 119 full-thickness supraspinatus tendon tears seen on MR arthrography. The six additional full-thickness supraspinatus tendon tears seen on MR arthrography but not seen on conventional MR exam were confirmed at arthroscopy.

Conclusions

Some full-thickness supraspinatus tendon tears are not seen on conventional MR exam but are seen on MR arthrography. This is most likely due to fibrosis at the supraspinatus tendon tear site simulating an intact tendon on conventional MR.     

Accuracy of magnetic resonance imaging, magnetic resonance arthrography and computed tomography for the detection of chondral lesions of the knee

Purpose

To assess the diagnostic test accuracy of magnetic resonance imaging (MRI), magnetic resonance arthrography (MRA) and computed tomography arthrography (CTA) for the detection of chondral lesions of the patellofemoral and tibiofemoral joints.

Methods

A review of published and unpublished literature sources was conducted on 22nd September 2011. All studies assessing the diagnostic test accuracy (sensitivity/specificity) of MRI or MRA or CTA for the assessment of adults with chondral (cartilage) lesions of the knee (tibiofemoral/patellofemoral joints) with surgical comparison (arthroscopic or open) as the reference test were included. Data were analysed through meta-analysis.

Results

Twenty-seven studies assessing 2,592 knees from 2,509 patients were included. The findings indicated that whilst presenting a high specificity (0.95?C0.99), the sensitivity of MRA, MRI and CTA ranged from 0.70 to 0.80. MRA was superior to MRI and CTA for the detection of patellofemoral joint chondral lesions and that higher field-strength MRI scanner and grade four lesions were more accurately detected compared with lower field-strength and grade one lesions. There appeared no substantial difference in diagnostic accuracy between the interpretation from musculoskeletal and general radiologists when undertaking an MRI review of tibiofemoral and patellofemoral chondral lesions.

Conclusions

Specialist radiological imaging is specific for cartilage disease in the knee but has poorer sensitivity to determine the therapeutic options in this population. Due to this limitation, there remains little indication to replace the ??gold-standard?? arthroscopic investigation with MRI, MRA or CTA for the assessment of adults with chondral lesions of the knee.

Level of evidence

II.     

Accuracy of linear intraoral measurements using cone beam CT and multidetector CT: a tale of two CTs

Objectives

The aim was to compare the accuracy of linear bone measurements of cone beam CT (CBCT) with multidetector CT (MDCT) and validate intraoral soft-tissue measurements in CBCT.

Methods

Comparable views of CBCT and MDCT were obtained from eight intact cadaveric heads. The anatomical positions of the gingival margin and the buccal alveolar bone ridge were determined. Image measurements (CBCT/MDCT) were performed upon multiplanar reformatted data sets and compared with the anatomical measurements; the number of non-assessable sites (NASs) was evaluated.

Results

Radiological measurements were accurate with a mean difference from anatomical measurements of 0.14 mm (CBCT) and 0.23 mm (MDCT). These differences were statistically not significant, but the limits of agreement for bone measurements were broader in MDCT (−1.35 mm; 1.82 mm) than in CBCT (−0.93 mm; 1.21 mm). The limits of agreement for soft-tissue measurements in CBCT were smaller (−0.77 mm; 1.07 mm), indicating a slightly higher accuracy. More NASs occurred in MDCT (14.5%) than in CBCT (8.3%).

Conclusions

CBCT is slightly more reliable for linear measurements than MDCT and less affected by metal artefacts. CBCT accuracy of linear intraoral soft-tissue measurements is similar to the accuracy of bone measurements.     

Intrinsic ligament and triangular fibrocartilage complex tears of the wrist: comparison of MDCT arthrography, conventional 3-T MRI, and MR arthrography

Purpose

This study compares the diagnostic performance of multidetector CT arthrography (CTA), conventional 3-T MR and MR arthrography (MRA) in detecting intrinsic ligament and triangular fibrocartilage complex (TFCC) tears of the wrist.

Materials and methods

Ten cadaveric wrists of five male subjects with an average age 49.6 years (range 26–59 years) were evaluated using CTA, conventional 3-T MR and MRA. We assessed the presence of scapholunate ligament (SLL), lunotriquetral ligament (LTL), and TFCC tears using a combination of conventional arthrography and arthroscopy as a gold standard. All images were evaluated in consensus by two musculoskeletal radiologists with sensitivity, specificity, and accuracy being calculated.

Results

Sensitivities/specificity/accuracy of CTA, conventional MRI, and MRA were 100 %/100 %/100 %, 66 %/86 %/80 %, 100 %/86 %/90 % for the detection of SLL tear, 100 %/80 %/90 %, 60 %/80 %/70 %, 100 %/80 %/90 % for the detection of LTL tear, and 100 %/100 %/100 %, 100 %/86 %/90 %, 100 %/100 %/100 % for the detection of TFCC tear. Overall CTA had the highest sensitivity, specificity, and accuracy among the three investigations while MRA performed better than conventional MR. CTA also had the highest sensitivity, specificity, and accuracy for identifying which component of the SLL and LTL was torn. Membranous tears of both SLL and LTL were better visualized than dorsal or volar tears on all three imaging modalities.

Conclusion

Both CT and MR arthrography have a very high degree of accuracy for diagnosing tears of the SLL, LTL, and TFCC with both being more accurate than conventional MR imaging.     

Pericruciate fat pad of the knee: anatomy and pericruciate fat pad inflammation: cadaveric and clinical study emphasizing MR imaging

Objective

The pericruciate fat pad is located in the intercondylar fossa, intimate with the cruciate ligaments. With MR imaging, signal abnormality of the pericruciate fat pad has been observed in patients with posterior knee pain. The purpose of this study was to describe the anatomy of the pericruciate fat pad in cadaveric specimens and to document the clinical spectrum of pericruciate fat pad inflammation.

Materials and Methods

Twelve cadaveric knees underwent MR imaging with T1 and T2 multiplanar images. Cadaveric sections were then prepared for macroscopic evaluation, with additional histologic analysis performed in four cases. MR images in seventeen patients (ten males, seven females; average age, 31.5?years; age range, 19–57?years) involved in intensive sporting activity and with posterior knee pain were reviewed.

Results

MR images in cadaveric specimens showed a fat pad that was located above and between the cruciate ligaments, near their attachment sites in the inner portion of the femoral condyles, within the intercondylar fossa. Fatty tissue covered by a thin layer of synovial membrane was confirmed at histology. Seventeen patients with posterior knee pain and without gross cartilage, meniscal, or ligamentous abnormalities all revealed an increased signal in this fat pad in fluid-sensitive fat-suppressed images, mainly in the sagittal and axial planes. In eight cases, enhancement of this fat pad was demonstrated following intravenous gadolinium administration.

Conclusions

The pericruciate fat pad is a structure located in the intercondylar fossa, intimate with both the anterior and posterior cruciate ligaments. Inflammatory changes in this fat pad may be found in patients, especially athletes with posterior knee pain.     

Emergency CT head and neck imaging: effects of swimmer’s position on dose and image quality

Objectives

To compare the effects of different arm positions on dose exposure and image quality (IQ) in cervical spine CT after trauma in different patient groups.

Methods

Patients in standard (STD?=?126) and in swimmer’s position (SWIM?=?254) were included. Body mass index (BMI subgroup 1?=?underweight to subgroup 4?=?obese), anterior–posterior diameter (AP), left–right diameter (LR), area of an ellipse (AoE) and angle between the humeral heads (optimal STD?<?3°, optimal SWIM?>?10°) were used as grouping criteria. Computed tomography dose index (CTDI) was documented. Two radiologists rated the IQ at three levels (CV1/2, CV4/5, CV7/T1) using a semi-quantitative scale (0?=?not diagnostic, 1?=?diagnostic with limitations, 2?=?diagnostic without limitations). The Mann–Whitney U test correlations of grouping criteria with dose effects and intra-class correlation (ICC) were calculated.

Results

ICC was 0.87. BMI grouping showed the strongest correlation with dose effects: CTDI of optimal STD versus optimal SWIM positioning was 3.17 mGy versus 2.46 mGy (subgroup 1), 5.47 mGy versus 3.97 mGy (subgroup 2), 7.35 mGy versus 5.96 mGy (subgroup 3) and 8.71 mGy versus 8.18 mGy (subgroup 4). Mean IQ at CV7/T1 was 1.65 versus 1.23 (subgroup 1), 1.27 versus 1.46 (subgroup 2), 1.06 versus 1.46 (subgroup 3), 0.79 versus 1.5 (subgroup 4).

Conclusion

Patients with a BMI?>?20 kg/m² benefited from both potential dose reduction and improved image quality at the critical cervicothoracic junction when swimmer’s position was used.

Key Points

? BMI is a useful metric for personalized optimization in CT for the c-spine. ? Using swimmer’s position, patients can benefit from dose reduction. ? In some patients a superior image quality can be achieved with swimmer’s position. ? For swimmer’s positioning an angle of more than 10° is optimal.     

Image noise-based dose adaptation in dynamic volume CT of the heart: dose and image quality optimisation in comparison with BMI-based dose adaptation

Objectives

To compare the image quality and radiation dose using image-noise (IN)-based determination of X-ray tube settings compared with a body mass index (BMI)-based protocol during CT coronary angiography (CTCA).

Methods

Two hundred consecutive patients referred for CTCA to our institution were divided into two groups: BMI-based, 100 patients had CTCA with the X-ray tube current adjusted to the patient’s BMI while maintaining a fixed tube potential of 120 kV; IN-based, 100 patients underwent imaging with the X-ray tube current and voltage adjusted to the IN measured within the mid-left ventricle on a pre-acquisition trans-axial image. Two independent cardiac radiologists performed blinded image quality assessment with quantification of the IN and signal-to-noise ratio (SNR) from the mid-LV and qualitative assessment using a three-point score. Radiation dose (CTDI and DLP) was recorded from the console.

Results

Results showed: IN (HU): BMI-based, 30.1?±?9.9; IN-based, 33.1?±?6.7; 32 % variation reduction (P?=?0.001); SNR: BMI-based, 18.6?±?7.1; IN-based, 15.4?±?3.7; 48 % variation reduction (P?<?0.0001). Visual scores: BMI-based, 2.3?±?0.6; IN-based, 2.2?±?0.5 (P?=?0.54). Radiation dose: CTDI (mGy), BMI-based, 22.68?±?8.9; IN-based, 17.16?±?7.6; 24.3 % reduction (P?<?0.001); DLP (mGy.cm), BMI-based, 309.3?±?127.5; IN-based, 230.6?±?105.5; 25.4 % reduction (P?<?0.001).

Conclusions

Image-noise-based stratification of X-ray tube parameters for CTCA results in 32 % improvement in image quality and 25 % reduction in radiation dose compared with a BMI-based protocol.

Key Points

? Image quality and radiation dose are closely related in CT coronary angiography. ? So too are the image quality, radiation dose and body mass index (BMI). ? An image-noise-based CTCA protocol reduces the radiation dose by 25 %. ? It improves inter-patient image homogeneity by 32 %.     

Low-dose unenhanced CT protocols according to individual body size for evaluating suspected renal colic: cumulative radiation exposures

Purpose

The aim of this study was to assess the radiation dose of dose-reduced unenhanced abdominal multidetector computed tomography (MDCT) scan protocols for suspected renal colic in patients within normal weight range and overweight-obese patients and to record the cumulative dose of repeated examinations.

Materials and methods

Over a 2-year period, we performed 1,026 unenhanced CT examinations for urolithiasis; among these, 675 were performed on 636 patients referred from the emergency department. Patients were divided into two groups on the basis of body mass index (BMI): normal weight (BMI <25 kg/m² group 1); overweight and obese (BMI >25 kg/m² group 2). For patients in group 1 and group 2, the protocols of our 64-row scanner prescribe tube current settings at 70 mAs and 150 mAs, respectively. The dose-length product (DLP) estimated by using the manufacturer’s software was converted into effective dose (ED).

Results

Mean DLP and ED were 177 and 345 mGy/cm and 2.4 and 4.8 mSv for group 1 and group 2, respectively. A subset of 25 patients (3.7%) underwent two or more examinations, with estimated ED ranging from 4.8 to 19.2 mSv.

Conclusions

Although radiation dose is nearly double in overweight-obese patients undergoing MDCT, it remains lower than that delivered by a standard-dose protocol. Patients with flank pain, who are often young, are at increased risk for serial CT examinations. Use of a low-dose protocol is mandatory in both normal-weight and obese patients to minimise radiation exposure.