CT-guided intervention with low radiation dose: feasibility and experience

Impact of radiation dose reduction and iterative image reconstruction on CT-guided spine biopsies

This study aimed to systematically evaluate the impact of dose reduction on image quality and confidence for intervention planning and guidance regarding computed tomography (CT)-based intervertebral disc and vertebral body biopsies. We retrospectively analyzed 96 patients who underwent multi-detector CT (MDCT) acquired for the purpose of biopsies, which were either derived from scanning with standard dose (SD) or low dose (LD; using tube current reduction). The SD cases were matched to LD cases considering sex, age, level of biopsy, presence of spinal instrumentation, and body diameter. All images for planning (reconstruction: "IMR1") and periprocedural guidance (reconstruction: "iDose4") were evaluated by two readers (R1 and R2) using Likert scales. Image noise was measured using attenuation values of paraspinal muscle tissue. The dose length product (DLP) was statistically significantly lower for LD scans regarding the planning scans (SD: 13.8 ± 8.2 mGy*cm, LD: 8.1 ± 4.4 mGy*cm, p < 0.01) and the interventional guidance scans (SD: 43.0 ± 48.8 mGy*cm, LD: 18.4 ± 7.3 mGy*cm, p < 0.01). Image quality, contrast, determination of the target structure, and confidence for planning or intervention guidance were rated good to perfect for SD and LD scans, showing no statistically significant differences between SD and LD scans (p > 0.05). Image noise was similar between SD and LD scans performed for planning of the interventional procedures (SD: 14.62 ± 2.83 HU vs. LD: 15.45 ± 3.22 HU, p = 0.24). Use of a LD protocol for MDCT-guided biopsies along the spine is a practical alternative, maintaining overall image quality and confidence. Increasing availability of model-based iterative reconstruction in clinical routine may facilitate further radiation dose reductions.

Comparison of acquisition and iterative reconstruction parameters in abdominal computed tomography-guided procedures: a phantom study

BACKGROUND

Many computed tomography (CT) navigation systems have been developed to help radiologists improve the accuracy and safety of the procedure. We evaluated the accuracy of one CT computer-assisted guided procedure with different reduction dose protocols.

METHODS

A total of 128 punctures were randomly made by two operators on two different anthropomorphic phantoms. The tube voltage was fixed to 100 kVp. Tube currents (mAs) were defined to obtain 4 dose levels: 180 mAs (D1.00), 90 mAs (D0.50), 45 mAs (D0.25) and 15 mAs (D0.10) with respective volume CT dose index (CTDIvol) of 7.02, 3.52, 1.75 and 0.59 mGy. The raw data were reconstructed using level 2 of advanced model-based iterative reconstruction (ADMIRE) (A2) for D1.00, A3 for D0.50, A4 for D0.25 and A5 for D0.10. Two 12-mm targets per phantom were selected. The mean Euclidean distance (EuD) between the tip of the needle and the isocenter of the target was measured for each puncture. The different measures were compared by paired Student's t-tests.

RESULTS

The mean EuD was 7.0±3.1 mm for the 128 punctures performed. Regardless of which phantom was considered, no significant difference in accuracy occurred between the 4 dose levels, which were 7.1±3.5 mm for D1.00; 7.1±3.1 mm for D0.50; 7.2±3.0 mm for D0.25 and 6.6±2.6 mm for D0.10.

CONCLUSIONS

Abdominal CT-guided procedures, using computer-assisted navigation and iterative reconstruction algorithms, allow precise punctures on anthropomorphic phantoms with a dose reduction of -92% compared to a standard protocol.

Impact of interventionalist's experience and gender on radiation dose and procedural time in CT-guided interventions-a retrospective analysis of 4380 cases over 10 years

Objectives

To investigate the impact of the interventionalist’s experience and gender on radiation dose and procedural time in CT-guided interventions.

Methods

We retrospectively analyzed 4380 CT-guided interventions performed at our institution with the same CT scanner from 2009 until 2018, 1287 (29%) by female and 3093 (71%) by male interventionalists. Radiation dose, number of CT fluoroscopy images taken per intervention, total procedural time, type of intervention, and degree of difficulty were derived from the saved dose reports and images. All 16 interventionalists included in this analysis performed their first CT-guided interventions during the study period, and interventions performed by each interventionalist were counted to assess the level of experience for each intervention in terms of the number of prior interventions performed by her or him. The Mann-Whitney U test (MWU test), multivariate regression, and linear mixed model analysis were performed.

Results

Assessment of the impact of gender with the MWU test revealed that female interventionalists took a significantly smaller number of images (p < 0.0001) and achieved a lower dose-length product per intervention (p < 0.0001) while taking more time per intervention (p = 0.0001). This finding was confirmed for most types of interventions when additionally accounting for other possible impact factors in multivariate regression analysis. In linear mixed model analysis, we found that radiation dose, number of images taken per intervention, and procedural time decreased statistically significantly with interventionalist’s experience.

Conclusions

Radiation doses of CT-guided interventions are reduced by interventionalist’s experience and, for most types of interventions, when performed by female interventionalists.

Key Points

• Radiation doses in CT-guided interventions are lower when performed by female interventionalists.

• Procedural times of CT-guided interventions are longer when performed by female interventionalists.

• Radiation doses of CT-guided interventions decrease with the interventionalist’s experience.

Electronic supplementary material

The online version of this article (10.1007/s00330-020-07185-x) contains supplementary material, which is available to authorized users.

Radiation exposure of radiologists during different types of CT-guided interventions: an evaluation using dosimeters placed above and under lead protection

Background

Computed tomography (CT) is widely used not only for diagnostic purposes but also for image guidance during different types of interventions. Therefore, radiation exposure of both patients and interventional radiologists remains a much-discussed topic.

Purpose

To quantify radiation exposure of interventional radiologists during multiple CT-guided interventions using dosimeters placed under and outside standard protective lead clothing.

Material and Methods

A total of 113 consecutive interventions covering three different types of procedures (grouped as periradicular infiltration therapy, biopsies, and drain placement) and performed using routine clinical protocols were prospectively analyzed. The interventions were performed by two radiologists of different experience levels with identically placed dosimeters outside and underneath their protective clothing. Personal doses (right hand, eye lens, thyroid gland, thorax, gonads) were cumulatively measured for each type of intervention and separately for the two radiologists.

Results

Personal dose was below the detection limit of the dosimeters during periradicular infiltration therapy. In the biopsy and drain placement groups, the highest dose was found for the right hand (maximum cumulative dose = 1.84 ± 1.30 mSv in 19 consecutive drain placements). Under the protective gear, exposure was only observed for drain placements performed by the less experienced radiologist (maximum = 0.05 ± 0.04 mSv for the eye lens).

Conclusion

Personal doses measured here were far below annual thresholds published by the International Commission on Radiological Protection. Therefore, performing multiple CT-guided interventions appears to be safe for interventional radiologists in terms of radiation exposure.

Body interventional procedures: which is the best method for CT guidance?

OBJECTIVES

To compare sequential fluoroscopy guidance with spiral guidance in terms of safety, effectiveness, speed and radiation in interventional whole body procedures.

METHODS

This study was a retrospective analysis of data from the prospective, randomised controlled, multicentre CTNAV2 study. The present analysis included 385 patients: 247 in the sequential group (SEQ) and 138 in the spiral group (SPI). Safety was assessed by the number of major complications. Effectiveness was measured according to the number of targets reached. Data on procedural time and radiation delivered to patients were also collected.

RESULTS

There was no significant difference between the two groups (SEQ vs SPI) regarding the success rate (99.6% vs 99.3%, p = 0.680), procedural time (7 min 40 s ± 5 min 48 s vs 7 min 13 s ± 7 min 33 s, p = 0.507), or major complications (2.43% vs 5.8%, p = 0.101). Radiation dose to patients was 84% lower in the sequential group (54.8 ± 51.8 mGy cm vs 352.6 ± 404 mGy cm, p < 0.0001).

CONCLUSIONS

Sequential CT fluoroscopy-guided whole-body interventional procedures seems to be as safe, effective and fast as spiral guidance, while also yielding a significant decrease in the radiation dose to patients.

KEY POINTS

• Sequential CT fluoroscopy and spiral acquisition are comparable in terms of safety, effectiveness and speed. • Procedural times are comparable despite an increased number of acquisitions in sequential fluoroscopy. • Radiation dose to patients is 84% lower in sequential fluoroscopy compared with spiral CT.

Ultralow dose computed tomography protocol for hook-wire localization of solitary pulmonary nodules prior to video-assisted thoracoscopic surgery

BACKGROUND

This study prospectively investigated the efficacy and radiation dose of ultralow dose computed tomography (CT)-guided hook-wire localization (HWL) at 100 kV with tin filtration (100Sn kV) for small solitary pulmonary nodules.

METHODS

All HWL procedures were performed on a third generation dual-source CT system. Eighty-eight consecutive patients undergoing CT-guided HWL were randomly assigned to standard dose CT (Group A: n = 44; reference 110 kV and 50 mA) or ultralow dose CT (Group B: n =44; ¹⁰⁰ Sn kV and 96 mA) protocols. The technical success rate, complications, subjective image quality, and radiation dose were compared between the groups.

RESULTS

The mean volume CT dose index and total dose-length product were significantly lower in Group B compared to Group A (0.32 mGy vs. 3.2 ± 1.1 mGy and 12.1 ± 0.97 mGy-cm vs. 120 ± 40.6 mGy-cm; P < 0.001). The effective dose in Group B was significantly lower than in Group A (0.17 ± 0.01 mSv vs. 1.68 ± 0.57 mSv, -89.8%; P < 0.001). The technical success rates were 100% for both groups. There were no significant differences in complication rates between the protocols (P > 0.05). The image quality of ultralow dose CT met the requirements for HWL procedure.

CONCLUSION

Ultralow dose CT-guided HWL of solitary pulmonary nodules performed at ¹⁰⁰ Sn kVp spectral shaping significantly reduced the radiation dose compared to standard dose CT, with high technical success and acceptable patient safety.

Radiation Dose and Risk Estimates of CT-Guided Percutaneous Liver Ablations and Factors Associated with Dose Reduction

PURPOSE

To determine the radiation dose associated with CT-guided percutaneous liver ablations and identify potential risk factors that result in higher radiation doses.

MATERIALS AND METHODS

Between June 2011 and June 2015, 245 consecutive patients underwent 304 CT-guided liver ablation treatments. Patient demographics, tumor characteristics and procedural parameters were identified and analyzed. The peak skin dose and effective dose were assessed for each procedure. Excess relative risk related to radiation effects was calculated. A logistic regression model was prepared by means of stepwise logistic regression to identify variables predictive of increased radiation exposure.

RESULTS

Tumor ablations were performed with microwave (n = 220), radiofrequency (n = 74) or irreversible electroporation (IRE) (n = 10). The mean peak skin dose for ablations was 239.2 ± 136.4 mGy, and the mean effective dose was 36.6 ± 22.3 mSv. Of the patient and procedural parameters that were analyzed, increasing weight, use of intravenous contrast and/or hydrodissection during the procedure, together with treatment of multiple lesions in the same sitting were all associated with higher radiation exposure. The mean increase in the absolute risk of fatal malignancy from a single procedure was 0.18% (range 0.02-0.9%). No deterministic skin changes were identified in the patient cohort.

CONCLUSION

The overall risk of stochastic and deterministic effects from radiation associated with CT-guided ablations is low compared with other inherent procedural complications. This study identifies several factors that are associated with higher radiation dose in percutaneous liver ablation procedures.

Practical dose reduction tips for abdominal interventional procedures using CT-guidance

Reducing the radiation dose should be an endeavor not only for diagnostic CT exams but also for interventional procedures using CT-guidance. Given that interventional procedures vary in scope and complexity, there is greater variability in radiation doses delivered during CT procedures. The goal in an interventional procedure is simply to advance the interventional instruments into the target lesions, and as such diagnostic level doses are not required and only narrow scan range scans need to be acquired. Adherence to the principles outlined in this article will allow such procedures to be performed with reduced radiation doses.

Comparison of measured and estimated maximum skin doses during CT fluoroscopy lung biopsies

PURPOSE

To measure patient-specific maximum skin dose (MSD) associated with CT fluoroscopy (CTF) lung biopsies and to compare measured MSD with the MSD estimated from phantom measurements, as well as with the CTDIvol of patient examinations.

METHODS

Data from 50 patients with lung lesions who underwent a CT fluoroscopy-guided biopsy were collected. The CT protocol consisted of a low-kilovoltage (80 kV) protocol used in combination with an algorithm for dose reduction to the radiology staff during the interventional procedure, HandCare (HC). MSD was assessed during each intervention using EBT2 gafchromic films positioned on patient skin. Lesion size, position, total fluoroscopy time, and patient-effective diameter were registered for each patient. Dose rates were also estimated at the surface of a normal-size anthropomorphic thorax phantom using a 10 cm pencil ionization chamber placed at every 30°, for a full rotation, with and without HC. Measured MSD was compared with MSD values estimated from the phantom measurements and with the cumulative CTDIvol of the procedure.

RESULTS

The median measured MSD was 141 mGy (range 38-410 mGy) while the median cumulative CTDIvol was 72 mGy (range 24-262 mGy). The ratio between the MSD estimated from phantom measurements and the measured MSD was 0.87 (range 0.12-4.1) on average. In 72% of cases the estimated MSD underestimated the measured MSD, while in 28% of the cases it overestimated it. The same trend was observed for the ratio of cumulative CTDIvol and measured MSD. No trend was observed as a function of patient size.

CONCLUSIONS

On average, estimated MSD from dose rate measurements on phantom as well as from CTDIvol of patient examinations underestimates the measured value of MSD. This can be attributed to deviations of the patient's body habitus from the standard phantom size and to patient positioning in the gantry during the procedure.

Reduced Kilovoltage in Computed Tomography–Guided Intervention in a Community Hospital: Effect on the Radiation Dose

Purpose

The purpose of this study was to determine whether low-kilovoltage (80 or 100 kV) computed tomography (CT)-guided interventions performed in a community-based hospital are feasible and to compare radiation exposure incurred with conventional 120 kV potential.

Materials and Methods

Effective doses (ED) received by patients who underwent CT-guided intervention were analysed before and after a low-dose kilovoltage protocol was instituted in our department. We performed CT-guided procedures of 93 consecutive patients by using conventional 120-kV tube voltage (50 patients) and a low voltage of 80 or 100 kV for the remainder of this cohort. Automatic tube current modulation was enabled to obtain the best image quality. Procedure details were prospectively recorded and included examination site and type, slice width, tube voltage and current, dose length product, volume CT dose index, and size-specific dose estimate. Dose length product was converted to ED to account for radiosensitivity of specific organs. Statistical comparisons with test differences in the ED, volume CT dose index, size-specific dose estimate, and effective diameter (patient size) were made by using the Student t test.

Results

All but 6 of the procedures performed at 80 kV were successful, for a success rate of 86%. At lower voltages, the ED was significantly ( P < .01) reduced, on average, by 57%, 73%, and 65% for the pelvic, chest, and abdomen procedures, respectively.

Conclusion

A low-dose radiation technique by using 80 or 100 kV results in a high technical success rate for pelvic, chest, and abdomen CT-guided interventional procedures, although dramatically decreasing radiation exposure. There was no significant difference in effective diameter (patient size) between the conventional and the low-dose groups, which would suggest that dose reduction was indeed a result of kVp change and not patient size.

[Computed tomography guidance: fluoroscopy and more]

Although ultrasound and magnetic resonance imaging are competitive imaging modalities for the guidance of needle-based interventions, computed tomography (CT) is the only modality suitable for image-guided interventions in all regions of the body, including the lungs and bone. The ongoing technical development of CT involves accelerated image acquisition, significantly improved spatial resolution, CT scanners with an extended gantry diameter, acceleration of the procedure through joystick control of relevant functions of interventional CT by the interventional radiologist and tube current modulation to protect the hands of the examiner and radiosensitive organs of the patient. CT fluoroscopy can be used as a real-time method (the intervention is monitored under continuous CT fluoroscopy) or as a quick check method (repeated acquisitions of individual CT fluoroscopic images after each change of needle or table position). For the two approaches, multislice CT fluoroscopy (MSCTF) technique with wide detectors is particularly useful because even in the case of needle deviation from the center slice the needle tip is simultaneously visualised in the neighboring slices. With the aid of this technique a precise placement of interventional devices is possible even in angled access routes and in the presence of pronounced respiratory organ movements. As the reduction of CT fluoroscopy time significantly reduces radiation exposure for the patient and staff, the combination of a quick check technique and a low milliampere technique with multislice CT fluoroscopy devices is advantageous.

Radiation dose reduction in CT-guided spine biopsies does not reduce diagnostic yield

BACKGROUND AND PURPOSE

CT-guided biopsy is the most commonly used method to obtain tissue for diagnosis in suspected cases of malignancy involving the spine. The purpose of this study was to demonstrate that a low-dose CT-guided spine biopsy protocol is as effective in tissue sampling as a regular-dose protocol, without adversely affecting procedural time or complication rates.

MATERIALS AND METHODS

We retrospectively reviewed all patients who underwent CT-guided spine procedures at our institution between May 2010 and October 2013. Biopsy duration, total number of scans, total volume CT dose index, total dose-length product, and diagnostic tissue yield of low-dose and regular-dose groups were compared.

RESULTS

Sixty-four patients were included, of whom 31 underwent low-dose and 33 regular-dose spine biopsies. There was a statistically significant difference in total volume CT dose index and total dose-length product between the low-dose and regular-dose groups (P < .0001). There was no significant difference in the total number of scans obtained (P = .3385), duration of procedure (P = .149), or diagnostic tissue yield (P = .6017).

CONCLUSIONS

Use of a low-dose CT-guided spine biopsy protocol is a practical alternative to regular-dose approaches, maintaining overall quality and efficiency at reduced ionizing radiation dose.

Radiation dose optimization for CT-guided interventional procedures in the abdomen and pelvis

Radiation dose to patients can be high for some CT-guided interventional procedures in the abdomen and pelvis, especially tumor ablations. Strategies for radiation dose reduction include choosing an alternative guidance modality that does not use radiation whenever feasible, restricting the cranio-caudal length of interventional scans to the interventional target, and refinement of technical skills in order to minimize the number of scans acquired for interventional guidance. Dose optimization for these procedures is best achieved by lowering the tube current relative to the prior diagnostic scan, choosing dose efficient scanning modes, and using intermittent-mode, narrowly collimated CT fluoroscopy for interventional guidance.

CT fluoroscopy guided percutaneous gastrostomy or jejunostomy without (CT-PG/PJ) or with simultaneous endoscopy (CT-PEG/PEJ) in otherwise untreatable patients

PURPOSE

Percutaneous endoscopic gastrostomy (PEG) or percutaneous endoscopic jejunostomy (PEJ) are substantial for patients with swallowing disorders to maintain enteral nutrition or to decompress palliatively intractable small bowel obstruction. Endoscopic placement can be impossible due to previous (gastric) operation, obesity, hepato-splenomegaly, peritoneal carcinosis, inadequate transillumination, or obstructed passage. Computed tomography (CT)-fluoroscopic guidance with or without endoscopy can enable placement of CT-PG/CT-PJ or CT-PEG/CT-PEJ if endoscopically guided placement fails. In this retrospective study, we will evaluate the feasibility and safety of this method.

METHODS

A total of 101 consecutive patients were referred to our department for feeding support (n = 87) or decompression (n = 14). Reasons were: ENT tumor (n = 51), esophageal cancer (n = 19), mediastinal mass (n = 2), neurological disorder (n = 15). Decompression tubes were placed because of cancer (n = 13) or Crohn's disease (n = 1). The following approaches were chosen: CT fluoroscopy and simultaneous gastroscopy (n = 61), inflation of the stomach via nasogastric tube (n = 29), and direct puncture under CT-fluoroscopic guidance (n = 11).

RESULTS

CT fluoroscopy-guided gastrostomy was feasible in 89 of 101 patients. No procedure-related mortality was observed. One tube was misplaced into the colon in a patient with a history of gastrectomy. No complication was seen after removal. Minor complications: dislodgement (n = 17), peristomal leakage (n = 7), wound infection (n = 1), superficial skin infection (n = 6), tube obstruction (n = 2).

CONCLUSIONS

CT fluoroscopy-guided PG/PJ or PEG/PEJ is feasible and safe and provides adequate feeding support or decompression. It offers the benefits of minimally invasive therapy even in patients with contraindications to established endoscopic methods, combining the advantages of both techniques. Long-term complications-mainly tube-related problems-are easily treated.

Cancer in pregnancy: cross-sectional oncologic imaging utilization at a tertiary care center with an algorithmic approach to imaging

PURPOSE

To review utilization of imaging in pregnant patients with malignancies and define an imaging algorithm in this patient population.

METHODS

Pregnant patients with concurrent diagnoses of malignancy from January 2002 to January 2011 were identified using an institutional electronic medical record system. Patients with history of malignancy concurrent with pregnancy who had documented cross-sectional imaging studies were included. Clinical charts were reviewed, and patient demographics, diagnoses, indication for imaging, imaging findings, and oncologic stage were recorded. Descriptive statistics were performed.

RESULTS

Thirty-eight women were identified with malignancy concurrent with pregnancy. Twenty-seven patients had cross-sectional imaging studies during their pregnancy. There were 20 new diagnoses of malignancy and 7 with recurrent tumor. The most common new malignancies were lymphoma (5/27, 19%) and breast cancer (4/27, 15%). Two thirds (18/27, 66%) of the patients underwent at least one imaging study associated with ionizing radiation. CT imaging was utilized in 13 (48%) of 27 patients and MRI was used in 14 (52%) of 27 patients. Fifteen (75%) of the 20 patients with new diagnoses underwent oncologic staging with imaging that meets the standard of care based on National Comprehensive Cancer Network guidelines. An imaging algorithm was created as a guideline for the most common malignancies in pregnancy.

CONCLUSIONS

Cross-sectional oncologic imaging in the pregnant patient involves a variety of imaging modalities including those with ionizing radiation. This imaging largely follows standard of care for the nonpregnant patient and is tailored to specific patient complaints. A generalized algorithm is offered here for imaging pregnant oncology patients.

CT-fluoroscopy in chest interventional radiology: sliding scale of imaging parameters based on radiation exposure dose and factors increasing radiation exposure dose

AIM

To verify the usefulness of a sliding scale of imaging parameters to reduce radiation exposure during chest interventional radiology (IR), and to identify factors that increase radiation exposure in order to obtain acceptable computed tomography (CT)-fluoroscopy image quality.

MATERIALS AND METHODS

The institutional review board approved this retrospective study, for which the need for informed consent was waived. Interventional radiologists determined the optimal CT-fluoroscopy imaging parameters using the sliding scale based on the radiation exposure dose. The imaging parameters were changed from those generating low radiation (120 kV/10 mA, 1.2 mGy/s) to others generating higher radiation exposure until acceptable image quality was obtained for each procedure. Validation of the imaging parameter sliding scale was done using regression analysis. Factors that increase radiation exposure were identified using multiple regression analysis.

RESULTS

In 125 patients, 217 procedures were performed, of which 72 procedures (33.2%, 72/217) were performed with imaging parameters of minimum radiation exposure, but increased radiation exposure was necessary in 145 (66.8%, 145/217). Significant correlation was found between the radiation exposure dose and the percentage achievement of acceptable image quality (R(2) = 0.98). Multivariate regression analysis showed that high body weight (p < 0.0001), long device passage (p < 0.0001), and lesions above the aortic arch (p = 0.04) were significant independent factors increasing radiation exposure.

CONCLUSION

Although increased radiation exposure dose might be necessary to obtain acceptable chest CT-fluoroscopy images depending on the patient, lesion, and procedure characteristics, a sliding scale of imaging parameters helps to reduce radiation exposure.

Radiation dose management: part 1, minimizing radiation dose in CT-guided procedures

OBJECTIVE

The purpose of this article is to discuss radiation dose during CT-guided interventions and to explain how radiologists can modify technical factors to minimize radiation doses. Scanner-displayed indexes of radiation exposure that are available during the procedure will be defined to increase awareness about CT radiation dose reduction during interventional procedures.

CONCLUSION

CT-guided fluoroscopic procedures are safe and effective methods of directed intervention; however, the increasing use of medical radiation is an important consideration. The appropriate use of imaging with an acceptable risk must be considered in every case. During CT-guided interventions, scanner parameters that can be used as a guide for effective dose management, including the CT dose index and dose-length product, are readily displayed. These parameters can be adjusted by modifying the longitudinal scan length, number of scans, and tube current-exposure time product (milliampere × second [mAs]). A team approach to radiation dose reduction will work the best.

Clinical demand for chest/abdomen/pelvis anatomy following thoracic or lumbar spine CT

The purpose of this study is to determine how often CT is repeated to obtain chest/abdomen/pelvis data outside the reconstructed field of view (FOV) on a prior spine CT. Radiology records of 1,239 consecutive thoracic and lumbar spine CT exams of 1,025 patients from January 1, 2006 to December 31, 2008 were retrospectively reviewed to identify patients who subsequently had CT studies of the chest, abdomen, and/or pelvis. The CT data were also evaluated for contrast enhancement, slice thickness, radiation dose, and reason for subsequent CT exam. Over 3 years, 290 of the 1,239 (24%) spine CT exams were followed by CT of the same anatomic region to evaluate extraspinal anatomy. The use or nonuse of contrast in these follow-up studies was the same as the preceding spine study in 91 cases, which were repeated on the same day (n = 37), within 7 days (n = 19), within 8-30 days (n = 15), or after 30 days (n = 20). Fourteen of 25 (56%) T spine CTs and 34 of 52 (65%) L spine CTs without contrast were followed by a chest CT or abdomen/pelvis CT without contrast within 7 days, respectively. Among 31 pediatric exams, 6 of 31 (19%) spine CTs were followed by a CT of the same anatomic region, all within 7 days. Reconstructing full FOV images of spine CT scans in addition to the standard coned down spine FOV may reduce redundant CT imaging and radiation dose.

Ultra-low-dose protocol for CT-guided lung biopsies

PURPOSE

Computed tomography (CT) scans are a significant source of radiation to patients. It was hypothesized that technical success and complication rates would not be significantly changed by radically lowering the CT dose during lung biopsies with an ultra-low-dose (ULD) protocol.

MATERIALS AND METHODS

A total of 100 consecutive patients aged 11-89 years who underwent biopsies of lung lesions were evaluated. Technical parameters were altered halfway through the study from the standard dose (140 kV localizing/100 kV subsequent guiding scans with auto-mA) to a ULD protocol (100 kV, 7.5 mAs) as part of a quality initiative. ULD studies were evaluated subjectively for image quality on a five-point scale. Patients' body mass indexes, total estimated radiation doses (dose-length product), technical success rates, and complications were compared between the standard-dose and the ULD groups.

RESULTS

Average radiation dose was reduced from 677.5 mGy·cm for the standard-dose group to 18.3 mGy·cm for the ULD group (P < .0001). In the ULD group, image quality was rated as adequate or better in 96% of cases. Pneumothoraces necessitating chest tube placements occurred in 10% and 6% of cases in the ULD and standard dose groups, respectively (P = .715). Technical success rates of 92% and 98% were obtained in the ULD and standard dose groups, respectively (P = .362).

CONCLUSIONS

Radiation dose to the chest during CT-guided percutaneous lung biopsies is reduced greater than 95% versus a standard protocol through the use of a ULD CT protocol without decreasing technical success or patient safety.

Optimizing dose in computed tomographic guided procedures

In the recent past, computed tomography (CT) use has grown by approximately 10% per year, with 62 million examinations performed in the USA in 2006. While these studies make up only 15% of the total number of radiologic examinations, they contribute approximately half of the public exposure due to medical radiation. CT-guided procedures comprise a small, but important minority of the total number of CT scans performed each year, as a significant dose can be delivered in this setting. This article reviews techniques to optimize patient exposure during CT-guided interventions.

Radiation dose reduction in computed tomography: techniques and future perspective

Despite universal consensus that computed tomography (CT) overwhelmingly benefits patients when used for appropriate indications, concerns have been raised regarding the potential risk of cancer induction from CT due to the exponentially increased use of CT in medicine. Keeping radiation dose as low as reasonably achievable, consistent with the diagnostic task, remains the most important strategy for decreasing this potential risk. This article summarizes the general technical strategies that are commonly used for radiation dose management in CT. Dose-management strategies for pediatric CT, cardiac CT, dual-energy CT, CT perfusion and interventional CT are specifically discussed, and future perspectives on CT dose reduction are presented.

[Percutaneous abdominopelvic interventional procedures using real-time CT fluoroscopy guidance at 21 mAs: an analysis of 99 consecutive cases]

PURPOSE

The purpose of our study was to retrospectively evaluate the efficacy, the limitations and the complications of real-time CT fluoroscopy (Carevision) as an adjunct to CT guidance for percutaneous abdominopelvic interventional procedures. Materials and methods. During a 28 month period, 99 patients (55 men, 44 women) with a mean age of 59 years had percutaneous abdominopelvic interventional procedure under CT guidance using CT fluoroscopy. Sixty-four patients had a percutaneous drainage of an abdominopelvic fluid collection with a Seldinger technique using an 8.5- to 14-F drainage catheter and 35 patients had a percutaneous biopsy using an 18-G automatic core biopsy needle.

RESULTS

In all cases, the quality of the real-time CT fluoroscopic images allowed to securely monitor needle advancement towards the target lesion and to confirm correct position of the needle tip. The diameters of target lesions ranged from 1.5 to 10 cm, with a mean value of 4.75 cm. No immediate complications were observed. The real-time CT fluoroscopy times ranged from 25 to 242 sec, with a mean time of 117 sec. All percutaneous procedures (100%) were successfully performed.

CONCLUSION

Our initial clinical experience suggests that real-time CT fluoroscopy allows to perform effective and secure percutaneous abdominopelvic interventional procedures. However, because of substantial radiation exposure, its use has to be limited to specific et selected cases.